draft-ietf-ospf-segment-routing-extensions-00.txt   draft-ietf-ospf-segment-routing-extensions-01.txt 
Open Shortest Path First IGP P. Psenak, Ed. Open Shortest Path First IGP P. Psenak, Ed.
Internet-Draft S. Previdi, Ed. Internet-Draft S. Previdi, Ed.
Intended status: Standards Track C. Filsfils Intended status: Standards Track C. Filsfils
Expires: December 21, 2014 Cisco Systems, Inc. Expires: January 4, 2015 Cisco Systems, Inc.
H. Gredler H. Gredler
Juniper Networks, Inc. Juniper Networks, Inc.
R. Shakir R. Shakir
British Telecom British Telecom
W. Henderickx W. Henderickx
Alcatel-Lucent Alcatel-Lucent
J. Tantsura J. Tantsura
Ericsson Ericsson
June 19, 2014 July 3, 2014
OSPF Extensions for Segment Routing OSPF Extensions for Segment Routing
draft-ietf-ospf-segment-routing-extensions-00 draft-ietf-ospf-segment-routing-extensions-01
Abstract Abstract
Segment Routing (SR) allows for a flexible definition of end-to-end Segment Routing (SR) allows for a flexible definition of end-to-end
paths within IGP topologies by encoding paths as sequences of paths within IGP topologies by encoding paths as sequences of
topological sub-paths, called "segments". These segments are topological sub-paths, called "segments". These segments are
advertised by the link-state routing protocols (IS-IS and OSPF). advertised by the link-state routing protocols (IS-IS and OSPF).
This draft describes the necessary OSPF extensions that need to be This draft describes the OSPF extensions required for Segment
introduced for 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 RFC 2119 [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
skipping to change at page 2, line 4 skipping to change at page 2, line 4
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 http://datatracker.ietf.org/drafts/current/. Drafts is at http://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 December 21, 2014. This Internet-Draft will expire on January 4, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 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
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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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 . . . . . . . . . . . . . . . . . . . . 4 2.1. SID/Label sub-TLV . . . . . . . . . . . . . . . . . . . . 4
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 . . . . . . . . . . . . . . . . . . . 5 3.2. SID/Label Range TLV . . . . . . . . . . . . . . . . . . . 5
4. OSPFv2 Extended Prefix Opaque LSA type . . . . . . . . . . . 7 4. OSPFv2 Extended Prefix Opaque LSA . . . . . . . . . . . . . . 7
4.1. OSPF Extended Prefix TLV . . . . . . . . . . . . . . . . 8 4.1. OSPF Extended Prefix TLV . . . . . . . . . . . . . . . . 8
4.2. Prefix SID Sub-TLV . . . . . . . . . . . . . . . . . . . 9 4.2. Prefix SID Sub-TLV . . . . . . . . . . . . . . . . . . . 9
4.3. SID/Label Binding sub-TLV . . . . . . . . . . . . . . . . 13 4.3. SID/Label Binding sub-TLV . . . . . . . . . . . . . . . . 13
4.3.1. ERO Metric sub-TLV . . . . . . . . . . . . . . . . . 15 4.3.1. ERO Metric sub-TLV . . . . . . . . . . . . . . . . . 15
4.3.2. ERO sub-TLVs . . . . . . . . . . . . . . . . . . . . 15 4.3.2. ERO sub-TLVs . . . . . . . . . . . . . . . . . . . . 15
5. Adjacency Segment Identifier (Adj-SID) . . . . . . . . . . . 20 5. Adjacency Segment Identifier (Adj-SID) . . . . . . . . . . . 20
5.1. OSPFv2 Extended Link Opaque LSA . . . . . . . . . . . . . 20 5.1. OSPFv2 Extended Link Opaque LSA . . . . . . . . . . . . . 20
5.2. OSPFv2 Extended Link TLV . . . . . . . . . . . . . . . . 21 5.2. OSPFv2 Extended Link TLV . . . . . . . . . . . . . . . . 21
5.3. Adj-SID sub-TLV . . . . . . . . . . . . . . . . . . . . . 22 5.3. Adj-SID sub-TLV . . . . . . . . . . . . . . . . . . . . . 21
5.4. LAN Adj-SID Sub-TLV . . . . . . . . . . . . . . . . . . . 23 5.4. LAN Adj-SID Sub-TLV . . . . . . . . . . . . . . . . . . . 23
6. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 25 6. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 24
6.1. Intra-area Segment routing in OSPFv2 . . . . . . . . . . 25 6.1. Intra-area Segment routing in OSPFv2 . . . . . . . . . . 24
6.2. Inter-area Segment routing in OSPFv2 . . . . . . . . . . 25 6.2. Inter-area Segment routing in OSPFv2 . . . . . . . . . . 25
6.3. SID for External Prefixes . . . . . . . . . . . . . . . . 26 6.3. SID for External Prefixes . . . . . . . . . . . . . . . . 26
6.4. Advertisement of Adj-SID . . . . . . . . . . . . . . . . 27 6.4. Advertisement of Adj-SID . . . . . . . . . . . . . . . . 26
6.4.1. Advertisement of Adj-SID on Point-to-Point Links . . 27 6.4.1. Advertisement of Adj-SID on Point-to-Point Links . . 26
6.4.2. Adjacency SID on Broadcast or NBMA Interfaces . . . . 27 6.4.2. Adjacency SID on Broadcast or NBMA Interfaces . . . . 27
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
7.1. OSPF Extend Prefix LSA TLV Registry . . . . . . . . . . . 28 7.1. OSPF Extend Prefix LSA TLV Registry . . . . . . . . . . . 27
7.2. OSPF Extend Prefix LSA sub-TLV Registry . . . . . . . . . 28 7.2. OSPF Extend Prefix LSA sub-TLV Registry . . . . . . . . . 28
7.3. OSPF Extend Link LSA TLV Registry . . . . . . . . . . . . 29 7.3. OSPF Extend Link LSA TLV Registry . . . . . . . . . . . . 29
7.4. OSPF Extend Link LSA sub-TLV Registry . . . . . . . . . . 29 7.4. OSPF Extend Link LSA sub-TLV Registry . . . . . . . . . . 29
8. Security Considerations . . . . . . . . . . . . . . . . . . . 30 8. Security Considerations . . . . . . . . . . . . . . . . . . . 30
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 30 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 30
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 30 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 30
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 30 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 30
11.1. Normative References . . . . . . . . . . . . . . . . . . 30 11.1. Normative References . . . . . . . . . . . . . . . . . . 30
11.2. Informative References . . . . . . . . . . . . . . . . . 31 11.2. Informative References . . . . . . . . . . . . . . . . . 31
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1. Introduction 1. Introduction
Segment Routing (SR) allows for a flexible definition of end-to-end Segment Routing (SR) allows for a flexible definition of end-to-end
paths within IGP topologies by encoding paths as sequences of paths within IGP topologies by encoding paths as sequences of
topological sub-paths, called "segments". These segments are topological sub-paths, called "segments". These segments are
advertised by the link-state routing protocols (IS-IS and OSPF). advertised by the link-state routing protocols (IS-IS and OSPF).
