ERO:

Explicit Route Object

IGP:

Interior Gateway Protocol

IS-IS:

Intermediate System to Intermediate System

LSR:

Label Switching Router

MSD:

Base MPLS Imposition Maximum SID Depth, as defined in [RFC 8491]

NAI:

Node or Adjacency Identifier

OSPF:

Open Shortest Path First

PCC:

Path Computation Client

PCE:

Path Computation Element

PCEP:

Path Computation Element Communication Protocol

RRO:

Record Route Object

SID:

Segment Identifier

SR:

Segment Routing

SR-DB:

Segment Routing Database: the collection of SRGBs, SRLBs, and SIDs and the objects they map to, advertised by a link-state IGP

SR-TE:

Segment Routing Traffic Engineering

SRGB:

Segment Routing Global Block

SRLB:

Segment Routing Local Block

• An ordered set of IP addresses representing network nodes/links.
• An ordered set of SIDs, with or without the corresponding IP addresses.
• An ordered set of MPLS labels, with or without corresponding IP addresses.

• Defines a new ERO subobject, a new RRO subobject, and new PCEP error codes.
• Specifies how two PCEP speakers can establish a PCEP session that can carry information about SR-TE paths.
• Specifies processing rules for the ERO subobject.
• Defines a new path setup type to be used in the PATH-SETUP-TYPE and PATH-SETUP-TYPE-CAPABILITY TLVs [RFC 8408].
• Defines a new sub-TLV for the PATH-SETUP-TYPE-CAPABILITY TLV.

• PST = 1:

  Traffic-engineering path is set up using Segment Routing.

 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=26               |            Length=4           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|         Reserved              |   Flags   |N|X|      MSD      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Reserved:

MUST be set to zero by the sender and MUST be ignored by the receiver.

Flags:

This document defines the following flag bits. The other bits MUST be set to zero by the sender and MUST be ignored by the receiver.

• N:

  A PCC sets this flag bit to 1 to indicate that it is capable of resolving a Node or Adjacency Identifier (NAI) to a SID.

  X:

  A PCC sets this flag bit to 1 to indicate that it does not impose any limit on the MSD.

Maximum SID Depth (MSD):

specifies the maximum number of SIDs (MPLS label stack depth in the context of this document) that a PCC is capable of imposing on a packet. Section 5.1 explains the relationship between this field and the X-Flag.

   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=36   |     Length    |  NT   |     Flags     |F|S|C|M|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                         SID (optional)                        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  //                   NAI (variable, optional)                  //
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The L-Flag:

Indicates whether the subobject represents a loose hop in the LSP [RFC 3209]. If this flag is set to zero, a PCC MUST NOT overwrite the SID value present in the SR-ERO subobject. Otherwise, a PCC MAY expand or replace one or more SID values in the received SR-ERO based on its local policy.

Type:

Set to 36.

Length:

Contains the total length of the subobject in octets. The Length MUST be at least 8 and MUST be a multiple of 4. An SR-ERO subobject MUST contain at least one SID or NAI. The flags described below indicate whether the SID or NAI fields are absent.

NAI Type (NT):

Indicates the type and format of the NAI contained in the object body, if any is present. If the F bit is set to zero (see below), then the NT field has no meaning and MUST be ignored by the receiver. This document describes the following NT values:

NT=0

The NAI is absent.

NT=1

The NAI is an IPv4 node ID.

NT=2

The NAI is an IPv6 node ID.

NT=3

The NAI is an IPv4 adjacency.

NT=4

The NAI is an IPv6 adjacency with global IPv6 addresses.

NT=5

The NAI is an unnumbered adjacency with IPv4 node IDs.

NT=6

The NAI is an IPv6 adjacency with link-local IPv6 addresses.

Flags:

Used to carry additional information pertaining to the SID. This document defines the following flag bits. The other bits MUST be set to zero by the sender and MUST be ignored by the receiver.

M:

If this bit is set to 1, the SID value represents an MPLS label stack entry as specified in [RFC 3032]. Otherwise, the SID value is an administratively configured value that represents an index into an MPLS label space (either SRGB or SRLB) per [RFC 8402].

