< draft-ietf-pce-segment-routing-14.txt   draft-ietf-pce-segment-routing-15.txt >
PCE S. Sivabalan PCE S. Sivabalan
Internet-Draft C. Filsfils Internet-Draft C. Filsfils
Intended status: Standards Track Cisco Systems, Inc. Updates: 8408 (if approved) Cisco Systems, Inc.
Expires: April 16, 2019 J. Tantsura Intended status: Standards Track J. Tantsura
Apstra, Inc. Expires: August 16, 2019 Apstra, Inc.
W. Henderickx W. Henderickx
Nokia Nokia
J. Hardwick J. Hardwick
Metaswitch Networks Metaswitch Networks
October 13, 2018 February 12, 2019
PCEP Extensions for Segment Routing PCEP Extensions for Segment Routing
draft-ietf-pce-segment-routing-14 draft-ietf-pce-segment-routing-15
Abstract Abstract
Segment Routing (SR) enables any head-end node to select any path Segment Routing (SR) enables any head-end node to select any path
without relying on a hop-by-hop signaling technique (e.g., LDP or without relying on a hop-by-hop signaling technique (e.g., LDP or
RSVP-TE). It depends only on "segments" that are advertised by Link- RSVP-TE). It depends only on "segments" that are advertised by link-
State Interior Gateway Protocols (IGPs). A Segment Routed Path can state Interior Gateway Protocols (IGPs). A Segment Routing Path can
be derived from a variety of mechanisms, including an IGP Shortest be derived from a variety of mechanisms, including an IGP Shortest
Path Tree (SPT), explicit configuration, or a Path Computation Path Tree (SPT), explicit configuration, or a Path Computation
Element (PCE). This document specifies extensions to the Path Element (PCE). This document specifies extensions to the Path
Computation Element Communication Protocol (PCEP) that allow a Computation Element Communication Protocol (PCEP) that allow a
stateful PCE to compute and initiate Traffic Engineering (TE) paths, stateful PCE to compute and initiate Traffic Engineering (TE) paths,
as well as a PCC to request a path subject to certain constraints and as well as a PCC to request a path subject to certain constraints and
optimization criteria in SR networks. optimization criteria in SR networks.
Requirements Language Requirements Language
skipping to change at page 2, line 10 skipping to change at page 2, line 10
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material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 16, 2019. This Internet-Draft will expire on August 16, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Overview of PCEP Operation in SR Networks . . . . . . . . . . 5 3. Overview of PCEP Operation in SR Networks . . . . . . . . . . 5
4. SR-Specific PCEP Message Extensions . . . . . . . . . . . . . 7 4. Object Formats . . . . . . . . . . . . . . . . . . . . . . . 7
5. Object Formats . . . . . . . . . . . . . . . . . . . . . . . 7 4.1. The OPEN Object . . . . . . . . . . . . . . . . . . . . . 7
5.1. The OPEN Object . . . . . . . . . . . . . . . . . . . . . 7 4.1.1. The Path Setup Type Capability TLV . . . . . . . . . 7
5.1.1. The SR PCE Capability sub-TLV . . . . . . . . . . . . 7 4.1.2. The SR PCE Capability sub-TLV . . . . . . . . . . . . 8
5.2. The RP/SRP Object . . . . . . . . . . . . . . . . . . . . 8 4.2. The RP/SRP Object . . . . . . . . . . . . . . . . . . . . 9
5.3. ERO . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.3. ERO . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.3.1. SR-ERO Subobject . . . . . . . . . . . . . . . . . . 9 4.3.1. SR-ERO Subobject . . . . . . . . . . . . . . . . . . 9
5.3.2. NAI Associated with SID . . . . . . . . . . . . . . . 11 4.3.2. NAI Associated with SID . . . . . . . . . . . . . . . 12
5.4. RRO . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.4. RRO . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.5. METRIC Object . . . . . . . . . . . . . . . . . . . . . . 13 4.5. METRIC Object . . . . . . . . . . . . . . . . . . . . . . 14
6. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 14 5. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.1. Exchanging the SR PCE Capability . . . . . . . . . . . . 14 5.1. Exchanging the SR PCE Capability . . . . . . . . . . . . 14
6.2. ERO Processing . . . . . . . . . . . . . . . . . . . . . 15 5.2. ERO Processing . . . . . . . . . . . . . . . . . . . . . 16
6.2.1. SR-ERO Validation . . . . . . . . . . . . . . . . . . 15 5.2.1. SR-ERO Validation . . . . . . . . . . . . . . . . . . 16
6.2.2. Interpreting the SR-ERO . . . . . . . . . . . . . . . 17 5.2.2. Interpreting the SR-ERO . . . . . . . . . . . . . . . 18
6.3. RRO Processing . . . . . . . . . . . . . . . . . . . . . 19 5.3. RRO Processing . . . . . . . . . . . . . . . . . . . . . 20
7. Backward Compatibility . . . . . . . . . . . . . . . . . . . 19 6. Backward Compatibility . . . . . . . . . . . . . . . . . . . 20
8. Management Considerations . . . . . . . . . . . . . . . . . . 20 7. Management Considerations . . . . . . . . . . . . . . . . . . 21
8.1. Controlling the Path Setup Type . . . . . . . . . . . . . 20 7.1. Controlling the Path Setup Type . . . . . . . . . . . . . 21
8.2. Migrating a Network to Use PCEP Segment Routed Paths . . 21 7.2. Migrating a Network to Use PCEP Segment Routed Paths . . 22
8.3. Verification of Network Operation . . . . . . . . . . . . 22 7.3. Verification of Network Operation . . . . . . . . . . . . 23
8.4. Relationship to Existing Management Models . . . . . . . 23 7.4. Relationship to Existing Management Models . . . . . . . 24
9. Security Considerations . . . . . . . . . . . . . . . . . . . 23 8. Security Considerations . . . . . . . . . . . . . . . . . . . 24
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
10.1. PCEP ERO and RRO subobjects . . . . . . . . . . . . . . 24 9.1. PCEP ERO and RRO subobjects . . . . . . . . . . . . . . . 25
10.2. New NAI Type Registry . . . . . . . . . . . . . . . . . 24 9.2. New NAI Type Registry . . . . . . . . . . . . . . . . . . 25
10.3. New SR-ERO Flag Registry . . . . . . . . . . . . . . . . 24 9.3. New SR-ERO Flag Registry . . . . . . . . . . . . . . . . 25
10.4. PCEP-Error Object . . . . . . . . . . . . . . . . . . . 25 9.4. PCEP-Error Object . . . . . . . . . . . . . . . . . . . . 26
10.5. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 26 9.5. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 27
10.6. New Path Setup Type . . . . . . . . . . . . . . . . . . 26 9.6. PATH-SETUP-TYPE-CAPABILITY Sub-TLV Type Indicators . . . 27
10.7. New Metric Type . . . . . . . . . . . . . . . . . . . . 27 9.7. New Path Setup Type . . . . . . . . . . . . . . . . . . . 28
10.8. SR PCE Capability Flags . . . . . . . . . . . . . . . . 27 9.8. New Metric Type . . . . . . . . . . . . . . . . . . . . . 28
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 27 9.9. SR PCE Capability Flags . . . . . . . . . . . . . . . . . 28
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 28 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 29
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 28 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 29
13.1. Normative References . . . . . . . . . . . . . . . . . . 28 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 29
13.2. Informative References . . . . . . . . . . . . . . . . . 29 12.1. Normative References . . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30 12.2. Informative References . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
1. Introduction 1. Introduction
Segment Routing (SR) leverages the source routing paradigm. Using Segment Routing (SR) leverages the source routing paradigm. Using
SR, a source node steers a packet through a path without relying on SR, a source node steers a packet through a path without relying on
hop-by-hop signaling protocols such as LDP or RSVP-TE. Each path is hop-by-hop signaling protocols such as LDP or RSVP-TE. Each path is
specified as an ordered list of instructions called "segments". Each specified as an ordered list of instructions called "segments". Each
segment is an instruction to route the packet to a specific place in segment is an instruction to route the packet to a specific place in
the network, or to perform a specific service on the packet. A the network, or to perform a function on the packet. A database of
database of segments can be distributed through the network using a segments can be distributed through the network using a routing
routing protocol (such as IS-IS or OSPF) or by any other means. protocol (such as IS-IS or OSPF) or by any other means. Several
Several types of segment are defined. A node segment represents an types of segment are defined. A node segment uniquely identifies a
ECMP-aware shortest-path to a specific node, and is always identified specific node in the SR domain. Each router in the SR domain
uniquely within the SR/IGP domain. An adjacency segment represents a associates a node segment with an ECMP-aware shortest path to the
node that it identifies. An adjacency segment represents a
unidirectional adjacency. An adjacency segment is local to the node unidirectional adjacency. An adjacency segment is local to the node
which advertises it. Both node segments and adjacency segments can which advertises it. Both node segments and adjacency segments can
be used for SR Traffic Engineering (SR-TE). be used for SR.
[RFC8402] describes the SR architecture. The corresponding IS-IS and [RFC8402] describes the SR architecture. The corresponding IS-IS and
OSPF extensions are specified in OSPF extensions are specified in
[I-D.ietf-isis-segment-routing-extensions] and [I-D.ietf-isis-segment-routing-extensions] and
[I-D.ietf-ospf-segment-routing-extensions], respectively. [I-D.ietf-ospf-segment-routing-extensions], respectively.
The SR architecture can be implemented using either an MPLS The SR architecture can be implemented using either an MPLS
forwarding plane [I-D.ietf-spring-segment-routing-mpls] or an IPv6 forwarding plane [I-D.ietf-spring-segment-routing-mpls] or an IPv6
forwarding plane [I-D.ietf-6man-segment-routing-header]. The MPLS forwarding plane [I-D.ietf-6man-segment-routing-header]. The MPLS
forwarding plane can be applied to SR without any change, in which forwarding plane can be applied to SR without any change, in which
case an SR path corresponds to an MPLS Label Switching Path (LSP). case an SR path corresponds to an MPLS Label Switching Path (LSP).
