< draft-ietf-ospf-ospfv3-segment-routing-extensions-10.txt   draft-ietf-ospf-ospfv3-segment-routing-extensions-11.txt >
Open Shortest Path First IGP P. Psenak, Ed. Open Shortest Path First IGP P. Psenak, Ed.
Internet-Draft S. Previdi, Ed. Internet-Draft C. Filsfils
Intended status: Standards Track C. Filsfils Intended status: Standards Track Cisco Systems, Inc.
Expires: March 9, 2018 Cisco Systems, Inc. Expires: July 30, 2018 S. Previdi, Ed.
Individual
H. Gredler H. Gredler
RtBrick Inc. RtBrick Inc.
R. Shakir R. Shakir
Google, Inc. Google, Inc.
W. Henderickx W. Henderickx
Nokia Nokia
J. Tantsura J. Tantsura
Individual Nuage Networks
September 5, 2017 January 26, 2018
OSPFv3 Extensions for Segment Routing OSPFv3 Extensions for Segment Routing
draft-ietf-ospf-ospfv3-segment-routing-extensions-10 draft-ietf-ospf-ospfv3-segment-routing-extensions-11
Abstract Abstract
Segment Routing (SR) allows for a flexible definition of end-to-end Segment Routing (SR) allows a flexible definition of end-to-end paths
paths within IGP topologies by encoding paths as sequences of within IGP topologies by encoding paths as sequences of topological
topological sub-paths, called "segments". These segments are sub-paths, called "segments". These segments are advertised by the
advertised by the link-state routing protocols (IS-IS and OSPF). link-state routing protocols (IS-IS and OSPF).
This draft describes the OSPFv3 extensions that are required for This draft describes the OSPFv3 extensions required for Segment
Segment Routing. Routing.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in [RFC2119].
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
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 March 9, 2018.
This Internet-Draft will expire on July 30, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
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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. Segment Routing Identifiers . . . . . . . . . . . . . . . . . 3 2. Segment Routing Identifiers . . . . . . . . . . . . . . . . . 3
2.1. SID/Label Sub-TLV . . . . . . . . . . . . . . . . . . . . 3 2.1. SID/Label Sub-TLV . . . . . . . . . . . . . . . . . . . . 3
3. Segment Routing Capabilities . . . . . . . . . . . . . . . . 4 3. Segment Routing Capabilities . . . . . . . . . . . . . . . . 4
3.1. SR-Algorithm TLV . . . . . . . . . . . . . . . . . . . . 4 3.1. SR-Algorithm TLV . . . . . . . . . . . . . . . . . . . . 4
3.2. SID/Label Range TLV . . . . . . . . . . . . . . . . . . . 6 3.2. SID/Label Range TLV . . . . . . . . . . . . . . . . . . . 6
3.3. SR Local Block Sub-TLV . . . . . . . . . . . . . . . . . 7 3.3. SR Local Block TLV . . . . . . . . . . . . . . . . . . . 8
3.4. SRMS Preference Sub-TLV . . . . . . . . . . . . . . . . . 9 3.4. SRMS Preference TLV . . . . . . . . . . . . . . . . . . . 10
3.5. SR-Forwarding Capabilities . . . . . . . . . . . . . . . 10 4. OSPFv3 Extended Prefix Range TLV . . . . . . . . . . . . . . 11
4. OSPFv3 Extended Prefix Range TLV . . . . . . . . . . . . . . 10 5. Prefix SID Sub-TLV . . . . . . . . . . . . . . . . . . . . . 14
5. Prefix SID Sub-TLV . . . . . . . . . . . . . . . . . . . . . 12 6. Adjacency Segment Identifier (Adj-SID) . . . . . . . . . . . 17
6. SID/Label Binding Sub-TLV . . . . . . . . . . . . . . . . . . 16 6.1. Adj-SID Sub-TLV . . . . . . . . . . . . . . . . . . . . . 17
6.1. ERO Metric Sub-TLV . . . . . . . . . . . . . . . . . . . 18 6.2. LAN Adj-SID Sub-TLV . . . . . . . . . . . . . . . . . . . 19
6.2. ERO Sub-TLVs . . . . . . . . . . . . . . . . . . . . . . 19 7. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 20
6.2.1. IPv4 ERO Sub-TLV . . . . . . . . . . . . . . . . . . 19 7.1. Intra-area Segment routing in OSPFv3 . . . . . . . . . . 20
6.2.2. IPv6 ERO Sub-TLV . . . . . . . . . . . . . . . . . . 20 7.2. Inter-area Segment routing in OSPFv3 . . . . . . . . . . 22
6.2.3. Unnumbered Interface ID ERO Sub-TLV . . . . . . . . . 21 7.3. Segment Routing for External Prefixes . . . . . . . . . . 23
6.2.4. IPv4 Backup ERO Sub-TLV . . . . . . . . . . . . . . . 22 7.4. Advertisement of Adj-SID . . . . . . . . . . . . . . . . 23
6.2.5. IPv6 Backup ERO Sub-TLV . . . . . . . . . . . . . . . 23 7.4.1. Advertisement of Adj-SID on Point-to-Point Links . . 23
6.2.6. Unnumbered Interface ID Backup ERO Sub-TLV . . . . . 24 7.4.2. Adjacency SID on Broadcast or NBMA Interfaces . . . . 23
7. Adjacency Segment Identifier (Adj-SID) . . . . . . . . . . . 25 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
7.1. Adj-SID Sub-TLV . . . . . . . . . . . . . . . . . . . . . 25 8.1. OSPFv3 Extend-LSA TLV Registry . . . . . . . . . . . . . 24
7.2. LAN Adj-SID Sub-TLV . . . . . . . . . . . . . . . . . . . 27 8.2. OSPFv3 Extend-LSA Sub-TLV registry . . . . . . . . . . . 24
8. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 29 9. Security Considerations . . . . . . . . . . . . . . . . . . . 24
8.1. Intra-area Segment routing in OSPFv3 . . . . . . . . . . 29 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 25
8.2. Inter-area Segment routing in OSPFv3 . . . . . . . . . . 30 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 25
8.3. SID for External Prefixes . . . . . . . . . . . . . . . . 31 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.4. Advertisement of Adj-SID . . . . . . . . . . . . . . . . 32 12.1. Normative References . . . . . . . . . . . . . . . . . . 25
8.4.1. Advertisement of Adj-SID on Point-to-Point Links . . 32 12.2. Informative References . . . . . . . . . . . . . . . . . 26
8.4.2. Adjacency SID on Broadcast or NBMA Interfaces . . . . 32 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32
9.1. OSPF Router Information (RI) TLVs Registry . . . . . . . 32
9.2. OSPFv3 Extend-LSA TLV Registry . . . . . . . . . . . . . 33
9.3. OSPFv3 Extend-LSA Sub-TLV registry . . . . . . . . . . . 33
10. Security Considerations . . . . . . . . . . . . . . . . . . . 33
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 33
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 34
12.1. Normative References . . . . . . . . . . . . . . . . . . 34
12.2. Informative References . . . . . . . . . . . . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35
1. Introduction 1. Introduction
Segment Routing (SR) allows for a flexible definition of end-to-end Segment Routing (SR) allows a flexible definition of end-to-end paths
paths within IGP topologies by encoding paths as sequences of within IGP topologies by encoding paths as sequences of topological
topological sub-paths, called "segments". These segments are sub-paths, called "segments". These segments are advertised by the
advertised by the link-state routing protocols (IS-IS and OSPF). link-state routing protocols (IS-IS and OSPF). Prefix segments
Prefix segments represent an ecmp-aware shortest-path to a prefix (or represent an ECMP-aware shortest-path to a prefix (or a node), as per
a node), as per the state of the IGP topology. Adjacency segments the state of the IGP topology. Adjacency segments represent a hop
represent a hop over a specific adjacency between two nodes in the over a specific adjacency between two nodes in the IGP. A prefix
IGP. A prefix segment is typically a multi-hop path while an segment is typically a multi-hop path while an adjacency segment, in
adjacency segment, in most of the cases, is a one-hop path. SR's most cases, is a one-hop path. SR's control-plane can be applied to
control-plane can be applied to both IPv6 and MPLS data-planes, and both IPv6 and MPLS data-planes, and does not require any additional
does not require any additional signaling (other than the regular signalling (other than IGP extensions). The IPv6 data plane is out
IGP). For example, when used in MPLS networks, SR paths do not of the scope of this specification - OSPFv3 extension for SR with
require any LDP or RSVP-TE signaling. Still, SR can interoperate in IPv6 data plane will be specified in a separate document. When used
the presence of LSPs established with RSVP or LDP. in MPLS networks, SR paths do not require any LDP or RSVP-TE
signalling. However, SR can interoperate in the presence of LSPs
established with RSVP or LDP.
This draft describes the OSPFv3 extensions required for segment There are additional segment types, e.g., Binding SID defined in
routing. [I-D.ietf-spring-segment-routing].
This draft describes the OSPFv3 extensions required for Segment
Routing with MPLS data plane.
Segment Routing architecture is described in Segment Routing architecture is described in
[I-D.ietf-spring-segment-routing]. [I-D.ietf-spring-segment-routing].
Segment Routing use cases are described in Segment Routing use cases are described in [RFC7855].
[I-D.filsfils-spring-segment-routing-use-cases].
2. Segment Routing Identifiers 2. Segment Routing Identifiers
Segment Routing defines various types of Segment Identifiers (SIDs): Segment Routing defines various types of Segment Identifiers (SIDs):
Prefix-SID, Adjacency-SID, LAN Adjacency SID and Binding SID. Prefix-SID, Adjacency-SID, LAN Adjacency SID, and Binding SID.
2.1. SID/Label Sub-TLV 2.1. SID/Label Sub-TLV
The SID/Label Sub-TLV appears in multiple TLVs or Sub-TLVs defined The SID/Label Sub-TLV appears in multiple TLVs or Sub-TLVs defined
later in this document. It is used to advertise the SID or label later in this document. It is used to advertise the SID or label
associated with a prefix or adjacency. The SID/Label TLV has associated with a prefix or adjacency. The SID/Label Sub-TLV has
following format: following format:
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 | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID/Label (variable) | | SID/Label (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
Type: TBD, suggested value 3 Type: 7
Length: variable, 3 or 4 bytes Length: Variable, 3 or 4 octets
SID/Label: if length is set to 3, then the 20 rightmost bits SID/Label: If length is set to 3, then the 20 rightmost bits
represent a label. If length is set to 4, then the value represent a label. If length is set to 4, then the value
represents a 32 bit SID. represents a 32-bit SID.
The receiving router MUST ignore the SID/Label Sub-TLV if the The receiving router MUST ignore the SID/Label Sub-TLV if the
length is other then 3 or 4. length is other then 3 or 4.
3. Segment Routing Capabilities 3. Segment Routing Capabilities
Segment Routing requires some additional capabilities of the router Segment Routing requires some additional router capabilities to be
to be advertised to other routers in the area. advertised to other routers in the area.
These SR capabilities are advertised in OSPFv3 Router Information LSA These SR capabilities are advertised in the OSPFv3 Router Information
(defined in [RFC4970]). Opaque LSA (defined in [RFC7770]).
