draft-ietf-idr-bgp-ls-segment-routing-msd-01.txt   draft-ietf-idr-bgp-ls-segment-routing-msd-02.txt 
IDR Working Group J. Tantsura IDR Working Group J. Tantsura
Internet-Draft Individual Internet-Draft Nuage Networks
Intended status: Standards Track U. Chunduri Intended status: Standards Track U. Chunduri
Expires: April 18, 2018 Huawei Technologies Expires: February 14, 2019 Huawei USA
G. Mirsky G. Mirsky
ZTE Corp. ZTE Corp.
S. Sivabalan S. Sivabalan
Cisco Cisco
October 15, 2017 August 13, 2018
Signaling Maximum SID Depth using Border Gateway Protocol Link-State Signaling MSD (Maximum SID Depth) using Border Gateway Protocol Link-
draft-ietf-idr-bgp-ls-segment-routing-msd-01 State
draft-ietf-idr-bgp-ls-segment-routing-msd-02
Abstract Abstract
This document proposes a way to signal Maximum SID Depth (MSD) This document defines a way for a Border Gateway Protocol Link-State
supported by a node at node and/or link granularity by a BGP-LS (BGP-LS) speaker to advertise multiple types of supported Maximum SID
speaker. In a Segment Routing (SR) enabled network a centralized Depths (MSDs) at node and/or link granularity.
controller that programs SR tunnels needs to know the MSD supported
by the head-end at node and/or link granularity to push the SID stack Such advertisements allow logically centralized entities (e.g.,
of an appropriate depth. MSD is relevant to the head-end of a SR centralized controllers) to determine whether a particular SID stack
tunnel or Binding-SID anchor node where Binding-SID expansions might can be supported in a given network.
result in creation of a new SID stack.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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 April 18, 2018. This Internet-Draft will expire on February 14, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2017 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.
Internet-DrafSignaling MSD (Maximum SID Depth) using BGP-LS August 2018
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
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used in this document . . . . . . . . . . . . 3 1.1. Conventions used in this document . . . . . . . . . . . . 3
1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3
1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
3. MSD supported by a node . . . . . . . . . . . . . . . . . . . 4 3. MSD supported by a node . . . . . . . . . . . . . . . . . . . 3
4. MSD supported on a link . . . . . . . . . . . . . . . . . . . 4 4. MSD supported on a link . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 5 8.1. Normative References . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction 1. Introduction
When Segment Routing tunnels are computed by a centralized When Segment Routing tunnels are computed by a centralized
controller, it is critical that the controller learns the MSD controller, it is critical that the controller learns the MSD
"Maximum SID Depth" of the node or link SR tunnel exits over, so the "Maximum SID Depth" of the node or link SR tunnel exits over, so the
SID stack depth of a path computed doesn't exceed the number of SIDs SID stack depth of a path computed doesn't exceed the number of SIDs
the node is capable of imposing. This document describes how to use the node is capable of imposing. This document describes how to use
BGP-LS to signal the MSD of a node or link to a centralized BGP-LS to signal the MSD of a node or link to a centralized
controller. controller.
PCEP SR extensions draft [I-D.ietf-pce-segment-routing] signals MSD PCEP SR extensions draft [I-D.ietf-pce-segment-routing] signals MSD
in SR PCE Capability TLV and METRIC Object. However, if PCEP is not in SR PCE Capability TLV and METRIC Object. However, if PCEP is not
supported/configured on the head-end of a SR tunnel or a Binding-SID supported/configured on the head-end of a SR tunnel or a Binding-SID
anchor node and controller does not participate in IGP routing, it anchor node and controller does not participate in IGP routing, it
has no way to learn the MSD of nodes and links which has been has no way to learn the MSD of nodes and links which has been
configured. BGP-LS [RFC7752] defines a way to expose topology and configured. BGP-LS [RFC7752] defines a way to expose topology and
associated attributes and capabilities of the nodes in that topology associated attributes and capabilities of the nodes in that topology
to a centralized controller. to a centralized controller.
MSD of sub-type 1, called Base MSD as defined in Section 3 is used to Other types of MSD are known to be useful. For example,
signal the number of SID's a node is capable of imposing, to be used [I-D.ietf-ospf-mpls-elc] and [I-D.ietf-isis-mpls-elc] define Readable
by a path computation element/controller. In case, there are
additional labels (e.g. service) that are to be pushed to the stack - Internet-DrafSignaling MSD (Maximum SID Depth) using BGP-LS August 2018
this would be signaled with an another MSD type (TBD), no adjustment
to the Base MSD should be made. In the future, new MSD types could Label Depth Capability (RLDC) that is used by a head-end to insert an
be defined to signal additional capabilities: entropy labels, labels Entropy Label (EL) at a depth that can be read by transit nodes.
that can be pushed thru recirculation, or another dataplane e.g IPv6.