This document is relevant to the MPLS forwarding plane only. In this This document is relevant to the MPLS forwarding plane only. In this
document, "Node-SID" and "Adjacency-SID" denote Node Segment document, "Node-SID" and "Adjacency-SID" denote Node Segment
Identifier and Adjacency Segment Identifier respectively. Identifier and Adjacency Segment Identifier respectively.
A Segment Routed path (SR path) can be derived from an IGP Shortest A Segment Routing path (SR path) can be derived from an IGP Shortest
Path Tree (SPT). SR-TE paths may not follow an IGP SPT. Such paths Path Tree (SPT). SR-TE paths may not follow an IGP SPT. Such paths
may be chosen by a suitable network planning tool and provisioned on may be chosen by a suitable network planning tool and provisioned on
the ingress node of the SR-TE path. the ingress node of the SR-TE path.
[RFC5440] describes the Path Computation Element Communication [RFC5440] describes the Path Computation Element Communication
Protocol (PCEP) for communication between a Path Computation Client Protocol (PCEP) for communication between a Path Computation Client
(PCC) and a Path Computation Element (PCE) or between a pair of PCEs. (PCC) and a Path Computation Element (PCE) or between a pair of PCEs.
A PCE computes paths for MPLS Traffic Engineering LSPs (MPLS-TE LSPs) A PCE computes paths for MPLS Traffic Engineering LSPs (MPLS-TE LSPs)
based on various constraints and optimization criteria. [RFC8231] based on various constraints and optimization criteria. [RFC8231]
specifies extensions to PCEP that allow a stateful PCE to compute and specifies extensions to PCEP that allow a stateful PCE to compute and
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pair of PCEs, delegation of LSP control, reporting of LSP state from pair of PCEs, delegation of LSP control, reporting of LSP state from
a PCC to a PCE, controlling the setup and path routing of an LSP from a PCC to a PCE, controlling the setup and path routing of an LSP from
a PCE to a PCC. Stateful PCEP extensions are intended for an a PCE to a PCC. Stateful PCEP extensions are intended for an
operational model in which LSPs are configured on the PCC, and operational model in which LSPs are configured on the PCC, and
control over them is delegated to the PCE. control over them is delegated to the PCE.
A mechanism to dynamically initiate LSPs on a PCC based on the A mechanism to dynamically initiate LSPs on a PCC based on the
requests from a stateful PCE or a controller using stateful PCE is requests from a stateful PCE or a controller using stateful PCE is
specified in [RFC8281]. This mechanism is useful in Software Defined specified in [RFC8281]. This mechanism is useful in Software Defined
Networking (SDN) applications, such as on-demand engineering, or Networking (SDN) applications, such as on-demand engineering, or
bandwidth calendaring. bandwidth calendaring [RFC8413].
It is possible to use a stateful PCE for computing one or more SR-TE It is possible to use a stateful PCE for computing one or more SR-TE
paths taking into account various constraints and objective paths taking into account various constraints and objective
functions. Once a path is chosen, the stateful PCE can initiate an functions. Once a path is chosen, the stateful PCE can initiate an
SR-TE path on a PCC using PCEP extensions specified in [RFC8281] SR-TE path on a PCC using PCEP extensions specified in [RFC8281]
using the SR specific PCEP extensions specified in this document. using the SR specific PCEP extensions specified in this document.
Additionally, using procedures described in this document, a PCC can Additionally, using procedures described in this document, a PCC can
request an SR path from either a stateful or a stateless PCE. request an SR path from either a stateful or a stateless PCE.
This specification relies on the procedures specified in [RFC8408] to This specification relies on the procedures specified in [RFC8408] to
exchange the segment routing capability and to specify that the path exchange the segment routing capability and to specify that the path
setup type of an LSP is segment routing. setup type of an LSP is segment routing. This specification also
updates [RFC8408] to clarify the use of sub-TLVs in the PATH-SETUP-
TYPE-CAPABILITY TLV. See Section 4.1.1 for details.
This specification provides a mechanism for a network controller This specification provides a mechanism for a network controller
(acting as a PCE) to instantiate candidate paths for an SR Policy (acting as a PCE) to instantiate candidate paths for an SR Policy
onto a head-end node (acting as a PCC) using PCEP. For more onto a head-end node (acting as a PCC) using PCEP. For more
information on the SR Policy Architecture, see information on the SR Policy Architecture, see
[I-D.ietf-spring-segment-routing-policy]. [I-D.ietf-spring-segment-routing-policy].
2. Terminology 2. Terminology
The following terminologies are used in this document: The following terminologies are used in this document:
ERO: Explicit Route Object ERO: Explicit Route Object
IGP: Interior Gateway Protocol IGP: Interior Gateway Protocol
IS-IS: Intermediate System to Intermediate System IS-IS: Intermediate System to Intermediate System
LSR: Label Switching Router LSR: Label Switching Router
MSD: Maximum SID Depth MSD: Base MPLS Imposition Maximum SID Depth, as defined in [RFC8491]
NAI: Node or Adjacency Identifier NAI: Node or Adjacency Identifier
OSPF: Open Shortest Path First OSPF: Open Shortest Path First
PCC: Path Computation Client PCC: Path Computation Client
PCE: Path Computation Element PCE: Path Computation Element
PCEP: Path Computation Element Communication Protocol PCEP: Path Computation Element Communication Protocol
RRO: Record Route Object RRO: Record Route Object
SID: Segment Identifier SID: Segment Identifier
SR: Segment Routing SR: Segment Routing
SR-DB: Segment Routing Database (as defined in SR-DB: Segment Routing Database: the collection of SRGBs, SRLBs and
[I-D.ietf-spring-segment-routing-policy]) SIDs and the objects they map to, advertised by a link state IGP
SRGB: Segment Routing Global Block
SRLB: Segment Routing Local Block
SR-TE: Segment Routing Traffic Engineering SR-TE: Segment Routing Traffic Engineering
3. Overview of PCEP Operation in SR Networks 3. Overview of PCEP Operation in SR Networks
In an SR network, the ingress node of an SR path prepends an SR In an SR network, the ingress node of an SR path prepends an SR
header to all outgoing packets. The SR header consists of a list of header to all outgoing packets. The SR header consists of a list of
SIDs (or MPLS labels in the context of this document). The header SIDs (or MPLS labels in the context of this document). The header
has all necessary information so that, in combination with the has all necessary information so that, in combination with the
information distributed by the IGP, the packets can be guided from information distributed by the IGP, the packets can be guided from
the ingress node to the egress node of the path; hence, there is no the ingress node to the egress node of the path; hence, there is no
need for any signaling protocol. need for any signaling protocol.
In PCEP messages, LSP route information is carried in the Explicit In PCEP messages, LSP route information is carried in the Explicit
Route Object (ERO), which consists of a sequence of subobjects. In Route Object (ERO), which consists of a sequence of subobjects. SR-
SR networks, an ingress node of an SR path prepends an SR header to TE paths computed by a PCE can be represented in an ERO in one of the
all outgoing packets. The SR header consists of a list of SIDs (or following forms:
MPLS labels in the context of this document). SR-TE paths computed
by a PCE can be represented in an ERO in one of the following forms:
o An ordered set of IP addresses representing network nodes/links. o An ordered set of IP addresses representing network nodes/links.
o An ordered set of SIDs, with or without the corresponding IP o An ordered set of SIDs, with or without the corresponding IP
addresses. addresses.
o An ordered set of MPLS labels, with or without corresponding IP o An ordered set of MPLS labels, with or without corresponding IP
address. address.
The PCC converts these into an MPLS label stack and next hop, as The PCC converts these into an MPLS label stack and next hop, as
described in Section 6.2.2. described in Section 5.2.2.
This document defines a new ERO subobject denoted by "SR-ERO This document defines a new ERO subobject denoted by "SR-ERO
subobject" capable of carrying a SID as well as the identity of the subobject" capable of carrying a SID as well as the identity of the
node/adjacency represented by the SID. SR-capable PCEP speakers node/adjacency represented by the SID. SR-capable PCEP speakers
should be able to generate and/or process such ERO subobject. An ERO should be able to generate and/or process such ERO subobject. An ERO
containing SR-ERO subobjects can be included in the PCEP Path containing SR-ERO subobjects can be included in the PCEP Path
Computation Reply (PCRep) message defined in [RFC5440], the PCEP LSP Computation Reply (PCRep) message defined in [RFC5440], the PCEP LSP
Initiate Request message (PCInitiate) defined in [RFC8281], as well Initiate Request message (PCInitiate) defined in [RFC8281], as well
as in the PCEP LSP Update Request (PCUpd) and PCEP LSP State Report as in the PCEP LSP Update Request (PCUpd) and PCEP LSP State Report
(PCRpt) messages defined in [RFC8231]. (PCRpt) messages defined in [RFC8231].
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o Defines a new path setup type to be used in the PATH-SETUP-TYPE o Defines a new path setup type to be used in the PATH-SETUP-TYPE
and PATH-SETUP-TYPE-CAPABILITY TLVs ([RFC8408]). and PATH-SETUP-TYPE-CAPABILITY TLVs ([RFC8408]).
o Defines a new sub-TLV for the PATH-SETUP-TYPE-CAPABILITY TLV. o Defines a new sub-TLV for the PATH-SETUP-TYPE-CAPABILITY TLV.
The extensions specified in this document complement the existing The extensions specified in this document complement the existing
PCEP specifications to support SR-TE paths. As such, the PCEP PCEP specifications to support SR-TE paths. As such, the PCEP
messages (e.g., Path Computation Request, Path Computation Reply, messages (e.g., Path Computation Request, Path Computation Reply,
Path Computation Report, Path Computation Update, Path Computation Path Computation Report, Path Computation Update, Path Computation
Initiate, etc.,) MUST be formatted according to [RFC5440], [RFC8231], Initiate, etc.,) are formatted according to [RFC5440], [RFC8231],
[RFC8281], and any other applicable PCEP specifications. [RFC8281], and any other applicable PCEP specifications.
4. SR-Specific PCEP Message Extensions 4. Object Formats
As defined in [RFC5440], a PCEP message consists of a common header 4.1. The OPEN Object
followed by a variable length body made up of mandatory and/or
optional objects. This document does not require any changes in the
format of the PCReq and PCRep messages specified in [RFC5440],
PCInitiate message specified in [RFC8281], and PCRpt and PCUpd
messages specified in [RFC8231].
