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Network Working Group                                         D. AwducheRequest for Comments: 3209                          Movaz Networks, Inc.Category: Standards Track                                      L. Berger                                                                  D. Gan                                                  Juniper Networks, Inc.                                                                   T. Li                                                  Procket Networks, Inc.                                                           V. Srinivasan                                             Cosine Communications, Inc.                                                              G. Swallow                                                     Cisco Systems, Inc.                                                           December 2001RSVP-TE: Extensions to RSVP for LSP TunnelsStatus of this Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2001).  All Rights Reserved.Abstract   This document describes the use of RSVP (Resource Reservation   Protocol), including all the necessary extensions, to establish   label-switched paths (LSPs) in MPLS (Multi-Protocol Label Switching).   Since the flow along an LSP is completely identified by the label   applied at the ingress node of the path, these paths may be treated   as tunnels.  A key application of LSP tunnels is traffic engineering   with MPLS as specified inRFC 2702.   We propose several additional objects that extend RSVP, allowing the   establishment of explicitly routed label switched paths using RSVP as   a signaling protocol.  The result is the instantiation of label-   switched tunnels which can be automatically routed away from network   failures, congestion, and bottlenecks.Awduche, et al.             Standards Track                     [Page 1]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001Contents1      Introduction   ..........................................31.1    Background  .............................................41.2    Terminology  ............................................62      Overview   ..............................................72.1    LSP Tunnels and Traffic Engineered Tunnels  .............72.2    Operation of LSP Tunnels  ...............................82.3    Service Classes  ........................................102.4    Reservation Styles  .....................................102.4.1  Fixed Filter (FF) Style  ................................102.4.2  Wildcard Filter (WF) Style  .............................112.4.3  Shared Explicit (SE) Style  .............................112.5    Rerouting Traffic Engineered Tunnels  ...................122.6    Path MTU  ...............................................133      LSP Tunnel related Message Formats  .....................153.1    Path Message  ...........................................153.2    Resv Message  ...........................................164      LSP Tunnel related Objects  .............................174.1    Label Object  ...........................................174.1.1  Handling Label Objects in Resv messages  ................174.1.2  Non-support of the Label Object  ........................194.2    Label Request Object  ...................................194.2.1  Label Request without Label Range  ......................194.2.2  Label Request with ATM Label Range  .....................204.2.3  Label Request with Frame Relay Label Range  .............214.2.4  Handling of LABEL_REQUEST  ..............................224.2.5  Non-support of the Label Request Object  ................234.3    Explicit Route Object  ..................................234.3.1  Applicability  ..........................................244.3.2  Semantics of the Explicit Route Object  .................244.3.3  Subobjects  .............................................254.3.4  Processing of the Explicit Route Object  ................284.3.5  Loops  ..................................................304.3.6  Forward Compatibility  ..................................304.3.7  Non-support of the Explicit Route Object  ...............314.4    Record Route Object  ....................................314.4.1  Subobjects  .............................................314.4.2  Applicability  ..........................................344.4.3  Processing RRO  .........................................354.4.4  Loop Detection  .........................................364.4.5  Forward Compatibility  ..................................374.4.6  Non-support of RRO  .....................................374.5    Error Codes for ERO and RRO  ............................374.6    Session, Sender Template, and Filter Spec Objects  ......384.6.1  Session Object  .........................................394.6.2  Sender Template Object  .................................404.6.3  Filter Specification Object  ............................42Awduche, et al.             Standards Track                     [Page 2]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 20014.6.4  Reroute and Bandwidth Increase Procedure  ...............424.7    Session Attribute Object  ...............................434.7.1  Format without resource affinities  .....................434.7.2  Format with resource affinities  ........................454.7.3  Procedures applying to both C-Types  ....................464.7.4  Resource Affinity Procedures   ..........................485      Hello Extension  ........................................495.1    Hello Message Format  ...................................505.2    HELLO Object formats  ...................................515.2.1  HELLO REQUEST object  ...................................515.2.2  HELLO ACK object  .......................................515.3    Hello Message Usage  ....................................525.4    Multi-Link Considerations  ..............................535.5    Compatibility  ..........................................546      Security Considerations  ................................547      IANA Considerations  ....................................547.1    Message Types  ..........................................557.2    Class Numbers and C-Types  ..............................55   7.3    Error Codes and Globally-Defined Error Value Sub-Codes  .  577.4    Subobject Definitions  ..................................578      Intellectual Property Considerations  ...................589      Acknowledgments  ........................................5810     References  .............................................5811     Authors' Addresses  .....................................6012     Full Copyright Statement  ...............................611. IntroductionSection 2.9 of the MPLS architecture [2] defines a label distribution   protocol as a set of procedures by which one Label Switched Router   (LSR) informs another of the meaning of labels used to forward   traffic between and through them.  The MPLS architecture does not   assume a single label distribution protocol.  This document is a   specification of extensions to RSVP for establishing label switched   paths (LSPs) in MPLS networks.   Several of the new features described in this document were motivated   by the requirements for traffic engineering over MPLS (see [3]).  In   particular, the extended RSVP protocol supports the instantiation of   explicitly routed LSPs, with or without resource reservations.  It   also supports smooth rerouting of LSPs, preemption, and loop   detection.   The LSPs created with RSVP can be used to carry the "Traffic Trunks"   described in [3].  The LSP which carries a traffic trunk and a   traffic trunk are distinct though closely related concepts.  For   example, two LSPs between the same source and destination could be   load shared to carry a single traffic trunk.  Conversely severalAwduche, et al.             Standards Track                     [Page 3]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   traffic trunks could be carried in the same LSP if, for instance, the   LSP were capable of carrying several service classes.  The   applicability of these extensions is discussed further in [10].   Since the traffic that flows along a label-switched path is defined   by the label applied at the ingress node of the LSP, these paths can   be treated as tunnels, tunneling below normal IP routing and   filtering mechanisms.  When an LSP is used in this way we refer to it   as an LSP tunnel.   LSP tunnels allow the implementation of a variety of policies related   to network performance optimization.  For example, LSP tunnels can be   automatically or manually routed away from network failures,   congestion, and bottlenecks.  Furthermore, multiple parallel LSP   tunnels can be established between two nodes, and traffic between the   two nodes can be mapped onto the LSP tunnels according to local   policy.  Although traffic engineering (that is, performance   optimization of operational networks) is expected to be an important   application of this specification, the extended RSVP protocol can be   used in a much wider context.   The purpose of this document is to describe the use of RSVP to   establish LSP tunnels.  The intent is to fully describe all the   objects, packet formats, and procedures required to realize   interoperable implementations.  A few new objects are also defined   that enhance management and diagnostics of LSP tunnels.   The document also describes a means of rapid node failure detection   via a new HELLO message.   All objects and messages described in this specification are optional   with respect to RSVP.  This document discusses what happens when an   object described here is not supported by a node.   Throughout this document, the discussion will be restricted to   unicast label switched paths.  Multicast LSPs are left for further   study.1.1. Background   Hosts and routers that support both RSVP [1] and Multi-Protocol Label   Switching [2] can associate labels with RSVP flows.  When MPLS and   RSVP are combined, the definition of a flow can be made more   flexible.  Once a label switched path (LSP) is established, the   traffic through the path is defined by the label applied at the   ingress node of the LSP.  The mapping of label to traffic can be   accomplished using a number of different criteria.  The set of   packets that are assigned the same label value by a specific node areAwduche, et al.             Standards Track                     [Page 4]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   said to belong to the same forwarding equivalence class (FEC) (see   [2]), and effectively define the "RSVP flow."  When traffic is mapped   onto a label-switched path in this way, we call the LSP an "LSP   Tunnel".  When labels are associated with traffic flows, it becomes   possible for a router to identify the appropriate reservation state   for a packet based on the packet's label value.   The signaling protocol model uses downstream-on-demand label   distribution.  A request to bind labels to a specific LSP tunnel is   initiated by an ingress node through the RSVP Path message.  For this   purpose, the RSVP Path message is augmented with a LABEL_REQUEST   object.  Labels are allocated downstream and distributed (propagated   upstream) by means of the RSVP Resv message.  For this purpose, the   RSVP Resv message is extended with a special LABEL object.  The   procedures for label allocation, distribution, binding, and stacking   are described in subsequent sections of this document.   The signaling protocol model also supports explicit routing   capability.  This is accomplished by incorporating a simple   EXPLICIT_ROUTE object into RSVP Path messages.  The EXPLICIT_ROUTE   object encapsulates a concatenation of hops which constitutes the   explicitly routed path.  Using this object, the paths taken by   label-switched RSVP-MPLS flows can be pre-determined, independent of   conventional IP routing.  The explicitly routed path can be   administratively specified, or automatically computed by a suitable   entity based on QoS and policy requirements, taking into   consideration the prevailing network state.  In general, path   computation can be control-driven or data-driven.  The mechanisms,   processes, and algorithms used to compute explicitly routed paths are   beyond the scope of this specification.   One useful application of explicit routing is traffic engineering.   Using explicitly routed LSPs, a node at the ingress edge of an MPLS   domain can control the path through which traffic traverses from   itself, through the MPLS network, to an egress node.  Explicit   routing can be used to optimize the utilization of network resources   and enhance traffic oriented performance characteristics.   The concept of explicitly routed label switched paths can be   generalized through the notion of abstract nodes.  An abstract node   is a group of nodes whose internal topology is opaque to the ingress   node of the LSP.  An abstract node is said to be simple if it   contains only one physical node.  Using this concept of abstraction,   an explicitly routed LSP can be specified as a sequence of IP   prefixes or a sequence of Autonomous Systems.Awduche, et al.             Standards Track                     [Page 5]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   The signaling protocol model supports the specification of an   explicit path as a sequence of strict and loose routes.  The   combination of abstract nodes, and strict and loose routes   significantly enhances the flexibility of path definitions.   An advantage of using RSVP to establish LSP tunnels is that it   enables the allocation of resources along the path.  For example,   bandwidth can be allocated to an LSP tunnel using standard RSVP   reservations and Integrated Services service classes [4].   While resource reservations are useful, they are not mandatory.   Indeed, an LSP can be instantiated without any resource reservations   whatsoever.  Such LSPs without resource reservations can be used, for   example, to carry best effort traffic.  They can also be used in many   other contexts, including implementation of fall-back and recovery   policies under fault conditions, and so forth.1.2. Terminology   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this   document are to be interpreted as described inRFC2119 [6].   The reader is assumed to be familiar with the terminology in [1], [2]   and [3].   Abstract Node      A group of nodes whose internal topology is opaque to the ingress      node of the LSP.  An abstract node is said to be simple if it      contains only one physical node.   Explicitly Routed LSP      An LSP whose path is established by a means other than normal IP      routing.   Label Switched Path      The path created by the concatenation of one or more label      switched hops, allowing a packet to be forwarded by swapping      labels from an MPLS node to another MPLS node.  For a more precise      definition see [2].   LSP      A Label Switched PathAwduche, et al.             