< draft-ietf-ospf-segment-routing-extensions-23.txt   draft-ietf-ospf-segment-routing-extensions-24.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 16, 2018 Cisco Systems, Inc. Expires: June 17, 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
December 13, 2017 December 14, 2017
OSPF Extensions for Segment Routing OSPF Extensions for Segment Routing
draft-ietf-ospf-segment-routing-extensions-23 draft-ietf-ospf-segment-routing-extensions-24
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 OSPFv2 extensions required 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 [RFC2119]. document are to be interpreted as described in [RFC2119].
Status of This Memo Status of This Memo
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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 https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 16, 2018. This Internet-Draft will expire on June 17, 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
(https://trustee.ietf.org/license-info) in effect on the date of (https://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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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 . . . . . . . . . . . . . . . . . . . . . 13 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 . . . . . . . . . . 20
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 . . . . . . . . . . . . . . . . 22
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 . . 22
7.4.2. Adjacency SID on Broadcast or NBMA Interfaces . . . . 21 7.4.2. Adjacency SID on Broadcast or NBMA Interfaces . . . . 22
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
8.1. OSPF Router Information (RI) TLVs Registry . . . . . . . 22 8.1. OSPF Router Information (RI) TLVs Registry . . . . . . . 23
8.2. OSPFv2 Extended Prefix Opaque LSA TLVs Registry . . . . . 22 8.2. OSPFv2 Extended Prefix Opaque LSA TLVs Registry . . . . . 23
8.3. OSPFv2 Extended Prefix TLV Sub-TLVs Registry . . . . . . 22 8.3. OSPFv2 Extended Prefix TLV Sub-TLVs Registry . . . . . . 23
8.4. OSPFv2 Extended Link TLV Sub-TLVs Registry . . . . . . . 22 8.4. OSPFv2 Extended Link TLV Sub-TLVs Registry . . . . . . . 23
8.5. IGP Algorithm Type Registry . . . . . . . . . . . . . . . 23 8.5. IGP Algorithm Type Registry . . . . . . . . . . . . . . . 23
9. Implementation Status . . . . . . . . . . . . . . . . . . . . 23 9. Implementation Status . . . . . . . . . . . . . . . . . . . . 24
10. Security Considerations . . . . . . . . . . . . . . . . . . . 25 10. Security Considerations . . . . . . . . . . . . . . . . . . . 25
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 25 11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 26
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 25 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 26
13.1. Normative References . . . . . . . . . . . . . . . . . . 26 13.1. Normative References . . . . . . . . . . . . . . . . . . 26
13.2. Informative References . . . . . . . . . . . . . . . . . 26 13.2. Informative References . . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
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
over a specific adjacency between two nodes in the IGP. A prefix over a specific adjacency between two nodes in the IGP. A prefix
segment is typically a multi-hop path while an adjacency segment, in segment is typically a multi-hop path while an adjacency segment, in
most cases, is a one-hop path. SR's control-plane can be applied to most cases, is a one-hop path. SR's control-plane can be applied to
both IPv6 and MPLS data-planes, and does not require any additional both IPv6 and MPLS data-planes, and does not require any additional
signalling (other than IGP extensions). The IPv6 data plane is out signalling (other than IGP extensions). The IPv6 data plane is out
of the scope of this specification - it is not applicable to OSPFv2 of the scope of this specification - it is not applicable to OSPFv2
which only supports the IPv4 address-family. For example, when used which only supports the IPv4 address-family. When used in MPLS
in MPLS networks, SR paths do not require any LDP or RSVP-TE networks, SR paths do not require any LDP or RSVP-TE signalling.
signalling. However, SR can interoperate in the presence of LSPs However, SR can interoperate in the presence of LSPs established with
established with RSVP or LDP. RSVP or LDP.
There are additional segment types, e.g., Binding SID defined in There are additional segment types, e.g., Binding SID defined in
[I-D.ietf-spring-segment-routing]. [I-D.ietf-spring-segment-routing].