5. Object Formats 4.1.1. The Path Setup Type Capability TLV
5.1. The OPEN Object [RFC8408] defines the PATH-SETUP-TYPE-CAPABILITY TLV for use in the
OPEN object. The PATH-SETUP-TYPE-CAPABILITY TLV contains an optional
list of sub-TLVs which are intended to convey parameters that are
associated with the path setup types supported by a PCEP speaker.
5.1.1. The SR PCE Capability sub-TLV This specification updates [RFC8408], as follows. It creates a new
registry which defines the valid type indicators of the sub-TLVs of
the PATH-SETUP-TYPE-CAPABILITY TLV (see Section 9.6). A PCEP speaker
MUST NOT include a sub-TLV in the PATH-SETUP-TYPE-CAPABILITY TLV
unless it appears in this registry. If a PCEP speaker receives a
sub-TLV whose type indicator does not match one of those from the
registry, or else is not recognised by the speaker, then the speaker
MUST ignore the sub-TLV.
4.1.2. The SR PCE Capability sub-TLV
This document defines a new Path Setup Type (PST) for SR, as follows: This document defines a new Path Setup Type (PST) for SR, as follows:
o PST = 1: Path is setup using Segment Routing Traffic Engineering. o PST = 1: Path is setup using Segment Routing Traffic Engineering.
A PCEP speaker SHOULD indicate its support of the function described A PCEP speaker SHOULD indicate its support of the function described
in this document by sending a PATH-SETUP-TYPE-CAPABILITY TLV in the in this document by sending a PATH-SETUP-TYPE-CAPABILITY TLV in the
OPEN object with this new PST included in the PST list. OPEN object with this new PST included in the PST list.
This document also defines the SR-PCE-CAPABILITY sub-TLV. PCEP This document also defines the SR-PCE-CAPABILITY sub-TLV. PCEP
skipping to change at page 8, line 17 skipping to change at page 8, line 27
capability. If a PCEP speaker includes PST=1 in the PST List of the capability. If a PCEP speaker includes PST=1 in the PST List of the
PATH-SETUP-TYPE-CAPABILITY TLV then it MUST also include the SR-PCE- PATH-SETUP-TYPE-CAPABILITY TLV then it MUST also include the SR-PCE-
CAPABILITY sub-TLV inside the PATH-SETUP-TYPE-CAPABILITY TLV. CAPABILITY sub-TLV inside the PATH-SETUP-TYPE-CAPABILITY TLV.
The format of the SR-PCE-CAPABILITY sub-TLV is shown in the following The format of the SR-PCE-CAPABILITY sub-TLV is shown in the following
figure: figure:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 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 | | Type=TBD11 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Flags |N|L| MSD | | Reserved | Flags |N|X| MSD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: SR-PCE-CAPABILITY sub-TLV format Figure 1: SR-PCE-CAPABILITY sub-TLV format
The code point for the TLV type is 26. The TLV length is 4 octets. The code point for the TLV type is TBD11. The TLV length is 4
octets.
The 32-bit value is formatted as follows. The 32-bit value is formatted as follows.
Reserved: MUST be set to zero by the sender and MUST be ignored by Reserved: MUST be set to zero by the sender and MUST be ignored by
the receiver. the receiver.
Flags: This document defines the following flag bits. The other 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 bits MUST be set to zero by the sender and MUST be ignored by the
receiver. receiver.
* N: A PCC sets this bit to 1 to indicate that it is capable of * N: A PCC sets this flag bit to 1 to indicate that it is capable
resolving a Node or Adjacency Identifier (NAI) to a SID. of resolving a Node or Adjacency Identifier (NAI) to a SID.
* L: A PCC sets this bit to 1 to indicate that it does not impose * X: A PCC sets this flag bit to 1 to indicate that it does not
any limit on the MSD. impose any limit on the MSD.
Maximum SID Depth (MSD): specifies the maximum number of SIDs (MPLS Maximum SID Depth (MSD): specifies the maximum number of SIDs (MPLS
label stack depth in the context of this document) that a PCC is label stack depth in the context of this document) that a PCC is
capable of imposing on a packet. Section 6.1 explains the capable of imposing on a packet. Section 5.1 explains the
relationship between this field and the L bit. relationship between this field and the X flag.
5.2. The RP/SRP Object 4.2. The RP/SRP Object
To set up an SR-TE LSP using SR, the RP or SRP object MUST include To set up an SR-TE LSP using SR, the RP (Request Parameters) or SRP
the PATH-SETUP-TYPE TLV, specified in [RFC8408], with the PST set to (Stateful PCE Request Parameters) object MUST include the PATH-SETUP-
1 (path setup using SR-TE). TYPE TLV, specified in [RFC8408], with the PST set to 1 (path setup
using SR-TE).
The LSP-IDENTIFIERS TLV MAY be present for the above PST type. The LSP-IDENTIFIERS TLV MAY be present for the above PST type.
5.3. ERO 4.3. ERO
An SR-TE path consists of one or more SIDs where each SID MAY be An SR-TE path consists of one or more SIDs where each SID MAY be
associated with the identifier that represents the node or adjacency associated with the identifier that represents the node or adjacency
corresponding to the SID. This identifier is referred to as the corresponding to the SID. This identifier is referred to as the
'Node or Adjacency Identifier' (NAI). As described later, a NAI can 'Node or Adjacency Identifier' (NAI). As described later, a NAI can
be represented in various formats (e.g., IPv4 address, IPv6 address, be represented in various formats (e.g., IPv4 address, IPv6 address,
etc). Furthermore, a NAI is used for troubleshooting purposes and, etc). Furthermore, a NAI is used for troubleshooting purposes and,
if necessary, to derive SID value as described below. if necessary, to derive SID value as described below.
The ERO specified in [RFC5440] is used to carry SR-TE path The ERO specified in [RFC5440] is used to carry SR-TE path
skipping to change at page 9, line 31 skipping to change at page 9, line 43
consists of one or more ERO subobjects, and MUST carry only SR-ERO consists of one or more ERO subobjects, and MUST carry only SR-ERO
subobjects. Note that an SR-ERO subobject does not need to have both subobjects. Note that an SR-ERO subobject does not need to have both
SID and NAI. However, at least one of them MUST be present. SID and NAI. However, at least one of them MUST be present.
When building the MPLS label stack from ERO, a PCC MUST assume that When building the MPLS label stack from ERO, a PCC MUST assume that
SR-ERO subobjects are organized as a last-in-first-out stack. The SR-ERO subobjects are organized as a last-in-first-out stack. The
first subobject relative to the beginning of ERO contains the first subobject relative to the beginning of ERO contains the
information about the topmost label. The last subobject contains information about the topmost label. The last subobject contains
information about the bottommost label. information about the bottommost label.
5.3.1. SR-ERO Subobject 4.3.1. SR-ERO Subobject
An SR-ERO subobject is formatted as shown in the following diagram. An SR-ERO subobject is formatted as shown in the following diagram.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 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| |L| Type=36 | Length | NT | Flags |F|S|C|M|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (optional) | | SID (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 10, line 4 skipping to change at page 10, line 22
// NAI (variable, optional) // // NAI (variable, optional) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: SR-ERO subobject format Figure 2: SR-ERO subobject format
The fields in the SR-ERO Subobject are as follows: The fields in the SR-ERO Subobject are as follows:
The 'L' Flag: Indicates whether the subobject represents a loose-hop The 'L' Flag: Indicates whether the subobject represents a loose-hop
in the LSP [RFC3209]. If this flag is set to zero, a PCC MUST NOT in the LSP [RFC3209]. If this flag is set to zero, a PCC MUST NOT
overwrite the SID value present in the SR-ERO subobject. overwrite the SID value present in the SR-ERO subobject.
Otherwise, a PCC MAY expand or replace one or more SID values in Otherwise, a PCC MAY expand or replace one or more SID values in
the received SR-ERO based on its local policy. the received SR-ERO based on its local policy.
Type: Set to 36. Type: Set to 36.
Length: Contains the total length of the subobject in octets, Length: Contains the total length of the subobject in octets. The
including the L, Type and Length fields. The Length MUST be at Length MUST be at least 8, and MUST be a multiple of 4. An SR-ERO
least 8, and MUST be a multiple of 4. An SR-ERO subobject MUST subobject MUST contain at least one of a SID or an NAI. The flags
contain at least one of a SID or an NAI. The length should described below indicate whether the SID or NAI fields are absent.
include the SID and NAI fields if and only if they are not absent.
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 NAI Type (NT): Indicates the type and format of the NAI contained in
the object body. This document describes the following NT values: 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=0 The NAI is absent.
NT=1 The NAI is an IPv4 node ID. NT=1 The NAI is an IPv4 node ID.
NT=2 The NAI is an IPv6 node ID. NT=2 The NAI is an IPv6 node ID.
NT=3 The NAI is an IPv4 adjacency. NT=3 The NAI is an IPv4 adjacency.
NT=4 The NAI is an IPv6 adjacency. NT=4 The NAI is an IPv6 adjacency.
skipping to change at page 11, line 25 skipping to change at page 11, line 41
body is absent. The F bit MUST be set to 1 if NT=0, and body is absent. The F bit MUST be set to 1 if NT=0, and
otherwise MUST be set to zero. The S and F bits MUST NOT both otherwise MUST be set to zero. The S and F bits MUST NOT both
be set to 1. be set to 1.
SID: The Segment Identifier. Depending on the M bit, it contains SID: The Segment Identifier. Depending on the M bit, it contains
either: either:
* A 4 octet index defining the offset into an MPLS label space * A 4 octet index defining the offset into an MPLS label space
per [RFC8402]. per [RFC8402].
* A 4 octet MPLS label, where the 20 most significant bits encode * A 4 octet MPLS Label Stack Entry, where the 20 most significant
the label value per [RFC3032]. bits encode the label value per [RFC3032].
NAI: The NAI associated with the SID. The NAI's format depends on 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 the value in the NT field, and is described in the following
section. section.
At least one of the SID and the NAI MUST be included in the SR-ERO At least one of the SID and the NAI MUST be included in the SR-ERO
subobject, and both MAY be included. subobject, and both MAY be included.