Standards Track                     [Page 6]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   LSP Tunnel      An LSP which is used to tunnel below normal IP routing and/or      filtering mechanisms.   Traffic Engineered Tunnel (TE Tunnel)      A set of one or more LSP Tunnels which carries a traffic trunk.   Traffic Trunk      A set of flows aggregated by their service class and then placed      on an LSP or set of LSPs called a traffic engineered tunnel.  For      further discussion see [3].2. Overview2.1. LSP Tunnels and Traffic Engineered Tunnels   According to [1], "RSVP defines a 'session' to be a data flow with a   particular destination and transport-layer protocol." However, when   RSVP and MPLS are combined, a flow or session can be defined with   greater flexibility and generality.  The ingress node of an LSP can   use a variety of means to determine which packets are assigned a   particular label.  Once a label is assigned to a set of packets, the   label effectively defines the "flow" through the LSP.  We refer to   such an LSP as an "LSP tunnel" because the traffic through it is   opaque to intermediate nodes along the label switched path.   New RSVP SESSION, SENDER_TEMPLATE, and FILTER_SPEC objects, called   LSP_TUNNEL_IPv4 and LSP_TUNNEL_IPv6 have been defined to support the   LSP tunnel feature.  The semantics of these objects, from the   perspective of a node along the label switched path, is that traffic   belonging to the LSP tunnel is identified solely on the basis of   packets arriving from the PHOP or "previous hop" (see [1]) with the   particular label value(s) assigned by this node to upstream senders   to the session.  In fact, the IPv4(v6) that appears in the object   name only denotes that the destination address is an IPv4(v6)   address.  When we refer to these objects generically, we use the   qualifier LSP_TUNNEL.   In some applications it is useful to associate sets of LSP tunnels.   This can be useful during reroute operations or to spread a traffic   trunk over multiple paths.  In the traffic engineering application   such sets are called traffic engineered tunnels (TE tunnels).  To   enable the identification and association of such LSP tunnels, two   identifiers are carried.  A tunnel ID is part of the SESSION object.   The SESSION object uniquely defines a traffic engineered tunnel.  TheAwduche, et al.             Standards Track                     [Page 7]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   SENDER_TEMPLATE and FILTER_SPEC objects carry an LSP ID.  The   SENDER_TEMPLATE (or FILTER_SPEC) object together with the SESSION   object uniquely identifies an LSP tunnel2.2. Operation of LSP Tunnels   This section summarizes some of the features supported by RSVP as   extended by this document related to the operation of LSP tunnels.   These include: (1) the capability to establish LSP tunnels with or   without QoS requirements, (2) the capability to dynamically reroute   an established LSP tunnel, (3) the capability to observe the actual   route traversed by an established LSP tunnel, (4) the capability to   identify and diagnose LSP tunnels, (5) the capability to preempt an   established LSP tunnel under administrative policy control, and (6)   the capability to perform downstream-on-demand label allocation,   distribution, and binding.  In the following paragraphs, these   features are briefly described.  More detailed descriptions can be   found in subsequent sections of this document.   To create an LSP tunnel, the first MPLS node on the path -- that is,   the sender node with respect to the path -- creates an RSVP Path   message with a session type of LSP_TUNNEL_IPv4 or LSP_TUNNEL_IPv6 and   inserts a LABEL_REQUEST object into the Path message.  The   LABEL_REQUEST object indicates that a label binding for this path is   requested and also provides an indication of the network layer   protocol that is to be carried over this path.  The reason for this   is that the network layer protocol sent down an LSP cannot be assumed   to be IP and cannot be deduced from the L2 header, which simply   identifies the higher layer protocol as MPLS.   If the sender node has knowledge of a route that has high likelihood   of meeting the tunnel's QoS requirements, or that makes efficient use   of network resources, or that satisfies some policy criteria, the   node can decide to use the route for some or all of its sessions.  To   do this, the sender node adds an EXPLICIT_ROUTE object to the RSVP   Path message.  The EXPLICIT_ROUTE object specifies the route as a   sequence of abstract nodes.   If, after a session has been successfully established, the sender   node discovers a better route, the sender can dynamically reroute the   session by simply changing the EXPLICIT_ROUTE object.  If problems   are encountered with an EXPLICIT_ROUTE object, either because it   causes a routing loop or because some intermediate routers do not   support it, the sender node is notified.   By adding a RECORD_ROUTE object to the Path message, the sender node   can receive information about the actual route that the LSP tunnel   traverses.  The sender node can also use this object to requestAwduche, et al.             Standards Track                     [Page 8]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   notification from the network concerning changes to the routing path.   The RECORD_ROUTE object is analogous to a path vector, and hence can   be used for loop detection.   Finally, a SESSION_ATTRIBUTE object can be added to Path messages to   aid in session identification and diagnostics.  Additional control   information, such as setup and hold priorities, resource affinities   (see [3]), and local-protection, are also included in this object.   Routers along the path may use the setup and hold priorities along   with SENDER_TSPEC and any POLICY_DATA objects contained in Path   messages as input to policy control.  For instance, in the traffic   engineering application, it is very useful to use the Path message as   a means of verifying that bandwidth exists at a particular priority   along an entire path before preempting any lower priority   reservations.  If a Path message is allowed to progress when there   are insufficient resources, then there is a danger that lower   priority reservations downstream of this point will unnecessarily be   preempted in a futile attempt to service this request.   When the EXPLICIT_ROUTE object (ERO) is present, the Path message is   forwarded towards its destination along a path specified by the ERO.   Each node along the path records the ERO in its path state block.   Nodes may also modify the ERO before forwarding the Path message.  In   this case the modified ERO SHOULD be stored in the path state block   in addition to the received ERO.   The LABEL_REQUEST object requests intermediate routers and receiver   nodes to provide a label binding for the session.  If a node is   incapable of providing a label binding, it sends a PathErr message   with an "unknown object class" error.  If the LABEL_REQUEST object is   not supported end to end, the sender node will be notified by the   first node which does not provide this support.   The destination node of a label-switched path responds to a   LABEL_REQUEST by including a LABEL object in its response RSVP Resv   message.  The LABEL object is inserted in the filter spec list   immediately following the filter spec to which it pertains.   The Resv message is sent back upstream towards the sender, following   the path state created by the Path message, in reverse order.  Note   that if the path state was created by use of an ERO, then the Resv   message will follow the reverse path of the ERO.   Each node that receives a Resv message containing a LABEL object uses   that label for outgoing traffic associated with this LSP tunnel.  If   the node is not the sender, it allocates a new label and places that   label in the corresponding LABEL object of the Resv message which itAwduche, et al.             Standards Track                     [Page 9]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   sends upstream to the PHOP.  The label sent upstream in the LABEL   object is the label which this node will use to identify incoming   traffic associated with this LSP tunnel.  This label also serves as   shorthand for the Filter Spec.  The node can now update its "Incoming   Label Map" (ILM), which is used to map incoming labeled packets to a   "Next Hop Label Forwarding Entry" (NHLFE), see [2].   When the Resv message propagates upstream to the sender node, a   label-switched path is effectively established.2.3. Service Classes   This document does not restrict the type of Integrated Service   requests for reservations.  However, an implementation SHOULD support   the Controlled-Load service [4] and the Null Service [16].2.4. Reservation Styles   The receiver node can select from among a set of possible reservation   styles for each session, and each RSVP session must have a particular   style.  Senders have no influence on the choice of reservation style.   The receiver can choose different reservation styles for different   LSPs.   An RSVP session can result in one or more LSPs, depending on the   reservation style chosen.   Some reservation styles, such as FF, dedicate a particular   reservation to an individual sender node.  Other reservation styles,   such as WF and SE, can share a reservation among several sender   nodes.  The following sections discuss the different reservation   styles and their advantages and disadvantages.  A more detailed   discussion of reservation styles can be found in [1].2.4.1. Fixed Filter (FF) Style   The Fixed Filter (FF) reservation style creates a distinct   reservation for traffic from each sender that is not shared by other   senders.  This style is common for applications in which traffic from   each sender is likely to be concurrent and independent.  The total   amount of reserved bandwidth on a link for sessions using FF is the   sum of the reservations for the individual senders.   Because each sender has its own reservation, a unique label is   assigned to each sender.  This can result in a point-to-point LSP   between every sender/receiver pair.Awduche, et al.             Standards Track                    [Page 10]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 20012.4.2. Wildcard Filter (WF) Style   With the Wildcard Filter (WF) reservation style, a single shared   reservation is used for all senders to a session.  The total   reservation on a link remains the same regardless of the number of   senders.   A single multipoint-to-point label-switched-path is created for all   senders to the session.  On links that senders to the session share,   a single label value is allocated to the session.  If there is only   one sender, the LSP looks like a normal point-to-point connection.   When multiple senders are present, a multipoint-to-point LSP (a   reversed tree) is created.   This style is useful for applications in which not all senders send   traffic at the same time.  A phone conference, for example, is an   application where not all speakers talk at the same time.  If,   however, all senders send simultaneously, then there is no means of   getting the proper reservations made.  Either the reserved bandwidth   on links close to the destination will be less than what is required   or then the reserved bandwidth on links close to some senders will be   greater than what is required.  This restricts the applicability of   WF for traffic engineering purposes.   Furthermore, because of the merging rules of WF, EXPLICIT_ROUTE   objects cannot be used with WF reservations.  As a result of this   issue and the lack of applicability to traffic engineering, use of WF   is not considered in this document.2.4.3. Shared Explicit (SE) Style   The Shared Explicit (SE) style allows a receiver to explicitly   specify the senders to be included in a reservation.  There is a   single reservation on a link for all the senders listed.  Because   each sender is explicitly listed in the Resv message, different   labels may be assigned to different senders, thereby creating   separate LSPs.   SE style reservations can be provided using multipoint-to-point   label-switched-path or LSP per sender.  Multipoint-to-point LSPs may   be used when path messages do not carry the EXPLICIT_ROUTE object, or   when Path messages have identical EXPLICIT_ROUTE objects.  In either   of these cases a common label may be assigned.Awduche, et al.             Standards Track                    [Page 11]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   Path messages from different senders can each carry their own ERO,   and the paths taken by the senders can converge and diverge at any   point in the network topology.  When Path messages have differing   EXPLICIT_ROUTE objects, separate LSPs for each EXPLICIT_ROUTE object   must be established.2.5. Rerouting Traffic Engineered Tunnels   One of the requirements for Traffic Engineering is the capability to   reroute an established TE tunnel under a number of conditions, based   on administrative policy.  For example, in some contexts, an   administrative policy may dictate that a given TE tunnel is to be   rerouted when a more "optimal" route becomes available.  Another   important context when TE tunnel reroute is usually required is upon   failure of a resource along the TE tunnel's established path.  Under   some policies, it may also be necessary to return the TE tunnel to   its original path when the failed resource becomes re-activated.   In general, it is highly desirable not to disrupt traffic, or   adversely impact network operations while TE tunnel rerouting is in   progress.  This adaptive and smooth rerouting requirement   necessitates establishing a new LSP tunnel and transferring traffic   from the old LSP tunnel onto it before tearing down the old LSP   tunnel.  This concept is called "make-before-break." A problem can   arise because the old and new LSP tunnels might compete with each   other for resources on network segments which they have in common.   Depending on availability of resources, this competition can cause   Admission Control to prevent the new LSP tunnel from being   established.  An advantage of using RSVP to establish LSP tunnels is   that it solves this problem very elegantly.   To support make-before-break in a smooth fashion, it is necessary   that on links that are common to the old and new LSPs, resources used   by the old LSP tunnel should not be released before traffic is   transitioned to the new LSP tunnel, and reservations should not be   counted twice because this might cause Admission Control to reject   the new LSP tunnel.   A similar situation can arise when one wants to increase the   bandwidth of a TE tunnel.  The new reservation will be for the full   amount needed, but the actual allocation needed is only the delta   between the new and old bandwidth.  If policy is being applied to   PATH messages by intermediate nodes, then a PATH message requesting   too much bandwidth will be rejected.  