C:

If the M bit and the C bit are both set to 1, then the TC, S, and TTL fields in the MPLS label stack entry are specified by the PCE. However, a PCC MAY choose to override these values according to its local policy and MPLS forwarding rules. If the M bit is set to 1 but the C bit is set to zero, then the TC, S, and TTL fields MUST be ignored by the PCC. The PCC MUST set these fields according to its local policy and MPLS forwarding rules. If the M bit is set to zero, then the C bit MUST be set to zero.

S:

When this bit is set to 1, the SID value in the subobject body is absent. In this case, the PCC is responsible for choosing the SID value, e.g., by looking it up in the SR-DB using the NAI that, in this case, MUST be present in the subobject. If the S bit is set to 1, then the M and C bits MUST be set to zero.

F:

When this bit is set to 1, the NAI value in the subobject body is absent. The F bit MUST be set to 1 if NT=0; otherwise, it MUST be set to zero. The S and F bits MUST NOT both be set to 1.

SID:

The Segment Identifier. Depending on the M bit, it contains either:

• A 4-octet index defining the offset into an MPLS label space per [RFC 8402] or
• A 4-octet MPLS label stack entry, where the 20 most significant bits encode the label value per [RFC 3032].

NAI:

The NAI associated with the SID. The NAI's format depends on the value in the NT field and is described in the following section.

IPv4 Node ID:

Specified as an IPv4 address. In this case, the NT value is 1, and the NAI field length is 4 octets.

IPv6 Node ID:

Specified as an IPv6 address. In this case, the NT value is 2, and the NAI field length is 16 octets.

IPv4 Adjacency:

Specified as a pair of IPv4 addresses. In this case, the NT value is 3, and the NAI field length is 8 octets. The format of the NAI is shown in the following figure:

  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                      Local IPv4 address                       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                     Remote IPv4 address                       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 3: NAI for IPv4 Adjacency

IPv6 Global Adjacency:

Specified as a pair of global IPv6 addresses. It is used to describe an IPv6 adjacency for a link that uses global IPv6 addresses. Each global IPv6 address is configured on a specific router interface, so together they identify an adjacency between a pair of routers. In this case, the NT value is 4, and the NAI field length is 32 octets. The format of the NAI is shown in the following figure:

  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //               Local IPv6 address (16 octets)                //
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //               Remote IPv6 address (16 octets)               //
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 4: NAI for IPv6 Global Adjacency

Unnumbered Adjacency with IPv4 NodeIDs:

Specified as a pair of (node ID, interface ID) tuples. In this case, the NT value is 5, and the NAI field length is 16 octets. The format of the NAI is shown in the following figure:

  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                      Local Node ID                            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                    Local Interface ID                         |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                      Remote Node ID                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   Remote Interface ID                         |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 5: NAI for Unnumbered Adjacency with IPv4 Node IDs

IPv6 Link-Local Adjacency:

Specified as a pair of (global IPv6 address, interface ID) tuples. It is used to describe an IPv6 adjacency for a link that uses only link-local IPv6 addresses. Each global IPv6 address is configured on a specific router, so together they identify a pair of adjacent routers. The interface IDs identify the link that the adjacency is formed over. In this case, the NT value is 6, and the NAI field length is 40 octets. The format of the NAI is shown in the following figure:

  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //               Local IPv6 address (16 octets)                //
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                    Local Interface ID                         |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //               Remote IPv6 address (16 octets)               //
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   Remote Interface ID                         |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 6: NAI for IPv6 Link-Local Adjacency

• T = 11:

  Maximum SID Depth of the requested path.

• If NT=0, the F bit MUST be 1, the S bit MUST be zero, and the Length MUST be 8.
• If NT=1, the F bit MUST be zero. If the S bit is 1, the Length MUST be 8; otherwise, the Length MUST be 12.
• If NT=2, the F bit MUST be zero. If the S bit is 1, the Length MUST be 20; otherwise, the Length MUST be 24.
• If NT=3, the F bit MUST be zero. If the S bit is 1, the Length MUST be 12; otherwise, the Length MUST be 16.
• If NT=4, the F bit MUST be zero. If the S bit is 1, the Length MUST be 36; otherwise, the Length MUST be 40.
• If NT=5, the F bit MUST be zero. If the S bit is 1, the Length MUST be 20; otherwise, the Length MUST be 24.
• If NT=6, the F bit MUST be zero. If the S bit is 1, the Length MUST be 44; otherwise, the Length MUST be 48.