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.ietf-spring-segment-routing]. [I-D.ietf-spring-segment-routing].
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3.1. SR-Algorithm TLV 3.1. SR-Algorithm TLV
The SR-Algorithm TLV is a top-level TLV of the Router Information The SR-Algorithm TLV is a top-level TLV of the Router Information
Opaque LSA (defined in [RFC7770]). Opaque LSA (defined in [RFC7770]).
The SR-Algorithm TLV is optional. It SHOULD only be advertised once The SR-Algorithm TLV is optional. It SHOULD only be advertised once
in the Router Information Opaque LSA. If the SR-Algorithm TLV is not in the Router Information Opaque LSA. If the SR-Algorithm TLV is not
advertised by the node, such node is considered as not being segment advertised by the node, such node is considered as not being segment
routing capable. routing capable.
An SR Router may use various algorithms when calculating reachability An SR Router can use various algorithms when calculating reachability
to OSPF routers or prefixes in an OSPF area. Examples of these to OSPF routers or prefixes in an OSPF area. Examples of these
algorithms are metric based Shortest Path First (SPF), various algorithms are metric based Shortest Path First (SPF), various
flavors of Constrained SPF, etc. The SR-Algorithm TLV allows a flavors of Constrained SPF, etc. The SR-Algorithm TLV allows a
router to advertise the algorithms currently used by the router to router to advertise the algorithms currently used by the router to
other routers in an OSPF area. The SR-Algorithm TLV has following other routers in an OSPF area. The SR-Algorithm TLV has following
format: 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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included. included.
1: Strict Shortest Path First (SPF) algorithm based on link 1: Strict Shortest Path First (SPF) algorithm based on link
metric. The algorithm is identical to Algorithm 0 but metric. The algorithm is identical to Algorithm 0 but
Algorithm 1 requires that all nodes along the path will honor Algorithm 1 requires that all nodes along the path will honor
the SPF routing decision. Local policy at the node claiming the SPF routing decision. Local policy at the node claiming
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 MUST 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 area-scoped Algorithm TLV in the Router Information LSA with the area-scoped
flooding scope SHOULD be used. If the SR-Algorithm TLV appears in flooding scope MUST 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 (RI) 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 MUST be used and subsequent
instances of the SR-Algorithm TLV SHOULD be ignored. instances of the SR-Algorithm TLV MUST 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
Section 5. Such index defines the offset in the SID/Label space Section 5. Such index defines the offset in the SID/Label space
advertised by the router. The SID/Label Range TLV is used to advertised by the router. The SID/Label Range TLV is used to
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where: where:
Type: 9 Type: 9
Length: Variable, in octets, dependent on Sub-TLVs. Length: Variable, in octets, dependent on Sub-TLVs.
Range Size: 3-octet SID/label range size (i.e., the number of SIDs Range Size: 3-octet SID/label range size (i.e., the number of SIDs
or labels in the range including the first SID/label). It MUST be or labels in the range including the first SID/label). It MUST be
greater than 0. greater than 0.
Reserved: SHOULD be set to 0 on transmission and MUST be ignored
on reception.
Initially, the only supported Sub-TLV is the SID/Label Sub-TLV as Initially, the only supported Sub-TLV is the SID/Label Sub-TLV as
defined in Section 2.1. The SID/Label Sub-TLV MUST be included in defined in Section 2.1. The SID/Label Sub-TLV MUST be included in
the SID/Label Range TLV. The SID/Label advertised in the SID/Label the SID/Label Range TLV. The SID/Label advertised in the SID/Label
Sub-TLV represents the first SID/Label in the advertised range. Sub-TLV represents the first SID/Label in the advertised range.
Only a single SID/Label Sub-TLV MAY be advertised in SID/Label Range Only a single SID/Label Sub-TLV MAY be advertised in SID/Label Range
TLV. If more then one SID/Label Sub-TLVs are present, the SID/Label TLV. If more then one SID/Label Sub-TLVs are present, the SID/Label
Range TLV MUST be ignored. Range TLV MUST be ignored.
