draft-ietf-ospf-segment-routing-extensions-03.txt   draft-ietf-ospf-segment-routing-extensions-04.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: June 5, 2015 Cisco Systems, Inc. Expires: August 5, 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
December 2, 2014 February 1, 2015
OSPF Extensions for Segment Routing OSPF Extensions for Segment Routing
draft-ietf-ospf-segment-routing-extensions-03 draft-ietf-ospf-segment-routing-extensions-04
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 OSPF extensions required for Segment This draft describes the OSPF extensions required for Segment
Routing. Routing.
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 June 5, 2015. This Internet-Draft will expire on August 5, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2015 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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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
skipping to change at page 2, line 43 skipping to change at page 2, line 43
6.2. ERO Sub-TLVs . . . . . . . . . . . . . . . . . . . . . . 14 6.2. ERO Sub-TLVs . . . . . . . . . . . . . . . . . . . . . . 14
6.2.1. IPv4 ERO Sub-TLV . . . . . . . . . . . . . . . . . . 15 6.2.1. IPv4 ERO Sub-TLV . . . . . . . . . . . . . . . . . . 15
6.2.2. Unnumbered Interface ID ERO Sub-TLV . . . . . . . . . 16 6.2.2. Unnumbered Interface ID ERO Sub-TLV . . . . . . . . . 16
6.2.3. IPv4 Backup ERO Sub-TLV . . . . . . . . . . . . . . . 17 6.2.3. IPv4 Backup ERO Sub-TLV . . . . . . . . . . . . . . . 17
6.2.4. Unnumbered Interface ID Backup ERO Sub-TLV . . . . . 18 6.2.4. Unnumbered Interface ID Backup ERO Sub-TLV . . . . . 18
7. Adjacency Segment Identifier (Adj-SID) . . . . . . . . . . . 19 7. Adjacency Segment Identifier (Adj-SID) . . . . . . . . . . . 19
7.1. Adj-SID Sub-TLV . . . . . . . . . . . . . . . . . . . . . 19 7.1. Adj-SID Sub-TLV . . . . . . . . . . . . . . . . . . . . . 19
7.2. LAN Adj-SID Sub-TLV . . . . . . . . . . . . . . . . . . . 20 7.2. LAN Adj-SID Sub-TLV . . . . . . . . . . . . . . . . . . . 20
8. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 22 8. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 22
8.1. Intra-area Segment routing in OSPFv2 . . . . . . . . . . 22 8.1. Intra-area Segment routing in OSPFv2 . . . . . . . . . . 22
8.2. Inter-area Segment routing in OSPFv2 . . . . . . . . . . 22 8.2. Inter-area Segment routing in OSPFv2 . . . . . . . . . . 23
8.3. SID for External Prefixes . . . . . . . . . . . . . . . . 23 8.3. SID for External Prefixes . . . . . . . . . . . . . . . . 24
8.4. Advertisement of Adj-SID . . . . . . . . . . . . . . . . 24 8.4. Advertisement of Adj-SID . . . . . . . . . . . . . . . . 24
8.4.1. Advertisement of Adj-SID on Point-to-Point Links . . 24 8.4.1. Advertisement of Adj-SID on Point-to-Point Links . . 24
8.4.2. Adjacency SID on Broadcast or NBMA Interfaces . . . . 24 8.4.2. Adjacency SID on Broadcast or NBMA Interfaces . . . . 25
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
9.1. OSPF OSPF Router Information (RI) TLVs Registry . . . . . 25 9.1. OSPF OSPF Router Information (RI) TLVs Registry . . . . . 25
9.2. OSPF Extended Prefix LSA TLV Registry . . . . . . . . . . 25 9.2. OSPF Extended Prefix LSA TLV Registry . . . . . . . . . . 25
9.3. OSPF Extended Prefix LSA Sub-TLV Registry . . . . . . . . 25 9.3. OSPF Extended Prefix LSA Sub-TLV Registry . . . . . . . . 25
9.4. OSPF Extended Link LSA Sub-TLV Registry . . . . . . . . . 25 9.4. OSPF Extended Link LSA Sub-TLV Registry . . . . . . . . . 26
10. Security Considerations . . . . . . . . . . . . . . . . . . . 25 10. Security Considerations . . . . . . . . . . . . . . . . . . . 26
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 26 11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 26
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 26
13.1. Normative References . . . . . . . . . . . . . . . . . . 26 13.1. Normative References . . . . . . . . . . . . . . . . . . 26
13.2. Informative References . . . . . . . . . . . . . . . . . 27 13.2. Informative References . . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
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
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plane can be applied to both IPv6 and MPLS data-planes, and does not plane can be applied to both IPv6 and MPLS data-planes, and does not
require any additional signalling (other than IGP extensions). For require any additional signalling (other than IGP extensions). For
example, when used in MPLS networks, SR paths do not require any LDP example, when used in MPLS networks, SR paths do not require any LDP
or RSVP-TE signalling. However, 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 OSPF extensions required for Segment This draft describes the OSPF extensions required for Segment
Routing. Routing.
