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Internet Engineering Task Force (IETF)                  JP. Vasseur, Ed.Request for Comments: 5711                                    G. SwallowUpdates:3209                                        Cisco Systems, Inc.Category: Standards Track                                       I. MineiISSN: 2070-1721                                         Juniper Networks                                                            January 2010Node Behavior upon Originating and Receiving Resource ReservationProtocol (RSVP) Path Error MessagesAbstract   The aim of this document is to describe a common practice with regard   to the behavior of nodes that send and receive a Resource Reservation   Protocol (RSVP) Traffic Engineering (TE) Path Error messages for a   preempted Multiprotocol Label Switching (MPLS) or Generalized MPLS   (GMPLS) Traffic Engineering Label Switched Path (TE LSP).  (For   reference to the notion of TE LSP preemption, seeRFC 3209.)  This   document does not define any new protocol extensions.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc5711.Vasseur, et al.              Standards Track                    [Page 1]

RFC 5711             Node Behavior with RSVP PathErr        January 2010Copyright Notice   Copyright (c) 2010 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Table of Contents1. Introduction ....................................................31.1. Requirements Language ......................................32. Protocol Behavior ...............................................32.1. Behavior at Detecting Nodes ................................42.2. Behavior at Receiving Nodes ................................52.3. Data-Plane Behavior ........................................53. RSVP PathErr Messages for a Preempted TE LSP ....................54. Security Considerations .........................................55. Acknowledgements ................................................66. References ......................................................66.1. Normative References .......................................66.2. Informative References .....................................6Vasseur, et al.              Standards Track                    [Page 2]

RFC 5711             Node Behavior with RSVP PathErr        January 20101.  Introduction   The aim of this document is to describe a common practice with regard   to the behavior of a node sending a Resource Reservation Protocol   (RSVP) Traffic Engineering (TE) Path Error message and to the   behavior of a node receiving an RSVP Path Error message for a   preempted Multiprotocol Label Switching (MPLS) and Generalized MPLS   (GMPLS) Traffic Engineering Label Switched Path (TE LSP).  (For   reference to the notion of TE LSP preemption, see [RFC3209]).   [RFC2205] defines two RSVP error message types: PathErr and ResvErr   that are generated when an error occurs.  Path Error messages   (PathErr) are used to report errors and travel upstream toward the   head-end of the flow.  Resv Error messages (ResvErr) travel   downstream toward the tail-end of the flow.   This document describes only PathErr message processing for the   specific case of a preempted TE LSP, where the term preemption is   defined in [RFC3209].1.1.  Requirements Language   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 inRFC 2119 [RFC2119].2.  Protocol Behavior   PathErr messages are routed hop-by-hop using the path state   established when a Path message is routed through the network from   the head-end to its tail-end.   As stated in [RFC2205], PathErr messages do not modify the state of   any node through which they pass; they are only reported to the head-   end of the TE LSP (Traffic Engineering Label Switched Path).   The format of the PathErr message is defined inSection 3. of   [RFC2205].   The ERROR_SPEC object includes the IP address of the node that   detected the error (Error Node Address), and specifies the error   through two fields.  The Error Code field encodes the category of the   error, for example, Policy Control Failure or Unknown object class.   The Error Value field qualifies the error code to indicate the error   with more precision.  [RFC3209] extends RSVP as defined in [RFC2205]   for the management of MPLS-TE LSPs.  [RFC3209] specifies several   additional conditions that trigger the sending of a RSVP PathErr   message for which new error codes and error values have been definedVasseur, et al.              Standards Track                    [Page 3]

RFC 5711             Node Behavior with RSVP PathErr        January 2010   that extend the list defined in [RFC2205].  The exact circumstances   under which a TE LSP is preempted and such PathErr messages are sent   are defined in [RFC3209] and will not be repeated here.   Values for the Error Code and Error Value fields defined in   [RFC2205], [RFC3209], and other documents are maintained in a   registry by the IANA.   The error conditions fall into two categories:   o  Fatal errors represent disruptive conditions for a TE LSP.   o  Non-fatal errors are non-disruptive conditions that have occurred      for this TE LSP.   PathErr messages may be used in two circumstances:   o  during TE LSP establishment, and   o  after a TE LSP has been successfully established.   Nodal behavior is dependent on which combination of the four cases   listed above applies.  The following sections describe the expected   behavior at nodes that perform a preemption action for a TE LSP (and   therefore report using error PathErr messages), and at nodes that   receive PathErr messages.  This text is a clarification and   restatement of the procedures set out in [RFC3209] and does not   define any new behavior.2.1.  Behavior at Detecting Nodes   In the case of fatal errors ("Hard Preemption"; seeSection 4.7.3 of   [RFC3209] ), the detecting node MUST send a PathErr message reporting   the error condition, and MUST clear the corresponding Path and Resv   (control plane) states.  A direct implication is that the data-plane   resources of such a TE LSP are also released, thus resulting in   traffic disruption.  It should be noted, however, that in fatal error   cases, the LSP has usually already failed in the data plane, and   traffic has already been disrupted.  When the error arises during LSP   establishment, the implications are different to when it arises on an   active LSP since no traffic flows until the LSP has been fully   established.  In the case of non-fatal errors, the detecting node   should send a PathErr message, and must not clear control plane or   data plane state.Vasseur, et al.              Standards Track                    [Page 4]