Multiple occurrences of the SID/Label Range TLV MAY be advertised, in Multiple occurrences of the SID/Label Range TLV MAY be advertised, in
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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 purpose of SID/ (link, area, or autonomous system (AS)). For the purpose of SID/
Label Range TLV advertisement, area-scoped flooding is REQUIRED. Label Range TLV advertisement, area-scoped flooding is REQUIRED.
3.3. SR Local Block TLV 3.3. SR Local Block TLV
The SR Local Block TLV (SRLB TLV) contains the range of labels the The SR Local Block TLV (SRLB TLV) contains the range of labels the
node has reserved for local SIDs. SIDs from the SRLB MAY be used for node has reserved for local SIDs. SIDs from the SRLB MAY be used for
Adjacency-SIDs, but also by components other than the OSPF protocol. Adjacency-SIDs, but also by components other than the OSPF protocol.
As an example, an application or a controller may instruct the router As an example, an application or a controller can instruct the router
to allocate a specific local SID. Some controllers or applications to allocate a specific local SID. Some controllers or applications
may use the control plane to discover the available set of local SIDs can use the control plane to discover the available set of local SIDs
on a particular router. In such cases, the SRLB is advertised in the on a particular router. In such cases, the SRLB is advertised in the
control plane. The requirement to advertise the SRLB is further control plane. The requirement to advertise the SRLB is further
described in [I-D.ietf-spring-segment-routing-mpls]. The SRLB TLV is described in [I-D.ietf-spring-segment-routing-mpls]. The SRLB TLV is
used to advertise the SRLB. used to advertise the SRLB.
The SRLB TLV is a top-level TLV of the Router Information Opaque LSA The SRLB TLV is a top-level TLV of the Router Information Opaque LSA
(defined in [RFC7770]). (defined in [RFC7770]).
The SRLB TLV MAY appear multiple times in the Router Information The SRLB TLV MAY appear multiple times in the Router Information
Opaque LSA and has the following format: Opaque LSA and has the following format:
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where: where:
Type: 14 Type: 14
Length: Variable, in octets, dependent on Sub-TLVs. Length: Variable, in octets, dependent on Sub-TLVs.
Range Size: 3-octet SID/label range size (i.e., the number of SIDs Range Size: 3-octet SID/label range size (i.e., the number of SIDs
or labels in the range including the first SID/label). It MUST be or labels in the range including the first SID/label). It MUST be
greater than 0. greater than 0.
Reserved: SHOULD be set to 0 on transmission and MUST be ignored
on reception.
Initially, the only supported Sub-TLV is the SID/Label Sub-TLV as Initially, the only supported Sub-TLV is the SID/Label Sub-TLV as
defined in Section 2.1. The SID/Label Sub-TLV MUST be included in defined in Section 2.1. The SID/Label Sub-TLV MUST be included in
the SRLB TLV. The SID/Label advertised in the SID/Label Sub-TLV the SRLB TLV. The SID/Label advertised in the SID/Label Sub-TLV
represents the first SID/Label in the advertised range. represents the first SID/Label in the advertised range.
Only a single SID/Label Sub-TLV MAY be advertised in the SRLB TLV. Only a single SID/Label Sub-TLV MAY be advertised in the SRLB TLV.
If more then one SID/Label Sub-TLVs are present, the SRLB TLV MUST be If more then one SID/Label Sub-TLVs are present, the SRLB TLV MUST be
ignored. ignored.
The originating router MUST NOT advertise overlapping ranges. The originating router MUST NOT advertise overlapping ranges.
Each time a SID from the SRLB is allocated, it SHOULD also be Each time a SID from the SRLB is allocated, it SHOULD also be
reported to all components (e.g., controller or applications) in reported to all components (e.g., controller or applications) in
order for these components to have an up-to-date view of the current order for these components to have an up-to-date view of the current
SRLB allocation. This is required to avoid collisions between SRLB allocation. This is required to avoid collisions between
allocation instructions. allocation instructions.