In this situation simply   increasing the bandwidth request without changing the   SENDER_TEMPLATE, could result in a tunnel being torn down, depending   upon local policy.Awduche, et al.             Standards Track                    [Page 12]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   The combination of the LSP_TUNNEL SESSION object and the SE   reservation style naturally accommodates smooth transitions in   bandwidth and routing.  The idea is that the old and new LSP tunnels   share resources along links which they have in common.  The   LSP_TUNNEL SESSION object is used to narrow the scope of the RSVP   session to the particular TE tunnel in question.  To uniquely   identify a TE tunnel, we use the combination of the destination IP   address (an address of the node which is the egress of the tunnel), a   Tunnel ID, and the tunnel ingress node's IP address, which is placed   in the Extended Tunnel ID field.   During the reroute or bandwidth-increase operation, the tunnel   ingress needs to appear as two different senders to the RSVP session.   This is achieved by the inclusion of the "LSP ID", which is carried   in the SENDER_TEMPLATE and FILTER_SPEC objects.  Since the semantics   of these objects are changed, a new C-Types are assigned.   To effect a reroute, the ingress node picks a new LSP ID and forms a   new SENDER_TEMPLATE.  The ingress node then creates a new ERO to   define the new path.  Thereafter the node sends a new Path Message   using the original SESSION object and the new SENDER_TEMPLATE and   ERO.  It continues to use the old LSP and refresh the old Path   message.  On links that are not held in common, the new Path message   is treated as a conventional new LSP tunnel setup.  On links held in   common, the shared SESSION object and SE style allow the LSP to be   established sharing resources with the old LSP.  Once the ingress   node receives a Resv message for the new LSP, it can transition   traffic to it and tear down the old LSP.   To effect a bandwidth-increase, a new Path Message with a new LSP_ID   can be used to attempt a larger bandwidth reservation while the   current LSP_ID continues to be refreshed to ensure that the   reservation is not lost if the larger reservation fails.2.6. Path MTU   Standard RSVP [1] and Int-Serv [11] provide the RSVP sender with the   minimum MTU available between the sender and the receiver.  This path   MTU identification capability is also provided for LSPs established   via RSVP.   Path MTU information is carried, depending on which is present, in   the Integrated Services or Null Service objects.  When using   Integrated Services objects, path MTU is provided based on the   procedures defined in [11].  Path MTU identification when using Null   Service objects is defined in [16].Awduche, et al.             Standards Track                    [Page 13]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   With standard RSVP, the path MTU information is used by the sender to   check which IP packets exceed the path MTU.  For packets that exceed   the path MTU, the sender either fragments the packets or, when the IP   datagram has the "Don't Fragment" bit set, issues an ICMP destination   unreachable message.  This path MTU related handling is also required   for LSPs established via RSVP.   The following algorithm applies to all unlabeled IP datagrams and to   any labeled packets which the node knows to be IP datagrams, to which   labels need to be added before forwarding.  For labeled packets the   bottom of stack is found, the IP header examined.   Using the terminology defined in [5], an LSR MUST execute the   following algorithm:   1. Let N be the number of bytes in the label stack (i.e, 4 times the      number of label stack entries) including labels to be added by      this node.   2. Let M be the smaller of the "Maximum Initially Labeled IP Datagram      Size" or of (Path MTU - N).   When the size of an IPv4 datagram (without labels) exceeds the value      of M,      If the DF bit is not set in the IPv4 header, then         (a) the datagram MUST be broken into fragments, each of whose             size is no greater than M, and         (b) each fragment MUST be labeled and then forwarded.      If the DF bit is set in the IPv4 header, then         (a) the datagram MUST NOT be forwarded         (b) Create an ICMP Destination Unreachable Message:              i. set its Code field [12] to "Fragmentation Required and                 DF Set",             ii. set its Next-Hop MTU field [13] to M         (c) If possible, transmit the ICMP Destination Unreachable             Message to the source of the of the discarded datagram.      When the size of an IPv6 datagram (without labels) exceeds the             value of M,Awduche, et al.             Standards Track                    [Page 14]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001         (a) the datagram MUST NOT be forwarded         (b) Create an ICMP Packet too Big Message with the Next-Hop             link MTU field [14] set to M         (c) If possible, transmit the ICMP Packet too Big Message to             the source of the of the discarded datagram.3. LSP Tunnel related Message Formats   Five new objects are defined in this section:      Object name          Applicable RSVP messages      ---------------      ------------------------      LABEL_REQUEST          Path      LABEL                  Resv      EXPLICIT_ROUTE         Path      RECORD_ROUTE           Path, Resv      SESSION_ATTRIBUTE      Path   New C-Types are also assigned for the SESSION, SENDER_TEMPLATE, and   FILTER_SPEC, objects.   Detailed descriptions of the new objects are given in later sections.   All new objects are OPTIONAL with respect to RSVP.  An implementation   can choose to support a subset of objects.  However, the   LABEL_REQUEST and LABEL objects are mandatory with respect to this   specification.   The LABEL and RECORD_ROUTE objects, are sender specific.  In Resv   messages they MUST appear after the associated FILTER_SPEC and prior   to any subsequent FILTER_SPEC.   The relative placement of EXPLICIT_ROUTE, LABEL_REQUEST, and   SESSION_ATTRIBUTE objects is simply a recommendation.  The ordering   of these objects is not important, so an implementation MUST be   prepared to accept objects in any order.3.1. Path Message   The format of the Path message is as follows:      <Path Message> ::=       <Common Header> [ <INTEGRITY> ]                               <SESSION> <RSVP_HOP>                               <TIME_VALUES>                               [ <EXPLICIT_ROUTE> ]                               <LABEL_REQUEST>                               [ <SESSION_ATTRIBUTE> ]Awduche, et al.             Standards Track                    [Page 15]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001                               [ <POLICY_DATA> ... ]                               <sender descriptor>      <sender descriptor> ::=  <SENDER_TEMPLATE> <SENDER_TSPEC>                               [ <ADSPEC> ]                               [ <RECORD_ROUTE> ]3.2. Resv Message   The format of the Resv message is as follows:      <Resv Message> ::=       <Common Header> [ <INTEGRITY> ]                               <SESSION>  <RSVP_HOP>                               <TIME_VALUES>                               [ <RESV_CONFIRM> ]  [ <SCOPE> ]                               [ <POLICY_DATA> ... ]                               <STYLE> <flow descriptor list>      <flow descriptor list> ::= <FF flow descriptor list>                               | <SE flow descriptor>      <FF flow descriptor list> ::= <FLOWSPEC> <FILTER_SPEC>                               <LABEL> [ <RECORD_ROUTE> ]                               | <FF flow descriptor list>                               <FF flow descriptor>      <FF flow descriptor> ::= [ <FLOWSPEC> ] <FILTER_SPEC> <LABEL>                               [ <RECORD_ROUTE> ]      <SE flow descriptor> ::= <FLOWSPEC> <SE filter spec list>      <SE filter spec list> ::= <SE filter spec>                               | <SE filter spec list> <SE filter spec>      <SE filter spec> ::=     <FILTER_SPEC> <LABEL> [ <RECORD_ROUTE> ]      Note:  LABEL and RECORD_ROUTE (if present), are bound to the             preceding FILTER_SPEC.  No more than one LABEL and/or             RECORD_ROUTE may follow each FILTER_SPEC.Awduche, et al.             Standards Track                    [Page 16]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 20014. LSP Tunnel related Objects4.1. Label Object   Labels MAY be carried in Resv messages.  For the FF and SE styles, a   label is associated with each sender.  The label for a sender MUST   immediately follow the FILTER_SPEC for that sender in the Resv   message.   The LABEL object has the following format:   LABEL class = 16, C_Type = 1    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           (top label)                         |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   The contents of a LABEL is a single label, encoded in 4 octets.  Each   generic MPLS label is an unsigned integer in the range 0 through   1048575.  Generic MPLS labels and FR labels are encoded right aligned   in 4 octets.  ATM labels are encoded with the VPI right justified in   bits 0-15 and the VCI right justified in bits 16-31.4.1.1. Handling Label Objects in Resv messages   In MPLS a node may support multiple label spaces, perhaps associating   a unique space with each incoming interface.  For the purposes of the   following discussion, the term "same label" means the identical label   value drawn from the identical label space.  Further, the following   applies only to unicast sessions.   Labels received in Resv messages on different interfaces are always   considered to be different even if the label value is the same.4.1.1.1. Downstream   The downstream node selects a label to represent the flow.  If a   label range has been specified in the label request, the label MUST   be drawn from that range.  If no label is available the node sends a   PathErr message with an error code of "routing problem" and an error   value of "label allocation failure".   If a node receives a Resv message that has assigned the same label   value to multiple senders, then that node MAY also assign a single   value to those same senders or to any subset of those senders.  NoteAwduche, et al.             Standards Track                    [Page 17]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   that if a node intends to police individual senders to a session, it   MUST assign unique labels to those senders.   In the case of ATM, one further condition applies.  Some ATM nodes   are not capable of merging streams.  These nodes MAY indicate this by   setting a bit in the label request to zero.  The M-bit in the   LABEL_REQUEST object of C-Type 2, label request with ATM label range,   serves this purpose.  The M-bit SHOULD be set by nodes which are   merge capable.  If for any senders the M-bit is not set, the   downstream node MUST assign unique labels to those senders.   Once a label is allocated, the node formats a new LABEL object.  The   node then sends the new LABEL object as part of the Resv message to   the previous hop.  The node SHOULD be prepared to forward packets   carrying the assigned label prior to sending the Resv message.  The   LABEL object SHOULD be kept in the Reservation State Block.  It is   then used in the next Resv refresh event for formatting the Resv   message.   A node is expected to send a Resv message before its refresh timers   expire if the contents of the LABEL object change.4.1.1.2. Upstream   A node uses the label carried in the LABEL object as the outgoing   label associated with the sender.  The router allocates a new label   and binds it to the incoming interface of this session/sender.  This   is the same interface that the router uses to forward Resv messages   to the previous hops.   Several circumstance can lead to an unacceptable label.      1. the node is a merge incapable ATM switch but the downstream         node has assigned the same label to two senders      2. The implicit null label was assigned, but the node is not         capable of doing a penultimate pop for the associated L3PID      3. The assigned label is outside the requested label range   In any of these events the node send a ResvErr message with an error   code of "routing problem" and an error value of "unacceptable label   value".Awduche, et al.             Standards Track                    [Page 18]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 20014.1.2. Non-support of the Label Object   Under normal circumstances, a node should never receive a LABEL   object in a Resv message unless it had included a LABEL_REQUEST   object in the corresponding Path message.  However, an RSVP router   that does not recognize the LABEL object sends a ResvErr with the   error code "Unknown object class" toward the receiver.  This causes   the reservation to fail.4.2. Label Request Object   The Label Request Class is 19.  Currently there are three possible   C_Types.  Type 1 is a Label Request without label range.  Type 2 is a   label request with an ATM label range.  Type 3 is a label request   with a Frame Relay label range.  The LABEL_REQUEST object formats are   shown below.4.2.1. Label Request without Label Range   Class = 19, C_Type = 1    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |           Reserved            |             L3PID             |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      Reserved         This field is reserved.  It MUST be set to zero on transmission         and MUST be ignored on receipt.      L3PID         an identifier of the layer 3 protocol using this path.         Standard Ethertype values are used.Awduche, et al.             Standards Track                    [Page 19]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 20014.2.2. Label Request with ATM Label Range   Class = 19, C_Type = 2    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |           Reserved            |             L3PID             |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |M| Res |    Minimum VPI        |      Minimum VCI              |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |  Res  |    Maximum VPI        |      Maximum VCI              |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      Reserved (Res)         This field is reserved.  It MUST be set to zero on transmission         and MUST be ignored on receipt.      L3PID         an identifier of the layer 3 protocol using this path.         Standard Ethertype values are used.      M         Setting this bit to one indicates that the node is capable of         merging in the data plane      Minimum VPI (12 bits)         This 12 bit field specifies the lower bound of a block of         Virtual Path Identifiers that is supported on the originating         switch.  If the VPI is less than 12-bits it MUST be right         justified in this field and preceding bits MUST be set to zero.      Minimum VCI (16 bits)         This 16 bit field specifies the lower bound of a block of         Virtual Connection Identifiers that is supported on the         originating switch.  