3.1. SR-Algorithm TLV 3.1. SR-Algorithm TLV
The SR-Algorithm TLV is a TLV of the OSPFv3 Router Information LSA The SR-Algorithm TLV is a top-level TLV of the OSPFv3 Router
(defined in [RFC4970]). Information Opaque LSA (defined in [RFC7770]).
The SR-Algorithm TLV is optional. It MAY only be advertised once in The SR-Algorithm TLV is optional. It SHOULD only be advertised once
the OSPFv3 Router Information LSA. If the SID/Label Range TLV, as in the OSPFv3 Router Information Opaque LSA. If the SR-Algorithm TLV
defined in Section 3.2, is advertised, then the SR-Algorithm TLV MUST is not advertised by the node, such node is considered as not being
also be advertised. If the SR-Algorithm TLV is not advertised by the segment routing capable.
node, such node is considered as not being segment routing capable.
An OSPFv3 router may use various algorithms when calculating An SR router can use various algorithms when calculating reachability
reachability to other nodes in area or to prefixes attached to these to OSPFv3 routers or prefixes in an OSPFv3 area. Examples of these
nodes. Examples of these algorithms are metric based Shortest Path algorithms are metric based Shortest Path First (SPF), various
First (SPF), various sorts of Constrained SPF, etc. The SR-Algorithm flavors of Constrained SPF, etc. The SR-Algorithm TLV allows a
TLV allows a router to advertise the algorithms that the router is router to advertise the algorithms currently used by the router to
currently using to other routers in an area. The SR-Algorithm TLV other routers in an OSPFv3 area. The SR-Algorithm TLV has following
has following structure: format:
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 | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Algorithm 1 | Algorithm... | Algorithm n | | | Algorithm 1 | Algorithm... | Algorithm n | |
+- -+ +- -+
| | | |
+ + + +
where: where:
Type: TBD, suggested value 8 Type: 8
Length: variable Length: Variable, in octets, dependent on number of algorithms
advertised.
Algorithm: Single octet identifying the algorithm. The following Algorithm: Single octet identifying the algorithm. The following
value has been defined: values are defined by this document:
0: Shortest Path First (SPF) algorithm based on link metric. 0: Shortest Path First (SPF) algorithm based on link metric.
This is the standard shortest path algorithm as computed by the This is the standard shortest path algorithm as computed by the
OSPF protocol. Consistent with the deployed practice for link- OSPFv3 protocol. Consistent with the deployed practice for
state protocols, Algorithm 0 permits any node to overwrite the link-state protocols, Algorithm 0 permits any node to overwrite
SPF path with a different path based on its local policy. If the SPF path with a different path based on its local policy.
the SR-Algorithm Sub-TLV is advertised, Algorithm 0 MUST be If the SR-Algorithm TLV is advertised, Algorithm 0 MUST be
included. included.
1: Strict Shortest Path First (SPF) algorithm based on link 1: Strict Shortest Path First (SPF) algorithm based on link
metric. The algorithm is identical to Algorithm 0 but metric. The algorithm is identical to Algorithm 0 but
Algorithm 1 requires that all nodes along the path will honor Algorithm 1 requires that all nodes along the path will honor
the SPF routing decision. Local policy at the node claiming the SPF routing decision. Local policy at the node claiming
the support of Algorithm 1 MUST NOT alter the forwarding support for Algorithm 1 MUST NOT alter the SPF paths computed
decision computed by Algorithm 1. by Algorithm 1.
When multiple SR-Algorithm sub-TLVs are received from a given router When multiple SR-Algorithm TLVs are received from a given router, the
the receiver SHOULD use the first occurrence of the sub-TLV in the receiver MUST use the first occurrence of the TLV in the OSPFV3
OSPFv3 Router Information LSA. If the SR-Algorithm sub-TLV appears Router Information Opaque LSA. If the SR-Algorithm TLV appears in
in multiple OSPFv3 Router Information LSAs that have different multiple OSPFv3 Router Information Opaque LSAs that have different
flooding scopes, the SR-Algorithm sub-TLV in the OSPFv3 Router flooding scopes, the SR-Algorithm TLV in the OSPFv3 Router
Information LSA with the lowest flooding scope SHOULD be used. If Information Opaque LSA with the area-scoped flooding scope MUST be
the SR-Algorithm sub-TLV appears in multiple OSPFv3 Router used. If the SR-Algorithm TLV appears in multiple OSPFv3 Router
Information LSAs that have the same flooding scope, the SR-Algorithm Information Opaque LSAs that have the same flooding scope, the SR-
sub-TLV in the OSPFv3 Router Information LSA with the numerically Algorithm TLV in the OSPFv3 Router Information Opaque LSA with the
smallest Instance ID SHOULD be used and subsequent instances of the numerically smallest Instance ID MUST be used and subsequent
SR-Algorithm sub-TLV SHOULD be ignored. instances of the SR-Algorithm TLV MUST be ignored.
The RI LSA can be advertised at any of the defined flooding scopes The OSPFv3 Router Information Opaque LSA can be advertised at any of
(link, area, or autonomous system (AS)). For the purpose of the SR- the defined opaque flooding scopes (link, area, or Autonomous System
Algorithm TLV propagation, area scope flooding is required. (AS)). For the purpose of SR-Algorithm TLV advertisement, area-
scoped flooding is REQUIRED.
3.2. SID/Label Range TLV 3.2. SID/Label Range TLV
The SID/Label Range TLV is a TLV of the OSPFv3 Router Information LSA Prefix SIDs MAY be advertised in a form of an index as described in
(defined in [RFC4970]). Section 5. Such index defines the offset in the SID/Label space
advertised by the router. The SID/Label Range TLV is used to
advertise such SID/Label space.
The SID/Label Sub-TLV MAY appear multiple times and has following The SID/Label Range TLV is a top-level TLV of the OSPFv3 Router
format: Information Opaque LSA (defined in [RFC7770]).
The SID/Label Range TLV MAY appear multiple times and has the
following format:
0 1 2 3 0 1 2 3
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 | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Range Size | Reserved | | Range Size | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs (variable) | | Sub-TLVs (variable) |
+- -+ +- -+
| | | |
+ + + +
where: where:
Type: TBD, suggested value 9 Type: 9
Length: variable Length: Variable, in octets, dependent on Sub-TLVs.
Range Size: 3 octets of SID/label range Range Size: 3-octet SID/label range size (i.e., the number of SIDs
or labels in the range including the first SID/label). It MUST be
greater than 0.
Initially, the only supported Sub-TLV is the SID/Label TLV as defined Reserved: SHOULD be set to 0 on transmission and MUST be ignored
in Section 2.1. The SID/Label advertised in the SID/Label TLV on reception.
represents the first SID/Label in the advertised range.
Multiple occurrence of the SID/Label Range TLV MAY be advertised, in Initially, the only supported Sub-TLV is the SID/Label Sub-TLV as
defined in Section 2.1. The SID/Label Sub-TLV MUST be included in
the SID/Label Range TLV. The SID/Label advertised in the SID/Label
Sub-TLV represents the first SID/Label in the advertised range.
Only a single SID/Label Sub-TLV MAY be advertised in SID/Label Range
TLV. If more then one SID/Label Sub-TLVs are present, the SID/Label
Range TLV MUST be ignored.
Multiple occurrences of the SID/Label Range TLV MAY be advertised, in
order to advertise multiple ranges. In such case: order to advertise multiple ranges. In such case:
o The originating router MUST encode each range into a different o The originating router MUST encode each range into a different
SID/Label Range TLV. SID/Label Range TLV.
o The originating router decides the order in which the set of SID/ o The originating router decides the order in which the set of SID/
Label Range TLVs are advertised in the OSPFv3 Router Information Label Range TLVs are advertised inside the Router Information
LSA. The originating router MUST ensure the order is same after a Opaque LSA. The originating router MUST ensure the order is the
graceful restart (using checkpointing, non-volatile storage or any same after a graceful restart (using checkpointing, non-volatile
other mechanism) in order to assure the SID/label range and SID storage, or any other mechanism) in order to assure the SID/label
index correspondence is preserved across graceful restarts. range and SID index correspondence is preserved across graceful
restarts.
o The receiving router must adhere to the order in which the ranges o The receiving router MUST adhere to the order in which the ranges
are advertised when calculating a SID/label from the SID index. are advertised when calculating a SID/label from a SID index.
o A router not supporting multiple occurrences of the SID/Label o The originating router MUST NOT advertise overlapping ranges.
Range TLV MUST use first advertised SID/Label Range TLV.
o When a router receives multiple overlapping ranges, it MUST
conform to the procedures defined in
[I-D.ietf-spring-conflict-resolution].
The following example illustrates the advertisement of multiple The following example illustrates the advertisement of multiple
ranges: ranges:
The originating router advertises the following ranges: The originating router advertises the following ranges:
Range 1: [100, 199]
Range 2: [1000, 1099]
Range 3: [500, 599]
The receiving routers concatenate the ranges and build the Segment Routing Global Block Range 1: Range Size: 100 SID/Label Sub-TLV: 100
(SRGB) is as follows: Range 1: Range Size: 100 SID/Label Sub-TLV: 1000
Range 1: Range Size: 100 SID/Label Sub-TLV: 500
SRGB = [100, 199] The receiving routers concatenate the ranges and build the Segment
[1000, 1099] Routing Global Block (SRGB) as follows:
[500, 599]
The indexes span multiple ranges: SRGB = [100, 199]
[1000, 1099]
[500, 599]
index=0 means label 100 The indexes span multiple ranges:
...
index 99 means label 199
index 100 means label 1000
index 199 means label 1099
...
index 200 means label 500
...
The RI LSA can be advertised at any of the defined flooding scopes index=0 means label 100
(link, area, or autonomous system (AS)). For the purpose of the SID/ ...
Label Range TLV propagation, area scope flooding is required. index 99 means label 199
index 100 means label 1000
index 199 means label 1099
...
index 200 means label 500
...
3.3. SR Local Block Sub-TLV The OSPFv3 Router Information Opaque LSA can be advertised at any of
the defined flooding scopes (link, area, or autonomous system (AS)).
For the purpose of SID/Label Range TLV advertisement, area-scoped
flooding is REQUIRED.
The SR Local Block (SRLB) Sub-TLV contains the range of labels the 3.3. SR Local Block TLV
node has reserved for local SIDs. Local SIDs are used, e.g., for
Adjacency-SIDs, and may also be allocated by other components than
OSPF protocol. As an example, an application or a controller may
instruct the router to allocate a specific local SID. Therefore, in
order for such applications or controllers to know what are the local
SIDs available in the router, it is required that the router
advertises its SRLB. The SRLB Sub-TLV is used for that purpose.
The SR Local Block (SRLB) Sub-TLV is a top-level TLV of the OSPFv3 The SR Local Block TLV (SRLB TLV) contains the range of labels the
Router Information Opaque LSA (defined in [RFC7770]). node has reserved for local SIDs. SIDs from the SRLB MAY be used for
Adjacency-SIDs, but also by components other than the OSPFv3
protocol. As an example, an application or a controller can instruct
the router to allocate a specific local SID. Some controllers or
applications can use the control plane to discover the available set
of local SIDs on a particular router. In such cases, the SRLB is
advertised in the control plane. The requirement to advertise the
SRLB is further described in [I-D.ietf-spring-segment-routing-mpls].
The SRLB TLV is used to advertise the SRLB.