Segment Routing architecture is described in Segment Routing architecture is described in
[I-D.filsfils-rtgwg-segment-routing]. [I-D.ietf-spring-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-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.
For the purpose of the advertisements of various SID values, new For the purpose of the advertisements of various SID values, new
Opaque LSAs [RFC5250] are defined in Opaque LSAs [RFC5250] are defined in
[I-D.ietf-ospf-prefix-link-attr]. These new LSAs are defined as [I-D.ietf-ospf-prefix-link-attr]. These new LSAs are defined as
generic containers that can be used to advertise any additional generic containers that can be used to advertise any additional
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... ...
The RI LSA can be advertised at any of the defined flooding scopes The RI LSA can be advertised at any of the defined flooding scopes
(link, area, or autonomous system (AS)). For the purposes 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. OSPF Extended Prefix Range TLV 4. OSPF Extended Prefix Range TLV
In some cases it is useful to advertise attributes for the range of In some cases it is useful to advertise attributes for the range of
prefixes. Segment Routing Mapping Server, which is described in prefixes. Segment Routing Mapping Server, which is described in
[I-D.filsfils-rtgwg-segment-routing] is an example, where we need a [I-D.filsfils-spring-segment-routing-ldp-interop], is an example,
single advertisement to advertise SIDs for multiple prefixes from a where we need a single advertisement to advertise SIDs for multiple
contiguous address range. prefixes from a contiguous address range.
OSPF Extended Prefix Range TLV, which is a new top level TLV of the OSPF Extended Prefix Range TLV, which is a new top level TLV of the
Extended Prefix LSA described in [I-D.ietf-ospf-prefix-link-attr] is Extended Prefix LSA described in [I-D.ietf-ospf-prefix-link-attr] is
defined for this purpose. defined for this purpose.
Multiple OSPF Extended Prefix Range TLVs MAY be advertised in each Multiple OSPF Extended Prefix Range TLVs MAY be advertised in each
OSPF Extended Prefix Opaque LSA, but all prefix ranges included in a OSPF Extended Prefix Opaque LSA, but all prefix ranges included in a
single OSPF Extended Prefix Opaque LSA MUST have the same flooding single OSPF Extended Prefix Opaque LSA MUST have the same flooding
scope. The OSPF Extended Prefix Range TLV has the following format: scope. The OSPF Extended Prefix Range TLV has the following format:
skipping to change at page 9, line 47 skipping to change at page 9, line 47
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 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+
|N |NP|M |E |V |L | | | | |NP|M |E |V |L | | |
+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+
where: where:
N-Flag: Node-SID flag. If set, then the Prefix-SID refers to
the router identified by the prefix. Typically, the N-Flag is
set to Prefix-SIDs corresponding to a router loopback address.
The N-Flag is set when the Prefix-SID is a Node-SID, as
described in [I-D.filsfils-rtgwg-segment-routing].
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 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]. described in [I-D.filsfils-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 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.
V-Flag: Value/Index Flag. If set, then the Prefix-SID carries V-Flag: Value/Index Flag. If set, then the Prefix-SID carries
an absolute value. If not set, then the Prefix-SID carries an an absolute value. If not set, then the Prefix-SID carries an
index. index.
skipping to change at page 13, line 51 skipping to change at page 13, line 46
where: where:
M-bit - When the bit is set the binding represents the M-bit - When the bit is set the binding represents the
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.ietf-spring-segment-routing].
The SID/Label Binding TLV supports the 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 6.1. ERO Metric Sub-TLV as defined in Section 6.1.
