draft-ietf-ospf-segment-routing-msd-00.txt   draft-ietf-ospf-segment-routing-msd-01.txt 
OSPF Working Group J. Tantsura OSPF Working Group J. Tantsura
Internet-Draft U. Chunduri Internet-Draft Individual
Intended status: Standards Track Individual Intended status: Standards Track U. Chunduri
Expires: May 20, 2017 November 16, 2016 Expires: September 9, 2017 Huawei Technologies
S. Aldrin
Google, Inc
P. Psenak
Cisco Systems
March 8, 2017
Signaling MSD (Maximum SID Depth) using OSPF Signaling MSD (Maximum SID Depth) using OSPF
draft-ietf-ospf-segment-routing-msd-00 draft-ietf-ospf-segment-routing-msd-01
Abstract Abstract
This document proposes a way to expose Maximum SID Depth (MSD) This document proposes a way to signal Maximum SID Depth (MSD)
supported by a node at node and/or link level by an OSPF Router. In supported by a node at node and/or link granularity by an OSPF
a Segment Routing (SR) enabled network a centralized controller that Router. In a Segment Routing (SR) enabled network a centralized
programs SR tunnels at the head-end node needs to know the MSD controller that programs SR tunnels needs to know the MSD supported
information at node level and/or link level to push the label stack by the head-end at node and/or link granularity to push the SID stack
of an appropriate depth . Here the term OSPF means both OSPFv2 and of an appropriate depth. MSD is relevant to the head-end of a SR
OSPFv3. tunnel or Binding-SID anchor node where Binding-SID expansions might
result in creation of a new SID stack. Here the term OSPF means both
OSPFv2 and OSPFv3.
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
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This Internet-Draft will expire on May 20, 2017. This Internet-Draft will expire on September 9, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
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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
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Node MSD TLV . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Node MSD TLV . . . . . . . . . . . . . . . . . . . . . . . . 4
4. LINK MSD sub-TLV . . . . . . . . . . . . . . . . . . . . . . 4 4. LINK MSD sub-TLV . . . . . . . . . . . . . . . . . . . . . . 5
5. Node MSD vs Link MSD conflict resolution . . . . . . . . . . 4 5. Node MSD vs Link MSD conflict resolution . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. Security Considerations . . . . . . . . . . . . . . . . . . . 5 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . 5 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . 5 10.1. Normative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 10.2. Informative References . . . . . . . . . . . . . . . . . 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 crucial that the controller knows the MSD "Maximum controller, it is critical that the controller learns the MSD
SID Depth" of the node or link SR tunnel exits over, so it doesn't "Maximum SID Depth" of the node or link SR tunnel exits over, so the
download a path with SID (label stack) of a depth more than the node SID stack depth of a path computed doesn't exceed the number of SIDs
or link used is capable of imposing. This document describes how to the node is capable of imposing. This document describes how to use
use OSPF to expose the MSD of the node or link to a centralized OSPF to signal the MSD of a node or link to a centralized controller.
controller.
PCEP SR extensions [I-D.ietf-pce-segment-routing] has defined MSD, to PCEP SR extensions draft [I-D.ietf-pce-segment-routing] signals MSD
signal in SR PCE Capability TLV, METRIC Object. However, If PCEP is in SR PCE Capability TLV and METRIC Object. However, if PCEP is not
not supported by a node (head-end of the SR tunnel) and controller supported/configured on the head-end of a SR tunnel or a Binding-SID
does not participate in IGP routing it has no way to learn the MSD of anchor node and controller does not participate in IGP routing, it
the node or link configured. BGP-LS [RFC7752] defines a way to has no way to learn the MSD of nodes and links which has been
expose topology and associated different attributes, capabilities of configured. BGP-LS [RFC7752] defines a way to expose topology and
the nodes in that topology to a centralized controller and MSD has associated attributes and capabilities of the nodes in that topology
been defined in [I-D.tantsura-bgp-ls-segment-routing-msd]. For this to a centralized controller. MSD signaling by BGP-LS has been
information to be advertised by BGP for the all nodes and links of defined in [I-D.tantsura-idr-bgp-ls-segment-routing-msd]. Typically,
the network, where this is provisioned, OSPF module should have this BGP-LS is configured on a small number of nodes, that do not
information in the LSDB. 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
capabilites SHOULD be distributed to every OSPF router in the
network.