If the VCI is less than 16-bits it MUST be         right justified in this field and preceding bits MUST be set to         zero.Awduche, et al.             Standards Track                    [Page 20]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001      Maximum VPI (12 bits)         This 12 bit field specifies the upper bound of a block of         Virtual Path Identifiers that is supported on the originating         switch.  If the VPI is less than 12-bits it MUST be right         justified in this field and preceding bits MUST be set to zero.      Maximum VCI (16 bits)         This 16 bit field specifies the upper bound of a block of         Virtual Connection Identifiers that is supported on the         originating switch.  If the VCI is less than 16-bits it MUST be         right justified in this field and preceding bits MUST be set to         zero.4.2.3. Label Request with Frame Relay Label Range   Class = 19, C_Type = 3    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |           Reserved            |             L3PID             |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   | Reserved    |DLI|                     Minimum DLCI            |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   | Reserved        |                     Maximum DLCI            |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      Reserved         This field is reserved.  It MUST be set to zero on transmission         and ignored on receipt.      L3PID         an identifier of the layer 3 protocol using this path.         Standard Ethertype values are used.      DLI         DLCI Length Indicator.  The number of bits in the DLCI.  The         following values are supported:                   Len    DLCI bits                    0        10                    2        23Awduche, et al.             Standards Track                    [Page 21]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001      Minimum DLCI         This 23-bit field specifies the lower bound of a block of Data         Link Connection Identifiers (DLCIs) that is supported on the         originating switch.  The DLCI MUST be right justified in this         field and unused bits MUST be set to 0.      Maximum DLCI         This 23-bit field specifies the upper bound of a block of Data         Link Connection Identifiers (DLCIs) that is supported on the         originating switch.  The DLCI MUST be right justified in this         field and unused bits MUST be set to 0.4.2.4. Handling of LABEL_REQUEST   To establish an LSP tunnel the sender creates a Path message with a   LABEL_REQUEST object.  The LABEL_REQUEST object indicates that a   label binding for this path is requested and provides an indication   of the network layer protocol that is to be carried over this path.   This permits non-IP network layer protocols to be sent down an LSP.   This information can also be useful in actual label allocation,   because some reserved labels are protocol specific, see [5].   The LABEL_REQUEST SHOULD be stored in the Path State Block, so that   Path refresh messages will also contain the LABEL_REQUEST object.   When the Path message reaches the receiver, the presence of the   LABEL_REQUEST object triggers the receiver to allocate a label and to   place the label in the LABEL object for the corresponding Resv   message.  If a label range was specified, the label MUST be allocated   from that range.  A receiver that accepts a LABEL_REQUEST object MUST   include a LABEL object in Resv messages pertaining to that Path   message.  If a LABEL_REQUEST object was not present in the Path   message, a node MUST NOT include a LABEL object in a Resv message for   that Path message's session and PHOP.   A node that sends a LABEL_REQUEST object MUST be ready to accept and   correctly process a LABEL object in the corresponding Resv messages.   A node that recognizes a LABEL_REQUEST object, but that is unable to   support it (possibly because of a failure to allocate labels) SHOULD   send a PathErr with the error code "Routing problem" and the error   value "MPLS label allocation failure."  This includes the case where   a label range has been specified and a label cannot be allocated from   that range.Awduche, et al.             Standards Track                    [Page 22]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   A node which receives and forwards a Path message each with a   LABEL_REQUEST object, MUST copy the L3PID from the received   LABEL_REQUEST object to the forwarded LABEL_REQUEST object.   If the receiver cannot support the protocol L3PID, it SHOULD send a   PathErr with the error code "Routing problem" and the error value   "Unsupported L3PID."  This causes the RSVP session to fail.4.2.5. Non-support of the Label Request Object   An RSVP router that does not recognize the LABEL_REQUEST object sends   a PathErr with the error code "Unknown object class" toward the   sender.  An RSVP router that recognizes the LABEL_REQUEST object but   does not recognize the C_Type sends a PathErr with the error code   "Unknown object C_Type" toward the sender.  This causes the path   setup to fail.  The sender should notify management that a LSP cannot   be established and possibly take action to continue the reservation   without the LABEL_REQUEST.   RSVP is designed to cope gracefully with non-RSVP routers anywhere   between senders and receivers.  However, obviously, non-RSVP routers   cannot convey labels via RSVP.  This means that if a router has a   neighbor that is known to not be RSVP capable, the router MUST NOT   advertise the LABEL_REQUEST object when sending messages that pass   through the non-RSVP routers.  The router SHOULD send a PathErr back   to the sender, with the error code "Routing problem" and the error   value "MPLS being negotiated, but a non-RSVP capable router stands in   the path."  This same message SHOULD be sent, if a router receives a   LABEL_REQUEST object in a message from a non-RSVP capable router.   See [1] for a description of how a downstream router can determine   the presence of non-RSVP routers.4.3. Explicit Route Object   Explicit routes are specified via the EXPLICIT_ROUTE object (ERO).   The Explicit Route Class is 20.  Currently one C_Type is defined,   Type 1 Explicit Route.  The EXPLICIT_ROUTE object has the following   format:Awduche, et al.             Standards Track                    [Page 23]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   Class = 20, C_Type = 1    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                                                               |   //                        (Subobjects)                          //   |                                                               |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   Subobjects   The contents of an EXPLICIT_ROUTE object are a series of variable-   length data items called subobjects.  The subobjects are defined insection 4.3.3 below.   If a Path message contains multiple EXPLICIT_ROUTE objects, only the   first object is meaningful.  Subsequent EXPLICIT_ROUTE objects MAY be   ignored and SHOULD NOT be propagated.4.3.1. Applicability   The EXPLICIT_ROUTE object is intended to be used only for unicast   situations.  Applications of explicit routing to multicast are a   topic for further research.   The EXPLICIT_ROUTE object is to be used only when all routers along   the explicit route support RSVP and the EXPLICIT_ROUTE object.  The   EXPLICIT_ROUTE object is assigned a class value of the form 0bbbbbbb.   RSVP routers that do not support the object will therefore respond   with an "Unknown Object Class" error.4.3.2. Semantics of the Explicit Route Object   An explicit route is a particular path in the network topology.   Typically, the explicit route is determined by a node, with the   intent of directing traffic along that path.   An explicit route is described as a list of groups of nodes along the   explicit route.  In addition to the ability to identify specific   nodes along the path, an explicit route can identify a group of nodes   that must be traversed along the path.  This capability allows the   routing system a significant amount of local flexibility in   fulfilling a request for an explicit route.  This capability allows   the generator of the explicit route to have imperfect information   about the details of the path.Awduche, et al.             Standards Track                    [Page 24]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   The explicit route is encoded as a series of subobjects contained in   an EXPLICIT_ROUTE object.  Each subobject identifies a group of nodes   in the explicit route.  An explicit route is thus a specification of   groups of nodes to be traversed.   To formalize the discussion, we call each group of nodes an abstract   node.  Thus, we say that an explicit route is a specification of a   set of abstract nodes to be traversed.  If an abstract node consists   of only one node, we refer to it as a simple abstract node.   As an example of the concept of abstract nodes, consider an explicit   route that consists solely of Autonomous System number subobjects.   Each subobject corresponds to an Autonomous System in the global   topology.  In this case, each Autonomous System is an abstract node,   and the explicit route is a path that includes each of the specified   Autonomous Systems.  There may be multiple hops within each   Autonomous System, but these are opaque to the source node for the   explicit route.4.3.3. Subobjects   The contents of an EXPLICIT_ROUTE object are a series of variable-   length data items called subobjects.  Each subobject has the form:    0                   1    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------//----------------+   |L|    Type     |     Length    | (Subobject contents)          |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------//----------------+      L         The L bit is an attribute of the subobject.  The L bit is set         if the subobject represents a loose hop in the explicit route.         If the bit is not set, the subobject represents a strict hop in         the explicit route.      Type         The Type indicates the type of contents of the subobject.         Currently defined values are:                   1   IPv4 prefix                   2   IPv6 prefix                  32   Autonomous system numberAwduche, et al.             Standards Track                    [Page 25]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001      Length         The Length contains the total length of the subobject in bytes,         including the L, Type and Length fields.  The Length MUST be at         least 4, and MUST be a multiple of 4.4.3.3.1. Strict and Loose Subobjects   The L bit in the subobject is a one-bit attribute.  If the L bit is   set, then the value of the attribute is 'loose.'  Otherwise, the   value of the attribute is 'strict.'  For brevity, we say that if the   value of the subobject attribute is 'loose' then it is a 'loose   subobject.'  Otherwise, it's a 'strict subobject.'  Further, we say   that the abstract node of a strict or loose subobject is a strict or   a loose node, respectively.  Loose and strict nodes are always   interpreted relative to their prior abstract nodes.   The path between a strict node and its preceding node MUST include   only network nodes from the strict node and its preceding abstract   node.   The path between a loose node and its preceding node MAY include   other network nodes that are not part of the strict node or its   preceding abstract node.4.3.3.2. Subobject 1:IPv4 prefix    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |L|    Type     |     Length    | IPv4 address (4 bytes)        |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   | IPv4 address (continued)      | Prefix Length |      Resvd    |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      L         The L bit is an attribute of the subobject.  The L bit is set         if the subobject represents a loose hop in the explicit route.         If the bit is not set, the subobject represents a strict hop in         the explicit route.      Type         0x01  IPv4 addressAwduche, et al.             Standards Track                    [Page 26]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001      Length         The Length contains the total length of the subobject in bytes,         including the Type and Length fields.  The Length is always 8.      IPv4 address         An IPv4 address.  This address is treated as a prefix based on         the prefix length value below.  Bits beyond the prefix are         ignored on receipt and SHOULD be set to zero on transmission.      Prefix length         Length in bits of the IPv4 prefix      Padding         Zero on transmission.  Ignored on receipt.   The contents of an IPv4 prefix subobject are a 4-octet IPv4 address,   a 1-octet prefix length, and a 1-octet pad.  The abstract node   represented by this subobject is the set of nodes that have an IP   address which lies within this prefix.  Note that a prefix length of   32 indicates a single IPv4 node.4.3.3.3. Subobject 2:IPv6 Prefix    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |L|    Type     |     Length    | IPv6 address (16 bytes)       |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   | IPv6 address (continued)                                      |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   | IPv6 address (continued)                                      |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   | IPv6 address (continued)                                      |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   | IPv6 address (continued)      | Prefix Length |      Resvd    |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      L         The L bit is an attribute of the subobject.  The L bit is set         if the subobject represents a loose hop in the explicit route.         If the bit is not set, the subobject represents a strict hop in         the explicit route.Awduche, et al.             Standards Track                    [Page 27]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001      Type         0x02  IPv6 address      Length         The Length contains the total length of the subobject in bytes,         including the Type and Length fields.  The Length is always 20.      IPv6 address         An IPv6 address.  This address is treated as a prefix based on         the prefix length value below.  Bits beyond the prefix are         ignored on receipt and SHOULD be set to zero on transmission.      Prefix Length         Length in bits of the IPv6 prefix.      Padding         Zero on transmission.  Ignored on receipt.   The contents of an IPv6 prefix subobject are a 16-octet IPv6 address,   a 1-octet prefix length, and a 1-octet pad.  The abstract node   represented by this subobject is the set of nodes that have an IP   address which lies within this prefix.  Note that a prefix length of   128 indicates a single IPv6 node.4.3.3.4. Subobject 32:Autonomous System Number   The contents of an Autonomous System (AS) number subobject are a 2-   octet AS number.  