ERO Sub-TLVs as defined in Section 6.2. ERO Sub-TLVs as defined in Section 6.2.
skipping to change at page 19, line 20 skipping to change at page 19, line 20
7. Adjacency Segment Identifier (Adj-SID) 7. 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 7.1. Adj-SID Sub-TLV
Adj-SID is an optional Sub-TLV of the Extended Link TLV defined in Adj-SID is an optional Sub-TLV of the Extended Link TLV defined in
[I-D.ietf-ospf-prefix-link-attr]. It MAY appear multiple times in [I-D.ietf-ospf-prefix-link-attr]. It MAY appear multiple times in
the Extended Link TLV. Examples where more than one Adj-SID may be the Extended Link TLV. Examples where more than one Adj-SID may be
used per neighbor are described in used per neighbor are described in section 4 of
[I-D.filsfils-rtgwg-segment-routing-use-cases]. The Adj-SID Sub-TLV [I-D.filsfils-spring-segment-routing-use-cases]. The Adj-SID Sub-TLV
has the following format: 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) |
skipping to change at page 19, line 51 skipping to change at page 19, line 51
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. If set, the Adj-SID refers to an B-Flag: Backup Flag. If set, the Adj-SID refers to an
adjacency being protected (e.g.: using IPFRR or MPLS-FRR) as adjacency being protected (e.g.: using IPFRR or MPLS-FRR) as
described in [I-D.filsfils-rtgwg-segment-routing-use-cases]. described in section 3.1 of
[I-D.filsfils-spring-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 Adj-SID carries
carries an absolute value. If not set, then the Prefix-SID an absolute value. If not set, then the Adj-SID carries an
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 Prefix-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 S-Flag. Set Flag. When set, the S-Flag indicates that the The S-Flag. Set Flag. When set, the S-Flag indicates that the
Adj-SID refers to a set of adjacencies (and therefore MAY be Adj-SID refers to a set of adjacencies (and therefore MAY be
assigned to other adjacencies as well). assigned to other adjacencies as well).
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.
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.ietf-spring-segment-routing].
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.
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 protected by an 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 section 3.1 of
[I-D.filsfils-rtgwg-segment-routing-use-cases]. [I-D.filsfils-spring-segment-routing-use-cases].
7.2. LAN Adj-SID Sub-TLV 7.2. LAN Adj-SID Sub-TLV
LAN Adj-SID is an optional Sub-TLV of the Extended Link TLV defined LAN Adj-SID is an optional Sub-TLV of the Extended Link TLV defined
in [I-D.ietf-ospf-prefix-link-attr]. It MAY appear multiple times in in [I-D.ietf-ospf-prefix-link-attr]. It MAY appear multiple times in
the Extended-Link TLV. It is used to advertise a SID/Label for an the Extended-Link TLV. It is used to advertise a SID/Label for an
adjacency to a non-DR node on a broadcast or NBMA network. adjacency to a non-DR node on a 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
skipping to change at page 21, line 34 skipping to change at page 21, line 34
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 LAN-Adj-SID refer to an B-Flag: Backup-flag: set if the LAN-Adj-SID refer to an
adjacency being protected (e.g.: using IPFRR or MPLS-FRR) as adjacency being protected (e.g.: using IPFRR or MPLS-FRR) as
described in [I-D.filsfils-rtgwg-segment-routing-use-cases]. described in section 3.1 of
[I-D.filsfils-spring-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 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.
The S-Flag. Set Flag. When set, the S-Flag indicates that the The S-Flag. Set Flag. When set, the S-Flag indicates that the
Adj-SID refers to a set of adjacencies (and therefore MAY be Adj-SID refers to a set of adjacencies (and therefore MAY be
assigned to other adjacencies as well). assigned to other adjacencies as well).
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.
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.ietf-spring-segment-routing].