Prefix segments represent an ecmp-aware shortest-path to a prefix (or Prefix segments represent an ecmp-aware shortest-path to a prefix (or
a node), as per the state of the IGP topology. Adjacency segments a node), as per the state of the IGP topology. Adjacency segments
represent a hop over a specific adjacency between two nodes in the represent a hop over a specific adjacency between two nodes in the
IGP. A prefix segment is typically a multi-hop path while an IGP. A prefix segment is typically a multi-hop path while an
adjacency segment, in most of the cases, is a one-hop path. SR's adjacency segment, in most cases, is a one-hop path. SR's control-
control-plane can be applied to both IPv6 and MPLS data-planes, and plane can be applied to both IPv6 and MPLS data-planes, and does not
do not require any additional signaling (other than the regular IGP). require any additional signalling (other than IGP extensions). For
For example, when used in MPLS networks, SR paths do not require any example, when used in MPLS networks, SR paths do not require any LDP
LDP or RSVP-TE signaling. Still, SR can interoperate in the presence or RSVP-TE signalling. However, SR can interoperate in the presence
of LSPs established with RSVP or LDP . of LSPs established with RSVP or LDP.
This draft describes the necessary OSPF extensions that need to be This draft describes the OSPF extensions required for Segment
introduced for Segment Routing. Routing.
Segment Routing architecture is described in Segment Routing architecture is described in
[I-D.filsfils-rtgwg-segment-routing]. [I-D.filsfils-rtgwg-segment-routing].
Segment Routing use cases are described in Segment Routing use cases are described in
[I-D.filsfils-rtgwg-segment-routing-use-cases]. [I-D.filsfils-rtgwg-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.
For the purpose of the advertisements of various SID values new For the purpose of the advertisements of various SID values, new
Opaque LSAs (defined in [RFC5250]) are defined. These new LSAs are Opaque LSAs (defined in [RFC5250]) are defined. These new LSAs are
defined as generic containers that can be used in order to advertise defined as generic containers that can be used to advertise any
any additional attributes associated with the prefix or link. These additional attributes associated with the prefix or link. These new
new Opaque LSAs are complementary to the existing LSAs and are not Opaque LSAs are complementary to the existing LSAs and are not aimed
aimed to replace any of the existing LSAs. to replace any of the existing LSAs.
2.1. SID/Label sub-TLV 2.1. SID/Label sub-TLV
SID/Label sub-TLV appears in multiple TLVs or sub-TLVs defined later SID/Label sub-TLV appears in multiple TLVs or sub-TLVs defined later
in this document. It is used to advertise SID or label associated in this document. It is used to advertise SID or label associated
with the prefix or adjacency. SID/Label TLV has following format: with the prefix or adjacency. SID/Label TLV has 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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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 SID/Label sub-TLV if the length The receiving router MUST ignore SID/Label sub-TLV if the length
is other then 3 or 4. 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 Router Information Opaque LSA These SR capabilities are advertised in the Router Information Opaque
(defined in [RFC4970]). LSA (defined in [RFC4970]).
3.1. SR-Algorithm TLV 3.1. SR-Algorithm TLV
SR-Algorithm TLV is a TLV of Router Information Opaque LSA (defined SR-Algorithm TLV is a top-level TLV of the Router Information Opaque
in [RFC4970]). LSA (defined in [RFC4970]).
The SR-Algorithm Sub-TLV is optional, it MAY only appear once inside The SR-Algorithm Sub-TLV is optional, it MAY only appear once inside
the Router Informational Opaque LSA. If the SID/Label Range TLV, as the Router Informational Opaque LSA. If the SID/Label Range TLV, as
defined in Section 3.2, is advertised, then SR-Algorithm TLV MUST defined in Section 3.2, is advertised, then SR-Algorithm TLV MUST
also be advertised. also be advertised.
Router may use various algorithms when calculating reachability to As SR Router may use various algorithms when calculating reachability
other nodes in area or to prefixes attached to these nodes. Examples to OSPF routers or prefixes in an OSPF area. Examples of these
of these algorithms are metric based Shortest Path First (SPF), algorithms are metric based Shortest Path First (SPF), various
various sorts of Constrained SPF, etc. SR-Algorithm TLV allows a flavors of Constrained SPF, etc. The SR-Algorithm TLV allows a
router to advertise algorithms that router is currently using to router to advertise the algorithms that the router is currently using
other routers in an area. SR-Algorithm TLV has following structure: to other routers in an OSPF area. The SR-Algorithm TLV has 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Algorithm 1 | Algorithm... | Algorithm n | | | Algorithm 1 | Algorithm... | Algorithm n | |
+- -+ +- -+
| | | |
+ + + +
where: where:
Type: TBD, suggested value 8 Type: TBD, suggested value 8
Length: variable Length: variable
Algorithm: one octet identifying the algorithm. The following Algorithm: Single octet identifying the algorithm. The following
value has been defined: value is defined by this document:
0: IGP metric based SPT. 0: IGP metric based Shortest Path Tree (SPT)
RI LSA can be advertised at any of the defined flooding scopes (link, The RI LSA can be advertised at any of the defined opaque flooding
area, or autonomous system (AS)). For the purpose of the SR- scopes (link, area, or Autonomous System (AS)). For the purpose of
Algorithm TLV propagation area scope flooding is required. the SR-Algorithm TLV propagation, area scope flooding is required.
3.2. SID/Label Range TLV 3.2. SID/Label Range TLV
The SID/Label Range TLV is a TLV of Router Information Opaque LSA The SID/Label Range TLV is a top-level TLV of Router Information
(defined in [RFC4970]). Opaque LSA (defined in [RFC4970]).
SID/Label Sub-TLV MAY appear multiple times and has following format: 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) |
+- -+ +- -+
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where: where:
Type: TBD, suggested value 9 Type: TBD, suggested value 9
Length: variable Length: variable
Range Size: 3 octet of the SID/label range Range Size: 3 octet of the SID/label range
Currently the only supported Sub-TLV is the SID/Label TLV as defined Currently the only supported Sub-TLV is the SID/Label TLV as defined
in Section 2.1. SID/Label advertised in SID/Label TLV represents the in Section 2.1. The SID/Label advertised in SID/Label TLV represents
first SID/Label from the advertised range. the first SID/Label in the advertised range.