The abstract node represented by this subobject is   the set of nodes belonging to the autonomous system.   The length of the AS number subobject is 4 octets.4.3.4. Processing of the Explicit Route Object4.3.4.1. Selection of the Next Hop   A node receiving a Path message containing an EXPLICIT_ROUTE object   must determine the next hop for this path.  This is necessary because   the next abstract node along the explicit route might be an IP subnet   or an Autonomous System.  Therefore, selection of this next hop may   involve a decision from a set of feasible alternatives.  The criteria   used to make a selection from feasible alternatives is implementation   dependent and can also be impacted by local policy, and is beyond theAwduche, et al.             Standards Track                    [Page 28]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   scope of this specification.  However, it is assumed that each node   will make a best effort attempt to determine a loop-free path.  Note   that paths so determined can be overridden by local policy.   To determine the next hop for the path, a node performs the following   steps:   1) The node receiving the RSVP message MUST first evaluate the first      subobject.  If the node is not part of the abstract node described      by the first subobject, it has received the message in error and      SHOULD return a "Bad initial subobject" error.  If there is no      first subobject, the message is also in error and the system      SHOULD return a "Bad EXPLICIT_ROUTE object" error.   2) If there is no second subobject, this indicates the end of the      explicit route.  The EXPLICIT_ROUTE object SHOULD be removed from      the Path message.  This node may or may not be the end of the      path.  Processing continues withsection 4.3.4.2, where a new      EXPLICIT_ROUTE object MAY be added to the Path message.   3) Next, the node evaluates the second subobject.  If the node is      also a part of the abstract node described by the second      subobject, then the node deletes the first subobject and continues      processing with step 2, above.  Note that this makes the second      subobject into the first subobject of the next iteration and      allows the node to identify the next abstract node on the path of      the message after possible repeated application(s) of steps 2 and      3.   4) Abstract Node Border Case: The node determines whether it is      topologically adjacent to the abstract node described by the      second subobject.  If so, the node selects a particular next hop      which is a member of the abstract node.  The node then deletes the      first subobject and continues processing withsection 4.3.4.2.   5) Interior of the Abstract Node Case: Otherwise, the node selects a      next hop within the abstract node of the first subobject (which      the node belongs to) that is along the path to the abstract node      of the second subobject (which is the next abstract node).  If no      such path exists then there are two cases:   5a) If the second subobject is a strict subobject, there is an error       and the node SHOULD return a "Bad strict node" error.   5b) Otherwise, if the second subobject is a loose subobject, the node       selects any next hop that is along the path to the next abstract       node.  If no path exists, there is an error, and the node SHOULD       return a "Bad loose node" error.Awduche, et al.             Standards Track                    [Page 29]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   6) Finally, the node replaces the first subobject with any subobject      that denotes an abstract node containing the next hop.  This is      necessary so that when the explicit route is received by the next      hop, it will be accepted.4.3.4.2. Adding subobjects to the Explicit Route Object   After selecting a next hop, the node MAY alter the explicit route in   the following ways.   If, as part of executing the algorithm insection 4.3.4.1, the   EXPLICIT_ROUTE object is removed, the node MAY add a new   EXPLICIT_ROUTE object.   Otherwise, if the node is a member of the abstract node for the first   subobject, a series of subobjects MAY be inserted before the first   subobject or MAY replace the first subobject.  Each subobject in this   series MUST denote an abstract node that is a subset of the current   abstract node.   Alternately, if the first subobject is a loose subobject, an   arbitrary series of subobjects MAY be inserted prior to the first   subobject.4.3.5. Loops   While the EXPLICIT_ROUTE object is of finite length, the existence of   loose nodes implies that it is possible to construct forwarding loops   during transients in the underlying routing protocol.  This can be   detected by the originator of the explicit route through the use of   another opaque route object called the RECORD_ROUTE object.  The   RECORD_ROUTE object is used to collect detailed path information and   is useful for loop detection and for diagnostics.4.3.6. Forward Compatibility   It is anticipated that new subobjects may be defined over time.  A   node which encounters an unrecognized subobject during its normal ERO   processing sends a PathErr with the error code "Routing Error" and   error value of "Bad Explicit Route Object" toward the sender.  The   EXPLICIT_ROUTE object is included, truncated (on the left) to the   offending subobject.  The presence of an unrecognized subobject which   is not encountered in a node's ERO processing SHOULD be ignored.  It   is passed forward along with the rest of the remaining ERO stack.Awduche, et al.             Standards Track                    [Page 30]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 20014.3.7. Non-support of the Explicit Route Object   An RSVP router that does not recognize the EXPLICIT_ROUTE object   sends a PathErr with the error code "Unknown object class" toward the   sender.  This causes the path setup to fail.  The sender should   notify management that a LSP cannot be established and possibly take   action to continue the reservation without the EXPLICIT_ROUTE or via   a different explicit route.4.4. Record Route Object   Routes can be recorded via the RECORD_ROUTE object (RRO).   Optionally, labels may also be recorded.  The Record Route Class is   21.  Currently one C_Type is defined, Type 1 Record Route.  The   RECORD_ROUTE object has the following format:   Class = 21, C_Type = 1    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                                                               |   //                        (Subobjects)                          //   |                                                               |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      Subobjects         The contents of a RECORD_ROUTE object are a series of         variable-length data items called subobjects.  The subobjects         are defined insection 4.4.1 below.   The RRO can be present in both RSVP Path and Resv messages.  If a   Path message contains multiple RROs, only the first RRO is   meaningful.  Subsequent RROs SHOULD be ignored and SHOULD NOT be   propagated.  Similarly, if in a Resv message multiple RROs are   encountered following a FILTER_SPEC before another FILTER_SPEC is   encountered, only the first RRO is meaningful.  Subsequent RROs   SHOULD be ignored and SHOULD NOT be propagated.4.4.1. Subobjects   The contents of a RECORD_ROUTE object are a series of variable-length   data items called subobjects.  Each subobject has its own Length   field.  The length contains the total length of the subobject in   bytes, including the Type and Length fields.  The length MUST always   be a multiple of 4, and at least 4.Awduche, et al.             Standards Track                    [Page 31]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   Subobjects are organized as a last-in-first-out stack.  The first   subobject relative to the beginning of RRO is considered the top.   The last subobject is considered the bottom.  When a new subobject is   added, it is always added to the top.   An empty RRO with no subobjects is considered illegal.   Three kinds of subobjects are currently defined.4.4.1.1. Subobject 1: IPv4 address    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |      Type     |     Length    | IPv4 address (4 bytes)        |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   | IPv4 address (continued)      | Prefix Length |      Flags    |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      Type         0x01  IPv4 address      Length         The Length contains the total length of the subobject in bytes,         including the Type and Length fields.  The Length is always 8.      IPv4 address         A 32-bit unicast, host address.  Any network-reachable         interface address is allowed here.  Illegal addresses, such as         certain loopback addresses, SHOULD NOT be used.      Prefix length         32      Flags         0x01  Local protection available               Indicates that the link downstream of this node is               protected via a local repair mechanism.  This flag can               only be set if the Local protection flag was set in the               SESSION_ATTRIBUTE object of the corresponding Path               message.Awduche, et al.             Standards Track                    [Page 32]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001         0x02  Local protection in use               Indicates that a local repair mechanism is in use to               maintain this tunnel (usually in the face of an outage               of the link it was previously routed over).4.4.1.2. Subobject 2: IPv6 address    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |      Type     |     Length    | IPv6 address (16 bytes)       |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   | IPv6 address (continued)                                      |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   | IPv6 address (continued)                                      |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   | IPv6 address (continued)                                      |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   | IPv6 address (continued)      | Prefix Length |      Flags    |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      Type         0x02  IPv6 address      Length         The Length contains the total length of the subobject in bytes,         including the Type and Length fields.  The Length is always 20.      IPv6 address         A 128-bit unicast host address.      Prefix length         128      Flags         0x01  Local protection available               Indicates that the link downstream of this node is               protected via a local repair mechanism.  This flag can               only be set if the Local protection flag was set in the               SESSION_ATTRIBUTE object of the corresponding Path               message.Awduche, et al.             Standards Track                    [Page 33]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001         0x02  Local protection in use               Indicates that a local repair mechanism is in use to               maintain this tunnel (usually in the face of an outage               of the link it was previously routed over).4.4.1.3. Subobject 3, Label    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |     Type      |     Length    |    Flags      |   C-Type      |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |       Contents of Label Object                                |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      Type         0x03  Label      Length         The Length contains the total length of the subobject in bytes,         including the Type and Length fields.      Flags         0x01 = Global label           This flag indicates that the label will be understood           if received on any interface.      C-Type         The C-Type of the included Label Object.  Copied from the Label         Object.      Contents of Label Object         The contents of the Label Object.  Copied from the Label Object4.4.2. Applicability   Only the procedures for use in unicast sessions are defined here.   There are three possible uses of RRO in RSVP.  First, an RRO can   function as a loop detection mechanism to discover L3 routing loops,   or loops inherent in the explicit route.  The exact procedure for   doing so is described later in this document.Awduche, et al.             Standards Track                    [Page 34]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   Second, an RRO collects up-to-date detailed path information hop-by-   hop about RSVP sessions, providing valuable information to the sender   or receiver.  Any path change (due to network topology changes) will   be reported.   Third, RRO syntax is designed so that, with minor changes, the whole   object can be used as input to the EXPLICIT_ROUTE object.  This is   useful if the sender receives RRO from the receiver in a Resv   message, applies it to EXPLICIT_ROUTE object in the next Path message   in order to "pin down session path".4.4.3. Processing RRO   Typically, a node initiates an RSVP session by adding the RRO to the   Path message.  The initial RRO contains only one subobject - the   sender's IP addresses.  If the node also desires label recording, it   sets the Label_Recording flag in the SESSION_ATTRIBUTE object.   When a Path message containing an RRO is received by an intermediate   router, the router stores a copy of it in the Path State Block.  The   RRO is then used in the next Path refresh event for formatting Path   messages.  When a new Path message is to be sent, the router adds a   new subobject to the RRO and appends the resulting RRO to the Path   message before transmission.   The newly added subobject MUST be this router's IP address.  The   address to be added SHOULD be the interface address of the outgoing   Path messages.  If there are multiple addresses to choose from, the   decision is a local matter.  However, it is RECOMMENDED that the same   address be chosen consistently.   When the Label_Recording flag is set in the SESSION_ATTRIBUTE object,   nodes doing route recording SHOULD include a Label Record subobject.   If the node is using a global label space, then it SHOULD set the   Global Label flag.   The Label Record subobject is pushed onto the RECORD_ROUTE object   prior to pushing on the node's IP address.  A node MUST NOT push on a   Label Record subobject without also pushing on an IPv4 or IPv6   subobject.   Note that on receipt of the initial Path message, a node is unlikely   to have a label to include.  Once a label is obtained, the node   SHOULD include the label in the RRO in the next Path refresh event.   If the newly added subobject causes the RRO to be too big to fit in a   Path (or Resv) message, the RRO object SHALL be dropped from the   message and message processing continues as normal.  A PathErr (orAwduche, et al.             Standards Track                    [Page 35]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   ResvErr) message SHOULD be sent back to the sender (or receiver).  