Open Shortest Path First IGP                              P. Psenak, Ed.Internet-Draft                                           S. Previdi, Ed.Intended status: Standards Track                             C. FilsfilsExpires: October 22, 2018                            Cisco Systems, Inc.                                                              H. Gredler                                                            RtBrick Inc.                                                               R. Shakir                                                            Google, Inc.                                                           W. Henderickx                                                                   Nokia                                                             J. Tantsura                                                              Individual                                                          April 20, 2018                  OSPF Extensions for Segment Routing             draft-ietf-ospf-segment-routing-extensions-25Abstract   Segment Routing (SR) allows a flexible definition of end-to-end paths   within IGP topologies by encoding paths as sequences of topological   sub-paths, called "segments".  These segments are advertised by the   link-state routing protocols (IS-IS and OSPF).   This draft describes the OSPFv2 extensions required for Segment   Routing.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 in [RFC2119].Status of This Memo   This Internet-Draft is submitted in full conformance with the   provisions of BCP 78 and BCP 79.   Internet-Drafts are working documents of the Internet Engineering   Task Force (IETF).  Note that other groups may also distribute   working documents as Internet-Drafts.  The list of current Internet-   Drafts is at https://datatracker.ietf.org/drafts/current/.   Internet-Drafts are draft documents valid for a maximum of six months   and may be updated, replaced, or obsoleted by other documents at any   time.  It is inappropriate to use Internet-Drafts as reference   material or to cite them other than as "work in progress."Psenak, et al.          Expires October 22, 2018                [Page 1]Internet-Draft     OSPF Extensions for Segment Routing        April 2018   This Internet-Draft will expire on October 22, 2018.Copyright Notice   Copyright (c) 2018 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject to BCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (https://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 Contents   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3   2.  Segment Routing Identifiers . . . . . . . . . . . . . . . . .   3     2.1.  SID/Label Sub-TLV . . . . . . . . . . . . . . . . . . . .   4   3.  Segment Routing Capabilities  . . . . . . . . . . . . . . . .   4     3.1.  SR-Algorithm TLV  . . . . . . . . . . . . . . . . . . . .   4     3.2.  SID/Label Range TLV . . . . . . . . . . . . . . . . . . .   6     3.3.  SR Local Block TLV  . . . . . . . . . . . . . . . . . . .   8     3.4.  SRMS Preference TLV . . . . . . . . . . . . . . . . . . .  10   4.  OSPF Extended Prefix Range TLV  . . . . . . . . . . . . . . .  11   5.  Prefix SID Sub-TLV  . . . . . . . . . . . . . . . . . . . . .  13   6.  Adjacency Segment Identifier (Adj-SID)  . . . . . . . . . . .  16     6.1.  Adj-SID Sub-TLV . . . . . . . . . . . . . . . . . . . . .  16     6.2.  LAN Adj-SID Sub-TLV . . . . . . . . . . . . . . . . . . .  18   7.  Elements of Procedure . . . . . . . . . . . . . . . . . . . .  19     7.1.  Intra-area Segment routing in OSPFv2  . . . . . . . . . .  20     7.2.  Inter-area Segment routing in OSPFv2  . . . . . . . . . .  20     7.3.  Segment Routing for External Prefixes . . . . . . . . . .  21     7.4.  Advertisement of Adj-SID  . . . . . . . . . . . . . . . .  22       7.4.1.  Advertisement of Adj-SID on Point-to-Point Links  . .  22       7.4.2.  Adjacency SID on Broadcast or NBMA Interfaces . . . .  22   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  22     8.1.  OSPF Router Information (RI) TLVs Registry  . . . . . . .  23     8.2.  OSPFv2 Extended Prefix Opaque LSA TLVs Registry . . . . .  23     8.3.  OSPFv2 Extended Prefix TLV Sub-TLVs Registry  . . . . . .  23     8.4.  OSPFv2 Extended Link TLV Sub-TLVs Registry  . . . . . . .  23     8.5.  IGP Algorithm Type Registry . . . . . . . . . . . . . . .  23   9.  Implementation Status . . . . . . . . . . . . . . . . . . . .  24   10. Security Considerations . . . . . . . . . . . . . . . . . . .  25   11. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  26Psenak, et al.          Expires October 22, 2018                [Page 2]Internet-Draft     OSPF Extensions for Segment Routing        April 2018   12. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  26   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  26     13.1.  Normative References . . . . . . . . . . . . . . . . . .  26     13.2.  Informative References . . . . . . . . . . . . . . . . .  27   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  281.  Introduction   Segment Routing (SR) allows a flexible definition of end-to-end paths   within IGP topologies by encoding paths as sequences of topological   sub-paths, called "segments".  These segments are advertised by the   link-state routing protocols (IS-IS and OSPF).  Prefix segments   represent an ECMP-aware shortest-path to a prefix (or a node), as per   the state of the IGP topology.  Adjacency segments represent a hop   over a specific adjacency between two nodes in the IGP.  A prefix   segment is typically a multi-hop path while an adjacency segment, in   most cases, is a one-hop path.  SR's control-plane can be applied to   both IPv6 and MPLS data-planes, and does not require any additional   signalling (other than IGP extensions).  The IPv6 data plane is out   of the scope of this specification - it is not applicable to OSPFv2   which only supports the IPv4 address-family.  When used in MPLS   networks, SR paths do not require any LDP or RSVP-TE signalling.   However, SR can interoperate in the presence of LSPs established with   RSVP or LDP.   There are additional segment types, e.g., Binding SID defined in   [I-D.ietf-spring-segment-routing].   This draft describes the OSPF extensions required for Segment   Routing.   Segment Routing architecture is described in   [I-D.ietf-spring-segment-routing].   Segment Routing use cases are described in [RFC7855].2.  Segment Routing Identifiers   Segment Routing defines various types of Segment Identifiers (SIDs):   Prefix-SID, Adjacency-SID, LAN Adjacency SID, and Binding SID.   Extended Prefix/Link Opaque LSAs defined in [RFC7684] are used for   advertisements of the various SID types.Psenak, et al.          Expires October 22, 2018                [Page 3]Internet-Draft     OSPF Extensions for Segment Routing        April 20182.1.  SID/Label Sub-TLV   The SID/Label Sub-TLV appears in multiple TLVs or Sub-TLVs defined   later in this document.  