draft-ietf-ospf-segment-routing-extensions-17.txt   draft-ietf-ospf-segment-routing-extensions-18.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 25, 2017 Cisco Systems, Inc. Expires: January 19, 2018 Cisco Systems, Inc.
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 Individual
June 23, 2017 July 18, 2017
OSPF Extensions for Segment Routing OSPF Extensions for Segment Routing
draft-ietf-ospf-segment-routing-extensions-17 draft-ietf-ospf-segment-routing-extensions-18
Abstract Abstract
Segment Routing (SR) allows a flexible definition of end-to-end paths Segment Routing (SR) allows a flexible definition of end-to-end paths
within IGP topologies by encoding paths as sequences of topological within IGP topologies by encoding paths as sequences of topological
sub-paths, called "segments". These segments are advertised by the sub-paths, called "segments". These segments are advertised by the
link-state routing protocols (IS-IS and OSPF). link-state routing protocols (IS-IS and OSPF).
This draft describes the OSPF extensions required for Segment This draft describes the OSPF extensions required for Segment
Routing. Routing.
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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 25, 2017. This Internet-Draft will expire on January 19, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 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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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 TLV . . . . . . . . . . . . . . . . . . . 8 3.3. SR Local Block TLV . . . . . . . . . . . . . . . . . . . 8
3.4. SRMS Preference TLV . . . . . . . . . . . . . . . . . . . 10 3.4. SRMS Preference TLV . . . . . . . . . . . . . . . . . . . 10
4. OSPF Extended Prefix Range TLV . . . . . . . . . . . . . . . 11 4. OSPF Extended Prefix Range TLV . . . . . . . . . . . . . . . 11
5. Prefix SID Sub-TLV . . . . . . . . . . . . . . . . . . . . . 12 5. Prefix SID Sub-TLV . . . . . . . . . . . . . . . . . . . . . 13
6. Adjacency Segment Identifier (Adj-SID) . . . . . . . . . . . 16 6. Adjacency Segment Identifier (Adj-SID) . . . . . . . . . . . 16
6.1. Adj-SID Sub-TLV . . . . . . . . . . . . . . . . . . . . . 16 6.1. Adj-SID Sub-TLV . . . . . . . . . . . . . . . . . . . . . 16
6.2. LAN Adj-SID Sub-TLV . . . . . . . . . . . . . . . . . . . 18 6.2. LAN Adj-SID Sub-TLV . . . . . . . . . . . . . . . . . . . 18
7. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 19 7. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 19
7.1. Intra-area Segment routing in OSPFv2 . . . . . . . . . . 19 7.1. Intra-area Segment routing in OSPFv2 . . . . . . . . . . 19
7.2. Inter-area Segment routing in OSPFv2 . . . . . . . . . . 20 7.2. Inter-area Segment routing in OSPFv2 . . . . . . . . . . 20
7.3. Segment Routing for External Prefixes . . . . . . . . . . 21 7.3. Segment Routing for External Prefixes . . . . . . . . . . 21
7.4. Advertisement of Adj-SID . . . . . . . . . . . . . . . . 21 7.4. Advertisement of Adj-SID . . . . . . . . . . . . . . . . 21
7.4.1. Advertisement of Adj-SID on Point-to-Point Links . . 21 7.4.1. Advertisement of Adj-SID on Point-to-Point Links . . 21
7.4.2. Adjacency SID on Broadcast or NBMA Interfaces . . . . 21 7.4.2. Adjacency SID on Broadcast or NBMA Interfaces . . . . 21
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8.1. OSPF OSPF Router Information (RI) TLVs Registry . . . . . 22 8.1. OSPF OSPF Router Information (RI) TLVs Registry . . . . . 22
8.2. OSPF Extended Prefix LSA TLV Registry . . . . . . . . . . 22 8.2. OSPF Extended Prefix LSA TLV Registry . . . . . . . . . . 22
8.3. OSPF Extended Prefix LSA Sub-TLV Registry . . . . . . . . 22 8.3. OSPF Extended Prefix LSA Sub-TLV Registry . . . . . . . . 22
8.4. OSPF Extended Link LSA Sub-TLV Registry . . . . . . . . . 22 8.4. OSPF Extended Link LSA Sub-TLV Registry . . . . . . . . . 22
9. Implementation Status . . . . . . . . . . . . . . . . . . . . 23 9. Implementation Status . . . . . . . . . . . . . . . . . . . . 23
10. Security Considerations . . . . . . . . . . . . . . . . . . . 24 10. Security Considerations . . . . . . . . . . . . . . . . . . . 24
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 25 11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 25
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 25 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 25
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