Within the context of OSPF, the reporting of local SIDs is done Within the context of OSPF, the reporting of local SIDs is done
through OSPF Sub-TLVs such as the Adjacency-SID (Section 6). through OSPF Sub-TLVs such as the Adjacency-SID (Section 6).
However, the reporting of allocated local SIDs may also be done However, the reporting of allocated local SIDs can also be done
through other means and protocols which are outside the scope of this through other means and protocols which are outside the scope of this
document. document.
A router advertising the SRLB TLV may also have other label ranges, A router advertising the SRLB TLV MAY also have other label ranges,
outside of the SRLB, used for its local allocation purposes which are outside of the SRLB, used for its local allocation purposes which are
NOT advertised in the SRLB TLV. For example, it is possible that an not advertised in the SRLB TLV. For example, it is possible that an
Adjacency-SID is allocated using a local label that is not part of Adjacency-SID is allocated using a local label that is not part of
the SRLB. the SRLB.
The 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 purpose of SRLB TLV (link, area, or autonomous system (AS)). For the purpose of SRLB TLV
advertisement, area-scoped flooding is REQUIRED. advertisement, area-scoped flooding is REQUIRED.
3.4. SRMS Preference TLV 3.4. SRMS Preference TLV
The Segment Routing Mapping Server Preference TLV (SRMS Preference The Segment Routing Mapping Server Preference TLV (SRMS Preference
skipping to change at page 10, line 41 skipping to change at page 10, line 45
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
Type: 15 Type: 15
Length: 4 octets Length: 4 octets
Preference: 1 octet. SRMS preference value from 0 to 255. Preference: 1 octet. SRMS preference value from 0 to 255.
Reserved: SHOULD be set to 0 on transmission and MUST be ignored
on reception.
When multiple SRMS Preference TLVs are received from a given router, When multiple SRMS Preference TLVs are received from a given router,
the receiver SHOULD use the first occurrence of the TLV in the Router the receiver MUST use the first occurrence of the TLV in the Router
Information LSA. If the SRMS Preference TLV appears in multiple Information LSA. If the SRMS Preference TLV appears in multiple
Router Information LSAs that have different flooding scopes, the SRMS Router Information LSAs that have different flooding scopes, the SRMS
Preference TLV in the Router Information LSA with the narrowest Preference TLV in the Router Information LSA with the narrowest
flooding scope SHOULD be used. If the SRMS Preference TLV appears in flooding scope MUST be used. If the SRMS Preference TLV appears in
multiple Router Information LSAs that have the same flooding scope, multiple Router Information LSAs that have the same flooding scope,
the SRMS Preference TLV in the Router Information LSA with the the SRMS Preference TLV in the Router Information LSA with the
numerically smallest Instance ID SHOULD be used and subsequent numerically smallest Instance ID MUST be used and subsequent
instances of the SRMS Preference TLV SHOULD be ignored. instances of the SRMS Preference TLV MUST be ignored.
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 purpose of the SRMS (link, area, or autonomous system (AS)). For the purpose of the SRMS
Preference TLV advertisement, AS-scoped flooding SHOULD be used. Preference TLV advertisement, AS-scoped flooding SHOULD be used.
This is because SRMS servers can be located in a different area then This is because SRMS servers can be located in a different area then
consumers of the SRMS advertisements. If the SRMS advertisements consumers of the SRMS advertisements. If the SRMS advertisements
from the SRMS server are only used inside the SRMS server's area, from the SRMS server are only used inside the SRMS server's area,
area-scoped flooding MAY be used. area-scoped flooding MAY be used.
4. OSPF Extended Prefix Range TLV 4. OSPF Extended Prefix Range TLV
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best one. The following rules are used to select the best best one. The following rules are used to select the best
range from the set of advertisements for the same Prefix range from the set of advertisements for the same Prefix
Range: Range:
An ABR always prefers intra-area Prefix Range An ABR always prefers intra-area Prefix Range
advertisements over inter-area advertisements. advertisements over inter-area advertisements.