Multiple occurrence of the SID/Label Range TLV MAY be advertised, in Multiple occurrence 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 in which order the set of SID/Label o The originating router decides in which order the set of SID/Label
Range TLVs are advertised inside Router Information Opaque LSA. Range TLVs are advertised inside Router Information Opaque LSA.
The originating router MUST ensure the order is same after a The originating router MUST ensure the order is same after a
graceful restart (using checkpointing, non-volatile storage or any graceful restart (using checkpointing, non-volatile storage or any
other mechanism) in order to guarantee the same order before and other mechanism) in order to SID/label range and SID index
after graceful restart. correspondence is preserved across graceful restarts.
o Receiving router must adhere to the order in which the ranges are o The receiving router must adhere to the order in which the ranges
advertised when calculating a SID/label from the SID index. are advertised when calculating a SID/label from a SID index.
Here follows an example of advertisement of multiple ranges: The following example illustrates the advertisement of multiple
ranges:
The originating router advertises following ranges: The originating router advertises following ranges:
Range 1: [100, 199] Range 1: [100, 199]
Range 2: [1000, 1099] Range 2: [1000, 1099]
Range 3: [500, 599] Range 3: [500, 599]
The receiving routers concatenate the ranges and build the SRGB The receiving routers concatenate the ranges and build the SRGB
is as follows: is as follows:
SRGB = [100, 199] SRGB = [100, 199]
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index=0 means label 100 index=0 means label 100
... ...
index 99 means label 199 index 99 means label 199
index 100 means label 1000 index 100 means label 1000
index 199 means label 1099 index 199 means label 1099
... ...
index 200 means label 500 index 200 means label 500
... ...
RI LSA can be advertised at any of the defined flooding scopes (link, The RI LSA can be advertised at any of the defined flooding scopes
area, or autonomous system (AS)). For the purpose of the SR- (link, area, or autonomous system (AS)). For the purposes of the SR-
Capability TLV propagation area scope flooding is required. Capability TLV propagation, area scope flooding is required.
4. OSPFv2 Extended Prefix Opaque LSA type 4. OSPFv2 Extended Prefix Opaque LSA
A new Opaque LSA (defined in [RFC5250]) is defined in OSPFv2 in order A new Opaque LSA (defined in [RFC5250]) is defined in OSPFv2 in order
to advertise additional prefix attributes: OSPFv2 Extended Prefix to advertise additional prefix attributes: OSPFv2 Extended Prefix
Opaque LSA. Opaque LSA.
Multiple OSPFv2 Extended Prefix Opaque LSAs can be advertised by a Multiple OSPFv2 Extended Prefix Opaque LSAs can be advertised by an
single router. Flooding scope of the OSPFv2 Extended Prefix Opaque OSPFv2 router. The flooding scope of the OSPFv2 Extended Prefix
LSA depends on the content inside the LSA and is in control of the Opaque LSA depends on the scope of the advertised prefixes and is
originating router. under the control of the advertising router. In some cases (e.g.,
mapping server deployment), the LSA flooding scope may be greater
than the scope of the corresponding prefixes.
The format of the OSPFv2 Extended Prefix Opaque LSA is as follows: The format of the OSPFv2 Extended Prefix Opaque LSA is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | 9, 10, or 11 | | LS age | Options | 9, 10, or 11 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque type | Instance | | Opaque type | Instance |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router | | Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number | | LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length | | LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+- TLVs -+ +- TLVs -+
| ... | | ... |
Opaque type used by OSPFv2 Extended Prefix Opaque LSA is 7. The opaque type used by OSPFv2 Extended Prefix Opaque LSA is 7.
The format of the TLVs within the body of the LSA is the same as the The format of the TLVs within the body of the LSA is the same as the
format used by the Traffic Engineering Extensions to OSPF defined in format used by the Traffic Engineering Extensions to OSPF defined in
[RFC3630]. The LSA payload consists of one or more nested [RFC3630]. The LSA payload consists of one or more nested
Type/Length/Value (TLV) triplets. The format of each TLV is: Type/Length/Value (TLV) triplets. The format of each TLV is:
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 |
skipping to change at page 8, line 46 skipping to change at page 8, line 46
The Length field defines the length of the value portion in octets. The Length field defines the length of the value portion in octets.
The TLV is padded to 4-octet alignment; padding is not included in The TLV is padded to 4-octet alignment; padding is not included in
the length field. Nested TLVs are also 32-bit aligned. Unrecognized the length field. Nested TLVs are also 32-bit aligned. Unrecognized
types are ignored. types are ignored.
4.1. OSPF Extended Prefix TLV 4.1. OSPF Extended Prefix TLV
The OSPF Extended Prefix TLV is used in order to advertise additional The OSPF Extended Prefix TLV is used in order to advertise additional
attributes associated with the prefix. Multiple OSPF Extended Prefix attributes associated with the prefix. Multiple OSPF Extended Prefix
TLVs MAY be carried in each OSPFv2 Extended Prefix Opaque LSA, TLVs MAY be advertised in each OSPFv2 Extended Prefix Opaque LSA but
however all prefixes included in the single OSPFv2 Extended Prefix all prefixes included in a single OSPFv2 Extended Prefix Opaque LSA
Opaque LSA MUST have the same flooding scope. The structure of the MUST have the same flooding scope. The OSPF Extended Prefix TLV has
OSPF Extended Prefix TLV is as follows: 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Route Type | Prefix Length | AF | Reserved | | Route Type | Prefix Length | AF | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Prefix (variable) | | Address Prefix (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 9, line 32 skipping to change at page 9, line 32
Length: variable Length: variable
Route type: type of the OSPF route. Supported types are: Route type: type of the OSPF route. Supported types are:
0 - unspecified 0 - unspecified
1 - intra-area 1 - intra-area
3 - inter-area 3 - inter-area
5 - external 5 - external
7 - NSSA external 7 - NSSA external
If the route type is 0 (unspecified) the information inside the If the route type is 0 (unspecified), the information inside the
OSPF External Prefix TLV applies to the prefix regardless of what OSPF External Prefix TLV applies to the prefix regardless of
route-type it is. This is useful when some prefix specific prefix's route-type. This is useful when some prefix specific
attributes are advertised by some external entity, which is not attributes are advertised by some external entity, which is not
aware of the route-type associated with the prefix. aware of the route-type associated with the prefix.
Prefix length: length of the prefix Prefix length: length of the prefix
AF: 0 - IPv4 unicast AF: 0 - IPv4 unicast
Address Prefix: the prefix itself encoded as an even multiple of Address Prefix: the prefix itself encoded as an even multiple of
32-bit words, padded with zeroed bits as necessary. This encoding 32-bit words, padded with zeroed bits as necessary. This encoding
consumes ((PrefixLength + 31) / 32) 32-bit words. The default consumes ((PrefixLength + 31) / 32) 32-bit words. The default
skipping to change at page 10, line 25 skipping to change at page 10, line 25
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
Type: TBD, suggested value 2. Type: TBD, suggested value 2.