It is used to advertise the SID or label   associated with a prefix or adjacency.  The SID/Label Sub-TLV has   following format:    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            |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                         SID/Label (variable)                  |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   where:      Type: 1      Length: Variable, 3 or 4 octet      SID/Label: If length is set to 3, then the 20 rightmost bits      represent a label.  If length is set to 4, then the value      represents a 32-bit SID.      The receiving router MUST ignore the SID/Label Sub-TLV if the      length is other then 3 or 4.3.  Segment Routing Capabilities   Segment Routing requires some additional router capabilities to be   advertised to other routers in the area.   These SR capabilities are advertised in the Router Information Opaque   LSA (defined in [RFC7770]).3.1.  SR-Algorithm TLV   The SR-Algorithm TLV is a top-level TLV of the Router Information   Opaque LSA (defined in [RFC7770]).   The SR-Algorithm TLV is optional.  It SHOULD only be advertised once   in the Router Information Opaque LSA.  If the SR-Algorithm TLV is not   advertised by the node, such node is considered as not being segment   routing capable.   An SR Router can use various algorithms when calculating reachability   to OSPF routers or prefixes in an OSPF area.  Examples of thesePsenak, et al.          Expires October 22, 2018                [Page 4]Internet-Draft     OSPF Extensions for Segment Routing        April 2018   algorithms are metric based Shortest Path First (SPF), various   flavors of Constrained SPF, etc.  The SR-Algorithm TLV allows a   router to advertise the algorithms currently used by the router to   other routers in an OSPF area.  The SR-Algorithm TLV has following   format:    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            |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |   Algorithm 1 | Algorithm...  |   Algorithm n |               |   +-                                                             -+   |                                                               |   +                                                               +   where:      Type: 8      Variable, in octets, dependent on number of algorithms advertised.      Algorithm: Single octet identifying the algorithm.  The following      values are defined by this document:         0: Shortest Path First (SPF) algorithm based on link metric.         This is the standard shortest path algorithm as computed by the         OSPF protocol.  Consistent with the deployed practice for link-         state protocols, Algorithm 0 permits any node to overwrite the         SPF path with a different path based on its local policy.  If         the SR-Algorithm TLV is advertised, Algorithm 0 MUST be         included.         1: Strict Shortest Path First (SPF) algorithm based on link         metric.  The algorithm is identical to Algorithm 0 but         Algorithm 1 requires that all nodes along the path will honor         the SPF routing decision.  Local policy at the node claiming         support for Algorithm 1 MUST NOT alter the SPF paths computed         by Algorithm 1.   When multiple SR-Algorithm TLVs are received from a given router, the   receiver MUST use the first occurrence of the TLV in the Router   Information LSA.  If the SR-Algorithm TLV appears in multiple Router   Information LSAs that have different flooding scopes, the SR-   Algorithm TLV in the Router Information LSA with the area-scoped   flooding scope MUST be used.  If the SR-Algorithm TLV appears in   multiple Router Information LSAs that have the same flooding scope,   the SR-Algorithm TLV in the Router Information (RI) LSA with thePsenak, et al.          Expires October 22, 2018                [Page 5]Internet-Draft     OSPF Extensions for Segment Routing        April 2018   numerically smallest Instance ID MUST be used and subsequent   instances of the SR-Algorithm TLV MUST be ignored.   The RI LSA can be advertised at any of the defined opaque flooding   scopes (link, area, or Autonomous System (AS)).  For the purpose of   SR-Algorithm TLV advertisement, area-scoped flooding is REQUIRED.3.2.  SID/Label Range TLV   Prefix SIDs MAY be advertised in a form of an index as described in   Section 5.  Such index defines the offset in the SID/Label space   advertised by the router.  The SID/Label Range TLV is used to   advertise such SID/Label space.   The SID/Label Range TLV is a top-level TLV of the Router Information   Opaque LSA (defined in [RFC7770]).   The SID/Label Range TLV MAY appear multiple times and has the   following format:    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            |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                    Range Size                 |   Reserved    |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                        Sub-TLVs (variable)                    |   +-                                                             -+   |                                                               |   +                                                               +   where:      Type: 9      Length: Variable, in octets, dependent on Sub-TLVs.      Range Size: 3-octet SID/label range size (i.e., the number of SIDs      or labels in the range including the first SID/label).  It MUST be      greater than 0.      Reserved: SHOULD be set to 0 on transmission and MUST be ignored      on reception.   Initially, the only supported Sub-TLV is the SID/Label Sub-TLV as   defined in Section 2.1.  The SID/Label Sub-TLV MUST be included inPsenak, et al.          Expires October 22, 2018                [Page 6]Internet-Draft     OSPF Extensions for Segment Routing        April 2018   the SID/Label Range TLV.  The SID/Label advertised in the SID/Label   Sub-TLV represents the first SID/Label in the advertised range.   Only a single SID/Label Sub-TLV MAY be advertised in SID/Label Range   TLV.  If more then one SID/Label Sub-TLVs are present, the SID/Label   Range TLV MUST be ignored.   Multiple occurrences of the SID/Label Range TLV MAY be advertised, in   order to advertise multiple ranges.  In such case:   o  The originating router MUST encode each range into a different      SID/Label Range TLV.   o  The originating router decides the order in which the set of SID/      Label Range TLVs are advertised inside the Router Information      Opaque LSA.  The originating router MUST ensure the order is the      same after a graceful restart (using checkpointing, non-volatile      storage, or any other mechanism) in order to assure the SID/label      range and SID index correspondence is preserved across graceful      restarts.   o  The receiving router MUST adhere to the order in which the ranges      are advertised when calculating a SID/label from a SID index.   o  The originating router MUST NOT advertise overlapping ranges.   