The SR Local Block Sub-TLV MAY appear multiple times in the OSPFv3 The SRLB TLV is a top-level TLV of the OSPFv3 Router Information
Router Information Opaque LSA and has the following format: Opaque LSA (defined in [RFC7770]).
The SRLB TLV MAY appear multiple times in the OSPFv3 Router
Information Opaque LSA and has the following format:
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 | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Range Size | Reserved | | Range Size | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs (variable) | | Sub-TLVs (variable) |
+- -+ +- -+
| | | |
+ + + +
where: where:
Type: TBD, suggested value 12 Type: 14
Length: variable Length: Variable, in octets, dependent on Sub-TLVs.
Range Size: 3 octets of the SID/label range. MUST be higher then Range Size: 3-octet SID/label range size (i.e., the number of SIDs
0. or labels in the range including the first SID/label). It MUST be
greater than 0.
Initially, the only supported Sub-TLV is the SID/Label TLV as defined Reserved: SHOULD be set to 0 on transmission and MUST be ignored
in Section 2.1. The SID/Label advertised in the SID/Label TLV on reception.
Initially, the only supported Sub-TLV is the SID/Label Sub-TLV as
defined in Section 2.1. The SID/Label Sub-TLV MUST be included in
the SRLB TLV. The SID/Label advertised in the SID/Label Sub-TLV
represents the first SID/Label in the advertised range. represents the first SID/Label in the advertised range.
When multiple SRLB sub-TLVs are received from a given router the Only a single SID/Label Sub-TLV MAY be advertised in the SRLB TLV.
behavior of the receiving system is undefined. If more then one SID/Label Sub-TLVs are present, the SRLB TLV MUST be
ignored.
The originating router MUST NOT advertise overlapping ranges. The originating router MUST NOT advertise overlapping ranges.
Each time a SID from the SRLB is allocated, it SHOULD also be Each time a SID from the SRLB is allocated, it SHOULD also be
reported to all components (e.g.: controller or applications) in reported to all components (e.g., controller or applications) in
order for these components to have an up-to-date view of the current order for these components to have an up-to-date view of the current
SRLB allocation. This is required to avoid collision between SRLB allocation. This is required to avoid collisions between
allocation instructions. allocation instructions.
Within the context of OSPFv3, the reporting of local SIDs is done Within the context of OSPFv3, the reporting of local SIDs is done
through OSPF Sub-TLVs such as the Adjacency-SID (Section 7). through OSPFv3 Sub-TLVs such as the Adjacency-SID (Section 6).
However, the reporting of allocated local SIDs may also be done However, the reporting of allocated local SIDs can also be done
through other means and protocols which mechanisms are outside the through other means and protocols which are outside the scope of this
scope of this document. document.
A router advertising the SRLB TLV may also have other label ranges, A router advertising the SRLB TLV MAY also have other label ranges,
outside of the SRLB, used for its local allocation purposes which are outside of the SRLB, used for its local allocation purposes which are
NOT advertised in the SRLB. For example, it is possible that an not advertised in the SRLB TLV. For example, it is possible that an
Adjacency-SID is allocated using a local label that is not part of Adjacency-SID is allocated using a local label that is not part of
the SRLB. the SRLB.
The OSPFv3 RI LSA can be advertised at any of the defined flooding The OSPFv3 Router Information Opaque LSA can be advertised at any of
scopes (link, area, or autonomous system (AS)). For the purpose of the defined flooding scopes (link, area, or autonomous system (AS)).
SR Local Block Sub-TLV TLV advertisement, area scope flooding is For the purpose of SRLB TLV advertisement, area-scoped flooding is
required. REQUIRED.
3.4. SRMS Preference Sub-TLV 3.4. SRMS Preference TLV
The Segment Routing Mapping Server (SRMS) Preference sub-TLV is used The Segment Routing Mapping Server Preference TLV (SRMS Preference
to advertise a preference associated with the node that acts as a SR TLV) is used to advertise a preference associated with the node that
Mapping Server. SRMS preference is defined in acts as an SR Mapping Server. The role of an SRMS is described in
[I-D.ietf-spring-conflict-resolution]. [I-D.ietf-spring-segment-routing-ldp-interop]. SRMS preference is
defined in [I-D.ietf-spring-conflict-resolution].
The SRMS Preference Sub-TLV is a top-level TLV of the OSPFv3 Router The SRMS Preference TLV is a top-level TLV of the OSPFv3 Router
Information Opaque LSA (defined in [RFC7770]). Information Opaque LSA (defined in [RFC7770]).
The SRMS Preference Sub-TLV MAY only be advertised once in the OSPFv3 The SRMS Preference TLV MAY only be advertised once in the OSPFv3
Router Information Opaque LSA and has the following format: Router Information Opaque LSA and has the following format:
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 | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Preference | Reserved | | Preference | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
Type: TBD, suggested value 13 Type: 15
Length: 4 octets Length: 4 octets
Preference: 1 octet. SRMS preference value from 0 to 255. Preference: 1 octet. SRMS preference value from 0 to 255.
When multiple SRMS Preference sub-TLVs are received from a given Reserved: SHOULD be set to 0 on transmission and MUST be ignored
router the receiver SHOULD use the first occurrence of the sub-TLV in on reception.
the OSPFv3 Router Information LSA. If the SRMS Preference sub-TLV
appears in multiple OSPFv3 Router Information LSAs that have
different flooding scopes, the SRLB sub-TLV in the OSPFv3 Router
Information LSA with the lowest flooding scope SHOULD be used. If
the SRMS Preference sub-TLV appears in multiple OSPFv3 Router
Information LSAs that have the same flooding scope, the SRMS
Preference sub-TLV in the OSPFv3 Router Information LSA with the
numerically smallest Instance ID SHOULD be used and subsequent
instances of the SRMS Preference sub-TLV SHOULD be ignored.
The OSPFv3 RI LSA can be advertised at any of the defined flooding
scopes (link, area, or autonomous system (AS)). For the purpose of
the SRMS Preference Sub-TLV advertisement, AS scope flooding is
required. If the SRMS advertisements from the SRMS server are only
used inside the area to which the SRMS server is attached, area scope
flooding may be used.
3.5. SR-Forwarding Capabilities
OSPFv3 router supporting Segment Routing needs to advertise its SR
data-plane capabilities. Data-plane capabilities are advertised in
OSPF Router Informational Capabilities TLV, which is defined in
section 2.3 of RFC 4970 [RFC4970].
Two new bits are allocated in the OSPF Router Informational
Capability Bits as follows:
Bit-6 - MPLS IPv6 flag. If set, then the router is capable of
processing SR MPLS encapsulated IPv6 packets on all interfaces.
Bit-7 - If set, then the router is capable of processing the IPv6 When multiple SRMS Preference TLVs are received from a given router,
Segment Routing Header on all interfaces as defined in the receiver MUST use the first occurrence of the TLV in the OSPFv3
[I-D.previdi-6man-segment-routing-header]. Router Information Opaque LSA. If the SRMS Preference TLV appears in
multiple OSPFv3 Router Information Opaque LSAs that have different
flooding scopes, the SRMS Preference TLV in the OSPFv3 Router
Information Opaque LSA with the narrowest flooding scope MUST be
used. If the SRMS Preference TLV appears in multiple OSPFv3 Router
Information Opaque LSAs that have the same flooding scope, the SRMS
Preference TLV in the OSPFv3 Router Information Opaque LSA with the
numerically smallest Instance ID MUST be used and subsequent
instances of the SRMS Preference TLV MUST be ignored.
For the purpose of the SR-Forwarding Capabilities propagation, area The OSPFv3 Router Information Opaque LSA can be advertised at any of
scope flooding is required. the defined flooding scopes (link, area, or autonomous system (AS)).
For the purpose of the SRMS Preference TLV advertisement, AS-scoped
flooding SHOULD be used. This is because SRMS servers can be located
in a different area then consumers of the SRMS advertisements. If
the SRMS advertisements from the SRMS server are only used inside the
SRMS server's area, area-scoped flooding MAY be used.
4. OSPFv3 Extended Prefix Range TLV 4. OSPFv3 Extended Prefix Range TLV
In some cases it is useful to advertise attributes for a range of In some cases it is useful to advertise attributes for a range of
prefixes. Segment Routing Mapping Server, which is described in prefixes. The Segment Routing Mapping Server, which is described in
[I-D.filsfils-spring-segment-routing-ldp-interop], is an example [I-D.ietf-spring-segment-routing-ldp-interop], is an example where we
where we need a single advertisement to advertise SIDs for multiple need a single advertisement to advertise SIDs for multiple prefixes
prefixes from a contiguous address range. The OSPFv3 Extended Prefix from a contiguous address range.
Range TLV is defined for this purpose.
The OSPFv3 Extended Prefix Range TLV is a new top level TLV of the The OSPFv3 Extended Prefix Range TLV, is defined for this purpose.
The OSPFv3 Extended Prefix Range TLV is a top level TLV of the
following LSAs defined in [I-D.ietf-ospf-ospfv3-lsa-extend]: following LSAs defined in [I-D.ietf-ospf-ospfv3-lsa-extend]:
E-Intra-Area-Prefix-LSA E-Intra-Area-Prefix-LSA
E-Inter-Area-Prefix-LSA E-Inter-Area-Prefix-LSA
E-AS-External-LSA E-AS-External-LSA
E-Type-7-LSA E-Type-7-LSA
Multiple OSPFv3 Extended Prefix Range TLVs MAY be advertised in these Multiple OSPFv3 Extended Prefix Range TLVs MAY be advertised in each
extended LSAs. The OSPFv3 Extended Prefix Range TLV has the LSA mentioned above. The OSPFv3 Extended Prefix Range TLV has the
following format: following format:
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 | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Length | AF | Range Size | | Prefix Length | AF | Range Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Reserved | | Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Prefix (variable) | | Address Prefix (variable) |
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs (variable) | | Sub-TLVs (variable) |
+- -+ +- -+
| | | |
where: where:
Type: TBD, suggested value 9. Type: 9
Length: variable Length: Variable, in octets, dependent on Sub-TLVs.
Prefix length: length of the prefix Prefix length: Length of prefix in bits.
AF: 0 - IPv6 unicast AF: Address family for the prefix.
Range size: represents the number of prefixes that are covered by AF: 0 - IPv4 unicast
AF: 1 - IPv6 unicast
Range size: Represents the number of prefixes that are covered by
the advertisement. The Range Size MUST NOT exceed the number of the advertisement. The Range Size MUST NOT exceed the number of
prefixes that could be satisfied by the prefix length without prefixes that could be satisfied by the prefix length without
including addresses from other than the IPv6 unicast address including:
class.
Flags: 1 octet field. The following flags are defined: IPv4 multicast address range (224.0.0.0/3), if the AF is IPv4
unicast
addresses from other than the IPv6 unicast address class, if
the AF is IPv6 unicast
Flags: Single octet field. The following flags are defined:
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+
|IA| | | | | | | | |IA| | | | | | | |
+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+
where: where:
IA-Flag: Inter-Area flag. If set, advertisement is of inter- IA-Flag: Inter-Area flag. If set, advertisement is of inter-
area type. ABR that is advertising the OSPF Extended Prefix area type. An ABR that is advertising the OSPFv3 Extended
Range TLV between areas MUST set this bit. Prefix Range TLV between areas MUST set this bit.
