< draft-ietf-isis-segment-routing-msd-01.txt   draft-ietf-isis-segment-routing-msd-02.txt >
IS-IS Working Group J. Tantsura IS-IS Working Group J. Tantsura
Internet-Draft Individual Internet-Draft Individual
Intended status: Standards Track U. Chunduri Intended status: Standards Track U. Chunduri
Expires: September 2, 2017 Huawei Expires: September 2, 2017 Huawei Technologies
S. Aldrin S. Aldrin
Google, Inc Google, Inc
L. Ginsberg L. Ginsberg
Cisco Systems Cisco Systems
March 1, 2017 March 1, 2017
Signaling MSD (Maximum SID Depth) using IS-IS Signaling MSD (Maximum SID Depth) using IS-IS
draft-ietf-isis-segment-routing-msd-01 draft-ietf-isis-segment-routing-msd-02
Abstract Abstract
This document proposes a way to signal Maximum SID Depth (MSD) This document proposes a way to signal Maximum SID Depth (MSD)
supported by a node at node and/or link granularity by an ISIS supported by a node at node and/or link granularity by an ISIS
Router. In a Segment Routing (SR) enabled network a centralized Router. In a Segment Routing (SR) enabled network a centralized
controller that programs SR tunnels needs to know the MSD supported 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 by the head-end at node and/or link granularity to push the SID stack
of an appropriate depth. MSD is relevent to the head-end of a SR of an appropriate depth. MSD is relevant to the head-end of a SR
tunnel or Binding-SID anchor node where Binding-SID expansions migth tunnel or Binding-SID anchor node where Binding-SID expansions might
result in creation of a new SID stack. 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-
skipping to change at page 2, line 30 skipping to change at page 2, line 30
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 4 3. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 4
4. LINK MSD Advertisement . . . . . . . . . . . . . . . . . . . 4 4. LINK MSD Advertisement . . . . . . . . . . . . . . . . . . . 4
5. Node MSD vs Link MSD conflict resolution . . . . . . . . . . 5 5. Node MSD vs Link MSD conflict resolution . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
10.1. Normative References . . . . . . . . . . . . . . . . . . 6 10.1. Normative References . . . . . . . . . . . . . . . . . . 7
10.2. Informative References . . . . . . . . . . . . . . . . . 7 10.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
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 that the node is SID stack depth of a path computed doesn't exceed the number of SIDs
capable of imposing. This document describes how to use IS-IS to the node is capable of imposing. This document describes how to use
signal the MSD of a node or link to a centralized controller. IS-IS to signal the MSD of a node or link to a centralized
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 MSD 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. MSD signaling by BGP-LS has been to a centralized controller. MSD signaling by BGP-LS has been
defined in [I-D.tantsura-idr-bgp-ls-segment-routing-msd]. Tipicaly, defined in [I-D.tantsura-idr-bgp-ls-segment-routing-msd]. Typically,
BGP-LS is configured on a small number of nodes, that do not BGP-LS is configured on a small number of nodes, that do not
necessarily act as head-ends. In order, for BGP-LS to signal MSD for necessarily act as head-ends. In order, for BGP-LS to signal MSD for
the all nodes and links in the network MSD is relevant, MSD the all nodes and links in the network MSD is relevant, MSD
capabilites should be distributed to every IS-IS router in the capabilites SHOULD be distributed to every IS-IS router in the
network. network.
[I-D.ietf-isis-mpls-elc] defines Readable Label Deepth Capability [I-D.ietf-isis-mpls-elc] defines Readable Label Depth Capability
(RLDC) that is used by a head-end to insert Entropy Label (EL) at (RLDC) that is used by a head-end to insert Entropy Label (EL) at
appropriate depth, so it coud be read by transit nodes. MSD in appropriate depth, so it could be read by transit nodes. MSD in
contrary signals ability to push SID's stack of a particular depth. contrary signals ability to push SID's stack of a particular depth.
MSD of type 1 (IANA Registry) is used to signal number of SID a node MSD of type 1 (IANA Registry) is used to signal the number of SIDs a
is capable of imposing, to be used by a path computation element/ node is capable of imposing, to be used by a path computation
controller and is only relevant to the part of the stack created as element/controller and is only relevant to the part of the stack
the result of the computation. In case, there are additional labels created as the result of the computation. In case, there are
(e.g. service) that are to be pushed to the stack - MSD SHOULD be additional labels (e.g. service) that are to be pushed to the stack -
adjusted to reflect that. In the future, new MSD types could be MSD SHOULD be adjusted to reflect that. In the future, new MSD types
defined to signal additional capabilities: entropy labels, labels could be defined to signal additional capabilities: entropy labels,
that can be pushed thru recirculation, etc. labels that can be pushed thru recirculation, etc.
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
ISIS: Intermediate System to Intermediate System IS-IS: Intermediate System to Intermediate System
MSD: Maximum SID Depth MSD: Maximum SID Depth
PCC: Path Computation Client 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 SID: Segment Identifier
skipping to change at page 4, line 7 skipping to change at page 4, line 7
SR: Segment Routing SR: Segment Routing
1.2. Requirements Language 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", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
2. Terminology 2. Terminology
This memo makes use of the terms defined in [RFC4971]. This memo makes use of the terms defined in [RFC7981].