An ABR does not consider inter-area Prefix Range An ABR does not consider inter-area Prefix Range
advertisements coming from non-backbone areas. advertisements coming from non-backbone areas.
Reserved: SHOULD be set to 0 on transmission and MUST be ignored
on reception.
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
described in Section 4. It MAY appear more than once in the parent described in Section 4. It MAY appear more than once in the parent
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index. index.
L-Flag: Local/Global Flag. If set, then the value/index L-Flag: Local/Global Flag. If set, then the value/index
carried by the Prefix-SID has local significance. If not set, carried by the Prefix-SID has local significance. If not set,
then the value/index carried by this Sub-TLV has global then the value/index carried by this Sub-TLV has global
significance. significance.
Other bits: Reserved. These MUST be zero when sent and are Other bits: Reserved. These MUST be zero when sent and are
ignored when received. ignored when received.
Reserved: SHOULD be set to 0 on transmission and MUST be ignored
on reception.
MT-ID: Multi-Topology ID (as defined in [RFC4915]). MT-ID: Multi-Topology ID (as defined in [RFC4915]).
Algorithm: Single octet identifying the algorithm the Prefix-SID Algorithm: Single octet identifying the algorithm the Prefix-SID
is associated with as defined in Section 3.1. is associated with as defined in Section 3.1.
A router receiving a Prefix-SID from a remote node and with an A router receiving a Prefix-SID from a remote node and with an
algorithm value that such remote node has not advertised in the algorithm value that such remote node has not advertised in the
SR-Algorithm Sub-TLV (Section 3.1) MUST ignore the Prefix-SID Sub- SR-Algorithm Sub-TLV (Section 3.1) MUST ignore the Prefix-SID Sub-
TLV. TLV.
skipping to change at page 15, line 11 skipping to change at page 15, line 23
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. If the penultimate hop popping mechanism used in the MPLS dataplane. If the
NP-flag is not set, then the received E-flag is ignored. NP-flag is not set, then the received E-flag is ignored.
If the NP-flag is set then: If the NP-flag is set then:
If the E-flag is not set, then any upstream neighbor of the 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 Prefix-SID originator MUST keep the Prefix-SID on top of the
stack. This is useful when the originator of the Prefix-SID must stack. This is useful when the originator of the Prefix-SID need
stitch the incoming packet into a continuing MPLS LSP to the final to stitch the incoming packet into a continuing MPLS LSP to the
destination. This could occur at an Area Border Router (prefix final destination. This could occur at an Area Border Router
propagation from one area to another) or at an AS Boundary Router (prefix propagation from one area to another) or at an AS Boundary
(prefix propagation from one domain to another). Router (prefix propagation from one domain to another).
If the E-flag is set, then any upstream neighbor of the Prefix-SID If the E-flag is set, then any upstream neighbor of the Prefix-SID
originator MUST replace the Prefix-SID with an Explicit-NULL originator MUST replace the Prefix-SID with an Explicit-NULL
label. This is useful, e.g., when the originator of the Prefix- label. This is useful, e.g., when the originator of the Prefix-
SID is the final destination for the related prefix and the SID is the final destination for the related prefix and the
originator wishes to receive the packet with the original EXP originator wishes to receive the packet with the original EXP
bits. bits.
When the M-Flag is set, the NP-flag and the E-flag MUST be ignored at When the M-Flag is set, the NP-flag and the E-flag MUST be ignored at
reception. reception.
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the Adj-SID refers to a group of adjacencies (and therefore MAY the Adj-SID refers to a group of adjacencies (and therefore MAY
be assigned to other adjacencies as well). be assigned to other adjacencies as well).
P-Flag. Persistent flag. When set, the P-Flag indicates that P-Flag. Persistent flag. When set, the P-Flag indicates that
the Adj-SID is persistently allocated, i.e., the Adj-SID value the Adj-SID is persistently allocated, i.e., the Adj-SID value
remains consistent across router restart and/or interface flap. remains consistent across router restart and/or interface flap.