5.3.2. NAI Associated with SID 4.3.2. NAI Associated with SID
This document defines the following NAIs: This document defines the following NAIs:
'IPv4 Node ID' is specified as an IPv4 address. In this case, the 'IPv4 Node ID' is specified as an IPv4 address. In this case, the
NT value is 1 and the NAI field length is 4 octets. NT value is 1 and the NAI field length is 4 octets.
'IPv6 Node ID' is specified as an IPv6 address. In this case, the 'IPv6 Node ID' is specified as an IPv6 address. In this case, the
NT value is 2 and the NAI field length is 16 octets. NT value is 2 and the NAI field length is 16 octets.
'IPv4 Adjacency' is specified as a pair of IPv4 addresses. In this 'IPv4 Adjacency' is specified as a pair of IPv4 addresses. In this
skipping to change at page 12, line 48 skipping to change at page 13, line 19
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface ID | | Local Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Node-ID | | Remote Node-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface ID | | Remote Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: NAI for Unnumbered adjacency with IPv4 Node IDs Figure 5: NAI for Unnumbered adjacency with IPv4 Node IDs
5.4. RRO 4.4. RRO
A PCC reports an SR-TE LSP to a PCE by sending a PCRpt message, per A PCC reports an SR-TE LSP to a PCE by sending a PCRpt message, per
[RFC8231]. The RRO on this message represents the SID list that was [RFC8231]. The RRO on this message represents the SID list that was
applied by the PCC, that is, the actual path taken by the LSP. The applied by the PCC, that is, the actual path taken by the LSP. The
procedures of [RFC8231] with respect to the RRO apply equally to this procedures of [RFC8231] with respect to the RRO apply equally to this
specification without change. specification without change.
An RRO contains one or more subobjects called "SR-RRO subobjects" An RRO contains one or more subobjects called "SR-RRO subobjects"
whose format is shown below: whose format is shown below:
skipping to change at page 13, line 30 skipping to change at page 14, line 5
Figure 6: SR-RRO Subobject format Figure 6: SR-RRO Subobject format
The format of the SR-RRO subobject is the same as that of the SR-ERO The format of the SR-RRO subobject is the same as that of the SR-ERO
subobject, but without the L flag. subobject, but without the L flag.
A PCC MUST order the SR-RRO subobjects such that the first subobject A PCC MUST order the SR-RRO subobjects such that the first subobject
relative to the beginning of the RRO identifies the first segment relative to the beginning of the RRO identifies the first segment
visited by the SR-TE LSP, and the last subobject identifies the final visited by the SR-TE LSP, and the last subobject identifies the final
segment of the SR-TE LSP, that is, its endpoint. segment of the SR-TE LSP, that is, its endpoint.
5.5. METRIC Object 4.5. METRIC Object
A PCC MAY request that PCE optimizes an individual path computation A PCC MAY request that PCE optimizes an individual path computation
request to minimize the SID depth of the computed path by using the request to minimize the SID depth of the computed path by using the
METRIC object defined in [RFC5440]. This document defines a new type METRIC object defined in [RFC5440]. This document defines a new type
for the METRIC object to be used for this purpose, as follows: for the METRIC object to be used for this purpose, as follows:
o T = 11: Maximum SID Depth of the requested path. o T = 11: Maximum SID Depth of the requested path.
If the PCC includes a METRIC object of this type on a path If the PCC includes a METRIC object of this type on a path
computation request, then the PCE MUST minimize the SID depth of the computation request, then the PCE minimizes the SID depth of the
computed path. If the B (bound) bit is set to to 1 in the METRIC computed path. If the B (bound) bit is set to to 1 in the METRIC
object, then the PCE MUST NOT return a path whose SID depth exceeds object, then the PCE MUST NOT return a path whose SID depth exceeds
the given metric-value. If the PCC did not set the L bit in its SR- the given metric-value. If the PCC did not set the X flag in its SR-
PCE-CAPABILITY TLV, then it MUST set the B bit to 1. If the PCC set PCE-CAPABILITY TLV, then it MUST set the B bit to 1. If the PCC set
the L bit in its SR-PCE-CAPABILITY TLV, then it MAY set the B bit to the X flag in its SR-PCE-CAPABILITY TLV, then it MAY set the B bit to
1 or zero. 1 or zero.
If a PCEP session is established with a non-zero default MSD value, If a PCEP session is established with a non-zero default MSD value,
then the PCC MUST NOT send an MSD METRIC object with an MSD greater then the PCC MUST NOT send an MSD METRIC object with an MSD greater
than the session's default MSD. If the PCE receives a path than the session's default MSD. If the PCE receives a path
computation request with an MSD METRIC object on such a session that computation request with an MSD METRIC object on such a session that
is greater than the session's default MSD, then it MUST consider the is greater than the session's default MSD, then it MUST consider the
request invalid and send a PCErr with Error-Type = 10 ("Reception of request invalid and send a PCErr with Error-Type = 10 ("Reception of
an invalid object") and Error-Value 9 ("MSD exceeds the default for an invalid object") and Error-Value 9 ("MSD exceeds the default for
the PCEP session"). the PCEP session").
6. Procedures 5. Procedures
6.1. Exchanging the SR PCE Capability 5.1. Exchanging the SR PCE Capability
A PCC indicates that it is capable of supporting the head-end A PCC indicates that it is capable of supporting the head-end
functions for SR-TE LSP by including the SR-PCE-CAPABILITY sub-TLV in functions for SR-TE LSP by including the SR-PCE-CAPABILITY sub-TLV in
the Open message that it sends to a PCE. A PCE indicates that it is the Open message that it sends to a PCE. A PCE indicates that it is
capable of computing SR-TE paths by including the SR-PCE-CAPABILITY capable of computing SR-TE paths by including the SR-PCE-CAPABILITY
sub-TLV in the Open message that it sends to a PCC. sub-TLV in the Open message that it sends to a PCC.
If a PCEP speaker receives a PATH-SETUP-TYPE-CAPABILITY TLV with a If a PCEP speaker receives a PATH-SETUP-TYPE-CAPABILITY TLV with a
PST list containing PST=1, and supports that path setup type, then it PST list containing PST=1, and supports that path setup type, then it
checks for the presence of the SR-PCE-CAPABILITY sub-TLV. If that checks for the presence of the SR-PCE-CAPABILITY sub-TLV. If that
sub-TLV is absent, then the PCEP speaker MUST send a PCErr message sub-TLV is absent, then the PCEP speaker MUST send a PCErr message
with Error-Type 10 (Reception of an invalid object) and Error-Value with Error-Type 10 (Reception of an invalid object) and Error-Value
TBD1 (to be assigned by IANA) (Missing PCE-SR-CAPABILITY sub-TLV) and TBD1 (Missing PCE-SR-CAPABILITY sub-TLV) and MUST then close the PCEP
MUST then close the PCEP session. If a PCEP speaker receives a PATH- session. If a PCEP speaker receives a PATH-SETUP-TYPE-CAPABILITY TLV
SETUP-TYPE-CAPABILITY TLV with a SR-PCE-CAPABILITY sub-TLV, but the with a SR-PCE-CAPABILITY sub-TLV, but the PST list does not contain
PST list does not contain PST=1, then the PCEP speaker MUST ignore PST=1, then the PCEP speaker MUST ignore the SR-PCE-CAPABILITY sub-
the SR-PCE-CAPABILITY sub-TLV. TLV.
If a PCC sets the N flag to 1, then the PCE MAY send an SR-ERO If a PCC sets the N flag to 1, then the PCE MAY send an SR-ERO
subobject containing NAI and no SID (see Section 6.2). Otherwise, subobject containing NAI and no SID (see Section 5.2). Otherwise,
the PCE MUST NOT send an SR-ERO subobject containing NAI and no SID. the PCE MUST NOT send an SR-ERO subobject containing NAI and no SID.
The number of SIDs that can be imposed on a packet depends on the The number of SIDs that can be imposed on a packet depends on the
PCC's data plane's capability. If a PCC sets the L flag to 1 then PCC's data plane's capability. If a PCC sets the X flag to 1 then
the MSD is not used and MUST be set to zero. If a PCE receives an the MSD is not used and MUST be set to zero. If a PCE receives an
SR-PCE-CAPABILITY sub-TLV with the L flag set to 1 then it MUST SR-PCE-CAPABILITY sub-TLV with the X flag set to 1 then it MUST
ignore the MSD field and MUST assume that the sender can impose a SID ignore the MSD field and assumes that the sender can impose a SID
stack of any depth. If a PCC sets the L flag to zero, then it sets stack of any depth. If a PCC sets the X flag to zero, then it sets
the MSD field to the maximum number of SIDs that it can impose on a the MSD field to the maximum number of SIDs that it can impose on a
packet. If a PCE receives an SR-PCE-CAPABILITY sub-TLV with the L packet. In this case, the PCC MUST set the MSD to a number greater
flag and MSD both set to zero then it MUST assume that the PCC is not than zero. If a PCE receives an SR-PCE-CAPABILITY sub-TLV with the X
capable of imposing a SID stack of any depth and hence is not SR-TE flag and MSD both set to zero then it MUST send a PCErr message with
capable, unless it learns a non-zero MSD for the PCC through some Error-Type 10 (Reception of an invalid object) and Error-Value TBD10
other means. (Maximum SID depth must be nonzero) and MUST then close the PCEP
session.
