draft-ietf-idr-bgp-ls-segment-routing-msd-16.txt   draft-ietf-idr-bgp-ls-segment-routing-msd-17.txt 
IDR Working Group J. Tantsura IDR Working Group J. Tantsura
Internet-Draft Apstra, Inc. Internet-Draft Apstra, Inc.
Intended status: Standards Track U. Chunduri Intended status: Standards Track U. Chunduri
Expires: October 1, 2020 Futurewei Technologies Expires: October 28, 2020 Futurewei Technologies
K. Talaulikar K. Talaulikar
Cisco Systems Cisco Systems
G. Mirsky G. Mirsky
ZTE Corp. ZTE Corp.
N. Triantafillis N. Triantafillis
Amazon Web Services Amazon Web Services
March 30, 2020 April 26, 2020
Signaling MSD (Maximum SID Depth) using Border Gateway Protocol - Link Signaling MSD (Maximum SID Depth) using Border Gateway Protocol - Link
State State
draft-ietf-idr-bgp-ls-segment-routing-msd-16 draft-ietf-idr-bgp-ls-segment-routing-msd-17
Abstract Abstract
This document defines a way for a Border Gateway Protocol - Link This document defines a way for a Border Gateway Protocol - Link
State (BGP-LS) speaker to advertise multiple types of supported State (BGP-LS) speaker to advertise multiple types of supported
Maximum SID Depths (MSDs) at node and/or link granularity. Maximum SID Depths (MSDs) at node and/or link granularity.
Such advertisements allow entities (e.g., centralized controllers) to Such advertisements allow entities (e.g., centralized controllers) to
determine whether a particular Segment Identifier (SID) stack can be determine whether a particular Segment Identifier (SID) stack can be
supported in a given network. supported in a given network.
skipping to change at page 1, line 44 skipping to change at page 1, line 44
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 October 1, 2020. This Internet-Draft will expire on October 28, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 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
skipping to change at page 2, line 38 skipping to change at page 2, line 38
4. Link MSD TLV . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Link MSD TLV . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Procedures for Defining and Using Node and Link MSD 5. Procedures for Defining and Using Node and Link MSD
Advertisements . . . . . . . . . . . . . . . . . . . . . . . 6 Advertisements . . . . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Manageability Considerations . . . . . . . . . . . . . . . . 6 7. Manageability Considerations . . . . . . . . . . . . . . . . 6
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7 8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
11.1. Normative References . . . . . . . . . . . . . . . . . . 8 11.1. Normative References . . . . . . . . . . . . . . . . . . 8
11.2. Informative References . . . . . . . . . . . . . . . . . 9 11.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction 1. Introduction
When Segment Routing (SR) [RFC8402] paths are computed by a When Segment Routing (SR) [RFC8402] paths are computed by a
centralized controller, it is critical that the controller learn the centralized controller, it is critical that the controller learns the
Maximum SID Depth (MSD) that can be imposed at each node/link on a Maximum SID Depth (MSD) that can be imposed at each node/link on a
given SR path. This ensures that the Segment Identifier (SID) stack given SR path. This ensures that the Segment Identifier (SID) stack
depth of a computed path doesn't exceed the number of SIDs the node depth of a computed path doesn't exceed the number of SIDs the node
is capable of imposing. is capable of imposing.
[RFC8664] defines how to signal MSD in the Path Computation Element [RFC8664] defines how to signal MSD in the Path Computation Element
Protocol (PCEP). The OSPF and IS-IS extensions for signaling of MSD Protocol (PCEP). The OSPF and IS-IS extensions for signaling of MSD
are defined in [RFC8476] and [RFC8491] respectively. are defined in [RFC8476] and [RFC8491] respectively.
However, if PCEP is not supported/configured on the head-end of a SR However, if PCEP is not supported/configured on the head-end of a SR
tunnel or a Binding-SID anchor node, and controller does not tunnel or a Binding-SID anchor node, and the controller does not
participate in IGP routing, it has no way of learning the MSD of participate in IGP routing, it has no way of learning the MSD of
nodes and links. BGP-LS [RFC7752] defines a way to expose topology nodes and links. BGP-LS [RFC7752] defines a way to expose topology
and associated attributes and capabilities of the nodes in that and associated attributes and capabilities of the nodes in that
topology to a centralized controller. topology to a centralized controller.