13.1. Normative References . . . . . . . . . . . . . . . . . . 25 13.1. Normative References . . . . . . . . . . . . . . . . . . 25
13.2. Informative References . . . . . . . . . . . . . . . . . 25 13.2. Informative References . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
1. Introduction 1. Introduction
Segment Routing (SR) allows a flexible definition of end-to-end paths Segment Routing (SR) allows a flexible definition of end-to-end paths
within IGP topologies by encoding paths as sequences of topological within IGP topologies by encoding paths as sequences of topological
sub-paths, called "segments". These segments are advertised by the sub-paths, called "segments". These segments are advertised by the
link-state routing protocols (IS-IS and OSPF). Prefix segments link-state routing protocols (IS-IS and OSPF). Prefix segments
represent an ECMP-aware shortest-path to a prefix (or a node), as per represent an ECMP-aware shortest-path to a prefix (or a node), as per
the state of the IGP topology. Adjacency segments represent a hop the state of the IGP topology. Adjacency segments represent a hop
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support for Algorithm 1 MUST NOT alter the SPF paths computed support for Algorithm 1 MUST NOT alter the SPF paths computed
by Algorithm 1. by Algorithm 1.
When multiple SR-Algorithm TLVs are received from a given router, the When multiple SR-Algorithm TLVs are received from a given router, the
receiver SHOULD use the first occurrence of the TLV in the Router receiver SHOULD use the first occurrence of the TLV in the Router
Information LSA. If the SR-Algorithm TLV appears in multiple Router Information LSA. If the SR-Algorithm TLV appears in multiple Router
Information LSAs that have different flooding scopes, the SR- Information LSAs that have different flooding scopes, the SR-
Algorithm TLV in the Router Information LSA with the narrowest Algorithm TLV in the Router Information LSA with the narrowest
flooding scope SHOULD be used. If the SR-Algorithm TLV appears in flooding scope SHOULD be used. If the SR-Algorithm TLV appears in
multiple Router Information LSAs that have the same flooding scope, multiple Router Information LSAs that have the same flooding scope,
the SR-Algorithm TLV in the Router Information LSA with the the SR-Algorithm TLV in the Router Information (RI) LSA with the
numerically smallest Instance ID SHOULD be used and subsequent numerically smallest Instance ID SHOULD be used and subsequent
instances of the SR-Algorithm TLV SHOULD be ignored. instances of the SR-Algorithm TLV SHOULD be ignored.
The RI LSA can be advertised at any of the defined opaque flooding The RI LSA can be advertised at any of the defined opaque flooding
scopes (link, area, or Autonomous System (AS)). For the purpose of scopes (link, area, or Autonomous System (AS)). For the purpose of
SR-Algorithm TLV advertisement, area-scoped flooding is REQUIRED. SR-Algorithm TLV advertisement, area-scoped flooding is REQUIRED.
3.2. SID/Label Range TLV 3.2. SID/Label Range TLV
Prefix SIDs MAY be advertised in a form of an index as described in Prefix SIDs MAY be advertised in a form of an index as described in
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o When a router receives multiple overlapping ranges, it MUST o When a router receives multiple overlapping ranges, it MUST
conform to the procedures defined in conform to the procedures defined in
[I-D.ietf-spring-conflict-resolution]. [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: Range Size: 100 SID/Label Sub-TLV: 199 Range 1: Range Size: 100 SID/Label Sub-TLV: 100
Range 1: Range Size: 100 SID/Label Sub-TLV: 1000 Range 1: Range Size: 100 SID/Label Sub-TLV: 1000
Range 1: Range Size: 100 SID/Label Sub-TLV: 500 Range 1: Range Size: 100 SID/Label Sub-TLV: 500
The receiving routers concatenate the ranges and build the Segment The receiving routers concatenate the ranges and build the Segment
Routing Global Block (SRGB) as follows: Routing Global Block (SRGB) as follows:
SRGB = [100, 199] SRGB = [100, 199]
[1000, 1099] [1000, 1099]
[500, 599] [500, 599]
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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. An ABR that is advertising the OSPF Extended Prefix area type. An ABR that is advertising the OSPF Extended Prefix
Range TLV between areas MUST set this bit. 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 advertisements
over inter-area advertisements.