• If the subobjects contain SID index values, then the PCC converts them into the corresponding MPLS labels by following the procedure defined in [RFC 8660].
• If the subobjects contain NAIs only, the PCC first converts each NAI into a SID index value and then proceeds as above. To convert an NAI to a SID index, the PCC looks for a fully specified prefix or adjacency matching the fields in the NAI. If the PCC finds a matching prefix/adjacency, and the matching prefix/adjacency has a SID associated with it, then the PCC uses that SID. If the PCC cannot find a matching prefix/adjacency, or if the matching prefix/adjacency has no SID associated with it, the PCC behaves as specified in Section 5.2.2.1.
• If the subobjects contain MPLS labels, then the PCC looks up the offset of the first subobject's label in its SRGB or SRLB. This gives the first SID. The PCC pushes the labels in any remaining subobjects onto the packet (with the final subobject specifying the bottom-of-stack label).

• If the PCC cannot find a SID index in the SR-DB, it MUST send a PCErr message with Error-Type = 10 ("Reception of an invalid object") and Error-value = 14 ("Unknown SID").
• If the PCC cannot find an NAI in the SR-DB, it MUST send a PCErr message with Error-Type = 10 ("Reception of an invalid object") and Error-value = 15 ("NAI cannot be resolved to a SID").
• If the PCC needs to convert a SID into an MPLS label value but cannot find the corresponding router's SRGB in the SR-DB, it MUST send a PCErr message with Error-Type = 10 ("Reception of an invalid object") and Error-value = 16 ("Could not find SRGB").
• If the PCC finds that a router's SRGB is not large enough for a SID index value, it MUST send a PCErr message with Error-Type = 10 ("Reception of an invalid object") and Error-value = 17 ("SID index exceeds SRGB size").
• If the PCC needs to convert a SID into an MPLS label value but cannot find the corresponding router's SRLB in the SR-DB, it MUST send a PCErr message with Error-Type = 10 ("Reception of an invalid object") and Error-value = 18 ("Could not find SRLB").
• If the PCC finds that a router's SRLB is not large enough for a SID index value, it MUST send a PCErr message with Error-Type = 10 ("Reception of an invalid object") and Error-value = 19 ("SID index exceeds SRLB size").
• If the number of labels in the computed label stack exceeds the maximum number of SIDs that the PCC can impose on the packet, it MUST send a PCErr message with Error-Type = 10 ("Reception of an invalid object") and Error-value = 3 ("Unsupported number of SR-ERO subobjects").

• The available path setup types are constrained to those that are supported by, or enabled on, the PCEP speakers. The PATH-SETUP-TYPE-CAPABILITY TLV indicates which path setup types a PCEP speaker supports. To use Segment Routing as a path setup type, it is a prerequisite that the PCC and PCE both include PST=1 in the list of supported path setup types in this TLV and also include the SR-PCE-CAPABILITY sub-TLV.
• When a PCE initiates an LSP, it proposes which path setup type to use by including it in the PATH-SETUP-TYPE TLV in the SRP object of the PCInitiate message. The PCE chooses the path setup type based on the capabilities of the network nodes on the path and on its local policy. The PCC MAY choose to accept the proposed path setup type or to reject the PCInitiate request, based on its local policy.
• When a PCC requests a path for an LSP, it can nominate a preferred path setup type by including it in the PATH-SETUP-TYPE TLV in the RP object of the PCReq message. The PCE MAY choose to reply with a path of the requested type, reply with a path of a different type, or reject the request, based on the capabilities of the network nodes on the path and on its local policy.