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.
skipping to change at page 22, line 31 skipping to change at page 22, line 33
An OSPFv2 router that supports segment routing MAY advertise Prefix- An OSPFv2 router that supports segment routing MAY advertise Prefix-
SIDs for any prefix to which it is advertising reachability (e.g., a 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 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 the Prefix-SID MUST be the same. This is required in order to allow
traffic load-balancing when multiple equal cost paths to the traffic load-balancing when 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-spring-segment-routing-ldp-interop]). The
Mapping Server advertises Prefix-SIDs for remote prefixes that exist Mapping Server advertises Prefix-SIDs for remote prefixes that exist
in the OSPFv2 routing domain. Multiple Mapping Servers can advertise in the OSPFv2 routing domain. Multiple Mapping Servers can advertise
Prefix-SIDs for the same prefix, in which case the same Prefix-SID Prefix-SIDs for the same prefix, in which case the same Prefix-SID
MUST be advertised by all of them. The flooding scope of the OSPF MUST be advertised by all of them. The flooding scope of the OSPF
Extended Prefix Opaque LSA that is generated by the SR Mapping Server Extended Prefix Opaque LSA that is generated by the SR Mapping Server
could be either area scoped or AS scoped and is determined based on could be either area scoped or AS scoped and is determined based on
the configuration of the SR Mapping Server. the configuration of the SR Mapping Server.
SR Mapping Server MUST use OSPF Extended Prefix Range TLV when
advertising SIDs for prefixes. Prefixes of different route-types can
be combined in a single OSPF Extended Prefix Range TLV advertised by
the SR Mapping Server.
Area scoped OSPF Extended Prefix Range TLV are propagated between
areas. Similar to propagation of prefixes between areas, ABR only
propagates the OSPF Extended Prefix Range TLV that it considers to be
the best from the set it received. The rules used to pick the best
OSPF Extended Prefix Range TLV is described in Section 4.
When propagating OSPF Extended Prefix Range TLV between areas, ABR
MUST set the IA-Flag, that is used to prevent redundant flooding of
the OSPF Extended Prefix Range TLV between areas as described in
Section 4.
If the Prefix-SID that is advertised in Prefix SID Sub-TLV is also
covered by the OSPF Extended Prefix Range TLV, the Prefix-SID
advertised in Prefix SID Sub-TLV MUST be preferred.
8.2. Inter-area Segment routing in OSPFv2 8.2. 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 [I-D.ietf-ospf-prefix-link-attr]. Prefix Opaque LSA, as described in [I-D.ietf-ospf-prefix-link-attr].
The flooding scope of the Extended Prefix Opaque LSA type will be set The flooding scope of the Extended Prefix Opaque LSA type will be set
skipping to change at page 23, line 17 skipping to change at page 23, line 40
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 (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-spring-segment-routing-ldp-interop]) when
propagating the 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 [I-D.ietf-ospf-prefix-link-attr]. Prefix Opaque LSA, as described in [I-D.ietf-ospf-prefix-link-attr].
The flooding scope of the Extended Prefix Opaque LSA type will be set The flooding scope of the Extended Prefix Opaque LSA type will be set
to area-scope. The route-type in OSPF Extended Prefix TLV is set to to area-scope. 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 inter-area. The Prefix-SID Sub-TLV will be included in this LSA and
the Prefix-SID will be set as follows: the Prefix-SID will be set as follows:
skipping to change at page 23, line 40 skipping to change at page 24, line 17
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 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-spring-segment-routing-ldp-interop]) when
propagating the Prefix-SID for the prefix to other areas. propagating the Prefix-SID for the prefix to other areas.
8.3. SID for External Prefixes 8.3. 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 an Extended SR, generates Type-5 LSAs, it should also originate an Extended
Prefix Opaque LSAs, as described in [I-D.ietf-ospf-prefix-link-attr]. Prefix Opaque LSAs, as described in [I-D.ietf-ospf-prefix-link-attr].
The flooding scope of the Extended Prefix Opaque LSA type is set to The flooding scope of the Extended Prefix Opaque LSA type is set to
AS-scope. The route-type in the OSPF Extended Prefix TLV is set to AS-scope. The route-type in the OSPF Extended Prefix TLV is set to
external. The Prefix-SID Sub-TLV is included in this LSA and the external. The Prefix-SID Sub-TLV is included in this LSA and the
skipping to change at page 24, line 13 skipping to change at page 24, line 39
that prefix. that prefix.
When an NSSA ABR translates Type-7 LSAs into Type-5 LSAs, it should When an NSSA ABR 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 that Type-7 LSA and finds the advertising router associated with that
path. If the advertising router has advertised a Prefix-SID for the path. If the advertising router has advertised a Prefix-SID for the
prefix, then the NSSA ABR uses it when advertising the Prefix-SID for prefix, then the NSSA ABR uses it when advertising the Prefix-SID for
the Type-5 prefix. Otherwise, the Prefix-SID advertised by any other the Type-5 prefix. Otherwise, the Prefix-SID advertised by any other
router will be used (e.g.: a Prefix-SID coming from an SR Mapping router will be used (e.g.: a Prefix-SID coming from an SR Mapping
Server as defined in [I-D.filsfils-rtgwg-segment-routing-use-cases]). Server as defined in
[I-D.filsfils-spring-segment-routing-ldp-interop]).