This bit is used to prevent redundant flooding of Prefix Range This bit is used to prevent redundant flooding of Prefix Range
TLVs between areas as follows: TLVs between areas as follows:
An ABR always prefers intra-area Prefix Range advertisement An ABR only propagates an inter-area Prefix Range
over inter-area one. advertisement from the backbone area to connected non-
backbone areas if the advertisement is considered to be the
best one. The following rules are used to select the best
range from the set of advertisements for the same Prefix
Range:
An ABR does not consider inter-area Prefix Range An ABR always prefers intra-area Prefix Range
advertisements coming from non backbone area. advertisements over inter-area advertisements.
An ABR propagates inter-area Prefix Range advertisement from An ABR does not consider inter-area Prefix Range
backbone area to connected non backbone areas only if such advertisements coming from non-backbone areas.
advertisement is considered to be the best one.
Address Prefix: the prefix, encoded as an even multiple of 32-bit Reserved: SHOULD be set to 0 on transmission and MUST be ignored
words, padded with zeroed bits as necessary. This encoding on reception.
consumes ((PrefixLength + 31) / 32) 32-bit words. The Address
Prefix represents the first prefix in the prefix range. Address Prefix:
For the address family IPv4 unicast, the prefix itself is
encoded as a 32-bit value. The default route is represented by
a prefix of length 0.
For the address family IPv6 unicast, the prefix, encoded as an
even multiple of 32-bit words, padded with zeroed bits as
necessary. This encoding consumes ((PrefixLength + 31) / 32)
32-bit words.
Prefix encoding for other address families is beyond the scope
of this specification.
5. Prefix SID Sub-TLV 5. Prefix SID Sub-TLV
The Prefix SID Sub-TLV is a Sub-TLV of the following OSPFv3 TLVs as The Prefix SID Sub-TLV is a Sub-TLV of the following OSPFv3 TLVs as
defined in [I-D.ietf-ospf-ospfv3-lsa-extend] and in Section 4: defined in [I-D.ietf-ospf-ospfv3-lsa-extend] and in Section 4:
Intra-Area Prefix TLV Intra-Area Prefix TLV
Inter-Area Prefix TLV Inter-Area Prefix TLV
skipping to change at page 13, line 14 skipping to change at page 14, line 30
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 | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Algorithm | Reserved | | Flags | Algorithm | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID/Index/Label (variable) | | SID/Index/Label (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
Type: TBD, suggested value 4. Type: 4
Length: variable Length: 7 or 8 octets, dependent on the V-flag
Flags: 1 octet field. The following flags are defined: Flags: Single octet field. The following flags are defined:
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+
| |NP|M |E |V |L | | | | |NP|M |E |V |L | | |
+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+
where: where:
NP-Flag: No-PHP flag. If set, then the penultimate hop MUST NP-Flag: No-PHP flag. If set, then the penultimate hop MUST
NOT pop the Prefix-SID before delivering the packet to the node NOT pop the Prefix-SID before delivering packets to the node
that advertised the Prefix-SID. that advertised the Prefix-SID.
M-Flag: Mapping Server Flag. If set, the SID is advertised M-Flag: Mapping Server Flag. If set, the SID was advertised by
from the Segment Routing Mapping Server functionality as a Segment Routing Mapping Server as described in
described in [I-D.filsfils-spring-segment-routing-ldp-interop]. [I-D.ietf-spring-segment-routing-ldp-interop].
E-Flag: Explicit-Null Flag. If set, any upstream neighbor of E-Flag: Explicit-Null Flag. If set, any upstream neighbor of
the Prefix-SID originator MUST replace the Prefix-SID with a the Prefix-SID originator MUST replace the Prefix-SID with the
Prefix-SID having an Explicit-NULL value (0 for IPv4) before Explicit-NULL label (0 for IPv4, 2 for IPv6) before forwarding
forwarding the packet. the packet.
The V-Flag: Value/Index Flag. If set, then the Prefix-SID V-Flag: Value/Index Flag. If set, then the Prefix-SID carries
carries an absolute value. If not set, then the Prefix-SID an absolute value. If not set, then the Prefix-SID carries an
carries an index. index.
The L-Flag: Local/Global Flag. If set, then the value/index L-Flag: Local/Global Flag. If set, then the value/index
carried by the Prefix-SID has local significance. If not set, carried by the Prefix-SID has local significance. If not set,
then the value/index carried by this Sub-TLV has global then the value/index carried by this Sub-TLV has global
significance. significance.
Other bits: Reserved. These MUST be zero when sent and are Other bits: Reserved. These MUST be zero when sent and are
ignored when received. ignored when received.
Algorithm: one octet identifying the algorithm the Prefix-SID is Reserved: SHOULD be set to 0 on transmission and MUST be ignored
associated with as defined in Section 3.1. on reception.
Algorithm: Single octet identifying the algorithm the Prefix-SID
is associated with as defined in Section 3.1.
A router receiving a Prefix-SID from a remote node and with an A router receiving a Prefix-SID from a remote node and with an
algorithm value that such remote node has not advertised in the algorithm value that such remote node has not advertised in the
SR-Algorithm sub-TLV (Section 3.1) MUST ignore the Prefix-SID sub- SR-Algorithm Sub-TLV (Section 3.1) MUST ignore the Prefix-SID Sub-
TLV. TLV.
SID/Index/Label: label or index value depending on the V-bit SID/Index/Label: According to the V and L flags, it contains
setting. either:
Examples:
A 32 bit global index defining the offset in the SID/Label
space advertised by this router - in this case the V and L
flags MUST NOT be set.
A 24 bit local label where the 20 rightmost bits are used A 32-bit index defining the offset in the SID/Label space
for encoding the label value - in this case the V and L advertised by this router.
flags MUST be set.
If multiple Prefix-SIDs are advertised for the same prefix, the A 24-bit label where the 20 rightmost bits are used for
receiving router MUST use the first encoded SID and MAY use the encoding the label value.
subsequent SIDs.
When propagating Prefix-SIDs between areas, if multiple prefix-SIDs If an OSPFv3 router advertises multiple Prefix-SIDs for the same
are advertised for a prefix, an implementation SHOULD preserve the prefix, topology and algorithm, all of them MUST be ignored.
original order when advertising prefix-SIDs to other areas. This
allows implementations that only support a single Prefix-SID to have
a consistent view across areas.
When calculating the outgoing label for the prefix, the router MUST When calculating the outgoing label for the prefix, the router MUST
take into account E and P flags advertised by the next-hop router, if take into account, as described below, the E, NP and M flags
next-hop router advertised the SID for the prefix. This MUST be done advertised by the next-hop router if that router advertised the SID
regardless of whether the next-hop router contributes to the best for the prefix. This MUST be done regardless of whether the next-hop
path to the prefix. router contributes to the best path to the prefix.
The NP-Flag (No-PHP) MUST be set for Prefix-SIDs allocated to inter- The NP-Flag (No-PHP) MUST be set and the E-flag MUST be clear for
area prefixes that are originated by the ABR based on intra-area or Prefix-SIDs allocated to inter-area prefixes that are originated by
inter-area reachability between areas. When the inter-area prefix is the ABR based on intra-area or inter-area reachability between areas,
generated based on a prefix which is directly attached to the ABR, unless the advertised prefix is directly attached to the ABR.
NP-Flag SHOULD NOT be set
The NP-Flag (No-PHP) MUST be set on the Prefix-SIDs allocated to
redistributed prefixes, unless the redistributed prefix is directly
attached to ASBR, in which case the NP-Flag SHOULD NOT be set.
If the NP-Flag is not set then any upstream neighbor of the Prefix- The NP-Flag (No-PHP) MUST be set and the E-flag MUST be clear for
Prefix-SIDs allocated to redistributed prefixes, unless the
redistributed prefix is directly attached to the ASBR.
If the NP-Flag is not set, then any upstream neighbor of the Prefix-
SID originator MUST pop the Prefix-SID. This is equivalent to the SID originator MUST pop the Prefix-SID. This is equivalent to the
penultimate hop popping mechanism used in the MPLS dataplane. In penultimate hop popping mechanism used in the MPLS dataplane. If the
such case, MPLS EXP bits of the Prefix-SID are not preserved for the NP-flag is not set, then the received E-flag is ignored.
final destination (the Prefix-SID being removed). If the NP-Flag is
clear then the received E-flag is ignored.
If the NP-Flag is set then: If the NP-flag is set then:
If the E-flag is not set then any upstream neighbor of the Prefix- If the E-flag is not set, then any upstream neighbor of the
SID originator MUST keep the Prefix-SID on top of the stack. This Prefix-SID originator MUST keep the Prefix-SID on top of the
is useful when the originator of the Prefix-SID must stitch the stack. This is useful when the originator of the Prefix-SID need
incoming packet into a continuing MPLS LSP to the final to stitch the incoming packet into a continuing MPLS LSP to the
destination. This could occur at an inter-area border router final destination. This could occur at an Area Border Router
(prefix propagation from one area to another) or at an inter- (prefix propagation from one area to another) or at an AS Boundary
domain border router (prefix propagation from one domain to Router (prefix propagation from one domain to another).
another).
If the E-flag is set then any upstream neighbor of the Prefix-SID If the E-flag is set, then any upstream neighbor of the Prefix-SID
originator MUST replace the Prefix-SID with a Prefix-SID having an originator MUST replace the Prefix-SID with an Explicit-NULL
Explicit-NULL value. This is useful, e.g., when the originator of label. This is useful, e.g., when the originator of the Prefix-
the Prefix-SID is the final destination for the related prefix and SID is the final destination for the related prefix and the
the originator wishes to receive the packet with the original EXP originator wishes to receive the packet with the original EXP
bits. bits.
When M-Flag is set, NP-flag and E-flag MUST be ignored at reception. When the M-Flag is set, the NP-flag and the E-flag MUST be ignored at
reception.
As the Mapping Server does not specify the originator of a prefix As the Mapping Server does not specify the originator of a prefix
advertisement it is not possible to determine PHP behavior solely advertisement, it is not possible to determine PHP behavior solely
based on the Mapping Server advertisement. However, PHP behavior may based on the Mapping Server advertisement. However, PHP behavior
safely be done in following cases: SHOULD be done in following cases:
Prefix is of intra-area type and the downstream neighbor is the The Prefix is intra-area type and the downstream neighbor is the
originator of the prefix. originator of the prefix.
Prefix is of inter-area type and downstream neighbor is an ABR, The Prefix is inter-area type and downstream neighbor is an ABR,
which is advertising the prefix reachability and is setting LA-bit which is advertising prefix reachability and is setting LA-bit in
in the Prefix Options as described in section 3.1 of the Prefix Options as described in
[I-D.ietf-ospf-ospfv3-lsa-extend]. [I-D.ietf-ospf-ospfv3-lsa-extend].
Prefix is of external type and downstream neighbor is an ASBR, The Prefix is external type and downstream neighbor is an ASBR,
which is advertising the prefix reachability and is setting LA-bit which is advertising prefix reachability and is setting LA-bit in
in the Prefix Options as described in section 3.1 of the Prefix Options as described in
[I-D.ietf-ospf-ospfv3-lsa-extend]. [I-D.ietf-ospf-ospfv3-lsa-extend].