An ABR does not consider inter-area Prefix Range
advertisements coming from non-backbone areas.
An ABR only propagates an inter-area Prefix Range An ABR only propagates an inter-area Prefix Range
advertisement from the backbone area to connected non- advertisement from the backbone area to connected non-
backbone areas if the advertisement is considered to be the backbone areas if the advertisement is considered to be the
best one. best one. The following rules are used to select the best
range from the set of advertisements for the same Prefix
Range:
An ABR always prefers intra-area Prefix Range
advertisements over inter-area advertisements.
An ABR does not consider inter-area Prefix Range
advertisements coming from non-backbone areas.
Address Prefix: For the address family IPv4 unicast, the prefix Address Prefix: For the address family IPv4 unicast, the prefix
itself is encoded as a 32-bit value. The default route is itself is encoded as a 32-bit value. The default route is
represented by a prefix of length 0. Prefix encoding for other represented by a prefix of length 0. Prefix encoding for other
address families is beyond the scope of this specification. 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 OSPF Extended Prefix TLV The Prefix SID Sub-TLV is a Sub-TLV of the OSPF Extended Prefix TLV
described in [RFC7684] and the OSPF Extended Prefix Range TLV described in [RFC7684] and the OSPF Extended Prefix Range TLV
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Existing security extensions as described in [RFC2328] and [RFC7684] Existing security extensions as described in [RFC2328] and [RFC7684]
apply to these segment routing extensions. While OSPF is under a apply to these segment routing extensions. While OSPF is under a
single administrative domain, there may be deployments where single administrative domain, there may be deployments where
potential attackers have access to one or more networks in the OSPF potential attackers have access to one or more networks in the OSPF
routing domain. In these deployments, stronger authentication routing domain. In these deployments, stronger authentication
mechanisms such as those specified in [RFC7474] SHOULD be used. mechanisms such as those specified in [RFC7474] SHOULD be used.
Implementations must assure that malformed TLV and Sub-TLV defined in Implementations must assure that malformed TLV and Sub-TLV defined in
this document are detected and do not provide a vulnerability for this document are detected and do not provide a vulnerability for
attackers to crash the OSPFv2 router or routing process. attackers to crash the OSPFv2 router or routing process. Reception
of malformed TLV or Sub-TLV SHOULD be counted and/or logged for
further analysis.
11. Contributors 11. Contributors
The following people gave a substantial contribution to the content The following people gave a substantial contribution to the content
of this document: Acee Lindem, Ahmed Bashandy, Martin Horneffer, of this document: Acee Lindem, Ahmed Bashandy, Martin Horneffer,
Bruno Decraene, Stephane Litkowski, Igor Milojevic, Rob Shakir and Bruno Decraene, Stephane Litkowski, Igor Milojevic, Rob Shakir and
Saku Ytti. Saku Ytti.
12. Acknowledgements 12. Acknowledgements
skipping to change at page 26, line 8 skipping to change at page 26, line 10
[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, <http://www.rfc-editor.org/info/rfc7770>. February 2016, <http://www.rfc-editor.org/info/rfc7770>.
13.2. Informative References 13.2. Informative References
[I-D.ietf-spring-conflict-resolution] [I-D.ietf-spring-conflict-resolution]
Ginsberg, L., Psenak, P., Previdi, S., and M. Pilka, Ginsberg, L., Psenak, P., Previdi, S., and M. Pilka,
"Segment Routing MPLS Conflict Resolution", draft-ietf- "Segment Routing MPLS Conflict Resolution", draft-ietf-
spring-conflict-resolution-04 (work in progress), May spring-conflict-resolution-05 (work in progress), July
2017. 2017.
[I-D.ietf-spring-segment-routing] [I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Decraene, B., Litkowski, S., Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
and R. Shakir, "Segment Routing Architecture", draft-ietf- and R. Shakir, "Segment Routing Architecture", draft-ietf-
spring-segment-routing-12 (work in progress), June 2017. spring-segment-routing-12 (work in progress), June 2017.
[I-D.ietf-spring-segment-routing-ldp-interop] [I-D.ietf-spring-segment-routing-ldp-interop]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., and Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., and
S. Litkowski, "Segment Routing interworking with LDP", S. Litkowski, "Segment Routing interworking with LDP",
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