Other bits: Reserved. These MUST be zero when sent and are Other bits: Reserved. These MUST be zero when sent and are
ignored when received. ignored when received.
Reserved: SHOULD be set to 0 on transmission and MUST be ignored
on reception.
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.ietf-spring-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.
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+---------------------------------------------------------------+ +---------------------------------------------------------------+
where: where:
Type: 3 Type: 3
Length: 11 or 12 octets, dependent on V-flag. Length: 11 or 12 octets, dependent on V-flag.
Flags: same as in Section 6.1 Flags: same as in Section 6.1
Reserved: SHOULD be set to 0 on transmission and MUST be ignored
on reception.
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.ietf-spring-segment-routing]. weight is defined in [I-D.ietf-spring-segment-routing].
Neighbor ID: The Router ID of the neighbor for which the LAN-Adj- Neighbor ID: The Router ID of the neighbor for which the LAN-Adj-
SID is advertised. SID is advertised.
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:
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the best from the set it received. The rules used to pick the best the best from the set it received. The rules used to pick the best
OSPF Extended Prefix Range TLV are described in Section 4. OSPF Extended Prefix Range TLV are described in Section 4.
When propagating an OSPF Extended Prefix Range TLV between areas, When propagating an OSPF Extended Prefix Range TLV between areas,
ABRs MUST set the IA-Flag, that is used to prevent redundant flooding ABRs MUST set the IA-Flag, that is used to prevent redundant flooding
of the OSPF Extended Prefix Range TLV between areas as described in of the OSPF Extended Prefix Range TLV between areas as described in
Section 4. Section 4.
7.2. Inter-area Segment routing in OSPFv2 7.2. 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 to propagate Prefix SIDs between areas. procedure is used 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 [RFC7684]. The flooding scope of Prefix Opaque LSA, as described in [RFC7684]. The flooding scope of
the Extended Prefix Opaque LSA type will be set to area-local scope. the Extended Prefix Opaque LSA type will be set to area-local scope.
The route-type in the OSPF Extended Prefix TLV is set to inter-area. The route-type in the OSPF Extended Prefix TLV is set to inter-area.
The Prefix-SID Sub-TLV will be included in this LSA and the Prefix- The Prefix-SID Sub-TLV will be included in this LSA and the Prefix-
SID value will be set as follows: SID value will be set as follows:
skipping to change at page 21, line 14 skipping to change at page 21, line 44
If no Prefix-SID was advertised for the prefix in the backbone If no Prefix-SID was advertised for the prefix in the backbone
area by the ABR that contributes to the best path to the prefix, area by the ABR that contributes to the best path to the prefix,
the originating ABR will use the Prefix-SID advertised by any the originating ABR will use the Prefix-SID advertised by any
other router when propagating the Prefix-SID for the prefix to other router when propagating the Prefix-SID for the prefix to
other areas. other areas.
7.3. Segment Routing for External Prefixes 7.3. Segment Routing 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 Extended Prefix
Opaque LSAs, as described in [RFC7684]. The flooding scope of the Opaque LSAs, as described in [RFC7684]. The flooding scope of the
Extended Prefix Opaque LSA type is set to AS-wide scope. The route- Extended Prefix Opaque LSA type is set to AS-wide scope. The route-
type in the OSPF Extended Prefix TLV is set to external. The Prefix- type in the OSPF Extended Prefix TLV is set to external. The Prefix-
SID Sub-TLV is included in this LSA and the Prefix-SID value will be SID Sub-TLV is included in this LSA and the Prefix-SID value will be
set to the SID that has been reserved for that prefix. set to the SID that has been reserved for that prefix.
When an NSSA ABR translates Type-7 LSAs into Type-5 LSAs, it should When an NSSA [RFC3101] ABR translates Type-7 LSAs into Type-5 LSAs,
also advertise the Prefix-SID for the prefix. The NSSA ABR it SHOULD 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. router will be used.