Length: variable Length: variable
Flags: 1 octet field. The following flags are defined: Flags: 1 octet field. The following flags are defined:
0 0 1 2 3 4 5 6 7
0 1 2 3 4 5 6 7 +--+--+--+--+--+--+--+--+
+-+-+-+-+-+-+-+-+ |N |NP|M |E |V |L | | |
|N|P|M|E|V|L| | +--+--+--+--+--+--+--+--+
+-+-+-+-+-+-+-+-+
where: where:
N-Flag: Node-SID flag. If set, then the Prefix-SID refers to N-Flag: Node-SID flag. If set, then the Prefix-SID refers to
the router identified by the prefix. Typically, the N-Flag is the router identified by the prefix. Typically, the N-Flag is
set on Prefix-SIDs attached to a router loopback address. The set on Prefix-SIDs attached to a router loopback address. The
N-Flag is set when the Prefix-SID is a Node- SID as described N-Flag is set when the Prefix-SID is a Node-SID, as described
in [I-D.filsfils-rtgwg-segment-routing]. in [I-D.filsfils-rtgwg-segment-routing].
P-Flag: no-PHP flag. If set, then the penultimate hop MUST NOT NP-Flag: no-PHP flag. If set, then the penultimate hop MUST
pop the Prefix-SID before delivering the packet to the node NOT pop the Prefix-SID before delivering the packet 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 is advertised
from the Segment Routing Mapping Server functionality as from the Segment Routing Mapping Server functionality as
described in [I-D.filsfils-rtgwg-segment-routing-use-cases]. described in [I-D.filsfils-rtgwg-segment-routing].
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 a
Prefix-SID having an Explicit-NULL value (0 for IPv4) before Prefix-SID having an Explicit-NULL value (0 for IPv4) before
forwarding the packet. forwarding the packet.
The V-Flag: Value/Index Flag. If set, then the Prefix-SID The V-Flag: Value/Index Flag. If set, then the Prefix-SID
carries an absolute value. If not set, then the Prefix-SID carries an absolute value. If not set, then the Prefix-SID
carries an index. carries an index.
skipping to change at page 12, line 5 skipping to change at page 12, line 5
original ordering, when advertising prefix-SIDs to other areas. This original ordering, when advertising prefix-SIDs to other areas. This
allows implementations that only use single Prefix-SID to have a allows implementations that only use single Prefix-SID to have a
consistent view across areas. 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 E and P flags advertised by the next-hop router, if
next-hop router advertised the SID for the prefix. This MUST be done next-hop router advertised the SID for the prefix. This MUST be done
regardless of next-hop router contributing to the best path to the regardless of next-hop router contributing to the best path to the
prefix or not. prefix or not.
P-Flag (no-PHP) MUST be set on the Prefix-SIDs allocated to inter- NP-Flag (no-PHP) MUST be set on the Prefix-SIDs allocated to inter-
area prefixes that are originated by the ABR based on intra-area or area prefixes that are originated by the ABR based on intra-area or
inter-area reachability between areas. In case the inter-area prefix inter-area reachability between areas. In case the inter-area prefix
is generated based on the prefix which is directly attached to the is generated based on the prefix which is directly attached to the
ABR, P-Flag SHOULD NOT be set ABR, NP-Flag SHOULD NOT be set
P-Flag (no-PHP) MUST NOT be set on the Prefix-SIDs allocated to NP-flag (no-PHP) MUST NOT be set on the Prefix-SIDs allocated to
redistributed prefixes, unless the redistributed prefix is directly redistributed prefixes, unless the redistributed prefix is directly
attached to ASBR, in which case the P-Flag SHOULD NOT be set. attached to ASBR, in which case the NP-flag SHOULD NOT be set.
If the P-flag is not set then any upstream neighbor of the Prefix-SID If the NP-flag is not set then any upstream neighbor of the Prefix-
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. In
such case MPLS EXP bits of the Prefix-SID are not preserved to the such case MPLS EXP bits of the Prefix-SID are not preserved to the
ultimate hop (the Prefix-SID being removed). If the P-flag is unset ultimate hop (the Prefix-SID being removed). If the NP-flag is clear
the received E-flag is ignored. the received E-flag is ignored.
If the P-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 Prefix-
SID originator MUST keep the Prefix-SID on top of the stack. This SID originator MUST keep the Prefix-SID on top of the stack. This
is useful when the originator of the Prefix-SID must stitch the is useful when the originator of the Prefix-SID must stitch the
incoming packet into a continuing MPLS LSP to the final incoming packet into a continuing MPLS LSP to the final
destination. This could occur at an inter-area border router destination. This could occur at an inter-area border router
(prefix propagation from one area to another) or at an inter- (prefix propagation from one area to another) or at an inter-
domain border router (prefix propagation from one domain to domain border 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 PrefixSID with a Prefix-SID having an originator MUST replace the PrefixSID with a Prefix-SID having an
Explicit-NULL value. This is useful, e.g., when the originator of Explicit-NULL value. This is useful, e.g., when the originator of
the Prefix-SID is the final destination for the related prefix and the Prefix-SID is the final destination for the related prefix and
the originator wishes to receive the packet with the original EXP the originator wishes to receive the packet with the original EXP
bits. bits.
When M-Flag is set, P-flag MUST be set and E-bit MUST NOT be set. When M-Flag is set, NP-flag MUST be set and E-bit MUST NOT be set.
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: 192.0.2.1/32, Prefix-SID: Index 1 Router-A: 192.0.2.1/32, Prefix-SID: Index 1
Router-B: 192.0.2.2/32, Prefix-SID: Index 2 Router-B: 192.0.2.2/32, Prefix-SID: Index 2
Router-C: 192.0.2.3/32, Prefix-SID: Index 3 Router-C: 192.0.2.3/32, Prefix-SID: Index 3
Router-D: 192.0.2.4/32, Prefix-SID: Index 4 Router-D: 192.0.2.4/32, Prefix-SID: Index 4
then the Prefix field in Extended Prefix TLV would be set to then the Prefix field in Extended Prefix TLV would be set to
skipping to change at page 13, line 22 skipping to change at page 13, line 22
10.1.5/24, Prefix-SID: Index 55 10.1.5/24, Prefix-SID: Index 55
10.1.6/24, Prefix-SID: Index 56 10.1.6/24, Prefix-SID: Index 56
10.1.7/24, Prefix-SID: Index 57 10.1.7/24, Prefix-SID: Index 57
then the Prefix field in Extended Prefix TLV would be set to then the Prefix field in Extended Prefix TLV would be set to
10.1.1.0, Prefix Length would be set to 24, Range Size in Prefix SID 10.1.1.0, Prefix Length would be set to 24, Range Size in Prefix SID
sub-TLV would be 7 and Index value would be set to 51. sub-TLV would be 7 and Index value would be set to 51.