When a Prefix-SID is advertised in an Extended Prefix Range TLV, then When a Prefix-SID is advertised in the OSPFv3 Extended Prefix Range
the value advertised in Prefix SID Sub-TLV is interpreted as a TLV, then the value advertised in the Prefix SID Sub-TLV is
starting SID value. interpreted as a starting SID/Label value.
Example 1: if the following router addresses (loopback addresses) Example 1: If the following router addresses (loopback addresses)
need to be mapped into the corresponding Prefix SID indexes: need to be mapped into the corresponding Prefix SID indexes:
Router-A: 192::1/128, Prefix-SID: Index 1 Router-A: 2001:DB8::1/128, Prefix-SID: Index 1
Router-B: 192::2/128, Prefix-SID: Index 2 Router-B: 2001:DB8::2/128, Prefix-SID: Index 2
Router-C: 192::3/128, Prefix-SID: Index 3 Router-C: 2001:DB8::3/128, Prefix-SID: Index 3
Router-D: 192::4/128, Prefix-SID: Index 4 Router-D: 2001:DB8::4/128, Prefix-SID: Index 4
then the Address Prefix field in the OSPFv3 Extended Prefix Range TLV then the Address Prefix field in the OSPFv3 Extended Prefix Range TLV
is set to 192::1, Prefix Length would be set to 128, Range Size would would be set to 2001:DB8::1, Prefix Length would be set to 128, Range
be set to 4 and the Index value in the Prefix-SID Sub-TLV would be Size would be set to 4, and the Index value in the Prefix-SID Sub-TLV
set to 1. would be set to 1.
Example 2: If the following prefixes need to be mapped into the Example 2: If the following prefixes need to be mapped into the
corresponding Prefix-SID indexes: corresponding Prefix-SID indexes:
10:1:1::0/120, Prefix-SID: Index 51 2001:DB8:1::0/120, Prefix-SID: Index 51
10:1:1::100/120, Prefix-SID: Index 52 2001:DB8:1::100/120, Prefix-SID: Index 52
10:1:1::200/120, Prefix-SID: Index 53 2001:DB8:1::200/120, Prefix-SID: Index 53
10:1:1::300/120, Prefix-SID: Index 54 2001:DB8:1::300/120, Prefix-SID: Index 54
10:1:1::400/120, Prefix-SID: Index 55 2001:DB8:1::400/120, Prefix-SID: Index 55
10:1:1::500/120, Prefix-SID: Index 56 2001:DB8:1::500/120, Prefix-SID: Index 56
10:1:1::600/120, Prefix-SID: Index 57 2001:DB8:1::600/120, Prefix-SID: Index 57
then the Address Prefix field in the OSPFv3 Extended Prefix Range TLV
is set to 10:1:1::0, Prefix Length would be set to 120, Range Size
would be set to 7 and the Index value in the Prefix-SID Sub-TLV would
be set to 51.
6. SID/Label Binding Sub-TLV
The SID/Label Binding Sub-TLV is used to advertise SID/Label mapping
for a path to the prefix.
The SID/Label Binding Sub-TLV MAY be originated by any router in an
OSPFv3 domain. The router may advertise a SID/Label binding to a FEC
along with at least a single 'nexthop style' anchor. The protocol
supports more than one 'nexthop style' anchor to be attached to a
SID/Label binding, which results into a simple path description
language. In analogy to RSVP the terminology for this is called an
'Explicit Route Object' (ERO). Since ERO style path notation allows
anchoring SID/label bindings to both link and node IP addresses, any
Label Switched Path (LSP) can be described. Furthermore, SID/Label
Bindings from external protocols can also be re-advertised.
The SID/Label Binding Sub-TLV may be used for advertising SID/Label
Bindings and their associated Primary and Backup paths. In one
single TLV, either a primary ERO Path, backup ERO Path, or both are
advertised. If a router wants to advertise multiple parallel paths,
then it can generate several TLVs for the same Prefix/FEC. Each
occurrence of a Binding TLV for a given FEC Prefix will add a new
path.
SID/Label Binding Sub-TLV is a Sub-TLV of the following OSPFv3 TLVs,
as defined in [I-D.ietf-ospf-ospfv3-lsa-extend] and in Section 4:
Intra-Area Prefix TLV
Inter-Area Prefix TLV
External Prefix TLV
OSPFv3 Extended Prefix Range TLV
Multiple SID/Label Binding Sub-TLVs can be present in these TLVs.
The SID/Label Binding Sub-TLV has following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Weight | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs (variable) |
+- -+
| |
where:
Type: TBD, suggested value 7
Length: variable
Flags: 1 octet field of following flags:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|M| |
+-+-+-+-+-+-+-+-+
where:
M-bit - When the bit is set the binding represents the
mirroring context as defined in
[I-D.minto-rsvp-lsp-egress-fast-protection].
Weight: weight used for load-balancing purposes. The use of the
weight is defined in section 3.5.1 of
[I-D.ietf-spring-segment-routing].
SID/Label Binding Sub-TLV currently supports following Sub-TLVs:
SID/Label Sub-TLV as described in Section 2.1. This Sub-TLV MUST
appear in the SID/Label Binding Sub-TLV and it MUST only appear
once.
ERO Metric Sub-TLV as defined in Section 6.1.
ERO Sub-TLVs as defined in Section 6.2.
6.1. ERO Metric Sub-TLV
The ERO Metric Sub-TLV is a Sub-TLV of the SID/Label Binding Sub-TLV.
The ERO Metric Sub-TLV advertises the cost of an ERO path. It is
used to compare the cost of a given source/destination path. A
router SHOULD advertise the ERO Metric Sub-TLV in an advertised ERO
TLV. The cost of the ERO Metric Sub-TLV SHOULD be set to the
cumulative IGP or TE path cost of the advertised ERO. Since
manipulation of the Metric field may attract or repel traffic to and
from the advertised segment, it MAY be manually overridden.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Metric (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ERO Metric Sub-TLV format
where:
Type: TBD, suggested value 8
Length: Always 4
Metric: A 4 octet metric representing the aggregate IGP or TE path
cost.
6.2. ERO Sub-TLVs
All 'ERO' information represents an ordered set which describes the
segments of a path. The first ERO Sub-TLV describes the first
segment of a path. Similiarly, the last ERO Sub-TLV describes the
segment closest to the egress point. If a router extends or stitches
a path, it MUST prepend the new segment's path information to the ERO
list. This applies equally to advertised backup EROs.
All ERO Sub-TLVs must immediately follow the (SID)/Label Sub-TLV.
All Backup ERO Sub-TLVs must immediately follow the last ERO Sub-TLV.
6.2.1. IPv4 ERO Sub-TLV
IPv4 ERO Sub-TLV is a Sub-TLV of the SID/Label Binding Sub-TLV.
The IPv4 ERO Sub-TLV describes a path segment using IPv4 Address
style of encoding. Its semantics have been borrowed from [RFC3209].
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv4 ERO Sub-TLV format
where:
Type: TBD, suggested value 9
Length: 8 bytes
Flags: 1 octet field of following flags:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|L| |
+-+-+-+-+-+-+-+-+
where:
L-bit - If the L-bit is set, then the segment path is
designated as 'loose'. Otherwise, the segment path is
designated as 'strict'.
IPv4 Address - the address of the explicit route hop.
6.2.2. IPv6 ERO Sub-TLV
IPv6 ERO Sub-TLV is a Sub-TLV of the SID/Label Binding Sub-TLV.
The IPv6 ERO Sub-TLV (Type TBA) describes a path segment using IPv6
Address style of encoding. Its semantics have been borrowed from
[RFC3209].
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+- -+
| |
+- IPv6 Address -+
| |
+- -+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv6 ERO Sub-TLV format
where:
Type: TBD, suggested value 10
Length: 8 bytes
Flags: 1 octet field of following flags:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|L| |
+-+-+-+-+-+-+-+-+
where:
L-bit - If the L-bit is set, then the segment path is
designated as 'loose'. Otherwise, the segment path is
designated as 'strict'.
IPv6 Address - the address of the explicit route hop.
6.2.3. Unnumbered Interface ID ERO Sub-TLV
The Unnumbered Interface ID ERO Sub-TLV is a Sub-TLV of the SID/Label
Binding Sub-TLV.
The appearance and semantics of the 'Unnumbered Interface ID' have
been borrowed from [RFC3477].
The Unnumbered Interface-ID ERO Sub-TLV describes a path segment that
spans over an unnumbered interface. Unnumbered interfaces are
referenced using the interface index. Interface indices are assigned
local to the router and therefore not unique within a domain. All
elements in an ERO path need to be unique within a domain and hence
need to be disambiguated using a domain unique Router-ID.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Unnumbered Interface ID ERO Sub-TLV format
Type: TBD, suggested value 11
Length: 12 bytes
Flags: 1 octet field of following flags:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|L| |
+-+-+-+-+-+-+-+-+
where:
L-bit - If the L-bit is set, then the segment path is
designated as 'loose'. Otherwise, the segment path is
designated as 'strict'.
Router-ID: Router-ID of the next-hop.
Interface ID: is the identifier assigned to the link by the router
specified by the Router-ID.
6.2.4. IPv4 Backup ERO Sub-TLV
IPv4 Prefix Backup ERO Sub-TLV is a Sub-TLV of the SID/Label Binding
Sub-TLV.
The IPv4 Backup ERO Sub-TLV describes a path segment using IPv4
Address style of encoding. Its semantics have been borrowed from
[RFC3209].
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv4 Backup ERO Sub-TLV format
where:
Type: TBD, suggested value 12
Length: 8 bytes
Flags: 1 octet field of following flags:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|L| |
+-+-+-+-+-+-+-+-+
where:
L-bit - If the L-bit is set, then the segment path is
designated as 'loose'. Otherwise, the segment path is
designated as 'strict'.'
IPv4 Address - the address of the explicit route hop.
6.2.5. IPv6 Backup ERO Sub-TLV
The IPv6 ERO Sub-TLV is a Sub-TLV of the SID/Label Binding Sub-TLV.
The IPv6 Backup ERO Sub-TLV describes a Backup path segment using
IPv6 Address style of encoding. Its appearance and semantics have
been borrowed from [RFC3209].
The 'L' bit in the Flags is a one-bit attribute. If the L bit is
set, then the value of the attribute is 'loose.' Otherwise, the
value of the attribute is 'strict.'
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+- -+
| |
+- IPv6 Address -+
| |
+- -+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv6 Backup ERO Sub-TLV format
where:
Type: TBD, suggested value 13
Length: 8 bytes
Flags: 1 octet field of following flags:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|L| |
+-+-+-+-+-+-+-+-+
where:
L-bit - If the L-bit is set, then the segment path is
designated as 'loose'. Otherwise, the segment path is
designated as 'strict'.
IPv6 Address - the address of the explicit route hop.
6.2.6. Unnumbered Interface ID Backup ERO Sub-TLV
The Unnumbered Interface ID Backup Sub-TLV is a Sub-TLV of the SID/
Label Binding Sub-TLV.
The appearance and semantics of the 'Unnumbered Interface ID' have
been borrowed from [RFC3477].