1.1. Conventions used in this document 1.1. Conventions used in this document
1.1.1. Terminology 1.1.1. Terminology
BGP-LS: Distribution of Link-State and TE Information using Border BGP-LS: Distribution of Link-State and TE Information using Border
Gateway Protocol Gateway Protocol
MSD: Maximum SID Depth MSD: Maximum SID Depth
skipping to change at page 3, line 34 skipping to change at page 3, line 33
PCEP: Path Computation Element Protocol PCEP: Path Computation Element Protocol
SID: Segment Identifier SID: Segment Identifier
SR: Segment routing SR: Segment routing
1.1.2. Requirements Language 1.1.2. 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", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in BCP
[RFC2119]. 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here .
2. Problem Statement 2. Problem Statement
In existing technology only PCEP has extension to signal the MSD (SR In existing technology only PCEP has extension to signal the MSD (SR
PCE Capability TLV/ METRIC Object as defined in PCE Capability TLV/ METRIC Object as defined in
[I-D.ietf-pce-segment-routing],If PCEP is not supported by the node [I-D.ietf-pce-segment-routing],If PCEP is not supported by the node
(head-end of the SR tunnel) controller has no way to learn the MSD of (head-end of the SR tunnel) controller has no way to learn the MSD of
the node/link configured. OSPF and IS-IS extensions are defined in: the node/link configured. OSPF and IS-IS extensions are defined in:
[I-D.ietf-ospf-segment-routing-msd] [I-D.ietf-ospf-segment-routing-msd]
[I-D.ietf-isis-segment-routing-msd] [I-D.ietf-isis-segment-routing-msd]
3. MSD supported by a node 3. MSD supported by a node
Node MSD is encoded in a new Node Attribute TLV, as defined in Node MSD is encoded in a new Node Attribute TLV, as defined in
[RFC7752] [RFC7752]
Internet-DrafSignaling MSD (Maximum SID Depth) using BGP-LS August 2018
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type and Value ... | Sub-Type and Value ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
Figure 1: Node attribute format Figure 1: Node attribute format
Type : A 2-octet field specifiying code-point of the new TLV type. Type : A 2-octet field specifying code-point of the new TLV type.
Code-point:(TBD1) from BGP-LS Node Descriptor, Link Descriptor, Code-point:(TBD1) from BGP-LS Node Descriptor, Link Descriptor,
Prefix Descriptor, and Attribute TLVs registry Prefix Descriptor, and Attribute TLVs registry
Length: A 2-octet field that indicates the length of the value Length: A 2-octet field that indicates the length of the value
portion portion
Sub-Type and value fields are as defined in corresponding OSPF Sub-Type and value fields are as defined in corresponding OSPF
[I-D.ietf-ospf-segment-routing-msd] and IS-IS [I-D.ietf-ospf-segment-routing-msd] and IS-IS
[I-D.ietf-isis-segment-routing-msd] extensions. [I-D.ietf-isis-segment-routing-msd] extensions.
skipping to change at page 4, line 46 skipping to change at page 4, line 43
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type and Value ... | Sub-Type and Value ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
Figure 2: Link attribute format Figure 2: Link attribute format
Type : A 2-octet field specifiying code-point of the new TLV type. Type : A 2-octet field specifying code-point of the new TLV type.
Code-point:(TBD2) from BGP-LS Node Descriptor, Link Descriptor, Code-point:(TBD2) from BGP-LS Node Descriptor, Link Descriptor,
Prefix Descriptor, and Attribute TLVs registry Prefix Descriptor, and Attribute TLVs registry
Length: A 2-octet field that indicates the length of the value Length: A 2-octet field that indicates the length of the value
portion portion
Sub-Type and value fields are as defined in corresponding OSPF Sub-Type and value fields are as defined in corresponding OSPF
[I-D.ietf-ospf-segment-routing-msd] and IS-IS [I-D.ietf-ospf-segment-routing-msd] and IS-IS
[I-D.ietf-isis-segment-routing-msd] extensions. [I-D.ietf-isis-segment-routing-msd] extensions.
Internet-DrafSignaling MSD (Maximum SID Depth) using BGP-LS August 2018
5. IANA Considerations 5. IANA Considerations
We request IANA assign code points from the registry BGP-LS Node We request IANA assign code points from the registry BGP-LS Node
Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs, Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs,
as follows: TLV Code Point Description IS-IS TLV/Sub-TLV Reference as follows: TLV Code Point Description IS-IS TLV/Sub-TLV Reference
TBD1 Node MSD 242/23 (this document) TBD2 Link MSD TBD1 Node MSD 242/23 (this document) TBD2 Link MSD
(22,23,25,141,222,223)/15 (this document) (22,23,25,141,222,223)/15 (this document)
6. Security Considerations 6. Security Considerations
Advertisement of the additional information defined in this document
that is false, e.g., an MSD that is incorrect, may result in a path
computation failing, having a service unavailable, or instantiation
of a path that can't be supported by the head-end (the node
performing the imposition).