4.3. SID/Label Binding sub-TLV 4.3. SID/Label Binding sub-TLV
SID/Label Binding sub-TLV is used to advertise SID/Label mapping for The SID/Label Binding sub-TLV is used to advertise a SID/Label
a path to the prefix. mapping for a path to the prefix.
The SID/Label Binding TLV MAY be originated by any router in an OSPF The SID/Label Binding TLV MAY be originated by any router in an OSPF
domain. The router may advertise a SID/Label binding to a FEC along domain. The router may advertise a SID/Label binding to a FEC along
with at least a single 'nexthop style' anchor. The protocol supports with at least a single 'nexthop style' anchor. The protocol supports
more than one 'nexthop style' anchor to be attached to a SID/Label more than one 'nexthop style' anchor to be attached to a SID/Label
binding, which results into a simple path description language. In binding, which results in a simple path description language. In
analogy to RSVP the terminology for this is called an 'Explicit Route analogy to RSVP, the terminology for this is called an 'Explicit
Object' (ERO). Since ERO style path notation allows to anchor SID/ Route Object' (ERO). Since ERO style path notation allows to anchor
label bindings to both link and node IP addresses any label switched SID/label bindings to both link and node IP addresses, any label
path, can be described. Furthermore also SID/Label Bindings from switched path can be described. Additionally, SID/Label Bindings
external protocols can get easily re-advertised. from external protocols can be easily re-advertised.
The SID/Label Binding TLV may be used for advertising SID/Label The SID/Label Binding TLV may be used for advertising SID/Label
Bindings and their associated Primary and Backup paths. In one Bindings and their associated Primary and Backup paths. In a single
single TLV either a primary ERO Path, a backup ERO Path or both are TLV, a primary ERO Path, backup ERO Path, or both can be advertised.
advertised. If a router wants to advertise multiple parallel paths If a router wants to advertise multiple parallel paths, then it can
then it can generate several TLVs for the same Prefix/FEC. Each generate several TLVs for the same Prefix/FEC. Each occurrence of a
occurrence of a Binding TLV with respect with a given FEC Prefix has Binding TLV for a given FEC Prefix will add a new path.
accumulating and not canceling semantics.
SID/Label Binding sub-TLV is as sub-TLV of the OSPF Extended Prefix The SID/Label Binding sub-TLV is a sub-TLV of the OSPF Extended
TLV. Multiple SID/Label Binding TLVs can be present in OSPF Extended Prefix TLV. Multiple SID/Label Binding TLVs can be present in OSPF
Prefix TLV. SID/Label Binding sub-TLV has following format: Extended Prefix TLV. The SID/Label Binding sub-TLV has 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 | Reserved | MT-ID | Weight | | Flags | Reserved | MT-ID | Weight |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Range Size | Reserved + | Range Size | Reserved +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 14, line 44 skipping to change at page 14, line 44
mirroring context as defined in mirroring context as defined in
[I-D.minto-rsvp-lsp-egress-fast-protection]. [I-D.minto-rsvp-lsp-egress-fast-protection].
MT-ID: Multi-Topology ID (as defined in [RFC4915]). MT-ID: Multi-Topology ID (as defined in [RFC4915]).
Weight: weight used for load-balancing purposes. The use of the Weight: weight used for load-balancing purposes. The use of the
weight is defined in [I-D.filsfils-rtgwg-segment-routing]. weight is defined in [I-D.filsfils-rtgwg-segment-routing].
Range Size: usage is the same as described in Section 4.2. Range Size: usage is the same as described in Section 4.2.
SID/Label Binding TLV currently supports following Sub-TLVs: The SID/Label Binding TLV supports the following Sub-TLVs:
SID/Label sub-TLV as described in Section 2.1. This sub-TLV MUST 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 appear in the SID/Label Binding Sub-TLV and it MUST only appear
once. once.
ERO Metric sub-TLV as defined in Section 4.3.1. ERO Metric sub-TLV as defined in Section 4.3.1.
ERO sub-TLVs as defined in Section 4.3.2. ERO sub-TLVs as defined in Section 4.3.2.
4.3.1. ERO Metric sub-TLV 4.3.1. ERO Metric sub-TLV
ERO Metric sub-TLV is a Sub-TLV of the SID/Label Binding TLV. ERO Metric sub-TLV is a Sub-TLV of the SID/Label Binding TLV.
The ERO Metric sub-TLV carries the cost of an ERO path. It is used The ERO Metric sub-TLV advertises the cost of an ERO path. It is
to compare the cost of a given source/destination path. A router used to compare the cost of a given source/destination path. A
SHOULD advertise the ERO Metric sub-TLV. The cost of the ERO Metric router SHOULD advertise the ERO Metric sub-TLV. The cost of the ERO
sub-TLV SHOULD be set to the cumulative IGP or TE path cost of the Metric sub-TLV SHOULD be set to the cumulative IGP or TE path cost of
advertised ERO. Since manipulation of the Metric field may attract the advertised ERO. Since manipulation of the Metric field may
or distract traffic from and to the advertised segment it MAY be attract or repel traffic to and from the advertised segment, it MAY
manually overridden. be manually overridden.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Metric (4 octets) | | Metric (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ERO Metric sub-TLV format ERO Metric sub-TLV format
skipping to change at page 16, line 5 skipping to change at page 16, line 5
closest to the egress point, contrary the first ERO sub-TLV describes closest to the egress point, contrary the first ERO sub-TLV describes
the first segment of a path. If a router extends or stitches a path the first segment of a path. If a router extends or stitches a path
it MUST prepend the new segments path information to the ERO list. it MUST prepend the new segments path information to the ERO list.
The above similarly applies to backup EROs. The above similarly applies to backup EROs.
All ERO Sub-TLVs must immediately follow the (SID)/Label Sub-TLV. All ERO Sub-TLVs must immediately follow the (SID)/Label Sub-TLV.
All Backup sub-ERO TLVs must immediately follow last ERO Sub-TLV. All Backup sub-ERO TLVs must immediately follow last ERO Sub-TLV.
4.3.2.1. IPv4 ERO subTLV 4.3.2.1. IPv4 ERO sub-TLV
IPv4 ERO sub-TLV is a Sub-TLV of the SID/Label Binding 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 The IPv4 ERO sub-TLV describes a path segment using IPv4 Address
style of encoding. Its semantics have been borrowed from [RFC3209]. style of encoding. Its semantics have been borrowed from [RFC3209].