The Unnumbered Interface-ID Backup ERO Sub-TLV describes a path
segment that spans over an unnumbered interface. Unnumbered
interfaces are referenced using the interface index. Interface
indices are assigned local to the router and are therefore not unique
within a domain. All elements in an ERO path need to be unique
within a domain and hence need to be disambiguated with specification
of the unique Router-ID.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Unnumbered Interface ID Backup ERO Sub-TLV format
where:
Type: TBD, suggested value 14
Length: 12 bytes
Flags: 1 octet field of following flags:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|L| |
+-+-+-+-+-+-+-+-+
where:
L-bit - If the L-bit is set, then the segment path is
designated as 'loose'. Otherwise, the segment path is
designated as 'strict'.
Router-ID: Router-ID of the next-hop.
Interface ID: is the identifier assigned to the link by the router then the Prefix field in the OSPFv3 Extended Prefix Range TLV would
specified by the Router-ID. be set to 2001:DB8:1::0, Prefix Length would be set to 120, Range
Size would be set to 7, and the Index value in the Prefix-SID Sub-TLV
would be set to 51.
7. Adjacency Segment Identifier (Adj-SID) 6. Adjacency Segment Identifier (Adj-SID)
An Adjacency Segment Identifier (Adj-SID) represents a router An Adjacency Segment Identifier (Adj-SID) represents a router
adjacency in Segment Routing. adjacency in Segment Routing.
7.1. Adj-SID Sub-TLV 6.1. Adj-SID Sub-TLV
The extended OSPFv3 LSAs, as defined in
[I-D.ietf-ospf-ospfv3-lsa-extend], are used to advertise prefix SID
in OSPFv3
The Adj-SID Sub-TLV is an optional Sub-TLV of the Router-Link TLV as Adj-SID is an optional Sub-TLV of the Router-Link TLV as defined in
defined in [I-D.ietf-ospf-ospfv3-lsa-extend]. It MAY appear multiple [I-D.ietf-ospf-ospfv3-lsa-extend]. It MAY appear multiple times in
times in Router-Link TLV. Examples where more than one Adj-SID may the Router-Link TLV. The Adj-SID Sub-TLV has the following format:
be used per neighbor are described in section 4 of
[I-D.filsfils-spring-segment-routing-use-cases]. The Adj-SID Sub-TLV
has the following format:
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 | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Weight | Reserved | | Flags | Weight | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID/Label/Index (variable) | | SID/Label/Index (variable) |
+---------------------------------------------------------------+ +---------------------------------------------------------------+
where: where:
Type: TBD, suggested value 5. Type: 5
Length: variable. Length: 7 or 8 octets, dependent on the V flag.
Flags. 1 octet field of following flags: Flags: Single octet field containing the following flags:
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|B|V|L|G|P| | |B|V|L|G|P| |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
where: where:
B-Flag: Backup-flag. If set, the Adj-SID refers to an B-Flag: Backup Flag. If set, the Adj-SID refers to an
adjacency that is eligible for protection (e.g.: using IPFRR or adjacency that is eligible for protection (e.g., using IPFRR or
MPLS-FRR) as described in section 3.5 of MPLS-FRR) as described in section 3.5 of
[I-D.ietf-spring-segment-routing]. [I-D.ietf-spring-segment-routing].
The V-Flag: Value/Index Flag. If set, then the Adj-SID carries The V-Flag: Value/Index Flag. If set, then the Adj-SID carries
an absolute value. If not set, then the Adj-SID carries an an absolute value. If not set, then the Adj-SID carries an
index. index.
The L-Flag: Local/Global Flag. If set, then the value/index The L-Flag: Local/Global Flag. If set, then the value/index
carried by the Adj-SID has local significance. If not set, carried by the Adj-SID has local significance. If not set,
then the value/index carried by this Sub-TLV has global then the value/index carried by this Sub-TLV has global
significance. significance.
The G-Flag. Group Flag. When set, the G-Flag indicates that The G-Flag: Group Flag. When set, the G-Flag indicates that
the Adj-SID refers to a set of adjacencies (and therefore MAY the Adj-SID refers to a group of adjacencies (and therefore MAY
be assigned to other adjacencies as well). be assigned to other adjacencies as well).
P-Flag. Persistent flag. When set, the P-Flag indicates that P-Flag. Persistent flag. When set, the P-Flag indicates that
the Adj-SID is persistently allocated, i.e., the Adj-SID value the Adj-SID is persistently allocated, i.e., the Adj-SID value
remains consistent across router restart and/or interface flap. remains consistent across router restart and/or interface flap.
Other bits: Reserved. These MUST be zero when sent and are Other bits: Reserved. These MUST be zero when sent and are
ignored when received. ignored when received.
Weight: weight used for load-balancing purposes. The use of the Reserved: SHOULD be set to 0 on transmission and MUST be ignored
weight is defined in section 3.5.1 of on reception.
[I-D.ietf-spring-segment-routing].
SID/Index/Label: label or index value depending on the V-bit
setting.
Examples: Weight: Weight used for load-balancing purposes. The use of the
weight is defined in [I-D.ietf-spring-segment-routing].
A 32 bit global index defining the offset in the SID/Label SID/Index/Label: According to the V and L flags, it contains
space advertised by this router - in this case the V and L either:
flags MUST NOT be set.
A 24 bit local label where the 20 rightmost bits are used A 32-bit index defining the offset in the SID/Label space
for encoding the label value - in this case the V and L advertised by this router.
flags MUST be set.
16 octet IPv6 address - in this case the V-flag MUST be set. A 24-bit label where the 20 rightmost bits are used for
The L-flag MUST NOT be set if the IPv6 address is globally encoding the label value.
unique.
An SR capable router MAY allocate an Adj-SID for each of its An SR capable router MAY allocate an Adj-SID for each of its
adjacencies and set the B-Flag when the adjacency is eligible for adjacencies and set the B-Flag when the adjacency is eligible for
protection by an FRR mechanism (IP or MPLS) as described in section protection by an FRR mechanism (IP or MPLS) as described in
3.5 of [I-D.ietf-spring-segment-routing]. [I-D.ietf-spring-segment-routing].
An SR capable router MAY allocate more than one Adj-SID to an An SR capable router MAY allocate more than one Adj-SID to an
adjacency adjacency
An SR capable router MAY allocate the same Adj-SID to different An SR capable router MAY allocate the same Adj-SID to different
adjacencies adjacencies
When the P-flag is not set, the Adj-SID MAY be persistent. When the When the P-flag is not set, the Adj-SID MAY be persistent. When the
P-flag is set, the Adj-SID MUST be persistent. P-flag is set, the Adj-SID MUST be persistent.
7.2. LAN Adj-SID Sub-TLV 6.2. LAN Adj-SID Sub-TLV
The LAN Adj-SID is an optional Sub-TLV of the Router-Link TLV. It LAN Adj-SID is an optional Sub-TLV of the Router-Link TLV. It MAY
MAY appear multiple times in the Router-Link TLV. It is used to appear multiple times in the Router-Link TLV. It is used to
advertise a SID/Label for an adjacency to a non-DR neighbor on a advertise a SID/Label for an adjacency to a non-DR router on a
broadcast or NBMA network. broadcast, NBMA, or hybrid [RFC6845] network.
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 | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Weight | Reserved | | Flags | Weight | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor ID | | Neighbor ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID/Label/Index (variable) | | SID/Label/Index (variable) |
+---------------------------------------------------------------+ +---------------------------------------------------------------+
where: where:
Type: TBD, suggested value 6. Type: 6
Length: variable.
Flags. 1 octet field of following flags:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|B|V|L|G|P| |
+-+-+-+-+-+-+-+-+
where:
B-Flag: Backup-flag: set if the LAN-Adj-SID refer to an
adjacency that is eligible for protection (e.g.: using IPFRR or
MPLS-FRR) as described in section 3.1 of
[I-D.filsfils-spring-segment-routing-use-cases].
The V-Flag: Value/Index Flag. If set, then the LAN Adj-SID
carries an absolute value. If not set, then the LAN Adj-SID
carries an index.
The L-Flag: Local/Global Flag. If set, then the value/index
carried by the LAN Adj-SID has local significance. If not set,
then the value/index carried by this subTLV has global
significance.
The G-Flag. Group Flag. When set, the G-Flag indicates that
the LAN Adj-SID refers to a set of adjacencies (and therefore
MAY be assigned to other adjacencies as well).
P-Flag. Persistent flag. When set, the P-Flag indicates that
the Adj-SID is persistently allocated, i.e., the Adj-SID value
remains consistent across router restart and/or interface flap.
Other bits: Reserved. These MUST be zero when sent and are Length: 11 or 12 octets, dependent on V-flag.
ignored when received.
Weight: weight used for load-balancing purposes. The use of the Flags: same as in Section 6.1
weight is defined in section 3.5.1 of
[I-D.ietf-spring-segment-routing].
Neighbor ID: The Router ID of the neighbor for which the Adj-SID Weight: Weight used for load-balancing purposes. The use of the
is advertised. weight is defined in [I-D.ietf-spring-segment-routing].
SID/Index/Label: label or index value depending on the V-bit Reserved: SHOULD be set to 0 on transmission and MUST be ignored
setting. on reception.
Examples: Neighbor ID: The Router ID of the neighbor for which the LAN-Adj-
SID is advertised.
A 32 bit global index defining the offset in the SID/Label SID/Index/Label: According to the V and L flags, it contains
space advertised by this router - in this case the V and L either:
flags MUST NOT be set.
A 24 bit local label where the 20 rightmost bits are used A 32-bit index defining the offset in the SID/Label space
for encoding the label value - in this case the V and L advertised by this router.
flags MUST be set.
16 octet IPv6 address - in this case the V-flag MUST be set. A 24-bit label where the 20 rightmost bits are used for
The L-flag MUST NOT be set if the IPv6 address is globally encoding the label value.
unique.
When the P-flag is not set, the Adj-SID MAY be persistent. When When the P-flag is not set, the Adj-SID MAY be persistent. When
the P-flag is set, the Adj-SID MUST be persistent. the P-flag is set, the Adj-SID MUST be persistent.
8. Elements of Procedure 7. Elements of Procedure
8.1. Intra-area Segment routing in OSPFv3 7.1. Intra-area Segment routing in OSPFv3
An OSPFv3 router that supports segment routing MAY advertise Prefix- An OSPFv3 router that supports segment routing MAY advertise Prefix-
SIDs for any prefix that it is advertising reachability for (e.g., SIDs for any prefix to which it is advertising reachability (e.g., a
loopback IP address) as described in Section 5. loopback IP address as described in Section 5).
If multiple routers advertise a Prefix-SID for the same prefix, then
the Prefix-SID MUST be the same. This is required in order to allow
traffic load-balancing when multiple equal cost paths to the
destination exist in the network.