An   error code of "Notify" and an error value of "RRO too large for MTU"   is used.  If the receiver receives such a ResvErr, it SHOULD send a   PathErr message with error code of "Notify" and an error value of   "RRO notification".   A sender receiving either of these error values SHOULD remove the RRO   from the Path message.   Nodes SHOULD resend the above PathErr or ResvErr message each n   seconds where n is the greater of 15 and the refresh interval for the   associated Path or RESV message.  The node MAY apply limits and/or   back-off timers to limit the number of messages sent.   An RSVP router can decide to send Path messages before its refresh   time if the RRO in the next Path message is different from the   previous one.  This can happen if the contents of the RRO received   from the previous hop router changes or if this RRO is newly added to   (or deleted from) the Path message.   When the destination node of an RSVP session receives a Path message   with an RRO, this indicates that the sender node needs route   recording.  The destination node initiates the RRO process by adding   an RRO to Resv messages.  The processing mirrors that of the Path   messages.  The only difference is that the RRO in a Resv message   records the path information in the reverse direction.   Note that each node along the path will now have the complete route   from source to destination.  The Path RRO will have the route from   the source to this node; the Resv RRO will have the route from this   node to the destination.  This is useful for network management.   A received Path message without an RRO indicates that the sender node   no longer needs route recording.  Subsequent Resv messages SHALL NOT   contain an RRO.4.4.4. Loop Detection   As part of processing an incoming RRO, an intermediate router looks   into all subobjects contained within the RRO.  If the router   determines that it is already in the list, a forwarding loop exists.   An RSVP session is loop-free if downstream nodes receive Path   messages or upstream nodes receive Resv messages with no routing   loops detected in the contained RRO.Awduche, et al.             Standards Track                    [Page 36]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   There are two broad classifications of forwarding loops.  The first   class is the transient loop, which occurs as a normal part of   operations as L3 routing tries to converge on a consistent forwarding   path for all destinations.  The second class of forwarding loop is   the permanent loop, which normally results from network mis-   configuration.   The action performed by a node on receipt of an RRO depends on the   message type in which the RRO is received.   For Path messages containing a forwarding loop, the router builds and   sends a "Routing problem" PathErr message, with the error value "loop   detected," and drops the Path message.  Until the loop is eliminated,   this session is not suitable for forwarding data packets.  How the   loop eliminated is beyond the scope of this document.   For Resv messages containing a forwarding loop, the router simply   drops the message.  Resv messages should not loop if Path messages do   not loop.4.4.5. Forward Compatibility   New subobjects may be defined for the RRO.  When processing an RRO,   unrecognized subobjects SHOULD be ignored and passed on.  When   processing an RRO for loop detection, a node SHOULD parse over any   unrecognized objects.  Loop detection works by detecting subobjects   which were inserted by the node itself on an earlier pass of the   object.  This ensures that the subobjects necessary for loop   detection are always understood.4.4.6. Non-support of RRO   The RRO object is to be used only when all routers along the path   support RSVP and the RRO object.  The RRO object is assigned a class   value of the form 0bbbbbbb.  RSVP routers that do not support the   object will therefore respond with an "Unknown Object Class" error.4.5. Error Codes for ERO and RRO   In the processing described above, certain errors must be reported as   either a "Routing Problem" or "Notify".  The value of the "Routing   Problem" error code is 24; the value of the "Notify" error code is   25.Awduche, et al.             Standards Track                    [Page 37]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   The following defines error values for the Routing Problem Error   Code:      Value    Error:         1     Bad EXPLICIT_ROUTE object         2     Bad strict node         3     Bad loose node         4     Bad initial subobject         5     No route available toward destination         6     Unacceptable label value         7     RRO indicated routing loops         8     MPLS being negotiated, but a non-RSVP-capable router               stands in the path         9     MPLS label allocation failure        10     Unsupported L3PID   For the Notify Error Code, the 16 bits of the Error Value field are:         ss00 cccc cccc cccc   The high order bits are as defined under Error Code 1. (See [1]).   When ss = 00, the following subcodes are defined:         1    RRO too large for MTU         2    RRO notification         3    Tunnel locally repaired4.6. Session, Sender Template, and Filter Spec Objects   New C-Types are defined for the SESSION, SENDER_TEMPLATE and   FILTER_SPEC objects.   The LSP_TUNNEL objects have the following format:Awduche, et al.             Standards Track                    [Page 38]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 20014.6.1. Session Object4.6.1.1. LSP_TUNNEL_IPv4 Session Object   Class = SESSION, LSP_TUNNEL_IPv4 C-Type = 7    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                   IPv4 tunnel end point address               |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |  MUST be zero                 |      Tunnel ID                |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                       Extended Tunnel ID                      |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      IPv4 tunnel end point address         IPv4 address of the egress node for the tunnel.      Tunnel ID         A 16-bit identifier used in the SESSION that remains constant         over the life of the tunnel.      Extended Tunnel ID         A 32-bit identifier used in the SESSION that remains constant         over the life of the tunnel.  Normally set to all zeros.         Ingress nodes that wish to narrow the scope of a SESSION to the         ingress-egress pair may place their IPv4 address here as a         globally unique identifier.Awduche, et al.             Standards Track                    [Page 39]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 20014.6.1.2. LSP_TUNNEL_IPv6 Session Object   Class = SESSION, LSP_TUNNEL_IPv6 C_Type = 8    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                                                               |   +                                                               +   |                   IPv6 tunnel end point address               |   +                                                               +   |                            (16 bytes)                         |   +                                                               +   |                                                               |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |  MUST be zero                 |      Tunnel ID                |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                                                               |   +                                                               +   |                       Extended Tunnel ID                      |   +                                                               +   |                            (16 bytes)                         |   +                                                               +   |                                                               |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      IPv6 tunnel end point address         IPv6 address of the egress node for the tunnel.      Tunnel ID         A 16-bit identifier used in the SESSION that remains constant         over the life of the tunnel.      Extended Tunnel ID         A 16-byte identifier used in the SESSION that remains constant         over the life of the tunnel.  Normally set to all zeros.         Ingress nodes that wish to narrow the scope of a SESSION to the         ingress-egress pair may place their IPv6 address here as a         globally unique identifier.4.6.2. Sender Template Object4.6.2.1. LSP_TUNNEL_IPv4 Sender Template Object   Class = SENDER_TEMPLATE, LSP_TUNNEL_IPv4 C-Type = 7Awduche, et al.             Standards Track                    [Page 40]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                   IPv4 tunnel sender address                  |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |  MUST be zero                 |            LSP ID             |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      IPv4 tunnel sender address         IPv4 address for a sender node      LSP ID         A 16-bit identifier used in the SENDER_TEMPLATE and the         FILTER_SPEC that can be changed to allow a sender to share         resources with itself.4.6.2.2. LSP_TUNNEL_IPv6 Sender Template Object   Class = SENDER_TEMPLATE, LSP_TUNNEL_IPv6 C_Type = 8    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                                                               |   +                                                               +   |                   IPv6 tunnel sender address                  |   +                                                               +   |                            (16 bytes)                         |   +                                                               +   |                                                               |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |  MUST be zero                 |            LSP ID             |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      IPv6 tunnel sender address         IPv6 address for a sender node      LSP ID         A 16-bit identifier used in the SENDER_TEMPLATE and the         FILTER_SPEC that can be changed to allow a sender to share         resources with itself.Awduche, et al.             Standards Track                    [Page 41]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 20014.6.3. Filter Specification Object4.6.3.1. LSP_TUNNEL_IPv4 Filter Specification Object      Class = FILTER SPECIFICATION, LSP_TUNNEL_IPv4 C-Type = 7   The format of the LSP_TUNNEL_IPv4 FILTER_SPEC object is identical to   the LSP_TUNNEL_IPv4 SENDER_TEMPLATE object.4.6.3.2. LSP_TUNNEL_IPv6 Filter Specification Object      Class = FILTER SPECIFICATION, LSP_TUNNEL_IPv6 C_Type = 8   The format of the LSP_TUNNEL_IPv6 FILTER_SPEC object is identical to   the LSP_TUNNEL_IPv6 SENDER_TEMPLATE object.4.6.4. Reroute and Bandwidth Increase Procedure   This section describes how to setup a tunnel that is capable of   maintaining resource reservations (without double counting) while it   is being rerouted or while it is attempting to increase its   bandwidth.  In the initial Path message, the ingress node forms a   SESSION object, assigns a Tunnel_ID, and places its IPv4 address in   the Extended_Tunnel_ID.  It also forms a SENDER_TEMPLATE and assigns   a LSP_ID.  Tunnel setup then proceeds according to the normal   procedure.   On receipt of the Path message, the egress node sends a Resv message   with the STYLE Shared Explicit toward the ingress node.   When an ingress node with an established path wants to change that   path, it forms a new Path message as follows.  The existing SESSION   object is used.  In particular the Tunnel_ID and Extended_Tunnel_ID   are unchanged.  The ingress node picks a new LSP_ID to form a new   SENDER_TEMPLATE.  It creates an EXPLICIT_ROUTE object for the new   route.  The new Path message is sent.  The ingress node refreshes   both the old and new path messages.   The egress node responds with a Resv message with an SE flow   descriptor formatted as:      <FLOWSPEC><old_FILTER_SPEC><old_LABEL_OBJECT><new_FILTER_SPEC>      <new_LABEL_OBJECT>   (Note that if the PHOPs are different, then two messages are sent   each with the appropriate FILTER_SPEC and LABEL_OBJECT.)Awduche, et al.             Standards Track                    [Page 42]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   When the ingress node receives the Resv Message(s), it may begin   using the new route.  It SHOULD send a PathTear message for the old   route.4.7. Session Attribute Object   The Session Attribute Class is 207.  Two C_Types are defined,   LSP_TUNNEL, C-Type = 7 and LSP_TUNNEL_RA, C-Type = 1.  The   LSP_TUNNEL_RA C-Type includes all the same fields as the LSP_TUNNEL   C-Type.  Additionally it carries resource affinity information.  The   formats are as follows:4.7.1. Format without resource affinities   SESSION_ATTRIBUTE class = 207, LSP_TUNNEL C-Type = 7    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |   Setup Prio  | Holding Prio  |     Flags     |  Name Length  |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                                                               |   //          Session Name      (NULL padded display string)      //   |                                                               |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      Setup Priority         The priority of the session with respect to taking resources,         in the range of 0 to 7.  The value 0 is the highest priority.         The Setup Priority is used in deciding whether this session can         preempt another session.      Holding Priority         The priority of the session with respect to holding resources,         in the range of 0 to 7.  The value 0 is the highest priority.         Holding Priority is used in deciding whether this session can         be preempted by another session.Awduche, et al.             Standards Track                    [Page 43]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001      Flags         0x01  Local protection desired               This flag permits transit routers to use a local repair               mechanism which may result in violation of the explicit               route object.  When a fault is detected on an adjacent               downstream link or node, a transit router can reroute               traffic for fast service restoration.         0x02  Label recording desired               This flag indicates that label information should be               included when doing a route record.         0x04  SE Style desired               This flag indicates that the tunnel ingress node may               choose to reroute this tunnel without tearing it down.               A tunnel egress node SHOULD use the SE Style when               responding with a Resv message.      Name Length         The length of the display string before padding, in bytes.      Session Name         A null padded string of characters.Awduche, et al.             