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 | Reserved | | Flags | Reserved |
skipping to change at page 16, line 46 skipping to change at page 16, line 46
where: where:
L-bit - If the L bit is set, then the value of the attribute is L-bit - If the L bit is set, then the value of the attribute is
'loose.' Otherwise, the value of the attribute is 'strict.' 'loose.' Otherwise, the value of the attribute is 'strict.'
IPv4 Address - the address of the explicit route hop. IPv4 Address - the address of the explicit route hop.
4.3.2.2. Unnumbered Interface ID ERO sub-TLV 4.3.2.2. Unnumbered Interface ID ERO sub-TLV
Unnumbered Interface ID ERO sub-TLV is a Sub-TLV of the SID/Label Unnumbered Interface ID ERO sub-TLV is a sub-TLV of the SID/Label
Binding sub-TLV. Binding sub-TLV.
The appearance and semantics of the 'Unnumbered Interface ID' have The appearance and semantics of the 'Unnumbered Interface ID' have
been borrowed from [RFC3477]. been borrowed from [RFC3477].
The Unnumbered Interface-ID ERO sub-TLV describes a path segment that The Unnumbered Interface-ID ERO sub-TLV describes a path segment that
spans over an unnumbered interface. Unnumbered interfaces are includes an unnumbered interface. Unnumbered interfaces are
referenced using the interface index. Interface indices are assigned referenced using the interface index. Interface indices are assigned
local to the router and therefore not unique within a domain. All 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 elements in an ERO path need to be unique within a domain and hence
need to be disambiguated using a domain unique Router-ID. need to be disambiguated using a domain unique Router-ID.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 18, line 48 skipping to change at page 18, line 48
where: where:
L-bit - If the L bit is set, then the value of the attribute is L-bit - If the L bit is set, then the value of the attribute is
'loose.' Otherwise, the value of the attribute is 'strict.' 'loose.' Otherwise, the value of the attribute is 'strict.'
IPv4 Address - the address of the explicit route hop. IPv4 Address - the address of the explicit route hop.
4.3.2.4. Unnumbered Interface ID Backup ERO sub-TLV 4.3.2.4. Unnumbered Interface ID Backup ERO sub-TLV
Unnumbered Interface ID Backup -sub-TLV is a sub-TLV of the SID/Label Unnumbered Interface ID Backup sub-TLV is a sub-TLV of the SID/Label
Binding sub-TLV. Binding sub-TLV.
The appearance and semantics of the 'Unnumbered Interface ID' have The appearance and semantics of the 'Unnumbered Interface ID' have
been borrowed from [RFC3477]. been borrowed from [RFC3477].
The Unnumbered Interface-ID ERO sub-TLV describes a path segment that The Unnumbered Interface-ID ERO sub-TLV describes a path segment that
spans over an unnumbered interface. Unnumbered interfaces are includes an unnumbered interface. Unnumbered interfaces are
referenced using the interface index. Interface indices are assigned referenced using the interface index. Interface indices are assigned
local to the router and therefore not unique within a domain. All 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 elements in an ERO path need to be unique within a domain and hence
need to be disambiguated using a domain unique Router-ID. need to be disambiguated using a domain unique Router-ID.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 20, line 8 skipping to change at page 20, line 8
'loose.' Otherwise, the value of the attribute is 'strict.' 'loose.' Otherwise, the value of the attribute is 'strict.'
Router-ID: Router-ID of the next-hop. Router-ID: Router-ID of the next-hop.
Interface ID: is the identifier assigned to the link by the router Interface ID: is the identifier assigned to the link by the router
specified by the Router-ID. specified by the Router-ID.
5. Adjacency Segment Identifier (Adj-SID) 5. 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. At the current stage of Segment adjacency in Segment Routing.
Routing architecture it is assumed that the Adj-SID value has local
significance (to the router).
5.1. OSPFv2 Extended Link Opaque LSA 5.1. OSPFv2 Extended Link Opaque LSA
A new Opaque LSA (defined in [RFC5250] is defined in OSPFv2 in order A new Opaque LSA (defined in [RFC5250] is defined in OSPFv2 in order
to advertise additional link attributes: the OSPFv2 Extended Link to advertise additional link attributes: the OSPFv2 Extended Link
Opaque LSA. Opaque LSA.
The OSPFv2 Extended Link Opaque LSA has an area flooding scope. The OSPFv2 Extended Link Opaque LSA has an area flooding scope.
Multiple OSPFv2 Extended Link Opaque LSAs can be advertised by a Multiple OSPFv2 Extended Link Opaque LSAs can be advertised by a
single router in an area. single router in an area.
skipping to change at page 21, line 23 skipping to change at page 21, line 14
The Length field defines the length of the value portion in octets. The Length field defines the length of the value portion in octets.
The TLV is padded to 4-octet alignment; padding is not included in The TLV is padded to 4-octet alignment; padding is not included in
the length field. Nested TLVs are also 32-bit aligned. Unrecognized the length field. Nested TLVs are also 32-bit aligned. Unrecognized
types are ignored. types are ignored.
5.2. OSPFv2 Extended Link TLV 5.2. OSPFv2 Extended Link TLV
OSPFv2 Extended Link TLV is used in order to advertise various OSPFv2 Extended Link TLV is used in order to advertise various
attributes of the link. It describes a single link and is attributes of the link. It describes a single link and is
constructed of a set of Sub-TLVs. There are no ordering requirements constructed of a set of Sub-TLVs. There are no ordering requirements
for the Sub-TLVs. Only one Extended Link TLV SHALL be carried in for the Sub-TLVs. Only one Extended Link TLV SHALL be advertised in
each Extended Link Opaque LSA, allowing for fine granularity changes each Extended Link Opaque LSA, allowing for fine granularity changes
in the topology. in the topology.
The Extended Link TLV has following format: The Extended Link TLV has 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 22, line 9 skipping to change at page 21, line 49
Length is variable. Length is variable.
Link-Type: as defined in section A.4.2 of [RFC2328]. Link-Type: as defined in section A.4.2 of [RFC2328].
Link-ID: as defined in section A.4.2 of [RFC2328]. Link-ID: as defined in section A.4.2 of [RFC2328].
Link Data: as defined in section A.4.2 of [RFC2328]. Link Data: as defined in section A.4.2 of [RFC2328].