8.4. Advertisement of Adj-SID 8.4. 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 7.
8.4.1. Advertisement of Adj-SID on Point-to-Point Links 8.4.1. Advertisement of Adj-SID on Point-to-Point Links
An Adj-SID MAY be advertised for any adjacency on a p2p link that is 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 in neighbor state 2-Way or higher. If the adjacency on a p2p link
skipping to change at page 27, line 10 skipping to change at page 27, line 32
[RFC4970] Lindem, A., Shen, N., Vasseur, JP., Aggarwal, R., and S. [RFC4970] Lindem, A., Shen, N., Vasseur, JP., Aggarwal, R., and S.
Shaffer, "Extensions to OSPF for Advertising Optional Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 4970, July 2007. Router Capabilities", RFC 4970, July 2007.
[RFC5250] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The [RFC5250] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The
OSPF Opaque LSA Option", RFC 5250, July 2008. OSPF Opaque LSA Option", RFC 5250, July 2008.
13.2. Informative References 13.2. Informative References
[I-D.filsfils-rtgwg-segment-routing] [I-D.filsfils-spring-segment-routing-ldp-interop]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R., Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R.,
Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe, Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe,
"Segment Routing Architecture", draft-filsfils-rtgwg- "Segment Routing interoperability with LDP", draft-
segment-routing-01 (work in progress), October 2013. filsfils-spring-segment-routing-ldp-interop-02 (work in
progress), September 2014.
[I-D.filsfils-rtgwg-segment-routing-use-cases] [I-D.filsfils-spring-segment-routing-use-cases]
Filsfils, C., Francois, P., Previdi, S., Decraene, B., Filsfils, C., Francois, P., Previdi, S., Decraene, B.,
Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R., Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R.,
Ytti, S., Henderickx, W., Tantsura, J., Kini, S., and E. Ytti, S., Henderickx, W., Tantsura, J., Kini, S., and E.
Crabbe, "Segment Routing Use Cases", draft-filsfils-rtgwg- Crabbe, "Segment Routing Use Cases", draft-filsfils-
segment-routing-use-cases-02 (work in progress), October spring-segment-routing-use-cases-01 (work in progress),
2013. October 2014.
[I-D.gredler-ospf-label-advertisement] [I-D.gredler-ospf-label-advertisement]
Gredler, H., Amante, S., Scholl, T., and L. Jalil, Gredler, H., Amante, S., Scholl, T., and L. Jalil,
"Advertising MPLS labels in OSPF", draft-gredler-ospf- "Advertising MPLS labels in OSPF", draft-gredler-ospf-
label-advertisement-03 (work in progress), May 2013. label-advertisement-03 (work in progress), May 2013.
[I-D.ietf-ospf-prefix-link-attr] [I-D.ietf-ospf-prefix-link-attr]
Psenak, P., Gredler, H., Shakir, R., Henderickx, W., Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", draft-ietf-ospf-prefix-link-attr-01 (work Advertisement", draft-ietf-ospf-prefix-link-attr-02 (work
in progress), September 2014. in progress), December 2014.
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., Horneffer, M., Shakir, R., Tantsura, J.,
and E. Crabbe, "Segment Routing Architecture", draft-ietf-
spring-segment-routing-00 (work in progress), December
2014.
[I-D.minto-rsvp-lsp-egress-fast-protection] [I-D.minto-rsvp-lsp-egress-fast-protection]
Jeganathan, J., Gredler, H., and Y. Shen, "RSVP-TE LSP Jeganathan, J., Gredler, H., and Y. Shen, "RSVP-TE LSP
egress fast-protection", draft-minto-rsvp-lsp-egress-fast- egress fast-protection", draft-minto-rsvp-lsp-egress-fast-
protection-03 (work in progress), November 2013. protection-03 (work in progress), November 2013.
Authors' Addresses Authors' Addresses
Peter Psenak (editor) Peter Psenak (editor)
Cisco Systems, Inc. Cisco Systems, Inc.
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