o  When a router receives multiple overlapping ranges, it MUST      conform to the procedures defined in      [I-D.ietf-spring-segment-routing-mpls].   The following example illustrates the advertisement of multiple   ranges:Psenak, et al.          Expires October 22, 2018                [Page 7]Internet-Draft     OSPF Extensions for Segment Routing        April 2018      The originating router advertises the following ranges:         Range 1: Range Size: 100   SID/Label Sub-TLV: 100         Range 1: Range Size: 100   SID/Label Sub-TLV: 1000         Range 1: Range Size: 100   SID/Label Sub-TLV: 500      The receiving routers concatenate the ranges and build the Segment      Routing Global Block (SRGB) as follows:      SRGB = [100, 199]             [1000, 1099]             [500, 599]      The indexes span multiple ranges:         index=0 means label 100         ...         index 99 means label 199         index 100 means label 1000         index 199 means label 1099         ...         index 200 means label 500         ...   The RI LSA can be advertised at any of the defined flooding scopes   (link, area, or autonomous system (AS)).  For the purpose of SID/   Label Range TLV advertisement, area-scoped flooding is REQUIRED.3.3.  SR Local Block TLV   The SR Local Block TLV (SRLB TLV) contains the range of labels the   node has reserved for local SIDs.  SIDs from the SRLB MAY be used for   Adjacency-SIDs, but also by components other than the OSPF protocol.   As an example, an application or a controller can instruct the router   to allocate a specific local SID.  Some controllers or applications   can use the control plane to discover the available set of local SIDs   on a particular router.  In such cases, the SRLB is advertised in the   control plane.  The requirement to advertise the SRLB is further   described in [I-D.ietf-spring-segment-routing-mpls].  The SRLB TLV is   used to advertise the SRLB.   The SRLB TLV is a top-level TLV of the Router Information Opaque LSA   (defined in [RFC7770]).   The SRLB TLV MAY appear multiple times in the Router Information   Opaque LSA and has the following format:Psenak, et al.          Expires October 22, 2018                [Page 8]Internet-Draft     OSPF Extensions for Segment Routing        April 2018    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            |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                    Range Size                 |   Reserved    |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                        Sub-TLVs (variable)                    |   +-                                                             -+   |                                                               |   +                                                               +   where:      Type: 14      Length: Variable, in octets, dependent on Sub-TLVs.      Range Size: 3-octet SID/label range size (i.e., the number of SIDs      or labels in the range including the first SID/label).  It MUST be      greater than 0.      Reserved: SHOULD be set to 0 on transmission and MUST be ignored      on reception.   Initially, the only supported Sub-TLV is the SID/Label Sub-TLV as   defined in Section 2.1.  The SID/Label Sub-TLV MUST be included in   the SRLB TLV.  The SID/Label advertised in the SID/Label Sub-TLV   represents the first SID/Label in the advertised range.   Only a single SID/Label Sub-TLV MAY be advertised in the SRLB TLV.   If more then one SID/Label Sub-TLVs are present, the SRLB TLV MUST be   ignored.   The originating router MUST NOT advertise overlapping ranges.   Each time a SID from the SRLB is allocated, it SHOULD also be   reported to all components (e.g., controller or applications) in   order for these components to have an up-to-date view of the current   SRLB allocation.  This is required to avoid collisions between   allocation instructions.   Within the context of OSPF, the reporting of local SIDs is done   through OSPF Sub-TLVs such as the Adjacency-SID (Section 6).   However, the reporting of allocated local SIDs can also be done   through other means and protocols which are outside the scope of this   document.Psenak, et al.          Expires October 22, 2018                [Page 9]Internet-Draft     OSPF Extensions for Segment Routing        April 2018   A router advertising the SRLB TLV MAY also have other label ranges,   outside of the SRLB, used for its local allocation purposes which are   not advertised in the SRLB TLV.  For example, it is possible that an   Adjacency-SID is allocated using a local label that is not part of   the SRLB.   The RI LSA can be advertised at any of the defined flooding scopes   (link, area, or autonomous system (AS)).  For the purpose of SRLB TLV   advertisement, area-scoped flooding is REQUIRED.3.4.  SRMS Preference TLV   The Segment Routing Mapping Server Preference TLV (SRMS Preference   TLV) is used to advertise a preference associated with the node that   acts as an SR Mapping Server.  The role of an SRMS is described in   [I-D.ietf-spring-segment-routing-ldp-interop].  SRMS preference is   defined in [I-D.ietf-spring-segment-routing-ldp-interop].   The SRMS Preference TLV is a top-level TLV of the Router Information   Opaque LSA (defined in [RFC7770]).   The SRMS Preference TLV MAY only be advertised once in the Router   Information Opaque LSA and has the following format:    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            |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |   Preference    |                 Reserved                    |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   where:      Type: 15      Length: 4 octets      Preference: 1 octet.  SRMS preference value from 0 to 255.      Reserved: SHOULD be set to 0 on transmission and MUST be ignored      on reception.   When multiple SRMS Preference TLVs are received from a given router,   the receiver MUST use the first occurrence of the TLV in the Router   Information LSA.  If the SRMS Preference TLV appears in multiple   Router Information LSAs that have different flooding scopes, the SRMS   Preference TLV in the Router Information LSA with the narrowestPsenak, et al.          Expires October 22, 2018               [Page 10]Internet-Draft     OSPF Extensions for Segment Routing        April 2018   flooding scope MUST be used.  If the SRMS Preference TLV appears in   multiple Router Information LSAs that have the same flooding scope,   the SRMS Preference TLV in the Router Information LSA with the   numerically smallest Instance ID MUST be used and subsequent   instances of the SRMS Preference TLV MUST be ignored.   The RI LSA can be advertised at any of the defined flooding scopes   (link, area, or autonomous system (AS)).  For the purpose of the SRMS   Preference TLV advertisement, AS-scoped flooding SHOULD be used.   This is because SRMS servers can be located in a different area then   consumers of the SRMS advertisements.  If the SRMS advertisements   from the SRMS server are only used inside the SRMS server's area,   area-scoped flooding MAY be used.4.  