7.4. Advertisement of Adj-SID 7.4. Advertisement of Adj-SID
The Adjacency Segment Routing Identifier (Adj-SID) is advertised The Adjacency Segment Routing Identifier (Adj-SID) is advertised
skipping to change at page 23, line 12 skipping to change at page 23, line 46
o 3 - LAN Adj-SID/Label Sub-TLV o 3 - LAN Adj-SID/Label Sub-TLV
8.5. IGP Algorithm Type Registry 8.5. IGP Algorithm Type Registry
IANA is requested to set up a registry called "IGP Algorithm Type" IANA is requested to set up a registry called "IGP Algorithm Type"
under a new category of "Interior Gateway Protocol (IGP) Parameters" under a new category of "Interior Gateway Protocol (IGP) Parameters"
IANA registries. The registration policy for this registry is IANA registries. The registration policy for this registry is
"Standards Action" ([RFC8126] and [RFC7120]). "Standards Action" ([RFC8126] and [RFC7120]).
Values in this registry must come from the range 0-255. Values in this registry come from the range 0-255.
The initial values in the IGP Algorithm Type registry are: The initial values in the IGP Algorithm Type registry are:
0: Shortest Path First (SPF) algorithm based on link metric. This 0: Shortest Path First (SPF) algorithm based on link metric. This
is the standard shortest path algorithm as computed by the IGP is the standard shortest path algorithm as computed by the IGP
protocol. Consistent with the deployed practice for link-state protocol. Consistent with the deployed practice for link-state
protocols, Algorithm 0 permits any node to overwrite the SPF path protocols, Algorithm 0 permits any node to overwrite the SPF path
with a different path based on its local policy. with a different path based on its local policy.
1: Strict Shortest Path First (SPF) algorithm based on link 1: Strict Shortest Path First (SPF) algorithm based on link
skipping to change at page 25, line 16 skipping to change at page 25, line 48
With the OSPFv2 segment routing extensions defined herein, OSPFv2 With the OSPFv2 segment routing extensions defined herein, OSPFv2
will now program the MPLS data plane [RFC3031] in addition to the IP will now program the MPLS data plane [RFC3031] in addition to the IP
data plane. Previously, LDP [RFC5036] or another label distribution data plane. Previously, LDP [RFC5036] or another label distribution
mechanism was required to advertise MPLS labels and program the MPLS mechanism was required to advertise MPLS labels and program the MPLS
data plane. data plane.
In general, the same types of attacks that can be carried out on the In general, the same types of attacks that can be carried out on the
IP control plane can be carried out on the MPLS control plane IP control plane can be carried out on the MPLS control plane
resulting in traffic being misrouted in the respective data planes. resulting in traffic being misrouted in the respective data planes.
However, the latter may be more difficult to detect and isolate. However, the latter can be more difficult to detect and isolate.
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 can 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. Reception attackers to crash the OSPFv2 router or routing process. Reception
of malformed TLV or Sub-TLV SHOULD be counted and/or logged for of malformed TLV or Sub-TLV SHOULD be counted and/or logged for
further analysis. Logging of malformed TLVs and Sub-TLVs should be further analysis. Logging of malformed TLVs and Sub-TLVs SHOULD be
rate-limited to prevent a Denial of Service (DoS) attack (distributed rate-limited to prevent a Denial of Service (DoS) attack (distributed
or otherwise) from overloading the OSPF control plane. or otherwise) from overloading the OSPF control plane.
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.
skipping to change at page 26, line 4 skipping to change at page 26, line 32
Saku Ytti. Saku Ytti.
12. Acknowledgements 12. Acknowledgements
We would like to thank Anton Smirnov for his contribution. We would like to thank Anton Smirnov for his contribution.
Thanks to Acee Lindem for the detail review of the draft, Thanks to Acee Lindem for the detail review of the draft,
corrections, as well as discussion about details of the encoding. corrections, as well as discussion about details of the encoding.