5.3. Adj-SID sub-TLV 5.3. Adj-SID sub-TLV
Adj-SID is an optional Sub-TLV of the Extended Link TLV. It MAY Adj-SID is an optional sub-TLV of the Extended Link TLV. It MAY
appear multiple times in Extended Link TLV. Examples where more than appear multiple times in the Extended Link TLV. Examples where more
one Adj-SID may be used per neighbor are described in than one Adj-SID may be used per neighbor are described in
[I-D.filsfils-rtgwg-segment-routing-use-cases]. The structure of the
Adj-SID Sub-TLV is as follows: [I-D.filsfils-rtgwg-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 | Reserved | MT-ID | Weight | | Flags | Reserved | MT-ID | Weight |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID/Label/Index (variable) | | SID/Label/Index (variable) |
+---------------------------------------------------------------+ +---------------------------------------------------------------+
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Flags. 1 octet field of following flags: Flags. 1 octet field of following flags:
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|B|V|L|S| | |B|V|L|S| |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
where: where:
B-Flag: Backup-flag: set if the Adj-SID refer to an adjacency B-Flag: Backup-flag: set if the Adj-SID refers to an adjacency
being protected (e.g.: using IPFRR or MPLS-FRR) as described in being protected (e.g.: using IPFRR or MPLS-FRR) as described in
[I-D.filsfils-rtgwg-segment-routing-use-cases]. [I-D.filsfils-rtgwg-segment-routing-use-cases].
The V-Flag: Value/Index Flag. If set, then the Prefix-SID The V-Flag: Value/Index Flag. If set, then the Prefix-SID
carries an absolute value. If not set, then the Prefix-SID carries an absolute value. If not set, then the Prefix-SID
carries an index. carries an 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 PrefixSID has local significance. If not set, carried by the PrefixSID has local significance. If not set,
then the value/index carried by this subTLV has global then the value/index carried by this subTLV has global
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SID/Index/Label: according to the V and L flags, it contains SID/Index/Label: according to the V and L flags, it contains
either: either:
A 32 bit index defining the offset in the SID/Label space A 32 bit index defining the offset in the SID/Label space
advertised by this router. advertised by this router.
A 24 bit label where the 20 rightmost bits are used for A 24 bit label where the 20 rightmost bits are used for
encoding the label value. encoding the label value.
A 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 protected by a adjacencies and set the B-Flag when the adjacency is protected by an
FRR mechanism (IP or MPLS) as described in FRR mechanism (IP or MPLS) as described in
[I-D.filsfils-rtgwg-segment-routing-use-cases]. [I-D.filsfils-rtgwg-segment-routing-use-cases].
5.4. LAN Adj-SID Sub-TLV 5.4. LAN Adj-SID Sub-TLV
LAN Adj-SID is an optional Sub-TLV of the Extended Link TLV. It MAY LAN Adj-SID is an optional sub-TLV of the Extended Link TLV. It MAY
appear multiple times in Extended Link TLV. It is used to advertise appear multiple times in Extended Link TLV. It is used to advertise
SID/Label for adjacency to non-DR node on broadcast or NBMA network. SID/Label for adjacency to non-DR node on broadcast or NBMA 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 | Reserved | MT-ID | Weight | | Flags | Reserved | MT-ID | Weight |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 25, line 10 skipping to change at page 24, line 51
advertised by this router. advertised by this router.
A 24 bit label where the 20 rightmost bits are used for A 24 bit label where the 20 rightmost bits are used for
encoding the label value. encoding the label value.
6. Elements of Procedure 6. Elements of Procedure
6.1. Intra-area Segment routing in OSPFv2 6.1. Intra-area Segment routing in OSPFv2
The OSPFv2 node that supports segment routing MAY advertise Prefix- The OSPFv2 node 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 4.2. loopback IP address as described in Section 4.2).
If multiple routers advertise Prefix-SID for the same prefix, then If multiple routers advertise Prefix-SID for the same prefix, then
the Prefix-SID MUST be the same. This is required in order to allow the Prefix-SID MUST be the same. This is required in order to allow
traffic load-balancing if multiple equal cost paths to the traffic load-balancing if multiple equal cost paths to the
destination exist in the network. destination exist in the network.
Prefix-SID can also be advertised by the SR Mapping Servers (as Prefix-SID can also be advertised by the SR Mapping Servers (as
described in [I-D.filsfils-rtgwg-segment-routing-use-cases]). The described in [I-D.filsfils-rtgwg-segment-routing-use-cases]). The
Mapping Server advertise Prefix-SID for remote prefixes that exist in Mapping Server advertises Prefix-SIDs for remote prefixes that exist
the network. Multiple Mapping Servers can advertise Prefix-SID for in the OSPFv2 routing domain. Multiple Mapping Servers can advertise
the same prefix, in which case the same Prefix-SID MUST be advertised Prefix-SIDs for the same prefix, in which case the same Prefix-SID
by all of them. Flooding scope of the OSPF Extended Prefix Opaque MUST be advertised by all of them. The flooding scope of the OSPF
LSA that is generated by the SR Mapping Server could be either area Extended Prefix Opaque LSA that is generated by the SR Mapping Server
scope or autonomous system scope and is decided based on the could be either area scoped or AS scoped and is determined based on
configuration of the SR Mapping Server. the configuration of the SR Mapping Server.
6.2. Inter-area Segment routing in OSPFv2 6.2. Inter-area Segment routing in OSPFv2
In order to support SR in a multi-area environment, OSPFv2 must In order to support SR in a multi-area environment, OSPFv2 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 in order to propagate Prefix SIDs between areas.
When an OSPF ABR advertises a Type-3 Summary LSA from an intra-area When an OSPF ABR advertises a Type-3 Summary LSA from an intra-area
prefix to all its connected areas, it will also originate an Extended prefix to all its connected areas, it will also originate an Extended
Prefix Opaque LSA, as described in Section 4. The flooding scope of Prefix Opaque LSA, as described in Section 4. The flooding scope of
the Extended Prefix Opaque LSA type will be set to area-scope. The the Extended Prefix Opaque LSA type will be set to area-scope. The
route-type in OSPF Extended Prefix TLV is set to inter-area. The route-type in OSPF Extended Prefix TLV is set to inter-area. The
Prefix-SID Sub-TLV will be included in this LSA and the Prefix-SID Prefix-SID Sub-TLV will be included in this LSA and the Prefix-SID
value will be set as follows: value 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 source
area and find out the advertising router associated with its best area and find the advertising router associated with its best path
path to that prefix. to that prefix.
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, by the router that contributes to the best path to the prefix,
then the ABR will use the Prefix-SID advertised by any other then the ABR will use the Prefix-SID advertised by any other
router (e.g.: a Prefix-SID coming from an SR Mapping Server as router (e.g.: a Prefix-SID coming from an SR Mapping Server as
defined in [I-D.filsfils-rtgwg-segment-routing-use-cases]) when defined in [I-D.filsfils-rtgwg-segment-routing-use-cases]) when
propagating Prefix-SID for the prefix to other areas. propagating the Prefix-SID for the prefix to other areas.