OSPF Extended Prefix Range TLV   In some cases it is useful to advertise attributes for a range of   prefixes.  The Segment Routing Mapping Server, which is described in   [I-D.ietf-spring-segment-routing-ldp-interop], is an example where we   need a single advertisement to advertise SIDs for multiple prefixes   from a contiguous address range.   The OSPF Extended Prefix Range TLV, which is a top level TLV of the   Extended Prefix LSA described in [RFC7684] is defined for this   purpose.   Multiple OSPF Extended Prefix Range TLVs MAY be advertised in each   OSPF Extended Prefix Opaque LSA, but all prefix ranges included in a   single OSPF Extended Prefix Opaque LSA MUST have the same flooding   scope.  The OSPF Extended Prefix Range TLV has the following format:    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            |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   | Prefix Length |     AF        |         Range Size            |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |   Flags       |                Reserved                       |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                     Address Prefix (variable)                 |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                      Sub-TLVs (variable)                      |   +-                                                             -+   |                                                               |   where:Psenak, et al.          Expires October 22, 2018               [Page 11]Internet-Draft     OSPF Extensions for Segment Routing        April 2018      Type: 2      Length: Variable, in octets, dependent on Sub-TLVs.      Prefix length: Length of prefix in bits.      AF: Address family for the prefix.  Currently, the only supported      value is 0 for IPv4 unicast.  The inclusion of address family in      this TLV allows for future extension.      Range size: Represents the number of prefixes that are covered by      the advertisement.  The Range Size MUST NOT exceed the number of      prefixes that could be satisfied by the prefix length without      including the IPv4 multicast address range (224.0.0.0/3).      Flags: Single octet field.  The following flags are defined:     0  1  2  3  4  5  6  7   +--+--+--+--+--+--+--+--+   |IA|  |  |  |  |  |  |  |   +--+--+--+--+--+--+--+--+   where:         IA-Flag: Inter-Area flag.  If set, advertisement is of inter-         area type.  An ABR that is advertising the OSPF Extended Prefix         Range TLV between areas MUST set this bit.         This bit is used to prevent redundant flooding of Prefix Range         TLVs between areas as follows:            An ABR only propagates an inter-area Prefix Range            advertisement from the backbone area to connected non-            backbone areas if the advertisement is considered to be the            best one.  The following rules are used to select the best            range from the set of advertisements for the same Prefix            Range:               An ABR always prefers intra-area Prefix Range               advertisements over inter-area advertisements.               An ABR does not consider inter-area Prefix Range               advertisements coming from non-backbone areas.      Reserved: SHOULD be set to 0 on transmission and MUST be ignored      on reception.Psenak, et al.          Expires October 22, 2018               [Page 12]Internet-Draft     OSPF Extensions for Segment Routing        April 2018      Address Prefix: For the address family IPv4 unicast, the prefix      itself is encoded as a 32-bit value.  The default route is      represented by a prefix of length 0.  Prefix encoding for other      address families is beyond the scope of this specification.5.  Prefix SID Sub-TLV   The Prefix SID Sub-TLV is a Sub-TLV of the OSPF Extended Prefix TLV   described in [RFC7684] and the OSPF Extended Prefix Range TLV   described in Section 4.  It MAY appear more than once in the parent   TLV and has the following format:    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    |   Reserved    |      MT-ID    |    Algorithm  |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                     SID/Index/Label (variable)                |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   where:      Type: 2      Length: 7 or 8 octets, dependent on the V-flag      Flags: Single octet field.  The following flags are defined:     0  1  2  3  4  5  6  7   +--+--+--+--+--+--+--+--+   |  |NP|M |E |V |L |  |  |   +--+--+--+--+--+--+--+--+   where:         NP-Flag: No-PHP flag.  If set, then the penultimate hop MUST         NOT pop the Prefix-SID before delivering packets to the node         that advertised the Prefix-SID.         M-Flag: Mapping Server Flag.  If set, the SID was advertised by         a Segment Routing Mapping Server as described in         [I-D.ietf-spring-segment-routing-ldp-interop].Psenak, et al.          Expires October 22, 2018               [Page 13]Internet-Draft     OSPF Extensions for Segment Routing        April 2018         E-Flag: Explicit-Null Flag.  If set, any upstream neighbor of         the Prefix-SID originator MUST replace the Prefix-SID with the         Explicit-NULL label (0 for IPv4) before forwarding the packet.         V-Flag: Value/Index Flag.  If set, then the Prefix-SID carries         an absolute value.  If not set, then the Prefix-SID carries an         index.         L-Flag: Local/Global Flag.  If set, then the value/index         carried by the Prefix-SID has local significance.  If not set,         then the value/index carried by this Sub-TLV has global         significance.         Other bits: Reserved.  These MUST be zero when sent and are         ignored when received.      Reserved: SHOULD be set to 0 on transmission and MUST be ignored      on reception.      MT-ID: Multi-Topology ID (as defined in [RFC4915]).      Algorithm: Single octet identifying the algorithm the Prefix-SID      is associated with as defined in Section 3.1.      A router receiving a Prefix-SID from a remote node and with an      algorithm value that such remote node has not advertised in the      SR-Algorithm Sub-TLV (Section 3.1) MUST ignore the Prefix-SID Sub-      TLV.      SID/Index/Label: According to the V and L flags, it contains      either:         A 32-bit index defining the offset in the SID/Label space         advertised by this router.         A 24-bit label where the 20 rightmost bits are used for         encoding the label value.   If an OSPF router advertises multiple Prefix-SIDs for the same   prefix, topology and algorithm, all of them MUST be ignored.   When calculating the outgoing label for the prefix, the router MUST   take into account, as described below, the E, NP and M flags   advertised by the next-hop router if that router advertised the SID   for the prefix.  This MUST be done regardless of whether the next-hop   router contributes to the best path to the prefix.Psenak, et al.          