Note that the MSD value exchanged via the SR-PCE-CAPABILITY sub-TLV Note that the MSD value exchanged via the SR-PCE-CAPABILITY sub-TLV
indicates the SID/label imposition limit for the PCC node. However, indicates the SID/label imposition limit for the PCC node. It is
if a PCE learns the MSD value of a PCC node via different means, e.g anticipated that, in many deployments, the PCCs will have network
routing protocols, as specified in: interfaces that are homogeneous with respect to MSD (that is, each
[I-D.ietf-isis-segment-routing-msd]; interface has the same MSD). In such cases, having a per-node MSD on
the PCEP session is sufficient; the PCE SHOULD interpret this to mean
[I-D.ietf-ospf-segment-routing-msd]; that all network interfaces on the PCC have the given MSD. However,
[I-D.ietf-idr-bgp-ls-segment-routing-msd], then it ignores the MSD the PCE MAY also learn a per-node MSD and a per-interface MSD from
value in the SR-PCE-CAPABILITY sub-TLV. Furthermore, whenever a PCE the routing protocols, as specified in: [RFC8491]; [RFC8476];
learns the MSD for a link via different means, it MUST use that value [I-D.ietf-idr-bgp-ls-segment-routing-msd]. If the PCE learns the
for that link regardless of the MSD value exchanged in the SR-PCE- per-node MSD of a PCC from a routing protocol, then it MUST ignore
CAPABILITY sub-TLV. the per-node MSD value in the SR-PCE-CAPABILITY sub-TLV and use the
per-node MSD learned from the routing protocol instead. If the PCE
learns the MSD of a network interface on a PCC from a routing
protocol, then it MUST use the per-interface MSD instead of the MSD
value in the SR-PCE-CAPABILITY sub-TLV when it computes a path that
uses that interface.
Once an SR-capable PCEP session is established with a non-zero MSD Once an SR-capable PCEP session is established with a non-zero MSD
value, the corresponding PCE MUST NOT send SR-TE paths with a number value, the corresponding PCE MUST NOT send SR-TE paths with a number
of SIDs exceeding that MSD value. If a PCC needs to modify the MSD of SIDs exceeding that MSD value. If a PCC needs to modify the MSD
value, it MUST close the PCEP session and re-establish it with the value, it MUST close the PCEP session and re-establish it with the
new MSD value. If a PCEP session is established with a non-zero MSD new MSD value. If a PCEP session is established with a non-zero MSD
value, and the PCC receives an SR-TE path containing more SIDs than value, and the PCC receives an SR-TE path containing more SIDs than
specified in the MSD value, the PCC MUST send a PCErr message with specified in the MSD value, the PCC MUST send a PCErr message with
Error-Type 10 (Reception of an invalid object) and Error-Value 3 Error-Type 10 (Reception of an invalid object) and Error-Value 3
(Unsupported number of Segment ERO subobjects). If a PCEP session is (Unsupported number of Segment ERO subobjects). If a PCEP session is
established with an MSD value of zero, then the PCC MAY specify an established with an MSD value of zero, then the PCC MAY specify an
MSD for each path computation request that it sends to the PCE, by MSD for each path computation request that it sends to the PCE, by
including a "maximum SID depth" metric object on the request, as including a "maximum SID depth" metric object on the request, as
defined in Section 5.5. defined in Section 4.5.
The N flag, L flag and MSD value inside the SR-PCE-CAPABILITY sub-TLV The N flag, X flag and MSD value inside the SR-PCE-CAPABILITY sub-TLV
are meaningful only in the Open message sent from a PCC to a PCE. As are meaningful only in the Open message sent from a PCC to a PCE. As
such, a PCE MUST set the N flag to zero, the L flag to 1 and MSD such, a PCE MUST set the N flag to zero, the X flag to 1 and MSD
value to zero in an outbound message to a PCC. Similarly, a PCC MUST value to zero in an outbound message to a PCC. Similarly, a PCC MUST
ignore any MSD value received from a PCE. If a PCE receives multiple ignore any MSD value received from a PCE. If a PCE receives multiple
SR-PCE-CAPABILITY sub-TLVs in an Open message, it processes only the SR-PCE-CAPABILITY sub-TLVs in an Open message, it processes only the
first sub-TLV received. first sub-TLV received.
6.2. ERO Processing 5.2. ERO Processing
6.2.1. SR-ERO Validation 5.2.1. SR-ERO Validation
If a PCC does not support the SR PCE Capability and thus cannot If a PCC does not support the SR PCE Capability and thus cannot
recognize the SR-ERO or SR-RRO subobjects, it will respond according recognize the SR-ERO or SR-RRO subobjects, it will respond according
to the rules for a malformed object per [RFC5440]. to the rules for a malformed object per [RFC5440].
On receiving an SR-ERO, a PCC MUST validate that the Length field, On receiving an SR-ERO, a PCC MUST validate that the Length field,
the S bit, the F bit and the NT field are consistent, as follows. the S bit, the F bit and the NT field are consistent, as follows.
o If NT=0, the F bit MUST be 1, the S bit MUST be zero and the o If NT=0, the F bit MUST be 1, the S bit MUST be zero and the
Length MUST be 8. Length MUST be 8.
skipping to change at page 17, line 42 skipping to change at page 18, line 25
index value, or no SID. If a PCC detects that the SR-ERO subobjects index value, or no SID. If a PCC detects that the SR-ERO subobjects
are a mixture of more than one of these types, then it MUST send a are a mixture of more than one of these types, then it MUST send a
PCErr message with Error-Type = 10 ("Reception of an invalid object") PCErr message with Error-Type = 10 ("Reception of an invalid object")
and Error-Value = TBD9 ("Inconsistent SIDs in SR-ERO / SR-RRO and Error-Value = TBD9 ("Inconsistent SIDs in SR-ERO / SR-RRO
subobjects"). subobjects").
If an ERO specifies a new SR-TE path for an existing LSP and the PCC If an ERO specifies a new SR-TE path for an existing LSP and the PCC
determines that the ERO contains SR-ERO subobjects that are not determines that the ERO contains SR-ERO subobjects that are not
valid, then the PCC MUST NOT update the LSP. valid, then the PCC MUST NOT update the LSP.
6.2.2. Interpreting the SR-ERO 5.2.2. Interpreting the SR-ERO
The SR-ERO contains a sequence of subobjects. According to The SR-ERO contains a sequence of subobjects. Each SR-ERO subobject
[I-D.ietf-spring-segment-routing-policy], each SR-ERO subobject in in the sequence identifies a segment that the traffic will be
the sequence identifies a segment that the traffic will be directed directed to, in the order given. That is, the first subobject
to, in the order given. That is, the first subobject identifies the identifies the first segment the traffic will be directed to, the
first segment the traffic will be directed to, the second SR-ERO second subobject represents the second segment, and so on.
subobject represents the second segment, and so on.
The PCC interprets the SR-ERO by converting it to an MPLS label stack The PCC interprets the SR-ERO by converting it to an MPLS label stack
plus a next hop. The PCC sends packets along the segment routed path plus a next hop. The PCC sends packets along the segment routed path
by prepending the MPLS label stack onto the packets and sending the by prepending the MPLS label stack onto the packets and sending the
resulting, modified packet to the next hop. resulting, modified packet to the next hop.
The PCC uses a different procedure to do this conversion, depending The PCC uses a different procedure to do this conversion, depending
on the information that the PCE has provided in the subobjects. on the information that the PCE has provided in the subobjects.
o If the subobjects contain SID index values, then the PCC converts o If the subobjects contain SID index values, then the PCC converts
them into the corresponding MPLS labels by following the procedure them into the corresponding MPLS labels by following the procedure
defined in [I-D.ietf-spring-segment-routing-mpls]. defined in [I-D.ietf-spring-segment-routing-mpls].
o If the subobjects contain NAI only, then the PCC first converts o If the subobjects contain NAI only, the PCC first converts each
each NAI into a SID index value by looking it up in its local NAI into a SID index value and then proceeds as above. To convert
database, and then proceeds as above. 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.
o If the subobjects contain MPLS labels, then the PCC looks up the o 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 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 gives the first SID. The PCC pushes the labels in any remaining
subobjects onto the packet (with the final subobject specifying subobjects onto the packet (with the final subobject specifying
the bottom-of-stack label) and then directs the packet to the the bottom-of-stack label).
segment identified by the first SID.
6.2.2.1. Handling Errors During SR-ERO Conversion For all cases above, after the PCC has imposed the label stack on the
packet, it sends the packet to the segment identified by the first
SID.
5.2.2.1. Handling Errors During SR-ERO Conversion
There are several errors that can occur during the process of There are several errors that can occur during the process of
converting an SR-ERO sequence to an MPLS label stack and a next hop. converting an SR-ERO sequence to an MPLS label stack and a next hop.
The PCC deals with them as follows. The PCC deals with them as follows.
o If the PCC cannot find a SID index in the SR-DB, it MUST send a o 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 PCErr message with Error-Type = 10 ("Reception of an invalid
object") and Error-Value = TBD3 ("Unknown SID"). object") and Error-Value = TBD3 ("Unknown SID").
o If the PCC cannot find an NAI in the SR-DB, it MUST send a PCErr o If the PCC cannot find an NAI in the SR-DB, it MUST send a PCErr
skipping to change at page 19, line 22 skipping to change at page 20, line 15
o If the number of labels in the computed label stack exceeds the o 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 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 MUST send a PCErr message with Error-Type = 10 ("Reception of an
invalid object") and Error-Value = 3 ("Unsupported number of invalid object") and Error-Value = 3 ("Unsupported number of
Segment ERO subobjects"). Segment ERO subobjects").
If an ERO specifies a new SR-TE path for an existing LSP and the PCC If an ERO specifies a new SR-TE path for an existing LSP and the PCC
encounters an error while processing the ERO, then the PCC MUST NOT encounters an error while processing the ERO, then the PCC MUST NOT
update the LSP. update the LSP.
6.3. RRO Processing 5.3. RRO Processing
The syntax checking rules that apply to the SR-RRO subobject are The syntax checking rules that apply to the SR-RRO subobject are
identical to those of the SR-ERO subobject, except as noted below. identical to those of the SR-ERO subobject, except as noted below.
If a PCEP speaker receives an SR-RRO subobject in which both SID and If a PCEP speaker receives an SR-RRO subobject in which both SID and
NAI are absent, it MUST consider the entire RRO invalid and send a NAI are absent, it MUST consider the entire RRO invalid and send a
PCErr message with Error-Type = 10 ("Reception of an invalid object") PCErr message with Error-Type = 10 ("Reception of an invalid object")
and Error-Value = 7 ("Both SID and NAI are absent in SR-RRO and Error-Value = 7 ("Both SID and NAI are absent in SR-RRO
subobject"). subobject").
skipping to change at page 19, line 47 skipping to change at page 20, line 40
subobject types"). subobject types").