This document defines extensions to BGP-LS to advertise one or more This document defines extensions to BGP-LS to advertise one or more
types of MSDs at node and/or link granularity. Other types of MSD types of MSDs at node and/or link granularity. Other types of MSD
are known to be useful. For example, [I-D.ietf-ospf-mpls-elc] and are known to be useful. For example, [I-D.ietf-ospf-mpls-elc] and
[I-D.ietf-isis-mpls-elc] define Readable Label Depth Capability [I-D.ietf-isis-mpls-elc] define Readable Label Depth Capability
(RLDC) that is used by a head-end to insert an Entropy Label (EL) at (RLDC) that is used by a head-end to insert an Entropy Label (EL) at
skipping to change at page 3, line 33 skipping to change at page 3, line 33
not enabled. For example, in a non-SR MPLS network, MSD defines the not enabled. For example, in a non-SR MPLS network, MSD defines the
maximum label depth. maximum label depth.
1.1. Conventions used in this document 1.1. Conventions used in this document
1.1.1. Terminology 1.1.1. Terminology
MSD: Maximum SID Depth - the number of SIDs supported by a node or a MSD: Maximum SID Depth - the number of SIDs supported by a node or a
link on a node link on a node
PCC: Path Computation Client
PCE: Path Computation Element PCE: Path Computation Element
PCEP: Path Computation Element Protocol PCEP: Path Computation Element Protocol
SID: Segment Identifier as defined in [RFC8402] SID: Segment Identifier as defined in [RFC8402]
SR: Segment Routing SR: Segment Routing
Label Imposition: Imposition is the act of modifying and/or adding Label Imposition: Imposition is the act of modifying and/or adding
labels to the outgoing label stack associated with a packet. This labels to the outgoing label stack associated with a packet. This
skipping to change at page 7, line 29 skipping to change at page 7, line 24
PCE to perform path computations taking into consideration the size PCE to perform path computations taking into consideration the size
of SID stack that the specific head-end node may be able to impose. of SID stack that the specific head-end node may be able to impose.
Errors in the encoding or decoding of the MSD information may result Errors in the encoding or decoding of the MSD information may result
in the unavailability of such information to the SR PCE or incorrect in the unavailability of such information to the SR PCE or incorrect
information being made available to it. This may result in the head- information being made available to it. This may result in the head-
end node not being able to instantiate the desired SR path in its end node not being able to instantiate the desired SR path in its
forwarding and provide the SR based optimization functionality. The forwarding and provide the SR based optimization functionality. The
handling of such errors by applications like SR PCE may be handling of such errors by applications like SR PCE may be
implementation specific and out of scope of this document. implementation specific and out of scope of this document.
The extensions specified in this document, do not specify any new The extensions specified in this document do not specify any new
configuration or monitoring aspects in BGP or BGP-LS. The configuration or monitoring aspects in BGP or BGP-LS. The
specification of BGP models is an ongoing work based on the specification of BGP models is an ongoing work based on the
[I-D.ietf-idr-bgp-model]. [I-D.ietf-idr-bgp-model].
8. Security Considerations 8. Security Considerations
The advertisement of an incorrect MSD value may have negative The advertisement of an incorrect MSD value may have negative
consequences. If the value is smaller than supported, path consequences. If the value is smaller than supported, path
computation may fail to compute a viable path. If the value is computation may fail to compute a viable path. If the value is
larger than supported, an attempt to instantiate a path that can't be larger than supported, an attempt to instantiate a path that can't be
skipping to change at page 9, line 21 skipping to change at page 9, line 14
[I-D.ietf-isis-mpls-elc] [I-D.ietf-isis-mpls-elc]
Xu, X., Kini, S., Psenak, P., Filsfils, C., Litkowski, S., Xu, X., Kini, S., Psenak, P., Filsfils, C., Litkowski, S.,
and M. Bocci, "Signaling Entropy Label Capability and and M. Bocci, "Signaling Entropy Label Capability and
Entropy Readable Label Depth Using IS-IS", draft-ietf- Entropy Readable Label Depth Using IS-IS", draft-ietf-
isis-mpls-elc-11 (work in progress), March 2020. isis-mpls-elc-11 (work in progress), March 2020.
[I-D.ietf-ospf-mpls-elc] [I-D.ietf-ospf-mpls-elc]
Xu, X., Kini, S., Psenak, P., Filsfils, C., Litkowski, S., Xu, X., Kini, S., Psenak, P., Filsfils, C., Litkowski, S.,
and M. Bocci, "Signaling Entropy Label Capability and and M. Bocci, "Signaling Entropy Label Capability and
Entropy Readable Label-stack Depth Using OSPF", draft- Entropy Readable Label Depth Using OSPF", draft-ietf-ospf-
ietf-ospf-mpls-elc-12 (work in progress), October 2019. mpls-elc-13 (work in progress), April 2020.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001, DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3031>. <https://www.rfc-editor.org/info/rfc3031>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271, Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006, DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>. <https://www.rfc-editor.org/info/rfc4271>.
 End of changes. 10 change blocks. 
13 lines changed or deleted 11 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/