Expires October 22, 2018               [Page 14]Internet-Draft     OSPF Extensions for Segment Routing        April 2018   The NP-Flag (No-PHP) MUST be set and the E-flag MUST be clear for   Prefix-SIDs allocated to inter-area prefixes that are originated by   the ABR based on intra-area or inter-area reachability between areas,   unless the advertised prefix is directly attached to the ABR.   The NP-Flag (No-PHP) MUST be set and the E-flag MUST be clear for   Prefix-SIDs allocated to redistributed prefixes, unless the   redistributed prefix is directly attached to the ASBR.   If the NP-Flag is not set, then any upstream neighbor of the Prefix-   SID originator MUST pop the Prefix-SID.  This is equivalent to the   penultimate hop popping mechanism used in the MPLS dataplane.  If the   NP-flag is not set, then the received E-flag is ignored.   If the NP-flag is set then:      If the E-flag is not set, then any upstream neighbor of the      Prefix-SID originator MUST keep the Prefix-SID on top of the      stack.  This is useful when the originator of the Prefix-SID need      to stitch the incoming packet into a continuing MPLS LSP to the      final destination.  This could occur at an Area Border Router      (prefix propagation from one area to another) or at an AS Boundary      Router (prefix propagation from one domain to another).      If the E-flag is set, then any upstream neighbor of the Prefix-SID      originator MUST replace the Prefix-SID with an Explicit-NULL      label.  This is useful, e.g., when the originator of the Prefix-      SID is the final destination for the related prefix and the      originator wishes to receive the packet with the original EXP      bits.   When the M-Flag is set, the NP-flag and the E-flag MUST be ignored at   reception.   As the Mapping Server does not specify the originator of a prefix   advertisement, it is not possible to determine PHP behavior solely   based on the Mapping Server advertisement.  However, PHP behavior   SHOULD be done in following cases:      The Prefix is intra-area type and the downstream neighbor is the      originator of the prefix.      The Prefix is inter-area type and downstream neighbor is an ABR,      which is advertising prefix reachability and is also generating      the Extended Prefix TLV with the A-flag set for this prefix as      described in section 2.1 of [RFC7684].Psenak, et al.          Expires October 22, 2018               [Page 15]Internet-Draft     OSPF Extensions for Segment Routing        April 2018      The Prefix is external type and downstream neighbor is an ASBR,      which is advertising prefix reachability and is also generating      the Extended Prefix TLV with the A-flag set for this prefix as      described in section 2.1 of [RFC7684].   When a Prefix-SID is advertised in an Extended Prefix Range TLV, then   the value advertised in the Prefix SID Sub-TLV is interpreted as a   starting SID/Label value.   Example 1: If the following router addresses (loopback addresses)   need to be mapped into the corresponding Prefix SID indexes:             Router-A: 192.0.2.1/32, Prefix-SID: Index 1             Router-B: 192.0.2.2/32, Prefix-SID: Index 2             Router-C: 192.0.2.3/32, Prefix-SID: Index 3             Router-D: 192.0.2.4/32, Prefix-SID: Index 4   then the Prefix field in the Extended Prefix Range TLV would be set   to 192.0.2.1, Prefix Length would be set to 32, Range Size would be   set to 4, and the Index value in the Prefix-SID Sub-TLV would be set   to 1.   Example 2: If the following prefixes need to be mapped into the   corresponding Prefix-SID indexes:             192.0.2.0/30, Prefix-SID: Index 51             192.0.2.4/30, Prefix-SID: Index 52             192.0.2.8/30, Prefix-SID: Index 53             192.0.2.12/30, Prefix-SID: Index 54             192.0.2.16/30, Prefix-SID: Index 55             192.0.2.20/30, Prefix-SID: Index 56             192.0.2.24/30, Prefix-SID: Index 57   then the Prefix field in the Extended Prefix Range TLV would be set   to 192.0.2.0, Prefix Length would be set to 30, Range Size would be   7, and the Index value in the Prefix-SID Sub-TLV would be set to 51.6.  Adjacency Segment Identifier (Adj-SID)   An Adjacency Segment Identifier (Adj-SID) represents a router   adjacency in Segment Routing.6.1.  Adj-SID Sub-TLV   Adj-SID is an optional Sub-TLV of the Extended Link TLV defined in   [RFC7684].  It MAY appear multiple times in the Extended Link TLV.   The Adj-SID Sub-TLV has the following format:Psenak, et al.          Expires October 22, 2018               [Page 16]Internet-Draft     OSPF Extensions for Segment Routing        April 2018    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     |    Reserved   |   MT-ID       |  Weight       |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                   SID/Label/Index (variable)                  |   +---------------------------------------------------------------+   where:      Type: 2      Length: 7 or 8 octets, dependent on the V flag.      Flags: Single octet field containing the following flags:    0 1 2 3 4 5 6 7   +-+-+-+-+-+-+-+-+   |B|V|L|G|P|     |   +-+-+-+-+-+-+-+-+   where:         B-Flag: Backup Flag.  If set, the Adj-SID refers to an         adjacency that is eligible for protection (e.g., using IPFRR or         MPLS-FRR) as described in section 3.5 of         [I-D.ietf-spring-segment-routing].         The V-Flag: Value/Index Flag.  If set, then the Adj-SID carries         an absolute value.  If not set, then the Adj-SID carries an         index.         The L-Flag: Local/Global Flag.  If set, then the value/index         carried by the Adj-SID has local significance.  If not set,         then the value/index carried by this Sub-TLV has global         significance.         The G-Flag: Group Flag.  When set, the G-Flag indicates that         the Adj-SID refers to a group of adjacencies (and therefore MAY         be assigned to other adjacencies as well).         P-Flag.  Persistent flag.  When set, the P-Flag indicates that         the Adj-SID is persistently allocated, i.e., the Adj-SID value         remains consistent across router restart and/or interface flap.Psenak, et al.          Expires October 22, 2018               [Page 17]Internet-Draft     OSPF Extensions for Segment Routing        April 2018         Other bits: Reserved.  These MUST be zero when sent and are         ignored when received.      Reserved: SHOULD be set to 0 on transmission and MUST be ignored      on reception.      MT-ID: Multi-Topology ID (as defined in [RFC4915].      Weight: Weight used for load-balancing purposes.  The use of the      weight is defined in [I-D.ietf-spring-segment-routing].      SID/Index/Label: According to the V and L flags, it contains      either:         A 32-bit index defining the offset in the SID/Label space         advertised by this router.         A 24-bit label where the 20 rightmost bits are used for         encoding the label value.   