RFC 5711             Node Behavior with RSVP PathErr        January 20102.2.  Behavior at Receiving Nodes   Nodes that receive PathErr messages are all of the nodes along the   path of the TE LSP upstream of the node that detected the error.   This includes the head-end node.  In accordance withSection 3.7.1 of   [RFC2205], a node receiving a PathErr message takes no action upon   it, and consequently the node must not clear Path or Resv control-   plane or data-plane state.  This is true regardless of whether the   error condition reported by the PathErr is fatal or non-fatal.  RSVP   states should only be affected upon receiving a PathTear or ResvTear   message, or in the event of a Path or Resv state timeout.  Further   discussion of the processing of these events is outside the scope of   this document.   Note that [RFC3473] defines a Path_State_Removed flag in the   ERROR_SPEC object carried on a PathErr message.  This field may be   set to change the behavior of upstream nodes that receive the PathErr   message.  When set, the flag indicates that the message sender has   removed Path state (and any associated Resv and data-plane state) for   the TE LSP.  The message receiver should do likewise before   forwarding the message, but may retain state and clear the flag   before forwarding the message.2.3.  Data-Plane Behavior   Any node clearing either or both the Path or the Resv state of a TE   LSP MUST also free up the data-plane resources allocated to the   corresponding TE LSP.3.  RSVP PathErr Messages for a Preempted TE LSP   Two Error Codes have been defined to report a preempted TE LSP:   o  As defined in [RFC2750]: Error Code=2: "Policy Control Failure",      Error Value=5: "Flow was preempted"   o  As defined in [RFC2205], Error Code=12: "Service preempted"   They are both fatal errors.4.  Security Considerations   This document does not define any new procedures, but clarifies those   defined in other documents where security considerations are already   specified in [RFC3209] and [RFC3473].  This document does not raise   specific security issues beyond those of existing MPLS-TE.  ByVasseur, et al.              Standards Track                    [Page 5]

RFC 5711             Node Behavior with RSVP PathErr        January 2010   clarifying the procedures, this document reduces the security risk   introduced by non-conformant implementations.  See [SEC_FMWK] for   further discussion of MPLS security issues.5.  Acknowledgements   The authors would like to thank Carol Iturralde, Ashok Narayanan, Rom   Reuther, and Reshad Rahman.6.  References6.1.  Normative References   [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate               Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC2205]   Braden, B., Zhang, L., Berson, S., Herzog, S., and S.               Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1               Functional Specification",RFC 2205, September 1997.   [RFC2750]   Herzog, S., "RSVP Extensions for Policy Control",RFC 2750, January 2000.   [RFC3209]   Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,               and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP               Tunnels",RFC 3209, December 2001.   [RFC3473]   Berger, L., "Generalized Multi-Protocol Label Switching               (GMPLS) Signaling Resource ReserVation Protocol-Traffic               Engineering (RSVP-TE) Extensions",RFC 3473,               January 2003.6.2.  Informative References   [SEC_FMWK]  Fang, L., Ed., "Security Framework for MPLS and GMPLS               Networks", Work in Progress, October 2009.Vasseur, et al.              Standards Track                    [Page 6]

RFC 5711             Node Behavior with RSVP PathErr        January 2010Authors' Addresses   JP Vasseur (editor)   Cisco Systems, Inc.   1414 Massachusetts Avenue   Boxborough, MA  01719   USA   EMail: jpv@cisco.com   George Swallow   Cisco Systems, Inc.   1414 Massachusetts Avenue   Boxborough, MA  01719   USA   EMail: swallow@cisco.com   Ina Minei   Juniper Networks   1194 North Mathilda Ave.   Sunnyvale, CA  94089   USA   EMail: ina@juniper.netVasseur, et al.              Standards Track                    [Page 7]