The SR-RRO subobjects can be classified according to whether they The SR-RRO subobjects can be classified according to whether they
contain a SID representing an MPLS label value or a SID representing contain a SID representing an MPLS label value or a SID representing
an index value, or no SID. If a PCE detects that the SR-RRO an index value, or no SID. If a PCE detects that the SR-RRO
subobjects are a mixture of more than one of these types, then it subobjects are a mixture of more than one of these types, then it
MUST send a PCErr message with Error-Type = 10 ("Reception of an MUST send a PCErr message with Error-Type = 10 ("Reception of an
invalid object") and Error-Value = TBD9 ("Inconsistent SIDs in SR-ERO invalid object") and Error-Value = TBD9 ("Inconsistent SIDs in SR-ERO
/ SR-RRO subobjects"). / SR-RRO subobjects").
7. Backward Compatibility 6. Backward Compatibility
A PCEP speaker that does not support the SR PCEP capability cannot A PCEP speaker that does not support the SR PCEP capability cannot
recognize the SR-ERO or SR-RRO subobjects. As such, it responds recognize the SR-ERO or SR-RRO subobjects. As such, it responds
according to the rules for a malformed object, per [RFC5440]. according to the rules for a malformed object, per [RFC5440].
Some implementations, which are compliant with an earlier version of Some implementations, which are compliant with an earlier version of
this specification, do not send the PATH-SETUP-TYPE-CAPABILITY TLV in this specification, do not send the PATH-SETUP-TYPE-CAPABILITY TLV in
their OPEN objects. Instead, to indicate that they support SR, these their OPEN objects. Instead, to indicate that they support SR, these
implementations include the SR-CAPABILITY-TLV as a top-level TLV in implementations include the SR-CAPABILITY-TLV as a top-level TLV in
the OPEN object. Unfortunately, some of these implementations made the OPEN object. Unfortunately, some of these implementations made
skipping to change at page 20, line 21 skipping to change at page 21, line 13
form. Therefore, if a PCEP speaker receives an OPEN object in which form. Therefore, if a PCEP speaker receives an OPEN object in which
the SR-CAPABILITY-TLV appears as a top-level TLV, then it MUST the SR-CAPABILITY-TLV appears as a top-level TLV, then it MUST
interpret this as though the sender had sent a PATH-SETUP-TYPE- interpret this as though the sender had sent a PATH-SETUP-TYPE-
CAPABILITY TLV with a PST list of (0, 1) (that is, both RSVP-TE and CAPABILITY TLV with a PST list of (0, 1) (that is, both RSVP-TE and
SR-TE PSTs are supported) and with the SR-CAPABILITY-TLV as a sub- SR-TE PSTs are supported) and with the SR-CAPABILITY-TLV as a sub-
TLV. If a PCEP speaker receives an OPEN object in which both the SR- TLV. If a PCEP speaker receives an OPEN object in which both the SR-
CAPABILITY-TLV and PATH-SETUP-TYPE-CAPABILITY TLV appear as top-level CAPABILITY-TLV and PATH-SETUP-TYPE-CAPABILITY TLV appear as top-level
TLVs, then it MUST ignore the top-level SR-CAPABILITY-TLV and process TLVs, then it MUST ignore the top-level SR-CAPABILITY-TLV and process
only the PATH-SETUP-TYPE-CAPABILITY TLV. only the PATH-SETUP-TYPE-CAPABILITY TLV.
8. Management Considerations 7. Management Considerations
This document adds a new path setup type to PCEP to allow LSPs to be This document adds a new path setup type to PCEP to allow LSPs to be
set up using segment routing techniques. This path setup type may be set up using segment routing techniques. This path setup type may be
used with PCEP alongside other path setup types, such as RSVP-TE, or used with PCEP alongside other path setup types, such as RSVP-TE, or
it may be used exclusively. it may be used exclusively.
8.1. Controlling the Path Setup Type 7.1. Controlling the Path Setup Type
The following factors control which path setup type is used for a The following factors control which path setup type is used for a
given LSP. given LSP.
o The available path setup types are constrained to those that are o The available path setup types are constrained to those that are
supported by, or enabled on, the PCEP speakers. The PATH-SETUP- supported by, or enabled on, the PCEP speakers. The PATH-SETUP-
TYPE-CAPABILITY TLV indicates which path setup types a PCEP TYPE-CAPABILITY TLV indicates which path setup types a PCEP
speaker supports. To use segment routing as a path setup type, it 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 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 list of supported path setup types in this TLV, and also include
skipping to change at page 21, line 34 skipping to change at page 22, line 29
requested for an LSP nominates segment routing or RSVP-TE as the requested for an LSP nominates segment routing or RSVP-TE as the
path setup type. path setup type.
o PCC implementations MAY allow the operator to configure a o PCC implementations MAY allow the operator to configure a
preference for the PCC to nominate segment routing or RSVP-TE as preference for the PCC to nominate segment routing or RSVP-TE as
the path setup type if none is specified for an LSP. the path setup type if none is specified for an LSP.
o PCC implementations SHOULD allow the operator to configure a PCC o PCC implementations SHOULD allow the operator to configure a PCC
to refuse to set up an LSP using an undesired path setup type. to refuse to set up an LSP using an undesired path setup type.
8.2. Migrating a Network to Use PCEP Segment Routed Paths 7.2. Migrating a Network to Use PCEP Segment Routed Paths
This section discusses the steps that the operator takes when This section discusses the steps that the operator takes when
migrating a network to enable PCEP to set up paths using segment migrating a network to enable PCEP to set up paths using segment
routing as the path setup type. routing as the path setup type.
o The operator enables the segment routing PST on the PCE servers. o The operator enables the segment routing PST on the PCE servers.
o The operator enables the segment routing PST on the PCCs. o The operator enables the segment routing PST on the PCCs.
o The operator resets each PCEP session. The PCEP sessions come o The operator resets each PCEP session. The PCEP sessions come
skipping to change at page 22, line 28 skipping to change at page 23, line 21
and wait instead for a manual reset. and wait instead for a manual reset.
Once segment routing is enabled on a PCEP session, it can be used as Once segment routing is enabled on a PCEP session, it can be used as
the path setup type for future LSPs. the path setup type for future LSPs.
User traffic is not automatically migrated from existing LSPs onto User traffic is not automatically migrated from existing LSPs onto
segment routed LSPs just by enabling the segment routing PST in PCEP. segment routed LSPs just by enabling the segment routing PST in PCEP.
The migration of user traffic from existing LSPs onto segment routing The migration of user traffic from existing LSPs onto segment routing
LSPs is beyond the scope of this document. LSPs is beyond the scope of this document.
8.3. Verification of Network Operation 7.3. Verification of Network Operation
The operator needs the following information to verify that PCEP is The operator needs the following information to verify that PCEP is
operating correctly with respect to the segment routing path setup operating correctly with respect to the segment routing path setup
type. type.
o An implementation SHOULD allow the operator to view whether the o An implementation SHOULD allow the operator to view whether the
PCEP speaker sent the segment routing PST capability to its peer. PCEP speaker sent the segment routing PST capability to its peer.
If the PCEP speaker is a PCC, then the implementation SHOULD also If the PCEP speaker is a PCC, then the implementation SHOULD also
allow the operator to view the values of the L and N flags that allow the operator to view the values of the L and N flags that
were sent, and the value of the MSD field that was sent. were sent, and the value of the MSD field that was sent.
skipping to change at page 23, line 15 skipping to change at page 24, line 7
o An implementation SHOULD allow the operator to view the PST that o An implementation SHOULD allow the operator to view the PST that
was proposed, or requested, for an LSP, and the PST that was was proposed, or requested, for an LSP, and the PST that was
actually used. actually used.
o If a PCEP speaker decides to use a different PST to the one that o If a PCEP speaker decides to use a different PST to the one that
was proposed, or requested, for an LSP, then the implementation was proposed, or requested, for an LSP, then the implementation
SHOULD create a log to inform the operator that the expected PST 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 has not been used. The log SHOULD give the reason for this choice
(local policy, equipment capability etc.) (local policy, equipment capability etc.)
o If a PCEP speaker rejects a segment routed path, then it SHOULD o If a PCEP speaker rejects a segment routing path, then it SHOULD
create a log to inform the operator, giving the reason for the create a log to inform the operator, giving the reason for the
decision (local policy, MSD exceeded etc.) decision (local policy, MSD exceeded etc.)
8.4. Relationship to Existing Management Models 7.4. Relationship to Existing Management Models
The PCEP YANG module [I-D.ietf-pce-pcep-yang] should include: The PCEP YANG module is defined in [I-D.ietf-pce-pcep-yang]. In
future, this YANG module should be extended or augmented to provide
the following additional information relating to segment routing:
o advertised PST capabilities and MSD per PCEP session. o The advertised PST capabilities and MSD per PCEP session.
o the PST configured for, and used by, each LSP. o The PST configured for, and used by, each LSP.
The PCEP MIB [RFC7420] could also be updated to include this The PCEP MIB [RFC7420] could also be updated to include this
information. information.
9. Security Considerations 8. Security Considerations
The security considerations described in [RFC5440], [RFC8281] and The security considerations described in [RFC5440], [RFC8231],
[RFC8408] are applicable to this specification. No additional [RFC8281] and [RFC8408] are applicable to this specification. No
security measure is required. additional security measure is required.
Note that this specification enables a network controller to Note that this specification enables a network controller to
instantiate a path in the network without the use of a hop-by-hop instantiate a path in the network without the use of a hop-by-hop
signaling protocol (such as RSVP-TE). This creates an additional signaling protocol (such as RSVP-TE). This creates an additional
vulnerability if the security mechanisms of [RFC5440] and [RFC8281] vulnerability if the security mechanisms of [RFC5440], [RFC8231] and
are not used, because an attacker could create a path which is not [RFC8281] are not used. If there is no integrity protection on the
subjected to the further verification checks that would be performed session, then an attacker could create a path which is not subjected
by the signaling protocol. to the further verification checks that would be performed by the
signaling protocol.