The Prefix-SID can also be advertised by the SR Mapping Servers (as A Prefix-SID can also be advertised by the SR Mapping Servers (as
described in [I-D.filsfils-spring-segment-routing-ldp-interop]). The described in [I-D.ietf-spring-segment-routing-ldp-interop]). A
Mapping Server advertises Prefix-SID for remote prefixes that exist Mapping Server advertises Prefix-SIDs for remote prefixes that exist
in the network. Multiple Mapping Servers can advertise Prefix-SID in the OSPFv3 routing domain. Multiple Mapping Servers can advertise
for the same prefix, in which case the same Prefix-SID MUST be Prefix-SIDs for the same prefix, in which case the same Prefix-SID
advertised by all of them. The SR Mapping Server could use either MUST be advertised by all of them. The SR Mapping Server could use
area scope or autonomous system flooding scope when advertising either area scope or autonomous system flooding scope when
Prefix SID for prefixes, based on the configuration of the SR Mapping advertising Prefix SID for prefixes, based on the configuration of
Server. Depending on the flooding scope used, the SR Mapping Server the SR Mapping Server. Depending on the flooding scope used, the SR
chooses the LSA that will be used. If the area flooding scope is Mapping Server chooses the OSPFv3 LSA type that will be used. If the
needed, E-Intra-Area-Prefix-LSA ([I-D.ietf-ospf-ospfv3-lsa-extend]) area flooding scope is needed, E-Intra-Area-Prefix-LSA
is used. If autonomous system flooding scope is needed, E-AS- ([I-D.ietf-ospf-ospfv3-lsa-extend]) is used. If autonomous system
External-LSA ([I-D.ietf-ospf-ospfv3-lsa-extend]) is used. flooding scope is needed, E-AS-External-LSA
([I-D.ietf-ospf-ospfv3-lsa-extend]) is used.
When a Prefix-SID is advertised by the Mapping Server, which is When a Prefix-SID is advertised by the Mapping Server, which is
indicated by the M-flag in the Prefix-SID Sub-TLV (Section 5), the indicated by the M-flag in the Prefix-SID Sub-TLV (Section 5), the
route type as implied by the LSA type is ignored and the Prefix-SID route type as implied by the LSA type is ignored and the Prefix-SID
is bound to the corresponding prefix independent of the route type. is bound to the corresponding prefix independent of the route type.
Advertisement of the Prefix-SID by the Mapping Server using Inter- Advertisement of the Prefix-SID by the Mapping Server using Inter-
Area Prefix TLV, External-Prefix TLV or Intra-Area-Prefix TLV Area Prefix TLV, External-Prefix TLV or Intra-Area-Prefix TLV
([I-D.ietf-ospf-ospfv3-lsa-extend]) does not itself contribute to the ([I-D.ietf-ospf-ospfv3-lsa-extend]) does not itself contribute to the
prefix reachability. The NU-bit MUST be set in the PrefixOptions prefix reachability. The NU-bit MUST be set in the PrefixOptions
field of the LSA which is used by the Mapping Server to advertise SID field of the LSA which is used by the Mapping Server to advertise SID
or SID range, which prevents the advertisement to contribute to or SID Range, which prevents the advertisement to contribute to the
prefix reachability. prefix reachability.
SR Mapping Server MUST use OSPF Extended Prefix Range TLV when An SR Mapping Server MUST use the OSPFv3 Extended Prefix Range TLVs
advertising SIDs for prefixes. Prefixes of different route-types can when advertising SIDs for prefixes. Prefixes of different route-
be combined in a single OSPF Extended Prefix Range TLV advertised by types can be combined in a single OSPFv3 Extended Prefix Range TLV
the SR Mapping Server. advertised by an SR Mapping Server.
Area scoped OSPF Extended Prefix Range TLV are propagated between Area-scoped OSPFv3 Extended Prefix Range TLVs are propagated between
areas. Similar to propagation of prefixes between areas, ABR only areas. Similar to propagation of prefixes between areas, an ABR only
propagates the OSPF Extended Prefix Range TLV that it considers to be propagates the OSPFv3 Extended Prefix Range TLV that it considers to
the best from the set it received. The rules used to pick the best be the best from the set it received. The rules used to pick the
OSPF Extended Prefix Range TLV is described in Section 4. best OSPFv3 Extended Prefix Range TLV are described in Section 4.
When propagating OSPF Extended Prefix Range TLV between areas, ABR When propagating an OSPFv3 Extended Prefix Range TLV between areas,
MUST set the IA-Flag, that is used to prevent redundant flooding of ABRs MUST set the IA-Flag, that is used to prevent redundant flooding
the OSPF Extended Prefix Range TLV between areas as described in of the OSPFv3 Extended Prefix Range TLV between areas as described in
Section 4. Section 4.
8.2. Inter-area Segment routing in OSPFv3 7.2. Inter-area Segment routing in OSPFv3
In order to support SR in a multi-area environment, OSPFv3 must In order to support SR in a multi-area environment, OSPFv3 MUST
propagate Prefix-SID information between areas. The following propagate Prefix-SID information between areas. The following
procedure is used in order to propagate Prefix SIDs between areas. procedure is used to propagate Prefix SIDs between areas.
When an OSPFv3 ABR advertises a Inter-Area-Prefix-LSA from an intra- When an OSPFv3 ABR advertises a Inter-Area-Prefix-LSA from an intra-
area prefix to all its connected areas, it will also include Prefix- area prefix to all its connected areas, it will also include Prefix-
SID Sub-TLV, as described in Section 5. The Prefix-SID value will be SID Sub-TLV, as described in Section 5. The Prefix-SID value will be
set as follows: set as follows:
The ABR will look at its best path to the prefix in the source The ABR will look at its best path to the prefix in the source
area and find out the advertising router associated with the best area and find the advertising router associated with the best path
path to that prefix. to that prefix.
The ABR will then determine if such router advertised a Prefix-SID The ABR will then determine if such router advertised a Prefix-SID
for the prefix and use it when advertising the Prefix-SID to other for the prefix and use it when advertising the Prefix-SID to other
connected areas. connected areas.
If no Prefix-SID was advertised for the prefix in the source area If no Prefix-SID was advertised for the prefix in the source area
by the router that contributes to the best path to the prefix, the by the router that contributes to the best path to the prefix, the
originating ABR will use the Prefix-SID advertised by any other originating ABR will use the Prefix-SID advertised by any other
router when propagating Prefix-SID for the prefix to other areas. router when propagating the Prefix-SID for the prefix to other
areas.
When an OSPFv3 ABR advertises Inter-Area-Prefix-LSA LSAs from an When an OSPFv3 ABR advertises Inter-Area-Prefix-LSA LSAs from an
inter-area route to all its connected areas it will also include inter-area route to all its connected areas, it will also include
Prefix-SID Sub-TLV, as described in Section 5. The Prefix-SID value Prefix-SID Sub-TLV, as described in Section 5. The Prefix-SID value
will be set as follows: will be set as follows:
The ABR will look at its best path to the prefix in the source The ABR will look at its best path to the prefix in the backbone
area and find out the advertising router associated with the best area and find the advertising router associated with the best path
path to that prefix. to that prefix.
The ABR will then look if such router advertised a Prefix-SID for The ABR will then determine if such router advertised a Prefix-SID
the prefix and use it when advertising the Prefix-SID to other for the prefix and use it when advertising the Prefix-SID to other
connected areas. connected areas.
If no Prefix-SID was advertised for the prefix in the source area If no Prefix-SID was advertised for the prefix in the backbone
by the ABR that contributes to the best path to the prefix, the area by the ABR that contributes to the best path to the prefix,
originating ABR will use the Prefix-SID advertised by any other the originating ABR will use the Prefix-SID advertised by any
router when propagating Prefix-SID for the prefix to other areas. other router when propagating the Prefix-SID for the prefix to
other areas.
8.3. SID for External Prefixes 7.3. Segment Routing for External Prefixes
AS-External-LSAs are flooded domain wide. When an ASBR, which AS-External-LSAs are flooded domain wide. When an ASBR, which
supports SR, generates E-AS-External-LSA, it should also include supports SR, generates E-AS-External-LSA, it SHOULD also include
Prefix-SID Sub-TLV, as described in Section 5. The Prefix-SID value Prefix-SID Sub-TLV, as described in Section 5. The Prefix-SID value
will be set to the SID that has been reserved for that prefix. will be set to the SID that has been reserved for that prefix.
When an NSSA ASBR translates an E-NSSA-LSA into an E-AS-External-LSA, When an NSSA [RFC3101] ABR translates an E-NSSA-LSA into an E-AS-
it should also advertise the Prefix-SID for the prefix. The NSSA ABR External-LSA, it SHOULD also advertise the Prefix-SID for the prefix.
determines its best path to the prefix advertised in the translated The NSSA ABR determines its best path to the prefix advertised in the
E-NSSA-LSA and finds the advertising router associated with that translated E-NSSA-LSA and finds the advertising router associated
path. If the advertising router has advertised a Prefix-SID for the with that path. If the advertising router has advertised a Prefix-
prefix, then the NSSA ABR uses it when advertising the Prefix-SID in SID for the prefix, then the NSSA ABR uses it when advertising the
the E-AS-External-LSA. Otherwise the Prefix-SID advertised by any Prefix-SID for the E-AS-External-LSA. Otherwise, the Prefix-SID
other router will be used. advertised by any other router will be used.
8.4. Advertisement of Adj-SID 7.4. Advertisement of Adj-SID
The Adjacency Segment Routing Identifier (Adj-SID) is advertised The Adjacency Segment Routing Identifier (Adj-SID) is advertised
using the Adj-SID Sub-TLV as described in Section 7. using the Adj-SID Sub-TLV as described in Section 6.
8.4.1. Advertisement of Adj-SID on Point-to-Point Links
An Adj-SID MAY be advertised for any adjacency on p2p link that is in
a state 2-Way or higher. If the adjacency on a p2p link transitions
from the FULL state, then the Adj-SID for that adjacency MAY be
removed from the area. If the adjacency transitions to a state lower
then 2-Way, then the Adj-SID advertisement MUST be removed from the
area.
8.4.2. Adjacency SID on Broadcast or NBMA Interfaces
Broadcast or NBMA networks in OSPFv3 are represented by a star
topology where the Designated Router (DR) is the central point to
which all other routers on the broadcast or NBMA network connect. As
a result, routers on the broadcast or NBMA network advertise only
their adjacency to the DR. Routers that do not act as DR do not form
or advertise adjacencies with each other. They do, however, maintain
a 2-Way adjacency state with each other and are directly reachable.
When Segment Routing is used, each router on the broadcast or NBMA
network MAY advertise the Adj-SID for its adjacency to the DR using
Adj-SID Sub-TLV as described in Section 7.1.
SR capable routers MAY also advertise an Adj-SID for other neighbors 7.4.1. Advertisement of Adj-SID on Point-to-Point Links
(e.g. BDR, DR-OTHER) on the broadcast or NBMA network using the LAN
ADJ-SID Sub-TLV as described in Section 7.2.
9. IANA Considerations An Adj-SID MAY be advertised for any adjacency on a P2P link that is
in neighbor state 2-Way or higher. If the adjacency on a P2P link
transitions from the FULL state, then the Adj-SID for that adjacency
MAY be removed from the area. If the adjacency transitions to a
state lower then 2-Way, then the Adj-SID advertisement MUST be
withdrawn from the area.
This specification updates several existing OSPF registries. 7.4.2. Adjacency SID on Broadcast or NBMA Interfaces
9.1. OSPF Router Information (RI) TLVs Registry Broadcast, NBMA, or hybrid [RFC6845] networks in OSPFv3 are
represented by a star topology where the Designated Router (DR) is
the central point to which all other routers on the broadcast, NBMA,
or hybrid network connect. As a result, routers on the broadcast,
NBMA, or hybrid network advertise only their adjacency to the DR.