An SR capable router MAY allocate an Adj-SID for each of its   adjacencies and set the B-Flag when the adjacency is eligible for   protection by an FRR mechanism (IP or MPLS) as described in section   3.5 of [I-D.ietf-spring-segment-routing].   An SR capable router MAY allocate more than one Adj-SID to an   adjacency   An SR capable router MAY allocate the same Adj-SID to different   adjacencies   When the P-flag is not set, the Adj-SID MAY be persistent.  When the   P-flag is set, the Adj-SID MUST be persistent.6.2.  LAN Adj-SID Sub-TLV   LAN Adj-SID is an optional Sub-TLV of the Extended Link TLV defined   in [RFC7684].  It MAY appear multiple times in the Extended-Link TLV.   It is used to advertise a SID/Label for an adjacency to a non-DR   router on a broadcast, NBMA, or hybrid [RFC6845] network.Psenak, et al.          Expires October 22, 2018               [Page 18]Internet-Draft     OSPF Extensions for Segment Routing        April 2018    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     |    Reserved   |     MT-ID     |    Weight     |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                        Neighbor ID                            |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                    SID/Label/Index (variable)                 |   +---------------------------------------------------------------+   where:      Type: 3      Length: 11 or 12 octets, dependent on V-flag.      Flags: same as in Section 6.1      Reserved: SHOULD be set to 0 on transmission and MUST be ignored      on reception.      MT-ID: Multi-Topology ID (as defined in [RFC4915].      Weight: Weight used for load-balancing purposes.  The use of the      weight is defined in [I-D.ietf-spring-segment-routing].      Neighbor ID: The Router ID of the neighbor for which the LAN-Adj-      SID is advertised.      SID/Index/Label: According to the V and L flags, it contains      either:         A 32-bit index defining the offset in the SID/Label space         advertised by this router.         A 24-bit label where the 20 rightmost bits are used for         encoding the label value.      When the P-flag is not set, the Adj-SID MAY be persistent.  When      the P-flag is set, the Adj-SID MUST be persistent.7.  Elements of ProcedurePsenak, et al.          Expires October 22, 2018               [Page 19]Internet-Draft     OSPF Extensions for Segment Routing        April 20187.1.  Intra-area Segment routing in OSPFv2   An OSPFv2 router that supports segment routing MAY advertise Prefix-   SIDs for any prefix to which it is advertising reachability (e.g., a   loopback IP address as described in Section 5).   A Prefix-SID can also be advertised by the SR Mapping Servers (as   described in [I-D.ietf-spring-segment-routing-ldp-interop]).  A   Mapping Server advertises Prefix-SIDs for remote prefixes that exist   in the OSPFv2 routing domain.  Multiple Mapping Servers can advertise   Prefix-SIDs for the same prefix, in which case the same Prefix-SID   MUST be advertised by all of them.  The flooding scope of the OSPF   Extended Prefix Opaque LSA that is generated by the SR Mapping Server   could be either area-scoped or AS-scoped and is determined based on   the configuration of the SR Mapping Server.   An SR Mapping Server MUST use the OSPF Extended Prefix Range TLV when   advertising SIDs for prefixes.  Prefixes of different route-types can   be combined in a single OSPF Extended Prefix Range TLV advertised by   an SR Mapping Server.  Because the OSPF Extended Prefix Range TLV   doesn't include a Route-Type field, as in the OSPF Extended Prefix   TLV, it is possible to include adjacent prefixes from different   Route-Types in the OSPF Extended Prefix Range TLV.   Area-scoped OSPF Extended Prefix Range TLVs are propagated between   areas.  Similar to propagation of prefixes between areas, an ABR only   propagates the OSPF Extended Prefix Range TLV that it considers to be   the best from the set it received.  The rules used to pick the best   OSPF Extended Prefix Range TLV are described in Section 4.   When propagating an OSPF Extended Prefix Range TLV between areas,   ABRs MUST set the IA-Flag, that is used to prevent redundant flooding   of the OSPF Extended Prefix Range TLV between areas as described in   Section 4.7.2.  Inter-area Segment routing in OSPFv2   In order to support SR in a multi-area environment, OSPFv2 MUST   propagate Prefix-SID information between areas.  The following   procedure is used to propagate Prefix SIDs between areas.   When an OSPF ABR advertises a Type-3 Summary LSA from an intra-area   prefix to all its connected areas, it will also originate an Extended   Prefix Opaque LSA, as described in [RFC7684].  The flooding scope of   the Extended Prefix Opaque LSA type will be set to area-local scope.   The route-type in the OSPF Extended Prefix TLV is set to inter-area.   The Prefix-SID Sub-TLV will be included in this LSA and the Prefix-   SID value will be set as follows:Psenak, et al.          Expires October 22, 2018               [Page 20]Internet-Draft     OSPF Extensions for Segment Routing        April 2018      The ABR will look at its best path to the prefix in the source      area and find the advertising router associated with the best path      to that prefix.      The ABR will then determine if such router advertised a Prefix-SID      for the prefix and use it when advertising the Prefix-SID to other      connected areas.      If no Prefix-SID was advertised for the prefix in the source area      by the router that contributes to the best path to the prefix, the      originating ABR will use the Prefix-SID advertised by any other      router when propagating the Prefix-SID for the prefix to other      areas.   When an OSPF ABR advertises Type-3 Summary LSAs from an inter-area   route to all its connected areas, it will also originate an Extended   Prefix Opaque LSA, as described in [RFC7684].  The flooding scope of   the Extended Prefix Opaque LSA type will be set to area-local scope.   The route-type in OSPF Extended Prefix TLV is set to inter-area.  The   Prefix-SID Sub-TLV will be included in this LSA and the Prefix-SID   will be set as follows:      The ABR will look at its best path to the prefix in the backbone      area and find the advertising router associated with the best path      to that prefix.      The ABR will then determine if such router advertised a Prefix-SID      for the prefix and use it when advertising the Prefix-SID to other      connected areas.      If no Prefix-SID was advertised for the prefix in the backbone      area by the ABR that contributes to the best path to the prefix,      the originating ABR will use the Prefix-SID advertised by any      other router when propagating the Prefix-SID for the prefix to      other areas.7.3.  Segment Routing for External Prefixes   Type-5 LSAs are flooded domain wide.  When an ASBR, which supports   SR, generates Type-5 LSAs, it SHOULD also originate Extended Prefix   Opaque LSAs, as described in [RFC7684].  