Note that this specification adds the MSD field to the OPEN message Note that this specification adds the MSD field to the OPEN message
(see Section 5.1.1) which discloses how many MPLS labels the sender (see Section 4.1.2) which discloses how many MPLS labels the sender
can push onto packets that it forwards into the network. If the can push onto packets that it forwards into the network. If the
security mechanisms of [RFC5440] and [RFC8281] are not used then an security mechanisms of [RFC8231] and [RFC8281] are not used with
attacker could use this new field to gain intelligence about the strong encryption, then an attacker could use this new field to gain
capabilities of the edge devices in the network. intelligence about the capabilities of the edge devices in the
network.
10. IANA Considerations
10.1. PCEP ERO and RRO subobjects 9. IANA Considerations
9.1. PCEP ERO and RRO subobjects
This document defines a new subobject type for the PCEP explicit This document defines a new subobject type for the PCEP explicit
route object (ERO), and a new subobject type for the PCEP record route object (ERO), and a new subobject type for the PCEP record
route object (RRO). The code points for subobject types of these route object (RRO). The code points for subobject types of these
objects is maintained in the RSVP parameters registry, under the objects is maintained in the RSVP parameters registry, under the
EXPLICIT_ROUTE and ROUTE_RECORD objects. IANA is requested to EXPLICIT_ROUTE and ROUTE_RECORD objects. IANA is requested to
confirm the early allocation of the following code points in the RSVP confirm the early allocation of the following code points in the RSVP
Parameters registry for each of the new subobject types defined in Parameters registry for each of the new subobject types defined in
this document. this document.
Object Subobject Subobject Type Object Subobject Subobject Type
--------------------- -------------------------- ------------------ --------------------- -------------------------- ------------------
EXPLICIT_ROUTE SR-ERO (PCEP-specific) 36 EXPLICIT_ROUTE SR-ERO (PCEP-specific) 36
ROUTE_RECORD SR-RRO (PCEP-specific) 36 ROUTE_RECORD SR-RRO (PCEP-specific) 36
10.2. New NAI Type Registry 9.2. New NAI Type Registry
IANA is requested to create a new sub-registry within the "Path IANA is requested to create a new sub-registry within the "Path
Computation Element Protocol (PCEP) Numbers" registry called "PCEP Computation Element Protocol (PCEP) Numbers" registry called "PCEP
SR-ERO NAI Types". The allocation policy for this new registry SR-ERO NAI Types". The allocation policy for this new registry
should be by IETF Review. The new registry should contain the should be by IETF Review. The new registry should contain the
following values: following values:
Value Description Reference Value Description Reference
0 NAI is absent. This document 0 NAI is absent. This document
1 NAI is an IPv4 node ID. This document 1 NAI is an IPv4 node ID. This document
2 NAI is an IPv6 node ID. This document 2 NAI is an IPv6 node ID. This document
3 NAI is an IPv4 adjacency. This document 3 NAI is an IPv4 adjacency. This document
4 NAI is an IPv6 adjacency. This document 4 NAI is an IPv6 adjacency. This document
5 NAI is an unnumbered This document 5 NAI is an unnumbered This document
adjacency with IPv4 node IDs. adjacency with IPv4 node IDs.
10.3. New SR-ERO Flag Registry 9.3. New SR-ERO Flag Registry
IANA is requested to create a new sub-registry, named "SR-ERO Flag IANA is requested to create a new sub-registry, named "SR-ERO Flag
Field", within the "Path Computation Element Protocol (PCEP) Numbers" Field", within the "Path Computation Element Protocol (PCEP) Numbers"
registry to manage the Flag field of the SR-ERO subobject. New registry to manage the Flag field of the SR-ERO subobject. New
values are to be assigned by Standards Action [RFC8126]. Each bit values are to be assigned by Standards Action [RFC8126]. Each bit
should be tracked with the following qualities: should be tracked with the following qualities:
o Bit number (counting from bit 0 as the most significant bit) o Bit number (counting from bit 0 as the most significant bit)
o Capability description o Capability description
o Defining RFC
o Defining RFC
The following values are defined in this document: The following values are defined in this document:
Bit Description Reference Bit Description Reference
0-7 Unassigned 0-7 Unassigned
8 NAI is absent (F) This document 8 NAI is absent (F) This document
9 SID is absent (S) This document 9 SID is absent (S) This document
10 SID specifies TC, S This document 10 SID specifies TC, S This document
and TTL in addition and TTL in addition
to an MPLS label (C) to an MPLS label (C)
11 SID specifies an MPLS This document 11 SID specifies an MPLS This document
label (M) label (M)
10.4. PCEP-Error Object 9.4. PCEP-Error Object
IANA is requested to confirm the early allocation of the code-points IANA is requested to confirm the early allocation of the code-points
in the PCEP-ERROR Object Error Types and Values registry for the in the PCEP-ERROR Object Error Types and Values registry for the
following new error-values: following new error-values:
Error-Type Meaning Error-Type Meaning
---------- ------- ---------- -------
10 Reception of an invalid object. 10 Reception of an invalid object.
Error-value = 2: Bad label value Error-value = 2: Bad label value
skipping to change at page 26, line 4 skipping to change at page 26, line 49
Error-value = 7: Both SID and NAI Error-value = 7: Both SID and NAI
are absent in SR- are absent in SR-
RRO subobject RRO subobject
Error-value = 9: MSD exceeds the Error-value = 9: MSD exceeds the
default for the default for the
PCEP session PCEP session
Error-value = 10: RRO mixes SR-RRO Error-value = 10: RRO mixes SR-RRO
subobjects with subobjects with
other subobject other subobject
types types
Error-value = TBD1: Missing PCE-SR- Error-value = TBD1: Missing PCE-SR-
CAPABILITY sub-TLV CAPABILITY sub-TLV
Error-value = TBD2: Unsupported NAI Error-value = TBD2: Unsupported NAI
Type in SR-ERO Type in SR-ERO
subobject subobject
Error-value = TBD3: Unknown SID Error-value = TBD3: Unknown SID
Error-value = TBD4: NAI cannot be Error-value = TBD4: NAI cannot be
resolved to a SID resolved to a SID
Error-value = TBD5: Could not find SRGB Error-value = TBD5: Could not find SRGB
Error-value = TBD6: SID index exceeds Error-value = TBD6: SID index exceeds
SRGB size SRGB size
Error-value = TBD7: Could not find SRLB Error-value = TBD7: Could not find SRLB
Error-value = TBD8: SID index exceeds Error-value = TBD8: SID index exceeds
SRLB size SRLB size
Error-value = TBD9: Inconsistent SIDs Error-value = TBD9: Inconsistent SIDs
in SR-ERO / SR-RRO in SR-ERO / SR-RRO
subobjects subobjects
Error-value = TBD10: MSD must be nonzero
Note to IANA: this draft originally had an early allocation for Note to IANA: this draft originally had an early allocation for
Error-value=11 (Malformed object) in the above list. However, we Error-value=11 (Malformed object) in the above list. However, we
have since moved the definition of that code point to RFC8408. have since moved the definition of that code point to RFC8408.
Note to IANA: some Error-values in the above list were defined after Note to IANA: some Error-values in the above list were defined after
the early allocation took place, and so do not currently have a code the early allocation took place, and so do not currently have a code
point assigned. Please assign code points from the indicated point assigned. Please assign code points from the indicated
registry and replace each instance of "TBD1", "TBD2" etc. in this registry and replace each instance of "TBD1", "TBD2" etc. in this
document with the respective code points. document with the respective code points.
Note to IANA: some of the Error-value descriptive strings above have Note to IANA: some of the Error-value descriptive strings above have
changed since the early allocation. Please refresh the registry. changed since the early allocation. Please refresh the registry.
10.5. PCEP TLV Type Indicators 9.5. PCEP TLV Type Indicators
IANA is requested to confirm the early allocation of the following IANA is requested to confirm the early allocation of the following
code point in the PCEP TLV Type Indicators registry. code point in the PCEP TLV Type Indicators registry. Note that this
TLV type indicator is deprecated but retained to ensure backwards
compatibility with early implementations of this specification. See
Section 6 for details.
Value Meaning Reference Value Meaning Reference
------------------------- ---------------------------- -------------- ------------------------- ---------------------------- --------------
26 SR-PCE-CAPABILITY This document 26 SR-PCE-CAPABILITY This document
(deprecated)
10.6. New Path Setup Type 9.6. PATH-SETUP-TYPE-CAPABILITY Sub-TLV Type Indicators
[RFC8408] requests that IANA creates a sub-registry within the "Path IANA is requested to create a new sub-registry, named "PATH-SETUP-
Computation Element Protocol (PCEP) Numbers" registry called "PCEP TYPE-CAPABILITY Sub-TLV Type Indicators", within the "Path
Path Setup Types". IANA is requested to allocate a new code point Computation Element Protocol (PCEP) Numbers" registry to manage the
within this registry, as follows: type indicator space for sub-TLVs of the PATH-SETUP-TYPE-CAPABILITY
TLV. New values are to be assigned by Standards Action [RFC8126].
The valid range of values in the registry is 0-65535. IANA is
requested to initialize the registry with the following values. All
other values in the registry should be marked as "Unassigned".
Value Meaning Reference
------------------------- ---------------------------- --------------
0 Reserved This document
TBD11 (recommended 26) SR-PCE-CAPABILITY This document
Note to IANA: Please replace each instance of "TBD11" in this
document with the allocated code point. We have recommended that
value 26 be used for consistency with the deprecated value in the
PCEP TLV Type Indicators registry.
9.7. New Path Setup Type
[RFC8408] created a sub-registry within the "Path Computation Element
Protocol (PCEP) Numbers" registry called "PCEP Path Setup Types".
IANA is requested to allocate a new code point within this registry,
as follows:
Value Description Reference Value Description Reference
------------------------- ---------------------------- -------------- ------------------------- ---------------------------- --------------
1 Traffic engineering path is This document 1 Traffic engineering path is This document
setup using Segment Routing. setup using Segment Routing.