Routers that do not act as DR do not form or advertise adjacencies
with each other. They do, however, maintain 2-Way adjacency state
with each other and are directly reachable.
o 8 (IANA Preallocated) - SR-Algorithm TLV When Segment Routing is used, each router on the broadcast, NBMA, or
hybrid network MAY advertise the Adj-SID for its adjacency to the DR
using the Adj-SID Sub-TLV as described in Section 6.1.
o 9 (IANA Preallocated) - SID/Label Range TLV SR capable routers MAY also advertise a LAN-Adj-SID for other
neighbors (e.g., BDR, DR-OTHER) on the broadcast, NBMA, or hybrid
network using the LAN-Adj-SID Sub-TLV as described in Section 6.2.
o 12 - SR Local Block Sub-TLV 8. IANA Considerations
o 13 - SRMS Preference Sub-TLV This specification updates several existing OSPFv3 registries.
9.2. OSPFv3 Extend-LSA TLV Registry 8.1. OSPFv3 Extend-LSA TLV Registry
Following values are allocated: Following values are allocated:
o suggested value 9 - OSPF Extended Prefix Range TLV o suggested value 9 - OSPFv3 Extended Prefix Range TLV
9.3. OSPFv3 Extend-LSA Sub-TLV registry
o suggested value 3 - SID/Label Sub-TLV
o suggested value 4 - Prefix SID Sub-TLV
o suggested value 5 - Adj-SID Sub-TLV 8.2. OSPFv3 Extend-LSA Sub-TLV registry
o suggested value 6 - LAN Adj-SID Sub-TLV o 4 - Prefix SID Sub-TLV
o suggested value 7 - SID/Label Binding Sub-TLV o 5 - Adj-SID Sub-TLV
o suggested value 8 - ERO Metric Sub-TLV o 6 - LAN Adj-SID Sub-TLV
o suggested value 9 - IPv4 ERO Sub-TLV o 7 - SID/Label Sub-TLV
o suggested value 10 - IPv6 ERO Sub-TLV 9. Security Considerations
o suggested value 11 - Unnumbered Interface ID ERO Sub-TLV With the OSPFv3 segment routing extensions defined herein, OSPFv3
will now program the MPLS data plane [RFC3031] in addition to the IP
data plane. Previously, LDP [RFC5036] or another label distribution
mechanism was required to advertise MPLS labels and program the MPLS
data plane.
o suggested value 12 - IPv4 Backup ERO Sub-TLV In general, the same types of attacks that can be carried out on the
IP control plane can be carried out on the MPLS control plane
resulting in traffic being misrouted in the respective data planes.
However, the latter can be more difficult to detect and isolate.
o suggested value 13 - IPv6 Backup ERO Sub-TLV Existing security extensions as described in [RFC5340] and
[I-D.ietf-ospf-ospfv3-lsa-extend] apply to these segment routing
extensions. While OSPFv3 is under a single administrative domain,
there can be deployments where potential attackers have access to one
or more networks in the OSPFv3 routing domain. In these deployments,
stronger authentication mechanisms such as those specified in
[RFC4552] SHOULD be used.
o suggested value 14 - Unnumbered Interface ID Backup ERO Sub-TLV Implementations MUST assure that malformed TLV and Sub-TLV defined in
this document are detected and do not provide a vulnerability for
attackers to crash the OSPFv3 router or routing process. Reception
of malformed TLV or Sub-TLV SHOULD be counted and/or logged for
further analysis. Logging of malformed TLVs and Sub-TLVs SHOULD be
rate-limited to prevent a Denial of Service (DoS) attack (distributed
or otherwise) from overloading the OSPFv3 control plane.
10. Security Considerations 10. Contributors
Implementations must assure that malformed permutations of the newly Acee Lindem gave a substantial contribution to the content of this
defined sub-TLvs do not result in errors which cause hard OSPFv3 document.
failures.
11. Acknowledgements 11. Acknowledgements
Thanks to Acee Lindem for the detail review of the draft,
corrections, as well as discussion about details of the encoding.
We would like to thank Anton Smirnov for his contribution. We would like to thank Anton Smirnov for his contribution.
Many thanks to Yakov Rekhter, John Drake and Shraddha Hedge for their
contribution on earlier definition of the "Binding / MPLS Label TLV".
12. References 12. References
12.1. Normative References 12.1. Normative References
[I-D.ietf-ospf-ospfv3-lsa-extend]
Lindem, A., Roy, A., Goethals, D., Vallem, V., and F.
Baker, "OSPFv3 LSA Extendibility", draft-ietf-ospf-ospfv3-
lsa-extend-23 (work in progress), January 2018.
[I-D.ietf-spring-conflict-resolution]
Ginsberg, L., Psenak, P., Previdi, S., and M. Pilka,
"Segment Routing MPLS Conflict Resolution", draft-ietf-
spring-conflict-resolution-05 (work in progress), July
2017.
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing
Architecture", draft-ietf-spring-segment-routing-15 (work
in progress), January 2018.
[I-D.ietf-spring-segment-routing-ldp-interop]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., and
S. Litkowski, "Segment Routing interworking with LDP",
draft-ietf-spring-segment-routing-ldp-interop-09 (work in
progress), September 2017.
[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>.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Label Switching Architecture", RFC 3031,
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3209>. <https://www.rfc-editor.org/info/rfc3031>.
[RFC3477] Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links [RFC3101] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option",
in Resource ReSerVation Protocol - Traffic Engineering RFC 3101, DOI 10.17487/RFC3101, January 2003,
(RSVP-TE)", RFC 3477, DOI 10.17487/RFC3477, January 2003, <https://www.rfc-editor.org/info/rfc3101>.
<https://www.rfc-editor.org/info/rfc3477>.
[RFC4970] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and [RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
S. Shaffer, "Extensions to OSPF for Advertising Optional "LDP Specification", RFC 5036, DOI 10.17487/RFC5036,
Router Capabilities", RFC 4970, DOI 10.17487/RFC4970, July October 2007, <https://www.rfc-editor.org/info/rfc5036>.
2007, <https://www.rfc-editor.org/info/rfc4970>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/info/rfc5340>.
[RFC6845] Sheth, N., Wang, L., and J. Zhang, "OSPF Hybrid Broadcast
and Point-to-Multipoint Interface Type", RFC 6845,
DOI 10.17487/RFC6845, January 2013,
<https://www.rfc-editor.org/info/rfc6845>.
[RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and [RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
S. Shaffer, "Extensions to OSPF for Advertising Optional S. Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 7770, DOI 10.17487/RFC7770, Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
February 2016, <https://www.rfc-editor.org/info/rfc7770>. February 2016, <https://www.rfc-editor.org/info/rfc7770>.
12.2. Informative References [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
[I-D.filsfils-spring-segment-routing-ldp-interop] RFC 8126, DOI 10.17487/RFC8126, June 2017,
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., <https://www.rfc-editor.org/info/rfc8126>.
Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R.,
Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe,
"Segment Routing interoperability with LDP", draft-
filsfils-spring-segment-routing-ldp-interop-02 (work in
progress), September 2014.
[I-D.filsfils-spring-segment-routing-use-cases]
Filsfils, C., Francois, P., Previdi, S., Decraene, B.,
Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R.,
Ytti, S., Henderickx, W., Tantsura, J., Kini, S., and E.
Crabbe, "Segment Routing Use Cases", draft-filsfils-
spring-segment-routing-use-cases-01 (work in progress),
October 2014.
[I-D.ietf-ospf-ospfv3-lsa-extend]
Lindem, A., Roy, A., Goethals, D., Vallem, V., and F.
Baker, "OSPFv3 LSA Extendibility", draft-ietf-ospf-ospfv3-
lsa-extend-14 (work in progress), April 2017.
[I-D.ietf-spring-conflict-resolution] 12.2. Informative References
Ginsberg, L., Psenak, P., Previdi, S., and M. Pilka,
"Segment Routing Conflict Resolution", draft-ietf-spring-
conflict-resolution-01 (work in progress), June 2016.
[I-D.ietf-spring-segment-routing] [I-D.ietf-spring-segment-routing-mpls]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., Horneffer, M., Shakir, R., Tantsura, J., Litkowski, S., and R. Shakir, "Segment Routing with MPLS
and E. Crabbe, "Segment Routing Architecture", draft-ietf- data plane", draft-ietf-spring-segment-routing-mpls-11
spring-segment-routing-01 (work in progress), February (work in progress), October 2017.
2015.
[I-D.minto-rsvp-lsp-egress-fast-protection] [RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality
Jeganathan, J., Gredler, H., and Y. Shen, "RSVP-TE LSP for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006,
egress fast-protection", draft-minto-rsvp-lsp-egress-fast- <https://www.rfc-editor.org/info/rfc4552>.
protection-03 (work in progress), November 2013.
[I-D.previdi-6man-segment-routing-header] [RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B.,
Previdi, S., Filsfils, C., Field, B., Leung, I., Linkova, Litkowski, S., Horneffer, M., and R. Shakir, "Source
J., Kosugi, T., Vyncke, E., and D. Lebrun, "IPv6 Segment Packet Routing in Networking (SPRING) Problem Statement
Routing Header (SRH)", draft-previdi-6man-segment-routing- and Requirements", RFC 7855, DOI 10.17487/RFC7855, May
header-08 (work in progress), October 2015. 2016, <https://www.rfc-editor.org/info/rfc7855>.
Authors' Addresses Authors' Addresses
Peter Psenak (editor) Peter Psenak (editor)
Cisco Systems, Inc. Cisco Systems, Inc.
Apollo Business Center Eurovea Centre, Central 3
Mlynske nivy 43 Pribinova Street 10
Bratislava 821 09 Bratislava 81109
Slovakia Slovakia
Email: ppsenak@cisco.com Email: ppsenak@cisco.com
Stefano Previdi (editor)
Cisco Systems, Inc.
Via Del Serafico, 200
Rome 00142
Italy
Email: sprevidi@cisco.com
Clarence Filsfils Clarence Filsfils
Cisco Systems, Inc. Cisco Systems, Inc.
Brussels Brussels
Belgium Belgium
Email: cfilsfil@cisco.com Email: cfilsfil@cisco.com
Stefano Previdi (editor)
Individual
Email: stefano.previdi@net
Hannes Gredler Hannes Gredler
RtBrick Inc. RtBrick Inc.
Austria Austria
Email: hannes@rtbrick.com Email: hannes@rtbrick.com
Rob Shakir Rob Shakir
Google, Inc. Google, Inc.
1600 Amphitheatre Parkway 1600 Amphitheatre Parkway
Mountain View, CA 94043 Mountain View, CA 94043
skipping to change at page 36, line 24 skipping to change at page 28, line 4
Email: hannes@rtbrick.com Email: hannes@rtbrick.com
Rob Shakir Rob Shakir
Google, Inc. Google, Inc.
1600 Amphitheatre Parkway 1600 Amphitheatre Parkway
Mountain View, CA 94043 Mountain View, CA 94043
US US
Email: robjs@google.com Email: robjs@google.com
Wim Henderickx Wim Henderickx
Nokia Nokia
Copernicuslaan 50 Copernicuslaan 50
Antwerp 2018 Antwerp 2018
BE BE
Email: wim.henderickx@nokia.com Email: wim.henderickx@nokia.com
Jeff Tantsura Jeff Tantsura
Individual Nuage Networks
US US
Email: jefftant.ietf@gmail.com Email: jefftant.ietf@gmail.com
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