The flooding scope of the   Extended Prefix Opaque LSA type is set to AS-wide scope.  The route-   type in the OSPF Extended Prefix TLV is set to external.  The Prefix-   SID Sub-TLV is included in this LSA and the Prefix-SID value will be   set to the SID that has been reserved for that prefix.   When an NSSA [RFC3101] ABR translates Type-7 LSAs into Type-5 LSAs,   it SHOULD also advertise the Prefix-SID for the prefix.  The NSSA ABRPsenak, et al.          Expires October 22, 2018               [Page 21]Internet-Draft     OSPF Extensions for Segment Routing        April 2018   determines its best path to the prefix advertised in the translated   Type-7 LSA and finds the advertising router associated with that   path.  If the advertising router has advertised a Prefix-SID for the   prefix, then the NSSA ABR uses it when advertising the Prefix-SID for   the Type-5 prefix.  Otherwise, the Prefix-SID advertised by any other   router will be used.7.4.  Advertisement of Adj-SID   The Adjacency Segment Routing Identifier (Adj-SID) is advertised   using the Adj-SID Sub-TLV as described in Section 6.7.4.1.  Advertisement of Adj-SID on Point-to-Point Links   An Adj-SID MAY be advertised for any adjacency on a P2P link that is   in neighbor state 2-Way or higher.  If the adjacency on a P2P link   transitions from the FULL state, then the Adj-SID for that adjacency   MAY be removed from the area.  If the adjacency transitions to a   state lower then 2-Way, then the Adj-SID advertisement MUST be   withdrawn from the area.7.4.2.  Adjacency SID on Broadcast or NBMA Interfaces   Broadcast, NBMA, or hybrid [RFC6845] networks in OSPF are represented   by a star topology where the Designated Router (DR) is the central   point to which all other routers on the broadcast, NBMA, or hybrid   network connect.  As a result, routers on the broadcast, NBMA, or   hybrid network advertise only their adjacency to the DR.  Routers   that do not act as DR do not form or advertise adjacencies with each   other.  They do, however, maintain 2-Way adjacency state with each   other and are directly reachable.   When Segment Routing is used, each router on the broadcast, NBMA, or   hybrid network MAY advertise the Adj-SID for its adjacency to the DR   using the Adj-SID Sub-TLV as described in Section 6.1.   SR capable routers MAY also advertise a LAN-Adj-SID for other   neighbors (e.g., BDR, DR-OTHER) on the broadcast, NBMA, or hybrid   network using the LAN-ADJ-SID Sub-TLV as described in Section 6.2.8.  IANA Considerations   This specification updates several existing OSPF registries.Psenak, et al.          Expires October 22, 2018               [Page 22]Internet-Draft     OSPF Extensions for Segment Routing        April 20188.1.  OSPF Router Information (RI) TLVs Registry   o 8 (IANA Preallocated) - SR-Algorithm TLV   o 9 (IANA Preallocated) - SID/Label Range TLV   o 14 - SR Local Block TLV   o 15 - SRMS Preference TLV8.2.  OSPFv2 Extended Prefix Opaque LSA TLVs Registry   Following values are allocated:   o 2 - OSPF Extended Prefix Range TLV8.3.  OSPFv2 Extended Prefix TLV Sub-TLVs Registry   Following values are allocated:   o 1 - SID/Label Sub-TLV   o 2 - Prefix SID Sub-TLV8.4.  OSPFv2 Extended Link TLV Sub-TLVs Registry   Following initial values are allocated:   o 1 - SID/Label Sub-TLV   o 2 - Adj-SID Sub-TLV   o 3 - LAN Adj-SID/Label Sub-TLV8.5.  IGP Algorithm Type Registry   IANA is requested to set up a registry called "IGP Algorithm Type"   under a new category of "Interior Gateway Protocol (IGP) Parameters"   IANA registries.  The registration policy for this registry is   "Standards Action" ([RFC8126] and [RFC7120]).   Values in this registry come from the range 0-255.   The initial values in the IGP Algorithm Type registry are:      0: Shortest Path First (SPF) algorithm based on link metric.  This      is the standard shortest path algorithm as computed by the IGP      protocol.  Consistent with the deployed practice for link-statePsenak, et al.          Expires October 22, 2018               [Page 23]Internet-Draft     OSPF Extensions for Segment Routing        April 2018      protocols, Algorithm 0 permits any node to overwrite the SPF path      with a different path based on its local policy.      1: Strict Shortest Path First (SPF) algorithm based on link      metric.  The algorithm is identical to Algorithm 0 but Algorithm 1      requires that all nodes along the path will honor the SPF routing      decision.  Local policy at the node claiming support for Algorithm      1 MUST NOT alter the SPF paths computed by Algorithm 1.9.  Implementation Status   An implementation survey with seven questions related to the   implementer's support of OSPFv2 Segment Routing was sent to the OSPF   WG list and several known implementers.  This section contains   responses from three implementers who completed the survey.  No   external means were used to verify the accuracy of the information   submitted by the respondents.  The respondents are considered experts   on the products they reported on.  Additionally, responses were   omitted from implementers who indicated that they have not   implemented the function yet.   This section will be removed before publication as an RFC.   Responses from Nokia (former Alcatel-Lucent):   Link to a web page describing the implementation:   https://infoproducts.alcatel-lucent.com/cgi-bin/dbaccessfilename.cgi/   3HE10799AAAATQZZA01_V1_7450%20ESS%207750%20SR%20and%207950%20XRS%20Un   icast%20Routing%20Protocols%20Guide%20R14.0.R1.pdf   The implementation's level of maturity: Production.   Coverage: We have implemented all sections and have support for the   latest draft.   Licensing: Part of the software package that needs to be purchased.   Implementation experience: Great spec.  We also performed inter-   operability testing with Cisco's OSPF Segment Routing implementation.   Contact information: wim.henderickx@nokia.com   Responses from Cisco Systems:   Link to a web page describing the implementation:   http://www.segment-routing.net/home/tutorialPsenak, et al.          Expires October 22, 2018               [Page 24]Internet-Draft     OSPF Extensions for Segment Routing        April 2018   The implementation's level of maturity: Production.   Coverage: All sections have been implemented according to the latest   draft.   Licensing: Part of a commercial software package.   Implementation experience: Many aspects of the draft are result of   the actual implementation experience, as the draft evolved from its   initial version to the current one.  Interoperability testing with   Alcatel-Lucent was performed, which confirmed the draft's ability to   serve as a reference for the implementors.   Contact information: ppsenak@cisco.com   Responses from Juniper:   The implementation's name and/or a link to a web page describing the   implementation:   Feature name is OSPF SPRING   The implementation's level of maturity: To be released in 16.2   (second half of 2016)   Coverage: All sections implemented except Sections 4, and 6.   