Standards Track                    [Page 44]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 20014.7.2. Format with resource affinities    SESSION_ATTRIBUTE class = 207, LSP_TUNNEL_RA C-Type = 1    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                         Exclude-any                           |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                         Include-any                           |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                         Include-all                           |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |   Setup Prio  | Holding Prio  |     Flags     |  Name Length  |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                                                               |   //          Session Name      (NULL padded display string)      //   |                                                               |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      Exclude-any         A 32-bit vector representing a set of attribute filters         associated with a tunnel any of which renders a link         unacceptable.      Include-any         A 32-bit vector representing a set of attribute filters         associated with a tunnel any of which renders a link acceptable         (with respect to this test).  A null set (all bits set to zero)         automatically passes.      Include-all         A 32-bit vector representing a set of attribute filters         associated with a tunnel all of which must be present for a         link to be acceptable (with respect to this test).  A null set         (all bits set to zero) automatically passes.      Setup Priority         The priority of the session with respect to taking resources,         in the range of 0 to 7.  The value 0 is the highest priority.         The Setup Priority is used in deciding whether this session can         preempt another session.Awduche, et al.             Standards Track                    [Page 45]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001      Holding Priority         The priority of the session with respect to holding resources,         in the range of 0 to 7.  The value 0 is the highest priority.         Holding Priority is used in deciding whether this session can         be preempted by another session.      Flags         0x01  Local protection desired               This flag permits transit routers to use a local repair               mechanism which may result in violation of the explicit               route object.  When a fault is detected on an adjacent               downstream link or node, a transit router can reroute               traffic for fast service restoration.         0x02  Label recording desired               This flag indicates that label information should be               included when doing a route record.         0x04  SE Style desired               This flag indicates that the tunnel ingress node may               choose to reroute this tunnel without tearing it down.               A tunnel egress node SHOULD use the SE Style when               responding with a Resv message.      Name Length         The length of the display string before padding, in bytes.      Session Name         A null padded string of characters.4.7.3. Procedures applying to both C-Types   The support of setup and holding priorities is OPTIONAL.  A node can   recognize this information but be unable to perform the requested   operation.  The node SHOULD pass the information downstream   unchanged.   As noted above, preemption is implemented by two priorities.  The   Setup Priority is the priority for taking resources.  The Holding   Priority is the priority for holding a resource.  Specifically, theAwduche, et al.             Standards Track                    [Page 46]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   Holding Priority is the priority at which resources assigned to this   session will be reserved.  The Setup Priority SHOULD never be higher   than the Holding Priority for a given session.   The setup and holding priorities are directly analogous to the   preemption and defending priorities as defined in [9].  While the   interaction of these two objects is ultimately a matter of policy,   the following default interaction is RECOMMENDED.   When both objects are present, the preemption priority policy element   is used.  A mapping between the priority spaces is defined as   follows.  A session attribute priority S is mapped to a preemption   priority P by the formula P = 2^(14-2S).  The reverse mapping is   shown in the following table.         Preemption Priority     Session Attribute Priority               0 - 3                         7               4 - 15                        6              16 - 63                        5              64 - 255                       4             256 - 1023                      3            1024 - 4095                      2            4096 - 16383                     1           16384 - 65535                     0   When a new Path message is considered for admission, the bandwidth   requested is compared with the bandwidth available at the priority   specified in the Setup Priority.   If the requested bandwidth is not available a PathErr message is   returned with an Error Code of 01, Admission Control Failure, and an   Error Value of 0x0002.  The first 0 in the Error Value indicates a   globally defined subcode and is not informational.  The 002 indicates   "requested bandwidth unavailable".   If the requested bandwidth is less than the unused bandwidth then   processing is complete.  If the requested bandwidth is available, but   is in use by lower priority sessions, then lower priority sessions   (beginning with the lowest priority) MAY be preempted to free the   necessary bandwidth.   When preemption is supported, each preempted reservation triggers a   TC_Preempt() upcall to local clients, passing a subcode that   indicates the reason.  A ResvErr and/or PathErr with the code "Policy   Control failure" SHOULD be sent toward the downstream receivers and   upstream senders.Awduche, et al.             Standards Track                    [Page 47]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   The support of local-protection is OPTIONAL.  A node may recognize   the local-protection Flag but may be unable to perform the requested   operation.  In this case, the node SHOULD pass the information   downstream unchanged.   The recording of the Label subobject in the ROUTE_RECORD object is   controlled by the label-recording-desired flag in the   SESSION_ATTRIBUTE object.  Since the Label subobject is not needed   for all applications, it is not automatically recorded.  The flag   allows applications to request this only when needed.   The contents of the Session Name field are a string, typically of   display-able characters.  The Length MUST always be a multiple of 4   and MUST be at least 8.  For an object length that is not a multiple   of 4, the object is padded with trailing NULL characters.  The Name   Length field contains the actual string length.4.7.4. Resource Affinity Procedures   Resource classes and resource class affinities are described in [3].   In this document we use the briefer term resource affinities for the   latter term.  Resource classes can be associated with links and   advertised in routing protocols.  Resource class affinities are used   by RSVP in two ways.  In order to be validated a link MUST pass the   three tests below.  If the test fails a PathErr with the code "policy   control failure" SHOULD be sent.   When a new reservation is considered for admission over a strict node   in an ERO, a node MAY validate the resource affinities with the   resource classes of that link.  When a node is choosing links in   order to extend a loose node of an ERO, the node MUST validate the   resource classes of those links against the resource affinities.  If   no acceptable links can be found to extend the ERO, the node SHOULD   send a PathErr message with an error code of "Routing Problem" and an   error value of "no route available toward destination".   In order to be validated a link MUST pass the following three tests.   To precisely describe the tests use the definitions in the object   description above.  We also define      Link-attr      A 32-bit vector representing attributes associated                     with a link.Awduche, et al.             Standards Track                    [Page 48]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   The three tests are      1. Exclude-any         This test excludes a link from consideration if the link         carries any of the attributes in the set.         (link-attr & exclude-any) == 0      2. Include-any         This test accepts a link if the link carries any of the         attributes in the set.         (include-any == 0) | ((link-attr & include-any) != 0)      3. Include-all         This test accepts a link only if the link carries all of the         attributes in the set.         (include-all == 0) | (((link-attr & include-all) ^ include-         all) == 0)   For a link to be acceptable, all three tests MUST pass.  If the test   fails, the node SHOULD send a PathErr message with an error code of   "Routing Problem" and an error value of "no route available toward   destination".   If a Path message contains multiple SESSION_ATTRIBUTE objects, only   the first SESSION_ATTRIBUTE object is meaningful.  Subsequent   SESSION_ATTRIBUTE objects can be ignored and need not be forwarded.   All RSVP routers, whether they support the SESSION_ATTRIBUTE object   or not, SHALL forward the object unmodified.  The presence of non-   RSVP routers anywhere between senders and receivers has no impact on   this object.5. Hello Extension   The RSVP Hello extension enables RSVP nodes to detect when a   neighboring node is not reachable.  The mechanism provides node to   node failure detection.  When such a failure is detected it is   handled much the same as a link layer communication failure.  This   mechanism is intended to be used when notification of link layer   failures is not available and unnumbered links are not used, or when   the failure detection mechanisms provided by the link layer are not   sufficient for timely node failure detection.Awduche, et al.             Standards Track                    [Page 49]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   It should be noted that node failure detection is not the same as a   link failure detection mechanism, particularly in the case of   multiple parallel unnumbered links.   The Hello extension is specifically designed so that one side can use   the mechanism while the other side does not.  Neighbor failure   detection may be initiated at any time.  This includes when neighbors   first learn about each other, or just when neighbors are sharing Resv   or Path state.   The Hello extension is composed of a Hello message, a HELLO REQUEST   object and a HELLO ACK object.  Hello processing between two   neighbors supports independent selection of, typically configured,   failure detection intervals.  Each neighbor can autonomously issue   HELLO REQUEST objects.  Each request is answered by an   acknowledgment.  Hello Messages also contain enough information so   that one neighbor can suppress issuing hello requests and still   perform neighbor failure detection.  A Hello message may be included   as a sub-message within a bundle message.   Neighbor failure detection is accomplished by collecting and storing   a neighbor's "instance" value.  If a change in value is seen or if   the neighbor is not properly reporting the locally advertised value,   then the neighbor is presumed to have reset.  When a neighbor's value   is seen to change or when communication is lost with a neighbor, then   the instance value advertised to that neighbor is also changed.  The   HELLO objects provide a mechanism for polling for and providing an   instance value.  A poll request also includes the sender's instance   value.  This allows the receiver of a poll to optionally treat the   poll as an implicit poll response.  This optional handling is an   optimization that can reduce the total number of polls and responses   processed by a pair of neighbors.  In all cases, when both sides   support the optimization the result will be only one set of polls and   responses per failure detection interval.  Depending on selected   intervals, the same benefit can occur even when only one neighbor   supports the optimization.5.1. Hello Message Format   Hello Messages are always sent between two RSVP neighbors.  The IP   source address is the IP address of the sending node.  The IP   destination address is the IP address of the neighbor node.   The HELLO mechanism is intended for use between immediate neighbors.   When HELLO messages are being the exchanged between immediate   neighbors, the IP TTL field of all outgoing HELLO messages SHOULD be   set to 1.Awduche, et al.             Standards Track                    [Page 50]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   The Hello message has a Msg Type of 20.  The Hello message format is   as follows:      <Hello Message> ::= <Common Header> [ <INTEGRITY> ]                              <HELLO>5.2. HELLO Object formats   The HELLO Class is 22.  There are two C_Types defined.5.2.1. HELLO REQUEST object   Class = HELLO Class, C_Type = 1    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                         Src_Instance                          |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                         Dst_Instance                          |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+5.2.2. HELLO ACK object   Class = HELLO Class, C_Type = 2    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                         Src_Instance                          |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                         Dst_Instance                          |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      Src_Instance: 32 bits      a 32 bit value that represents the sender's instance.  The      advertiser maintains a per neighbor representation/value.  This      value MUST change when the sender is reset, when the node reboots,      or when communication is lost to the neighboring node and      otherwise remains the same.  This field MUST NOT be set to zero      (0).      Dst_Instance: 32 bits      The most recently received Src_Instance value received from the      neighbor.  This field MUST be set to zero (0) when no value has      ever been seen from the neighbor.Awduche, et al.             Standards Track                    [Page 51]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 20015.3. Hello Message Usage   The Hello Message is completely OPTIONAL.  All messages may be   ignored by nodes which do not wish to participate in Hello message   processing.  The balance of this section is written assuming that the   receiver as well as the sender is participating.  In particular, the   use of MUST and SHOULD with respect to the receiver applies only to a   node that supports Hello message processing.   