3. Node MSD Advertisement 3. Node MSD Advertisement
A new sub-TLV within the body of IS-IS Router Capability TLV A new sub-TLV within the body of IS-IS Router Capability TLV
[RFC4971], Node MSD sub-TLV is defined to carry the provisioned MSD [RFC7981], Node MSD sub-TLV is defined to carry the provisioned MSD
of the router originating the Router Capability TLV. Node MSD is the of the router originating the Router Capability TLV. Node MSD is the
lowest MSD supported by the node and can be provisioned in IS-IS lowest MSD supported by the node of any interface and can be
instance. provisioned in IS-IS instance.
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 | Sub-Type and Value | | Type | Length | Sub-Type and Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Node MSD Sub-TLV Figure 1: Node MSD Sub-TLV
The Type (1 byte) of this sub-TLV is TBD (IANA). The Type (1 byte) of this sub-TLV is 23 (Suggested value - to be
assigned by IANA).
Length is variable (minimum of 2, multiple of 2 octets) and Length is variable (minimum of 2, multiple of 2 octets) and
represents the total length of value field. represents the total length of value field.
Value field consists of a 1 octet sub-type (IANA Registry) and 1 Value field consists of a 1 octet sub-type (IANA Registry) and 1
octet value. octet value.
Sub-Type 1 (IANA Section), MSD and the Value field contains maximum Sub-Type 1 (IANA Section), MSD and the Value field contains maximum
MSD of the router originating the Router Capability TLV. Node MSD of the router originating the Router Capability TLV. Node
Maximum MSD is a number in the range of 0-254. 0 represents lack of Maximum MSD is a number in the range of 0-254. 0 represents lack of
the ability to push MSD of any depth; any other value represents that the ability to push MSD of any depth; any other value represents that
of the node. This value SHOULD represent the lowest value supported of the node. This value SHOULD represent the lowest value supported
by node. by node.
Other Sub-types other than defined above are reserved for future Other Sub-types other than defined above are reserved for future
extensions. This TLV is optional. The scope of the advertisement is extensions. This sub-TLV is optional. The scope of the
specific to the deployment. advertisement is specific to the deployment.
4. LINK MSD Advertisement 4. LINK MSD Advertisement
A new sub-TLV - Link MSD sub-TLV is defined to carry the provisioned A new sub-TLV - Link MSD sub-TLV is defined for TLVs 22, 23, 141,
MSD of the interface associated with the link. 222, and 223 to carry the provisioned MSD of the interface associated
with the link.
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 | Sub-Type and Value | | Type | Length | Sub-Type and Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Link MSD Sub-TLV Figure 2: Link MSD Sub-TLV
The Type (1 byte) of this sub-TLV is TBD (IANA). The Type (1 byte) of this sub-TLV is 15 (Suggested value - to be
assigned by IANA).
Length is variable and similar to what is defined in Section 3. Length is variable and similar to what is defined in Section 3.
Value field consists of a 1 octet sub-type (IANA Registry) and 1 Value field consists of a 1 octet sub-type (IANA Registry) and 1
octet value. octet value.
Sub-Type 1 (IANA Section), MSD and the Value field contains Link MSD Sub-Type 1 (IANA Section), MSD and the Value field contains Link MSD
of the router originating the corresponding TLV's 22, 23, 141, 222, of the router originating the corresponding TLV's 22, 23, 141, 222,
and 223. Link MSD is a number in the range of 0-254. 0 represents and 223. Link MSD is a number in the range of 0-254. 0 represents
lack of the ability to push MSD of any depth; any other value lack of the ability to push MSD of any depth; any other value
skipping to change at page 5, line 36 skipping to change at page 5, line 37
5. Node MSD vs Link MSD conflict resolution 5. Node MSD vs Link MSD conflict resolution
When both Node MSD and Link MSD are present, the value in the Link When both Node MSD and Link MSD are present, the value in the Link
MSD MUST be used. MSD MUST be used.
6. IANA Considerations 6. IANA Considerations
This document includes a request to IANA to allocate sub-TLV type This document includes a request to IANA to allocate sub-TLV type
codes for the new sub TLV proposed in Section 3 of this document from codes for the new sub TLV proposed in Section 3 of this document from
IS-IS Router Capability TLV Registry as defined by [RFC4971]. Also IS-IS Router Capability TLV Registry as defined by [RFC7981].
for link MSD, we request IANA to allocate new sub-TLV codes as
Type: 23 (suggested - to be assigned by IANA)
Description: Node MSD
Also for link MSD, we request IANA to allocate new sub-TLV codes as
defined in Section 4 from Sub-TLVs for TLVs 22, 23, 141, 222 and 223 defined in Section 4 from Sub-TLVs for TLVs 22, 23, 141, 222 and 223
registry. registry.