When an OSPF ABR advertises Type-3 Summary LSAs from an inter-area When an OSPF ABR advertises Type-3 Summary LSAs from an inter-area
route to all its connected areas it will also originate an Extended route to all its connected areas it will also originate an Extended
Prefix Opaque LSA, as described in Section 4. The flooding scope of Prefix Opaque LSA, as described in Section 4. The flooding scope of
the Extended Prefix Opaque LSA type will be set to area-scope. The the Extended Prefix Opaque LSA type will be set to area-scope. The
route-type in OSPF Extended Prefix TLV is set to inter-area. The route-type in OSPF Extended Prefix TLV is set to inter-area. The
Prefix-SID Sub-TLV will be included in this LSA and the Prefix-SID Prefix-SID Sub-TLV will be included in this LSA and the Prefix-SID
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 source
area and find out the advertising router associated with its best area and find the advertising router associated with its 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 source area
by the ABR that contributes to the best path to the prefix, the by the ABR 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 (e.g.: a Prefix-SID coming from an SR Mapping Server as router (e.g.: a Prefix-SID coming from an SR Mapping Server as
defined in [I-D.filsfils-rtgwg-segment-routing-use-cases]) when defined in [I-D.filsfils-rtgwg-segment-routing-use-cases]) when
propagating Prefix-SID for the prefix to other areas. propagating the Prefix-SID for the prefix to other areas.
6.3. SID for External Prefixes 6.3. SID for External Prefixes
Type-5 LSAs are flooded domain wide. When an ASBR, which supports Type-5 LSAs are flooded domain wide. When an ASBR, which supports
SR, generates Type-5 LSAs, it should also originate Extended Prefix SR, generates Type-5 LSAs, it should also originate an Extended
Opaque LSAs, as described in Section 4. The flooding scope of the Prefix Opaque LSAs, as described in Section 4. The flooding scope of
Extended Prefix Opaque LSA type is set to AS-scope. The route-type the Extended Prefix Opaque LSA type is set to AS-scope. The route-
in OSPF Extended Prefix TLV is set to external. Prefix-SID Sub-TLV type in OSPF Extended Prefix TLV is set to external. The Prefix-SID
is included in this LSA and the Prefix-SID value will be set to the sub-TLV is included in this LSA and the Prefix-SID value will be set
SID that has been reserved for that prefix. to the SID that has been reserved for that prefix.
When a NSSA ASBR translates Type-7 LSAs into Type-5 LSAs, it should When a NSSA ASBR translates Type-7 LSAs into Type-5 LSAs, it should
also advertise the Prefix-SID for the prefix. The NSSA ABR also advertise the Prefix-SID for the prefix. The NSSA ABR
determines its best path to the prefix advertised in the translated determines its best path to the prefix advertised in the translated
Type-7 LSA and finds the advertising router associated with such Type-7 LSA and finds the advertising router associated with such
path. If such advertising router has advertised a Prefix-SID for the path. If such advertising router has advertised a Prefix-SID, for
prefix, then the NSSA ASBR uses it when advertising the Prefix-SID the prefix, then the NSSA ASBR uses it when advertising the Prefix-
for the Type-5 prefix. Otherwise the Prefix-SID advertised by any SID for the Type-5 prefix. Otherwise, the Prefix-SID advertised by
other router will be used (e.g.: a Prefix-SID coming from an SR any other router will be used (e.g.: a Prefix-SID coming from an SR
Mapping Server as defined in Mapping Server as defined in
[I-D.filsfils-rtgwg-segment-routing-use-cases]). [I-D.filsfils-rtgwg-segment-routing-use-cases]).
6.4. Advertisement of Adj-SID 6.4. 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 5. using the Adj-SID Sub-TLV as described in Section 5.
6.4.1. Advertisement of Adj-SID on Point-to-Point Links 6.4.1. Advertisement of Adj-SID on Point-to-Point Links
Adj-SID MAY be advertised for any adjacency on p2p link that is in a Adj-SID MAY be advertised for any adjacency on a p2p link that is in
state 2-Way or higher. If the adjacency on a p2p link transitions neighbor state 2-Way or higher. If the adjacency on a p2p link
from the FULL state, then the Adj-SID for that adjacency MAY be transitions from the FULL state, then the Adj-SID for that adjacency
removed from the area. If the adjacency transitions to a state lower MAY be removed from the area. If the adjacency transitions to a
then 2-Way, then the Adj-SID MUST be removed from the area. state lower then 2-Way, then the Adj-SID MUST be removed from the
area.
6.4.2. Adjacency SID on Broadcast or NBMA Interfaces 6.4.2. Adjacency SID on Broadcast or NBMA Interfaces
Broadcast or NBMA networks in OSPF are represented by a star topology Broadcast or NBMA networks in OSPF are represented by a star topology
where the Designated Router (DR) is the central point all other where the Designated Router (DR) is the central point all other
routers on the broadcast or NBMA network connect to. As a result, routers on the broadcast or NBMA network connect to. As a result,
routers on the broadcast or NBMA network advertise only their routers on the broadcast or NBMA network advertise only their
adjacency to DR and BDR. Routers that are neither DR nor BDR do not adjacency to DR and BDR. Routers that are neither DR nor BDR do not
form and do not advertise adjacencies between them. They, however, form and do not advertise adjacencies between them. They, however,
maintain a 2-Way adjacency state between them. maintain a 2-Way adjacency state between them.
skipping to change at page 30, line 22 skipping to change at page 30, line 15
8. Security Considerations 8. Security Considerations
In general, new LSAs defined in this document are subject to the same In general, new LSAs defined in this document are subject to the same
security concerns as those described in [RFC2328]. Additionally, security concerns as those described in [RFC2328]. Additionally,
implementations must assure that malformed TLV and Sub-TLV implementations must assure that malformed TLV and Sub-TLV
permutations do not result in errors which cause hard OSPF failures. permutations do not result in errors which cause hard OSPF failures.
9. Contributors 9. Contributors
The following people gave a substantial contribution to the content The following people gave a substantial contribution to the content
of this document: Ahmed Bashandy, Martin Horneffer, Bruno Decraene, of this document: Acee Lindem, Ahmed Bashandy, Martin Horneffer,
Stephane Litkowski, Igor Milojevic, Rob Shakir and Saku Ytti. Bruno Decraene, Stephane Litkowski, Igor Milojevic, Rob Shakir and
Saku Ytti.
10. Acknowledgements 10. Acknowledgements
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 Many thanks to Yakov Rekhter, John Drake and Shraddha Hedge for their
contribution on earlier incarnations of the "Binding / MPLS Label contribution on earlier incarnations of the "Binding / MPLS Label
TLV" in [I-D.gredler-ospf-label-advertisement]. TLV" in [I-D.gredler-ospf-label-advertisement].
Thanks to Acee Lindem for the detail review of the draft,
corrections, as well as discussion about details of the encoding.
11. References 11. References
11.1. Normative References 11.1. Normative References
[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, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
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