13. References 13. References
13.1. Normative References 13.1. Normative References
[I-D.ietf-spring-conflict-resolution]
Ginsberg, L., Psenak, P., Previdi, S., and M. Pilka,
"Segment Routing MPLS Conflict Resolution", draft-ietf-
spring-conflict-resolution-05 (work in progress), July
2017.
[I-D.ietf-spring-segment-routing] [I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B., Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing Litkowski, S., and R. Shakir, "Segment Routing
Architecture", draft-ietf-spring-segment-routing-13 (work Architecture", draft-ietf-spring-segment-routing-13 (work
in progress), October 2017. in progress), October 2017.
[I-D.ietf-spring-segment-routing-ldp-interop]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., and
S. Litkowski, "Segment Routing interworking with LDP",
draft-ietf-spring-segment-routing-ldp-interop-09 (work in
progress), September 2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>.
[RFC3101] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option",
RFC 3101, DOI 10.17487/RFC3101, January 2003,
<https://www.rfc-editor.org/info/rfc3101>.
[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
RFC 4915, DOI 10.17487/RFC4915, June 2007, RFC 4915, DOI 10.17487/RFC4915, June 2007,
<https://www.rfc-editor.org/info/rfc4915>. <https://www.rfc-editor.org/info/rfc4915>.
[RFC6845] Sheth, N., Wang, L., and J. Zhang, "OSPF Hybrid Broadcast [RFC6845] Sheth, N., Wang, L., and J. Zhang, "OSPF Hybrid Broadcast
and Point-to-Multipoint Interface Type", RFC 6845, and Point-to-Multipoint Interface Type", RFC 6845,
DOI 10.17487/RFC6845, January 2013, DOI 10.17487/RFC6845, January 2013,
<https://www.rfc-editor.org/info/rfc6845>. <https://www.rfc-editor.org/info/rfc6845>.
skipping to change at page 27, line 5 skipping to change at page 28, line 5
Router Capabilities", RFC 7770, DOI 10.17487/RFC7770, Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
February 2016, <https://www.rfc-editor.org/info/rfc7770>. February 2016, <https://www.rfc-editor.org/info/rfc7770>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26, Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>. <https://www.rfc-editor.org/info/rfc8126>.
13.2. Informative References 13.2. Informative References
[I-D.ietf-spring-conflict-resolution]
Ginsberg, L., Psenak, P., Previdi, S., and M. Pilka,
"Segment Routing MPLS Conflict Resolution", draft-ietf-
spring-conflict-resolution-05 (work in progress), July
2017.
[I-D.ietf-spring-segment-routing-ldp-interop]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., and
S. Litkowski, "Segment Routing interworking with LDP",
draft-ietf-spring-segment-routing-ldp-interop-09 (work in
progress), September 2017.
[I-D.ietf-spring-segment-routing-mpls] [I-D.ietf-spring-segment-routing-mpls]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing with MPLS Litkowski, S., and R. Shakir, "Segment Routing with MPLS
data plane", draft-ietf-spring-segment-routing-mpls-11 data plane", draft-ietf-spring-segment-routing-mpls-11
(work in progress), October 2017. (work in progress), October 2017.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>.
[RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed., [RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed.,
"Security Extension for OSPFv2 When Using Manual Key "Security Extension for OSPFv2 When Using Manual Key
Management", RFC 7474, DOI 10.17487/RFC7474, April 2015, Management", RFC 7474, DOI 10.17487/RFC7474, April 2015,
<https://www.rfc-editor.org/info/rfc7474>. <https://www.rfc-editor.org/info/rfc7474>.
[RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B., [RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B.,
Litkowski, S., Horneffer, M., and R. Shakir, "Source Litkowski, S., Horneffer, M., and R. Shakir, "Source
Packet Routing in Networking (SPRING) Problem Statement Packet Routing in Networking (SPRING) Problem Statement
and Requirements", RFC 7855, DOI 10.17487/RFC7855, May and Requirements", RFC 7855, DOI 10.17487/RFC7855, May
2016, <https://www.rfc-editor.org/info/rfc7855>. 2016, <https://www.rfc-editor.org/info/rfc7855>.
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