draft-ietf-ospf-segment-routing-msd-16.txt   draft-ietf-ospf-segment-routing-msd-17.txt 
OSPF Working Group J. Tantsura OSPF Working Group J. Tantsura
Internet-Draft Nuage Networks Internet-Draft Nuage Networks
Intended status: Standards Track U. Chunduri Intended status: Standards Track U. Chunduri
Expires: February 20, 2019 Huawei Technologies Expires: February 22, 2019 Huawei Technologies
S. Aldrin S. Aldrin
Google, Inc Google, Inc
P. Psenak P. Psenak
Cisco Systems Cisco Systems
August 19, 2018 August 21, 2018
Signaling MSD (Maximum SID Depth) using OSPF Signaling MSD (Maximum SID Depth) using OSPF
draft-ietf-ospf-segment-routing-msd-16 draft-ietf-ospf-segment-routing-msd-17
Abstract Abstract
This document defines a way for an Open Shortest Path First (OSPF) This document defines a way for an Open Shortest Path First (OSPF)
Router to advertise multiple types of supported Maximum SID Depths Router to advertise multiple types of supported Maximum SID Depths
(MSDs) at node and/or link granularity. Such advertisements allow (MSDs) at node and/or link granularity. Such advertisements allow
entities (e.g., centralized controllers) to determine whether a entities (e.g., centralized controllers) to determine whether a
particular SID stack can be supported in a given network. This particular SID stack can be supported in a given network. This
document defines only one type of MSD, but defines an encoding that document defines only one type of MSD, but defines an encoding that
can support other MSD types. Here the term OSPF means both OSPFv2 can support other MSD types. Here the term OSPF means both OSPFv2
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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 February 20, 2019. This Internet-Draft will expire on February 22, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 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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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 4 2. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 4
3. Link MSD sub-TLV . . . . . . . . . . . . . . . . . . . . . . 5 3. Link MSD sub-TLV . . . . . . . . . . . . . . . . . . . . . . 5
4. Using Node and Link MSD Advertisements . . . . . . . . . . . 6 4. Using Node and Link MSD Advertisements . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . 7 9.1. Normative References . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . 8 9.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction 1. Introduction
When Segment Routing (SR) paths are computed by a centralized When Segment Routing (SR) paths are computed by a centralized
controller, it is critical that the controller learns the Maximum SID controller, it is critical that the controller learns the Maximum SID
Depth (MSD) that can be imposed at each node/link on a given SR path Depth (MSD) that can be imposed at each node/link on a given SR path
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14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Node MSD Advertisement 2. Node MSD Advertisement
The node MSD TLV within the body of the OSPF RI Opaque LSA [RFC7770] The node MSD TLV within the body of the OSPF RI Opaque LSA [RFC7770]
is defined to carry the provisioned SID depth of the router is defined to carry the provisioned SID depth of the router
originating the RI LSA. Node MSD is the smallest MSD supported by originating the RI LSA. Node MSD is the smallest MSD supported by
the node on the set of interfaces configured for use by the the node on the set of interfaces configured for use by the
advertising IGP instance. MSD values may be learned via a hardware advertising IGP instance. MSD values may be learned via a hardware
API or may be provisioned.. API or may be provisioned.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MSD-Type | MSD-Value | | MSD-Type | MSD-Value | MSD-Type... | MSD-Value... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Node MSD TLV Figure 1: Node MSD TLV
The Type: TBD1 The Type: TBD1
Length: variable (multiple of 2 octets) and represents the total Length: variable (multiple of 2 octets) and represents the total
length of value field in octets. length of value field in octets.
Value: consists of one or more pairs of a 1 octet MSD-type and 1 Value: consists of one or more pairs of a 1 octet MSD-type and 1
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3. Link MSD sub-TLV 3. Link MSD sub-TLV
The link sub-TLV is defined to carry the MSD of the interface The link sub-TLV is defined to carry the MSD of the interface
associated with the link. MSD values may be learned via a hardware associated with the link. MSD values may be learned via a hardware
API or may be provisioned. API or may be provisioned.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | MSD-Type | MSD-Value | | MSD-Type | MSD-Value | MSD-Type... | MSD-Value... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Link MSD Sub-TLV Figure 2: Link MSD Sub-TLV
Type: Type:
For OSPFv2, the Link level MSD value is advertised as an optional For OSPFv2, the Link level MSD value is advertised as an optional
Sub-TLV of the OSPFv2 Extended Link TLV as defined in [RFC7684], and Sub-TLV of the OSPFv2 Extended Link TLV as defined in [RFC7684], and
has a type of TBD2. has a type of TBD2.
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advertisement of that MSD type. However, in some cases the lack of advertisement of that MSD type. However, in some cases the lack of
advertisement might imply that the functionality associated with the advertisement might imply that the functionality associated with the
MSD type is not supported. The correct interpretation MUST be MSD type is not supported. The correct interpretation MUST be
specified when an MSD type is defined. specified when an MSD type is defined.
5. IANA Considerations 5. IANA Considerations
This document requests IANA to allocate TLV type (TBD1) from the OSPF This document requests IANA to allocate TLV type (TBD1) from the OSPF
Router Information (RI) TLVs Registry as defined by [RFC7770]. IANA Router Information (RI) TLVs Registry as defined by [RFC7770]. IANA
has allocated the value 12 through the early assignment process. has allocated the value 12 through the early assignment process.
Also, this document requests IANA to allocate a sub-TLV type (TBD2) Also, this document requests IANA to allocate a sub-TLV type (TBD2)
from the OSPFv2 Extended Link TLV Sub-TLVs registry. IANA has from the OSPFv2 Extended Link TLV Sub-TLVs registry. IANA has
allocated the the value 6 through the early assignment process. allocated the value 6 through the early assignment process. Finally,
this document requests IANA to allocate a sub-TLV type (TBD3) from
Finally, this document requests IANA to allocate a sub-TLV type the OSPFv3 Extended-LSA Sub-TLV registry.
(TBD3) from the OSPFv3 Extended-LSA Sub-TLV registry.
6. Security Considerations 6. Security Considerations
Security concerns for OSPF are addressed in [RFC7474]. Further Security concerns for OSPF are addressed in [RFC7474]. Further
security analysis for OSPF protocol is done in [RFC6863] Security security analysis for OSPF protocol is done in [RFC6863] Security
considerations, as specified by [RFC7770], [RFC7684] and [RFC8362] considerations, as specified by [RFC7770], [RFC7684] and [RFC8362]
are applicable to this document. are applicable to this document.
Advertisement of an incorrect MSD value may result: in a path Advertisement of an incorrect MSD value may result: in a path
computation failing and the service unavailable or instantiation of a computation failing and the service unavailable or instantiation of a
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imposition). imposition).
7. Contributors 7. Contributors
The following people contributed to this document: The following people contributed to this document:
Les Ginsberg Les Ginsberg
Email: ginsberg@cisco.com Email: ginsberg@cisco.com
8. Acknowledgements 8. Acknowledgments
The authors would like to thank Acee Lindem, Ketan Talaulikar, Tal The authors would like to thank Acee Lindem, Ketan Talaulikar, Tal
Mizrahi, Stephane Litkowski and Bruno Decraene for their reviews and Mizrahi, Stephane Litkowski and Bruno Decraene for their reviews and
valuable comments. valuable comments.
9. References 9. References
9.1. Normative References 9.1. Normative References
[I-D.ietf-isis-segment-routing-msd] [I-D.ietf-isis-segment-routing-msd]
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