draft-ietf-ospf-segment-routing-extensions-15.txt   draft-ietf-ospf-segment-routing-extensions-16.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: November 23, 2017 Cisco Systems, Inc. Expires: November 24, 2017 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
May 22, 2017 May 23, 2017
OSPF Extensions for Segment Routing OSPF Extensions for Segment Routing
draft-ietf-ospf-segment-routing-extensions-15 draft-ietf-ospf-segment-routing-extensions-16
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 November 23, 2017. This Internet-Draft will expire on November 24, 2017.
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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take into account the E and P flags advertised by the next-hop router take into account the E and P flags advertised by the next-hop router
if that router advertised the SID for the prefix. This MUST be done if that router advertised the SID for the prefix. This MUST be done
regardless of whether the next-hop router contributes to the best regardless of whether the next-hop router contributes to the best
path to the prefix. path to the prefix.
The NP-Flag (No-PHP) MUST be set and the E-flag MUST be clear for The NP-Flag (No-PHP) MUST be set and the E-flag MUST be clear for
Prefix-SIDs allocated to inter-area prefixes that are originated by Prefix-SIDs allocated to inter-area prefixes that are originated by
the ABR based on intra-area or inter-area reachability between areas, the ABR based on intra-area or inter-area reachability between areas,
unless the advertised prefix is directly attached to the ABR. unless the advertised prefix is directly attached to the ABR.
The NP-Flag (No-PHP) MUST be be set and the E-flag MUST be clear for The NP-Flag (No-PHP) MUST be set and the E-flag MUST be clear for
Prefix-SIDs allocated to redistributed prefixes, unless the Prefix-SIDs allocated to redistributed prefixes, unless the
redistributed prefix is directly attached to the ASBR. redistributed prefix is directly attached to the ASBR.
If the NP-Flag is not set, then any upstream neighbor of the Prefix- If the NP-Flag is not set, then any upstream neighbor of the Prefix-
SID originator MUST pop the Prefix-SID. This is equivalent to the SID originator MUST pop the Prefix-SID. This is equivalent to the
penultimate hop popping mechanism used in the MPLS dataplane. In penultimate hop popping mechanism used in the MPLS dataplane. In
such case, MPLS EXP bits of the Prefix-SID are not preserved for the such case, MPLS EXP bits of the Prefix-SID are not preserved for the
final destination (the Prefix-SID being removed). If the NP-flag is final destination (the Prefix-SID being removed). If the NP-flag is
not set then the received E-flag is ignored. not set then the received E-flag is ignored.
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192.0.2.20/30, Prefix-SID: Index 56 192.0.2.20/30, Prefix-SID: Index 56
192.0.2.24/30, Prefix-SID: Index 57 192.0.2.24/30, Prefix-SID: Index 57
then the Prefix field in the Extended Prefix Range TLV would be set then the Prefix field in the Extended Prefix Range TLV would be set
to 192.0.2.0, Prefix Length would be set to 30, Range Size would be to 192.0.2.0, Prefix Length would be set to 30, Range Size would be
7, and the Index value in the Prefix-SID Sub-TLV would be set to 51. 7, and the Index value in the Prefix-SID Sub-TLV would be set to 51.
6. SID/Label Binding Sub-TLV 6. SID/Label Binding Sub-TLV
The SID/Label Binding Sub-TLV is used to advertise a SID/Label The SID/Label Binding Sub-TLV is used to advertise a SID/Label
mapping for a path to the a prefix. mapping for a path to the prefix.
The SID/Label Binding Sub-TLV MAY be originated by any router in an The SID/Label Binding Sub-TLV MAY be originated by any router in an
OSPF domain. The router may advertise a SID/Label binding to a FEC OSPF domain. The router may advertise a SID/Label binding to a FEC
along with at least a single 'nexthop style' anchor. The protocol along with at least a single 'nexthop style' anchor. The protocol
supports more than one 'nexthop style' anchor to be attached to a supports more than one 'nexthop style' anchor to be attached to a
SID/Label binding, which results in a simple path description SID/Label binding, which results in a simple path description
language. Analogous to RSVP, the terminology for this is called an language. Analogous to RSVP, the terminology for this is called an
'Explicit Route Object' (ERO). Since ERO-style path notation allows 'Explicit Route Object' (ERO). Since ERO-style path notation allows
anchoring SID/label bindings to both link and node IP addresses, any anchoring SID/label bindings to both link and node IP addresses, any
Label Switched Path (LSP) can be described. Additionally, SID/Label Label Switched Path (LSP) can be described. Additionally, SID/Label
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Length: Always 4 Length: Always 4
Metric: A 4-octet metric representing the aggregate IGP or TE path Metric: A 4-octet metric representing the aggregate IGP or TE path
cost. cost.
6.2. ERO Sub-TLVs 6.2. ERO Sub-TLVs
All ERO information represents an ordered set which describes the All ERO information represents an ordered set which describes the
segments of a path. The first ERO Sub-TLV describes the first segments of a path. The first ERO Sub-TLV describes the first
segment of a path. Similiarly, the last ERO Sub-TLV describes the segment of a path. Similarly, the last ERO Sub-TLV describes the
segment closest to the egress point. If a router extends or stitches segment closest to the egress point. If a router extends or stitches
a path, it MUST prepend the new segment's path information to the ERO a path, it MUST prepend the new segment's path information to the ERO
list. This applies equally to advertised backup EROs. list. This applies equally to advertised backup EROs.
All ERO sub-TLVs are sub-TLVs of the SID/Label Binding TLV. All ERO sub-TLVs are sub-TLVs of the SID/Label Binding TLV.
6.2.1. IPv4 ERO Sub-TLV 6.2.1. IPv4 ERO Sub-TLV
The IPv4 ERO Sub-TLV is a Sub-TLV of the SID/Label Binding Sub-TLV. The IPv4 ERO Sub-TLV is a Sub-TLV of the SID/Label Binding Sub-TLV.
 End of changes. 7 change blocks. 
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