This document also request IANA to create a new Sub-type registry as Type: 15 (suggested - to be assigned by IANA)
proposed in Section 3, Section 4.
Description: Link MSD
Per TLV information where LINK MSD sub-TLV can be part of:
TLV 22 23 141 222 223
----------------------
y y y y y
Figure 3: TLVs where LINK MSD Sub-TLV can be present
This document requests the creation of a new IANA managed registry to
identify MSD types as proposed in Section 3, Section 4. The
registration procedure is "Expert Review" as defined in [RFC5226].
Suggested registry name is "MSD Sub-types". Types are an unsigned 8
bit number. The following values are defined by this document
Value Name Reference Value Name Reference
----- --------------------- ------------- ----- --------------------- -------------
0 Reserved This document 0 Reserved This document
1 MSD This document 1 MSD This document
2-250 Unassigned This document 2-250 Unassigned This document
251-254 Experimental This document 251-254 Experimental This document
255 Reserved This document 255 Reserved This document
Figure 3: MSD Sub-type Codepoints Registry Figure 4: MSD Sub-type Codepoints Registry
7. Security Considerations 7. Security Considerations
This document describes a mechanism to signal Segment Routing MSD This document describes a mechanism to signal Segment Routing MSD
supported at node and/or link granularity through IS-IS LSPs and does supported at node and/or link granularity through IS-IS LSPs and does
not introduce any new security issues. not introduce any new security issues.
8. Contributors 8. Contributors
The following people contributed to this document: The following people contributed to this document:
skipping to change at page 6, line 35 skipping to change at page 7, line 4
Peter Psenak Peter Psenak
Email: ppsenak@cisco.com Email: ppsenak@cisco.com
9. Acknowledgements 9. Acknowledgements
The authors would like to thank Stephane Litkowski and Bruno Decraene The authors would like to thank Stephane Litkowski and Bruno Decraene
for their reviews and valuable comments. for their reviews and valuable comments.
10. References 10. References
10.1. Normative References 10.1. Normative References
[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,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC4971] Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal, Ed.,
"Intermediate System to Intermediate System (IS-IS)
Extensions for Advertising Router Information", RFC 4971,
DOI 10.17487/RFC4971, July 2007,
<http://www.rfc-editor.org/info/rfc4971>.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305, October Engineering", RFC 5305, DOI 10.17487/RFC5305, October
2008, <http://www.rfc-editor.org/info/rfc5305>. 2008, <http://www.rfc-editor.org/info/rfc5305>.
[RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions
for Advertising Router Information", RFC 7981,
DOI 10.17487/RFC7981, October 2016,
<http://www.rfc-editor.org/info/rfc7981>.
10.2. Informative References 10.2. Informative References
[I-D.ietf-isis-mpls-elc] [I-D.ietf-isis-mpls-elc]
Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S. Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.
Litkowski, "Signaling Entropy Label Capability Using IS- Litkowski, "Signaling Entropy Label Capability Using IS-
IS", draft-ietf-isis-mpls-elc-02 (work in progress), IS", draft-ietf-isis-mpls-elc-02 (work in progress),
October 2016. October 2016.
[I-D.ietf-pce-segment-routing] [I-D.ietf-pce-segment-routing]
Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E., Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E.,
skipping to change at page 7, line 36 skipping to change at page 8, line 5
[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
dual environments", RFC 1195, DOI 10.17487/RFC1195, dual environments", RFC 1195, DOI 10.17487/RFC1195,
December 1990, <http://www.rfc-editor.org/info/rfc1195>. December 1990, <http://www.rfc-editor.org/info/rfc1195>.
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120, Intermediate Systems (IS-ISs)", RFC 5120,
DOI 10.17487/RFC5120, February 2008, DOI 10.17487/RFC5120, February 2008,
<http://www.rfc-editor.org/info/rfc5120>. <http://www.rfc-editor.org/info/rfc5120>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[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,
<http://www.rfc-editor.org/info/rfc7752>. <http://www.rfc-editor.org/info/rfc7752>.
Authors' Addresses Authors' Addresses
Jeff Tantsura Jeff Tantsura
Individual Individual
skipping to change at page 8, line 4 skipping to change at page 8, line 22
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,
<http://www.rfc-editor.org/info/rfc7752>. <http://www.rfc-editor.org/info/rfc7752>.
Authors' Addresses Authors' Addresses
Jeff Tantsura Jeff Tantsura
Individual Individual
Email: jefftant.ietf@gmail.com Email: jefftant.ietf@gmail.com
Uma Chunduri Uma Chunduri
Huawei Huawei Technologies
Email: uma.chunduri@huawei.com Email: uma.chunduri@huawei.com
Sam Aldrin Sam Aldrin
Google, Inc Google, Inc
Email: aldrin.ietf@gmail.com Email: aldrin.ietf@gmail.com
Les Ginsberg Les Ginsberg
Cisco Systems Cisco Systems
 End of changes. 31 change blocks. 
48 lines changed or deleted 75 lines changed or added

This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/