This document does not introduce security issues beyond those This document does not introduce security issues beyond those
discussed in [RFC7752] discussed in [RFC7752], [I-D.ietf-ospf-segment-routing-msd] and
[I-D.ietf-isis-segment-routing-msd]
7. Acknowledgements 7. Acknowledgements
We like to thank Nikos Triantafillis, Stephane Litkowski and Bruno We like to thank Nikos Triantafillis, Acee Lindem, Ketan Talaulikar,
Decraene for their reviews and valuable comments. Stephane Litkowski and Bruno Decraene for their reviews and valuable
comments.
8. References 8. References
8.1. Normative References 8.1. Normative References
[I-D.ietf-isis-segment-routing-msd] [I-D.ietf-isis-segment-routing-msd]
Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg, Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg,
"Signaling MSD (Maximum SID Depth) using IS-IS", draft- "Signaling MSD (Maximum SID Depth) using IS-IS", draft-
ietf-isis-segment-routing-msd-04 (work in progress), June ietf-isis-segment-routing-msd-13 (work in progress), July
2017. 2018.
[I-D.ietf-ospf-segment-routing-msd] [I-D.ietf-ospf-segment-routing-msd]
Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak, Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak,
"Signaling MSD (Maximum SID Depth) using OSPF", draft- "Signaling MSD (Maximum SID Depth) using OSPF", draft-
ietf-ospf-segment-routing-msd-05 (work in progress), June ietf-ospf-segment-routing-msd-15 (work in progress), July
2017. 2018.
[I-D.ietf-pce-segment-routing] [I-D.ietf-pce-segment-routing]
Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "PCEP Extensions for Segment Routing", and J. Hardwick, "PCEP Extensions for Segment Routing",
draft-ietf-pce-segment-routing-10 (work in progress), draft-ietf-pce-segment-routing-12 (work in progress), June
October 2017. 2018.
Internet-DrafSignaling MSD (Maximum SID Depth) using BGP-LS August 2018
[I-D.ietf-spring-segment-routing-mpls] [I-D.ietf-spring-segment-routing-mpls]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., Bashandy, A., Filsfils, C., Previdi, S., 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-10 data plane", draft-ietf-spring-segment-routing-mpls-14
(work in progress), June 2017. (work in progress), June 2018.
[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>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752, Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016, DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>. <https://www.rfc-editor.org/info/rfc7752>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
8.2. Informative References 8.2. Informative References
[I-D.ietf-isis-mpls-elc]
Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.
Litkowski, "Signaling Entropy Label Capability and Entropy
Readable Label Depth Using IS-IS", draft-ietf-isis-mpls-
elc-05 (work in progress), July 2018.
[I-D.ietf-isis-segment-routing-extensions] [I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Filsfils, C., Bashandy, A., Gredler, H., Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
Litkowski, S., Decraene, B., and j. jefftant@gmail.com, Gredler, H., Litkowski, S., Decraene, B., and J. Tantsura,
"IS-IS Extensions for Segment Routing", draft-ietf-isis- "IS-IS Extensions for Segment Routing", draft-ietf-isis-
segment-routing-extensions-13 (work in progress), June segment-routing-extensions-19 (work in progress), July
2017. 2018.
[I-D.ietf-ospf-mpls-elc]
Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.
Litkowski, "Signaling Entropy Label Capability and Entropy
Readable Label-stack Depth Using OSPF", draft-ietf-ospf-
mpls-elc-06 (work in progress), August 2018.
[I-D.ietf-ospf-segment-routing-extensions] [I-D.ietf-ospf-segment-routing-extensions]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H., Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPF Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", draft-ietf-ospf-segment- Extensions for Segment Routing", draft-ietf-ospf-segment-
routing-extensions-19 (work in progress), August 2017. routing-extensions-25 (work in progress), April 2018.
Internet-DrafSignaling MSD (Maximum SID Depth) using BGP-LS August 2018
Authors' Addresses Authors' Addresses
Jeff Tantsura Jeff Tantsura
Individual Nuage Networks
Email: jefftant.ietf@gmail.com Email: jefftant.ietf@gmail.com
Uma Chunduri Uma Chunduri
Huawei Technologies Huawei USA
Email: uma.chunduri@huawei.com Email: uma.chunduri@huawei.com
Greg Mirsky Greg Mirsky
ZTE Corp. ZTE Corp.
Email: gregimirsky@gmail.com Email: gregimirsky@gmail.com
Siva Sivabalan Siva Sivabalan
Cisco Cisco
Email: msiva@cisco.com Email: msiva@cisco.com
 End of changes. 33 change blocks. 
48 lines changed or deleted 84 lines changed or added

This html diff was produced by rfcdiff 1.47. The latest version is available from http://tools.ietf.org/tools/rfcdiff/