• Implementations MUST allow the operator to enable and disable the Segment Routing path setup type on a PCEP-speaking device. Implementations MAY also allow the operator to enable and disable the RSVP-TE path setup type.
• PCE implementations MUST allow the operator to specify that an LSP should be instantiated using Segment Routing or RSVP-TE as the proposed path setup type.
• PCE implementations MAY allow the operator to configure a preference for the PCE to propose paths using Segment Routing or RSVP-TE in the absence of a specified path setup type.
• PCC implementations MUST allow the operator to specify that a path requested for an LSP nominates Segment Routing or RSVP-TE as the path setup type.
• PCC implementations MAY allow the operator to configure a preference for the PCC to nominate Segment Routing or RSVP-TE as the path setup type if none is specified for an LSP.
• PCC implementations SHOULD allow the operator to configure a PCC to refuse to set up an LSP using an undesired path setup type.

• The operator enables the Segment Routing PST on the PCE servers.
• The operator enables the Segment Routing PST on the PCCs.
• The operator resets each PCEP session. The PCEP sessions come back up with Segment Routing enabled.
• If the operator detects a problem, they can roll the network back to its initial state by disabling the Segment Routing PST on the PCEP speakers and resetting the PCEP sessions.

• An implementation SHOULD allow the operator to view whether the PCEP speaker sent the Segment Routing PST capability to its peer. If the PCEP speaker is a PCC, then the implementation SHOULD also allow the operator to view the values of the L-Flag and N-Flag that were sent and the value of the MSD field that was sent.
• An implementation SHOULD allow the operator to view whether the peer sent the Segment Routing PST capability. If the peer is a PCC, then the implementation SHOULD also allow the operator to view the values of the L-Flag and N-Flag and MSD fields that the peer sent.
• An implementation SHOULD allow the operator to view whether the Segment Routing PST is enabled on the PCEP session.
• If one PCEP speaker advertises the Segment Routing PST capability, but the other does not, then the implementation SHOULD create a log to inform the operator of the capability mismatch.
• An implementation SHOULD allow the operator to view the PST that was proposed, or requested, for an LSP and the PST that was actually used.
• If a PCEP speaker decides to use a different PST to the one that was proposed, or requested, for an LSP, then the implementation SHOULD create a log to inform the operator that the expected PST has not been used. The log SHOULD give the reason for this choice (local policy, equipment capability, etc.).
• If a PCEP speaker rejects a Segment Routing path, then it SHOULD create a log to inform the operator, giving the reason for the decision (local policy, MSD exceeded, etc.).

• The advertised PST capabilities and MSD per PCEP session.
• The PST configured for, and used by, each LSP.

• Bit number (counting from bit 0 as the most significant bit)
• Capability description
• Defining RFC

• Bit number (counting from bit 0 as the most significant bit)
• Capability description
• Defining RFC

[RFC2119]

S. Bradner, "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>.

[RFC3032]

E. Rosen, D. Tappan, G. Fedorkow, Y. Rekhter, D. Farinacci, T. Li, and A. Conta, "MPLS Label Stack Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<https://www.rfc-editor.org/info/rfc3032>.

[RFC5440]

JP. Vasseur, and JL. Le Roux, "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.

[RFC8174]

B. Leiba, "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017,
<https://www.rfc-editor.org/info/rfc8174>.

[RFC8231]

E. Crabbe, I. Minei, J. Medved, and R. Varga, "Path Computation Element Communication Protocol (PCEP) Extensions for Stateful PCE", RFC 8231, DOI 10.17487/RFC8231, September 2017,
<https://www.rfc-editor.org/info/rfc8231>.

[RFC8281]

E. Crabbe, I. Minei, S. Sivabalan, and R. Varga, "Path Computation Element Communication Protocol (PCEP) Extensions for PCE-Initiated LSP Setup in a Stateful PCE Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
<https://www.rfc-editor.org/info/rfc8281>.

[RFC8402]

C. Filsfils, S. Previdi, L. Ginsberg, B. Decraene, S. Litkowski, and R. Shakir, "Segment Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, July 2018,
<https://www.rfc-editor.org/info/rfc8402>.

[RFC8408]

S. Sivabalan, J. Tantsura, I. Minei, R. Varga, and J. Hardwick, "Conveying Path Setup Type in PCE Communication Protocol (PCEP) Messages", RFC 8408, DOI 10.17487/RFC8408, July 2018,
<https://www.rfc-editor.org/info/rfc8408>.