10.7. New Metric Type 9.8. New Metric Type
IANA is requested to confirm the early allocation of the following IANA is requested to confirm the early allocation of the following
code point in the PCEP METRIC object T field registry: code point in the PCEP METRIC object T field registry:
Value Description Reference Value Description Reference
------------------------- ---------------------------- -------------- ------------------------- ---------------------------- --------------
11 Segment-ID (SID) Depth. This document 11 Segment-ID (SID) Depth. This document
10.8. SR PCE Capability Flags 9.9. SR PCE Capability Flags
IANA is requested to create a new sub-registry, named "SR Capability IANA is requested to create a new sub-registry, named "SR Capability
Flag Field", within the "Path Computation Element Protocol (PCEP) Flag Field", within the "Path Computation Element Protocol (PCEP)
Numbers" registry to manage the Flag field of the SR-PCE-CAPABILITY Numbers" registry to manage the Flag field of the SR-PCE-CAPABILITY
TLV. New values are to be assigned by Standards Action [RFC8126]. TLV. New values are to be assigned by Standards Action [RFC8126].
Each bit should be tracked with the following qualities: Each bit should be tracked with the following qualities:
o Bit number (counting from bit 0 as the most significant bit) o Bit number (counting from bit 0 as the most significant bit)
o Capability description o Capability description
o Defining RFC o Defining RFC
skipping to change at page 27, line 30 skipping to change at page 29, line 4
IANA is requested to create a new sub-registry, named "SR Capability IANA is requested to create a new sub-registry, named "SR Capability
Flag Field", within the "Path Computation Element Protocol (PCEP) Flag Field", within the "Path Computation Element Protocol (PCEP)
Numbers" registry to manage the Flag field of the SR-PCE-CAPABILITY Numbers" registry to manage the Flag field of the SR-PCE-CAPABILITY
TLV. New values are to be assigned by Standards Action [RFC8126]. TLV. New values are to be assigned by Standards Action [RFC8126].
Each bit should be tracked with the following qualities: Each bit should be tracked with the following qualities:
o Bit number (counting from bit 0 as the most significant bit) o Bit number (counting from bit 0 as the most significant bit)
o Capability description o Capability description
o Defining RFC o Defining RFC
The following values are defined in this document: The following values are defined in this document:
Bit Description Reference Bit Description Reference
0-5 Unassigned 0-5 Unassigned
6 Node or Adjacency This document 6 Node or Adjacency This document
Identifier (NAI) is Identifier (NAI) is
supported (N) supported (N)
7 Unlimited Maximum SID This document 7 Unlimited Maximum SID This document
Depth (L) Depth (X)
11. Contributors Note to IANA: The name of bit 7 has changed from "Unlimited Maximum
SID Depth (L)" to "Unlimited Maximum SID Depth (X)".
10. Contributors
The following people contributed to this document: The following people contributed to this document:
- Lakshmi Sharma - Lakshmi Sharma
- Jan Medved - Jan Medved
- Edward Crabbe - Edward Crabbe
- Robert Raszuk - Robert Raszuk
- Victor Lopez - Victor Lopez
12. Acknowledgements 11. Acknowledgements
We thank Ina Minei, George Swallow, Marek Zavodsky, Dhruv Dhody, Ing- We thank Ina Minei, George Swallow, Marek Zavodsky, Dhruv Dhody, Ing-
Wher Chen and Tomas Janciga for the valuable comments. Wher Chen and Tomas Janciga for the valuable comments.
13. References 12. References
13.1. Normative References 12.1. Normative References
[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-18
(work in progress), December 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001, Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<https://www.rfc-editor.org/info/rfc3032>. <https://www.rfc-editor.org/info/rfc3032>.
skipping to change at page 29, line 10 skipping to change at page 30, line 36
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>. July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8408] Sivabalan, S., Tantsura, J., Minei, I., Varga, R., and J. [RFC8408] Sivabalan, S., Tantsura, J., Minei, I., Varga, R., and J.
Hardwick, "Conveying Path Setup Type in PCE Communication Hardwick, "Conveying Path Setup Type in PCE Communication
Protocol (PCEP) Messages", RFC 8408, DOI 10.17487/RFC8408, Protocol (PCEP) Messages", RFC 8408, DOI 10.17487/RFC8408,
July 2018, <https://www.rfc-editor.org/info/rfc8408>. July 2018, <https://www.rfc-editor.org/info/rfc8408>.
13.2. Informative References [RFC8491] Tantsura, J., Chunduri, U., Aldrin, S., 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>.
12.2. Informative References
[I-D.ietf-6man-segment-routing-header] [I-D.ietf-6man-segment-routing-header]
Filsfils, C., Previdi, S., Leddy, J., Matsushima, S., and Filsfils, C., Previdi, S., Leddy, J., Matsushima, S., and
d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header
(SRH)", draft-ietf-6man-segment-routing-header-14 (work in (SRH)", draft-ietf-6man-segment-routing-header-16 (work in
progress), June 2018. progress), February 2019.
[I-D.ietf-idr-bgp-ls-segment-routing-msd] [I-D.ietf-idr-bgp-ls-segment-routing-msd]
Tantsura, J., Chunduri, U., Mirsky, G., and S. Sivabalan, Tantsura, J., Chunduri, U., Mirsky, G., and S. Sivabalan,
"Signaling MSD (Maximum SID Depth) using Border Gateway "Signaling MSD (Maximum SID Depth) using Border Gateway
Protocol Link-State", draft-ietf-idr-bgp-ls-segment- Protocol Link-State", draft-ietf-idr-bgp-ls-segment-
routing-msd-02 (work in progress), August 2018. routing-msd-02 (work in progress), August 2018.
[I-D.ietf-isis-segment-routing-extensions] [I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A., Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
Gredler, H., Litkowski, S., Decraene, B., and J. Tantsura, Gredler, H., and B. Decraene, "IS-IS Extensions for
"IS-IS Extensions for Segment Routing", draft-ietf-isis- Segment Routing", draft-ietf-isis-segment-routing-
segment-routing-extensions-19 (work in progress), July extensions-22 (work in progress), December 2018.
2018.
[I-D.ietf-isis-segment-routing-msd]
Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg,
"Signaling MSD (Maximum SID Depth) using IS-IS", draft-
ietf-isis-segment-routing-msd-19 (work in progress),
October 2018.
[I-D.ietf-ospf-segment-routing-extensions] [I-D.ietf-ospf-segment-routing-extensions]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H., Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPF Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", draft-ietf-ospf-segment- Extensions for Segment Routing", draft-ietf-ospf-segment-
routing-extensions-25 (work in progress), April 2018. routing-extensions-27 (work in progress), December 2018.
[I-D.ietf-ospf-segment-routing-msd]
Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak,
"Signaling MSD (Maximum SID Depth) using OSPF", draft-
ietf-ospf-segment-routing-msd-23 (work in progress),
October 2018.
[I-D.ietf-pce-pcep-yang] [I-D.ietf-pce-pcep-yang]
Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A
YANG Data Model for Path Computation Element YANG Data Model for Path Computation Element
Communications Protocol (PCEP)", draft-ietf-pce-pcep- Communications Protocol (PCEP)", draft-ietf-pce-pcep-
yang-08 (work in progress), June 2018. yang-09 (work in progress), October 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-14
(work in progress), June 2018.
[I-D.ietf-spring-segment-routing-policy] [I-D.ietf-spring-segment-routing-policy]
Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d., Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d.,
bogdanov@google.com, b., and P. Mattes, "Segment Routing bogdanov@google.com, b., and P. Mattes, "Segment Routing
Policy Architecture", draft-ietf-spring-segment-routing- Policy Architecture", draft-ietf-spring-segment-routing-
policy-01 (work in progress), June 2018. policy-02 (work in progress), October 2018.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>. <https://www.rfc-editor.org/info/rfc3209>.
[RFC4657] Ash, J., Ed. and J. Le Roux, Ed., "Path Computation [RFC4657] Ash, J., Ed. and J. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol Generic Element (PCE) Communication Protocol Generic
Requirements", RFC 4657, DOI 10.17487/RFC4657, September Requirements", RFC 4657, DOI 10.17487/RFC4657, September
2006, <https://www.rfc-editor.org/info/rfc4657>. 2006, <https://www.rfc-editor.org/info/rfc4657>.
skipping to change at page 30, line 44 skipping to change at page 32, line 10
Hardwick, "Path Computation Element Communication Protocol Hardwick, "Path Computation Element Communication Protocol
(PCEP) Management Information Base (MIB) Module", (PCEP) Management Information Base (MIB) Module",
RFC 7420, DOI 10.17487/RFC7420, December 2014, RFC 7420, DOI 10.17487/RFC7420, December 2014,
<https://www.rfc-editor.org/info/rfc7420>. <https://www.rfc-editor.org/info/rfc7420>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26, Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>. <https://www.rfc-editor.org/info/rfc8126>.
[RFC8413] Zhuang, Y., Wu, Q., Chen, H., 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] Tantsura, J., Chunduri, U., Aldrin, S., 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>.
Authors' Addresses Authors' Addresses
Siva Sivabalan Siva Sivabalan
Cisco Systems, Inc. Cisco Systems, Inc.
2000 Innovation Drive 2000 Innovation Drive
Kanata, Ontario K2K 3E8 Kanata, Ontario K2K 3E8
Canada Canada
Email: msiva@cisco.com Email: msiva@cisco.com
Clarence Filsfils Clarence Filsfils
Cisco Systems, Inc. Cisco Systems, Inc.
Pegasus Parc Pegasus Parc
De kleetlaan 6a, DIEGEM BRABANT 1831 De kleetlaan 6a, DIEGEM BRABANT 1831
BELGIUM BELGIUM
Email: cfilsfil@cisco.com Email: cfilsfil@cisco.com
Jeff Tantsura Jeff Tantsura
Apstra, Inc. Apstra, Inc.
444 San Antonio Rd, 10A 333 Middlefield Rd #200
Palo Alto, CA 94306 Menlo Park, CA 94025
USA USA
Email: jefftant.ietf@gmail.com Email: jefftant.ietf@gmail.com
Wim Henderickx Wim Henderickx
Nokia Nokia
Copernicuslaan 50 Copernicuslaan 50
Antwerp 2018, CA 95134 Antwerp 2018, CA 95134
BELGIUM BELGIUM
Email: wim.henderickx@alcatel-lucent.com Email: wim.henderickx@alcatel-lucent.com
Jon Hardwick Jon Hardwick
Metaswitch Networks Metaswitch Networks
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