Licensing: JUNOS Licensing needed.   Implementation experience: NA   Contact information: shraddha@juniper.net10.  Security Considerations   With the OSPFv2 segment routing extensions defined herein, OSPFv2   will now program the MPLS data plane [RFC3031] in addition to the IP   data plane.  Previously, LDP [RFC5036] or another label distribution   mechanism was required to advertise MPLS labels and program the MPLS   data plane.   In general, the same types of attacks that can be carried out on the   IP control plane can be carried out on the MPLS control plane   resulting in traffic being misrouted in the respective data planes.   However, the latter can be more difficult to detect and isolate.   Existing security extensions as described in [RFC2328] and [RFC7684]   apply to these segment routing extensions.  While OSPF is under aPsenak, et al.          Expires October 22, 2018               [Page 25]Internet-Draft     OSPF Extensions for Segment Routing        April 2018   single administrative domain, there can be deployments where   potential attackers have access to one or more networks in the OSPF   routing domain.  In these deployments, stronger authentication   mechanisms such as those specified in [RFC7474] SHOULD be used.   Implementations MUST assure that malformed TLV and Sub-TLV defined in   this document are detected and do not provide a vulnerability for   attackers to crash the OSPFv2 router or routing process.  Reception   of malformed TLV or Sub-TLV SHOULD be counted and/or logged for   further analysis.  Logging of malformed TLVs and Sub-TLVs SHOULD be   rate-limited to prevent a Denial of Service (DoS) attack (distributed   or otherwise) from overloading the OSPF control plane.11.  Contributors   The following people gave a substantial contribution to the content   of this document: Acee Lindem, Ahmed Bashandy, Martin Horneffer,   Bruno Decraene, Stephane Litkowski, Igor Milojevic, Rob Shakir and   Saku Ytti.12.  Acknowledgements   We would like to thank Anton Smirnov for his contribution.   Thanks to Acee Lindem for the detail review of the draft,   corrections, as well as discussion about details of the encoding.13.  References13.1.  Normative References   [I-D.ietf-spring-segment-routing]              Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B.,              Litkowski, S., and R. Shakir, "Segment Routing              Architecture", draft-ietf-spring-segment-routing-15 (work              in progress), January 2018.   [I-D.ietf-spring-segment-routing-ldp-interop]              Bashandy, A., Filsfils, C., Previdi, S., Decraene, B., and              S. Litkowski, "Segment Routing interworking with LDP",              draft-ietf-spring-segment-routing-ldp-interop-11 (work in              progress), April 2018.   [I-D.ietf-spring-segment-routing-mpls]              Bashandy, A., Filsfils, C., Previdi, S., Decraene, B.,              Litkowski, S., and R. Shakir, "Segment Routing with MPLS              data plane", draft-ietf-spring-segment-routing-mpls-13              (work in progress), April 2018.Psenak, et al.          Expires October 22, 2018               [Page 26]Internet-Draft     OSPF Extensions for Segment Routing        April 2018   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels", BCP 14, RFC 2119,              DOI 10.17487/RFC2119, March 1997,              <https://www.rfc-editor.org/info/rfc2119>.   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328,              DOI 10.17487/RFC2328, April 1998,              <https://www.rfc-editor.org/info/rfc2328>.   [RFC3101]  Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option",              RFC 3101, DOI 10.17487/RFC3101, January 2003,              <https://www.rfc-editor.org/info/rfc3101>.   [RFC4915]  Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.              Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",              RFC 4915, DOI 10.17487/RFC4915, June 2007,              <https://www.rfc-editor.org/info/rfc4915>.   [RFC6845]  Sheth, N., Wang, L., and J. Zhang, "OSPF Hybrid Broadcast              and Point-to-Multipoint Interface Type", RFC 6845,              DOI 10.17487/RFC6845, January 2013,              <https://www.rfc-editor.org/info/rfc6845>.   [RFC7120]  Cotton, M., "Early IANA Allocation of Standards Track Code              Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January              2014, <https://www.rfc-editor.org/info/rfc7120>.   [RFC7684]  Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,              Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute              Advertisement", RFC 7684, DOI 10.17487/RFC7684, November              2015, <https://www.rfc-editor.org/info/rfc7684>.   [RFC7770]  Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and              S. Shaffer, "Extensions to OSPF for Advertising Optional              Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,              February 2016, <https://www.rfc-editor.org/info/rfc7770>.   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for              Writing an IANA Considerations Section in RFCs", BCP 26,              RFC 8126, DOI 10.17487/RFC8126, June 2017,              <https://www.rfc-editor.org/info/rfc8126>.13.2.  Informative References   [RFC7474]  Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed.,              "Security Extension for OSPFv2 When Using Manual Key              Management", RFC 7474, DOI 10.17487/RFC7474, April 2015,              <https://www.rfc-editor.org/info/rfc7474>.Psenak, et al.          Expires October 22, 2018               [Page 27]Internet-Draft     OSPF Extensions for Segment Routing        April 2018   [RFC7855]  Previdi, S., Ed., Filsfils, C., Ed., Decraene, B.,              Litkowski, S., Horneffer, M., and R. Shakir, "Source              Packet Routing in Networking (SPRING) Problem Statement              and Requirements", RFC 7855, DOI 10.17487/RFC7855, May              2016, <https://www.rfc-editor.org/info/rfc7855>.Authors' Addresses   Peter Psenak (editor)   Cisco Systems, Inc.   Apollo Business Center   Mlynske nivy 43   Bratislava  821 09   Slovakia   Email: ppsenak@cisco.com   Stefano Previdi (editor)   Cisco Systems, Inc.   Via Del Serafico, 200   Rome  00142   Italy   Email: stefano@previdi.net   Clarence Filsfils   Cisco Systems, Inc.   Brussels   Belgium   Email: cfilsfil@cisco.com   Hannes Gredler   RtBrick Inc.   Email: hannes@rtbrick.com   Rob Shakir   Google, Inc.   1600 Amphitheatre Parkway   Mountain View, CA  94043   US   Email: robjs@google.comPsenak, et al.          Expires October 22, 2018               [Page 28]Internet-Draft     OSPF Extensions for Segment Routing        April 2018   Wim Henderickx   Nokia   Copernicuslaan 50   Antwerp  2018   BE   Email: wim.henderickx@nokia.com   Jeff Tantsura   Individual   US   Email: jefftant.ietf@gmail.comPsenak, et al.          Expires October 22, 2018               [Page 29]