[RFC8491]

J. Tantsura, U. Chunduri, S. Aldrin, and L. Ginsberg, "Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491, DOI 10.17487/RFC8491, November 2018,
<https://www.rfc-editor.org/info/rfc8491>.

[RFC8660]

A Bashandy, C Filsfils, S Previdi, B Decraene, S Litkowski, and R Shakir, "Segment Routing with the MPLS Data Plane", RFC 8660, DOI 10.17487/RFC8660, December 2019,
<https://www.rfc-editor.org/info/rfc8660>.

[IPv6-SRH]

C Filsfils, D Dukes, S Previdi, J Leddy, S Matsushima, and D Voyer, "IPv6 Segment Routing Header (SRH)", Internet-Draft draft-ietf-6man-segment-routing-header-26, October 2019,
<https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header-26>.

[MSD-BGP]

J Tantsura, U Chunduri, K Talaulikar, G Mirsky, and N Triantafillis, "Signaling MSD (Maximum SID Depth) using Border Gateway Protocol Link-State", Internet-Draft draft-ietf-idr-bgp-ls-segment-routing-msd-09, October 2019,
<https://tools.ietf.org/html/draft-ietf-idr-bgp-ls-segment-routing-msd-09>.

[PCE-PCEP-YANG]

D Dhody, J Hardwick, V Beeram, and J Tantsura, "A YANG Data Model for Path Computation Element Communications Protocol (PCEP)", Internet-Draft draft-ietf-pce-pcep-yang-13, October 2019,
<https://tools.ietf.org/html/draft-ietf-pce-pcep-yang-13>.

[RFC3209]

D. Awduche, L. Berger, D. Gan, T. Li, V. Srinivasan, and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>.

[RFC4657]

J. Ash, and J.L. Le Roux, "Path Computation Element (PCE) Communication Protocol Generic Requirements", RFC 4657, DOI 10.17487/RFC4657, September 2006,
<https://www.rfc-editor.org/info/rfc4657>.

[RFC7420]

A. Koushik, E. Stephan, Q. Zhao, D. King, and J. Hardwick, "Path Computation Element Communication Protocol (PCEP) Management Information Base (MIB) Module", RFC 7420, DOI 10.17487/RFC7420, December 2014,
<https://www.rfc-editor.org/info/rfc7420>.

[RFC8126]

M. Cotton, B. Leiba, 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>.

[RFC8413]

Y. Zhuang, Q. Wu, H. Chen, and A. Farrel, "Framework for Scheduled Use of Resources", RFC 8413, DOI 10.17487/RFC8413, July 2018,
<https://www.rfc-editor.org/info/rfc8413>.

[RFC8476]

J. Tantsura, U. Chunduri, S. Aldrin, and P. Psenak, "Signaling Maximum SID Depth (MSD) Using OSPF", RFC 8476, DOI 10.17487/RFC8476, December 2018,
<https://www.rfc-editor.org/info/rfc8476>.

[RFC8665]

P Psenak, S Previdi, C Filsfils, H Gredler, R Shakir, W Henderickx, and J Tantsura, "OSPF Extensions for Segment Routing", RFC 8665, DOI 10.17487/RFC8665, December 2019,
<https://www.rfc-editor.org/info/rfc8665>.

[RFC8667]

S Previdi, L Ginsberg, C Filsfils, A Bashandy, H Gredler, and B Decraene, "IS-IS Extensions for Segment Routing", RFC 8667, DOI 10.17487/RFC8667, December 2019,
<https://www.rfc-editor.org/info/rfc8667>.

[SR-POLICY]

C Filsfils, S Sivabalan, D Voyer, A Bogdanov, and P Mattes, "Segment Routing Policy Architecture", Internet-Draft draft-ietf-spring-segment-routing-policy-05, November 2019,
<https://tools.ietf.org/html/draft-ietf-spring-segment-routing-policy-05>.

• Lakshmi Sharma
• Jan Medved
• Edward Crabbe
• Robert Raszuk
• Victor Lopez

Siva Sivabalan

Clarence Filsfils

Jeff Tantsura

Wim Henderickx

Jon Hardwick