A node periodically generates a Hello message containing a HELLO   REQUEST object for each neighbor who's status is being tracked.  The   periodicity is governed by the hello_interval.  This value MAY be   configured on a per neighbor basis.  The default value is 5 ms.   When generating a message containing a HELLO REQUEST object, the   sender fills in the Src_Instance field with a value representing it's   per neighbor instance.  This value MUST NOT change while the agent is   exchanging Hellos with the corresponding neighbor.  The sender also   fills in the Dst_Instance field with the Src_Instance value most   recently received from the neighbor.  For reference, call this   variable Neighbor_Src_Instance.  If no value has ever been received   from the neighbor or this node considers communication to the   neighbor to have been lost, the Neighbor_Src_Instance is set to zero   (0).  The generation of a message SHOULD be suppressed when a HELLO   REQUEST object was received from the destination node within the   prior hello_interval interval.   On receipt of a message containing a HELLO REQUEST object, the   receiver MUST generate a Hello message containing a HELLO ACK object.   The receiver SHOULD also verify that the neighbor has not reset.   This is done by comparing the sender's Src_Instance field value with   the previously received value.  If the Neighbor_Src_Instance value is   zero, and the Src_Instance field is non-zero, the   Neighbor_Src_Instance is updated with the new value.  If the value   differs or the Src_Instance field is zero, then the node MUST treat   the neighbor as if communication has been lost.   The receiver of a HELLO REQUEST object SHOULD also verify that the   neighbor is reflecting back the receiver's Instance value.  This is   done by comparing the received Dst_Instance field with the   Src_Instance field value most recently transmitted to that neighbor.   If the neighbor continues to advertise a wrong non-zero value after a   configured number of intervals, then the node MUST treat the neighbor   as if communication has been lost.   On receipt of a message containing a HELLO ACK object, the receiver   MUST verify that the neighbor has not reset.  This is done by   comparing the sender's Src_Instance field value with the previouslyAwduche, et al.             Standards Track                    [Page 52]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   received value.  If the Neighbor_Src_Instance value is zero, and the   Src_Instance field is non-zero, the Neighbor_Src_Instance is updated   with the new value.  If the value differs or the Src_Instance field   is zero, then the node MUST treat the neighbor as if communication   has been lost.   The receiver of a HELLO ACK object MUST also verify that the neighbor   is reflecting back the receiver's Instance value.  If the neighbor   advertises a wrong value in the Dst_Instance field, then a node MUST   treat the neighbor as if communication has been lost.   If no Instance values are received, via either REQUEST or ACK   objects, from a neighbor within a configured number of   hello_intervals, then a node MUST presume that it cannot communicate   with the neighbor.  The default for this number is 3.5.   When communication is lost or presumed to be lost as described above,   a node MAY re-initiate HELLOs.  If a node does re-initiate it MUST   use a Src_Instance value different than the one advertised in the   previous HELLO message.  This new value MUST continue to be   advertised to the corresponding neighbor until a reset or reboot   occurs, or until another communication failure is detected.  If a new   instance value has not been received from the neighbor, then the node   MUST advertise zero in the Dst_instance value field.5.4. Multi-Link Considerations   As previously noted, the Hello extension is targeted at detecting   node failures not per link failures.  When there is only one link   between neighboring nodes or when all links between a pair of nodes   fail, the distinction between node and link failures is not really   meaningful and handling of such failures has already been covered.   When there are multiple links shared between neighbors, there are   special considerations.  When the links between neighbors are   numbered, then Hellos MUST be run on each link and the previously   described mechanisms apply.   When the links are unnumbered, link failure detection MUST be   provided by some means other than Hellos.  Each node SHOULD use a   single Hello exchange with the neighbor.  The case where all links   have failed, is the same as the no received value case mentioned in   the previous section.Awduche, et al.             Standards Track                    [Page 53]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 20015.5. Compatibility   The Hello extension does not affect the processing of any other RSVP   message.  The only effect is to allow a link (node) down event to be   declared sooner than it would have been.  RSVP response to that   condition is unchanged.   The Hello extension is fully backwards compatible.  The Hello class   is assigned a class value of the form 0bbbbbbb.  Depending on the   implementation, implementations that do not support the extension   will either silently discard Hello messages or will respond with an   "Unknown Object Class" error.  In either case the sender will fail to   see an acknowledgment for the issued Hello.6. Security Considerations   In principle these extensions to RSVP pose no security exposures over   and aboveRFC 2205[1].  However, there is a slight change in the   trust model.  Traffic sent on a normal RSVP session can be filtered   according to source and destination addresses as well as port   numbers.  In this specification, filtering occurs only on the basis   of an incoming label.  For this reason an administration may wish to   limit the domain over which LSP tunnels can be established.  This can   be accomplished by setting filters on various ports to deny action on   a RSVP path message with a SESSION object of type LSP_TUNNEL_IPv4 (7)   or LSP_TUNNEL_IPv6 (8).7. IANA Considerations   IANA assigns values to RSVP protocol parameters.  Within the current   document an EXPLICIT_ROUTE object and a ROUTE_RECORD object are   defined.  Each of these objects contain subobjects.  This section   defines the rules for the assignment of subobject numbers.  This   section uses the terminology ofBCP 26 "Guidelines for Writing an   IANA Considerations Section in RFCs" [15].   EXPLICIT_ROUTE Subobject Type      EXPLICIT_ROUTE Subobject Type is a 7-bit number that identifies      the function of the subobject.  There are no range restrictions.      All possible values are available for assignment.      Following the policies outlined in [15], subobject types in the      range 0 - 63 (0x00 - 0x3F) are allocated through an IETF Consensus      action, codes in the range 64 - 95 (0x40 - 0x5F) are allocated as      First Come First Served, and codes in the range 96 - 127 (0x60 -      0x7F) are reserved for Private Use.Awduche, et al.             Standards Track                    [Page 54]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   ROUTE_RECORD Subobject Type      ROUTE_RECORD Subobject Type is an 8-bit number that identifies the      function of the subobject.  There are no range restrictions.  All      possible values are available for assignment.      Following the policies outlined in [15], subobject types in the      range 0 - 127 (0x00 - 0x7F) are allocated through an IETF      Consensus action, codes in the range 128 - 191 (0x80 - 0xBF) are      allocated as First Come First Served, and codes in the range 192 -      255 (0xC0 - 0xFF) are reserved for Private Use.      The following assignments are made in this document.7.1. Message Types   Message Message   Number  Name     20    Hello7.2. Class Numbers and C-Types   Class   Class   Number  Name     1     SESSION           Class Types or C-Types:                  7       LSP Tunnel IPv4                  8       LSP Tunnel IPv6     10    FILTER_SPEC           Class Types or C-Types:                  7       LSP Tunnel IPv4                  8       LSP Tunnel IPv6     11    SENDER_TEMPLATE           Class Types or C-Types:                  7       LSP Tunnel IPv4                  8       LSP Tunnel IPv6Awduche, et al.             Standards Track                    [Page 55]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001     16    RSVP_LABEL           Class Types or C-Types:                  1       Type 1 Label     19    LABEL_REQUEST           Class Types or C-Types:                  1       Without Label Range                  2       With ATM Label Range                  3       With Frame Relay Label Range     20    EXPLICIT_ROUTE           Class Types or C-Types:                  1       Type 1 Explicit Route     21    ROUTE_RECORD           Class Types or C-Types:                  1       Type 1 Route Record     22    HELLO           Class Types or C-Types:                  1       Request                  2       Acknowledgment    207    SESSION_ATTRIBUTE           Class Types or C-Types:                  1       LSP_TUNNEL_RA                  7       LSP TunnelAwduche, et al.             Standards Track                    [Page 56]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 20017.3. Error Codes and Globally-Defined Error Value Sub-Codes   The following list extends the basic list of Error Codes and Values   that are defined in [RFC2205].   Error Code    Meaning     24          Routing Problem                 This Error Code has the following globally-defined                 Error Value sub-codes:                  1       Bad EXPLICIT_ROUTE object                  2       Bad strict node                  3       Bad loose node                  4       Bad initial subobject                  5       No route available toward                           destination                  6       Unacceptable label value                  7       RRO indicated routing loops                  8       MPLS being negotiated, but a                          non-RSVP-capable router stands                            in the path                  9       MPLS label allocation failure                 10       Unsupported L3PID     25          Notify Error                This Error Code has the following globally-defined                Error Value sub-codes:                  1       RRO too large for MTU                  2       RRO Notification                  3       Tunnel locally repaired7.4. Subobject Definitions   Subobjects of the EXPLICIT_ROUTE object with C-Type 1:          1       IPv4 prefix          2       IPv6 prefix         32       Autonomous system numberAwduche, et al.             Standards Track                    [Page 57]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   Subobjects of the RECORD_ROUTE object with C-Type 1:          1       IPv4 address          2       IPv6 address          3       Label8. Intellectual Property Considerations   The IETF has been notified of intellectual property rights claimed in   regard to some or all of the specification contained in this   document.  For more information consult the online list of claimed   rights.9. Acknowledgments   This document contains ideas as well as text that have appeared in   previous Internet Drafts.  The authors of the current document wish   to thank the authors of those drafts.  They are Steven Blake, Bruce   Davie, Roch Guerin, Sanjay Kamat, Yakov Rekhter, Eric Rosen, and Arun   Viswanathan.  We also wish to thank Bora Akyol, Yoram Bernet and Alex   Mondrus for their comments on this document.10. References   [1]  Braden, R., Zhang, L., Berson, S., Herzog, S. and S. Jamin,        "Resource ReSerVation Protocol (RSVP) -- Version 1, Functional        Specification",RFC 2205, September 1997.   [2]  Rosen, E., Viswanathan, A. and R. Callon, "Multiprotocol Label        Switching Architecture",RFC 3031, January 2001.   [3]  Awduche, D., Malcolm, J., Agogbua, J., O'Dell and J. McManus,        "Requirements for Traffic Engineering over MPLS",RFC 2702,        September 1999.   [4]  Wroclawski, J., "Specification of the Controlled-Load Network        Element Service",RFC 2211, September 1997.   [5]  Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci, D.,        Li, T. and A. Conta, "MPLS Label Stack Encoding",RFC 3032,        January 2001.   [6]  Bradner, S., "Key words for use in RFCs to Indicate Requirement        Levels",BCP 14,RFC 2119, March 1997.   [7]  Almquist, P., "Type of Service in the Internet Protocol Suite",RFC 1349, July 1992.Awduche, et al.             Standards Track                    [Page 58]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 2001   [8]  Nichols, K., Blake, S., Baker, F. and D. Black, "Definition of        the Differentiated Services Field (DS Field) in the IPv4 and        IPv6 Headers",RFC 2474, December 1998.   [9]  Herzog, S., "Signaled Preemption Priority Policy Element",RFC2751, January 2000.   [10] Awduche, D., Hannan, A. and X. Xiao, "Applicability Statement        for Extensions to RSVP for LSP-Tunnels",RFC 3210, December        2001.   [11] Wroclawski, J., "The Use of RSVP with IETF Integrated Services",RFC 2210, September 1997.   [12] Postel, J., "Internet Control Message Protocol", STD 5,RFC 792,        September 1981.   [13] Mogul, J. and S. Deering, "Path MTU Discovery",RFC 1191,        November 1990.   [14] Conta, A. and S. Deering, "Internet Control Message Protocol        (ICMPv6) for the Internet Protocol Version 6 (IPv6)",RFC 2463,        December 1998.   [15] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA        Considerations Section in RFCs",BCP 26,RFC 2434, October 1998.   [16] Bernet, Y., Smiht, A. and B. Davie, "Specification of the Null        Service Type",RFC 2997, November 2000.Awduche, et al.             Standards Track                    [Page 59]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 200111. Authors' Addresses   Daniel O. Awduche   Movaz Networks, Inc.   7926 Jones Branch Drive, Suite 615   McLean, VA 22102   Voice: +1 703-298-5291   EMail: awduche@movaz.com   Lou Berger   Movaz Networks, Inc.   7926 Jones Branch Drive, Suite 615   McLean, VA 22102   Voice: +1 703 847 1801   EMail: lberger@movaz.com   Der-Hwa Gan   Juniper Networks, Inc.   385 Ravendale Drive   Mountain View, CA 94043   EMail: dhg@juniper.net   Tony Li   Procket Networks   3910 Freedom Circle, Ste. 102A   Santa Clara CA 95054   EMail: tli@procket.com   Vijay Srinivasan   Cosine Communications, Inc.   1200 Bridge Parkway   Redwood City, CA 94065   Voice: +1 650 628 4892   EMail: vsriniva@cosinecom.com   George Swallow   Cisco Systems, Inc.   250 Apollo Drive   Chelmsford, MA 01824   Voice: +1 978 244 8143   EMail: swallow@cisco.comAwduche, et al.             Standards Track                    [Page 60]

RFC 3209           Extensions to RSVP for LSP Tunnels      December 200112.  Full Copyright Statement   Copyright (C) The Internet Society (2001).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assigns.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Awduche, et al.             Standards Track                    [Page 61]