[I-D.ietf-ospf-mpls-elc] defines, RLSDC which indicates how many [I-D.ietf-ospf-mpls-elc] defines Readable Label Depth Capability
(RLDC) that is used by a head-end to insert Entropy Label (EL) at
appropriate depth, so it could be read by transit nodes. MSD in
contrary signals ability to push SID's stack of a particular depth.
MSD of type 1 (IANA Registry) is used to signal the number of SIDs a
node is capable of imposing, to be used by a path computation
element/controller and is only relevant to the part of the stack
created as the result of the computation. In case, there are
additional labels (e.g. service) that are to be pushed to the stack -
MSD SHOULD be adjusted to reflect that. In the future, new MSD types
could be defined to signal additional capabilities: entropy labels,
labels that can be pushed thru recirculation, or another dataplane
e.g IPv6.
[I-D.ietf-ospf-mpls-elc] defines, RLDC which indicates how many
labels a node can read to take a decision to insert an Entropy Label labels a node can read to take a decision to insert an Entropy Label
(EL) and is different than how many labels a node can push as defined (EL) and is different than how many labels a node can push as defined
by MSD in this draft. by MSD in this draft.
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
skipping to change at page 3, line 43 skipping to change at page 4, line 22
This memo makes use of the terms defined in [RFC4970]. This memo makes use of the terms defined in [RFC4970].
3. Node MSD TLV 3. Node MSD TLV
A new TLV within the body of the OSPF RI Opaque LSA, called Node MSD A new TLV within the body of the OSPF RI Opaque LSA, called Node MSD
TLV is defined to carry the provisioned SID depth of the router TLV is defined to carry the provisioned SID depth of the router
originating the RI LSA. Node MSD is the lowest MSD supported by the originating the RI LSA. Node MSD is the lowest MSD supported by the
node. node.
The Type (2 bytes) of this TLV is TBD. 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
Length is 2 bytes, and +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type and Value ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
the Value field contains MSD of the router originating the RI LSA. Figure 1: Node MSD TLV
Node 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 of The Type (2 bytes) of this TLV is 12 (Suggested value - to be
the node. This value SHOULD represent the lowest value supported by assigned by IANA).
node.
Length is variable (minimum of 2, multiple of 2 octets) and
represents the total length of value field.
Value field consists of a 1 octet sub-type (IANA Registry) and 1
octet value.
Sub-Type 1 (IANA Section), MSD and the Value field contains maximum
MSD of the router originating the RI LSA. Node 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 of the node.
This value SHOULD represent the lowest value supported by node.
Other Sub-types other than defined above are reserved for future
extensions.
This TLV is applicable to OSPFv2 and to OSPFv3 [RFC5838] and is This TLV is applicable to OSPFv2 and to OSPFv3 [RFC5838] and is
optional. The scope of the advertisement is specific to the optional. The scope of the advertisement is specific to the
deployment. deployment.
4. LINK MSD sub-TLV 4. LINK MSD sub-TLV
A new sub-TLV called Link MSD sub-TLV is defined to carry the A new sub-TLV called Link MSD sub-TLV is defined to carry the
provisioned SID depth of the interface associated with the link. provisioned SID depth of the interface associated with the link.
The Type (2 bytes) of this TLV is TBD. 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
Length is 2 bytes, and +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type and Value ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
the Value field contains Link MSD of the router originating the Figure 2: Link MSD Sub-TLV
corresponding LSA as specified for OSPFv3 and OSPFv3. Link MSD is a
number in the range of 0-254. 0 represents lack of the ability to The Type (2 bytes) of this TLV:
push MSD of any depth; any other value represents that of the
particular link MSD value.
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 OSPFv2 Extended Link TLV as defined in [RFC7684]. Sub-TLV of OSPFv2 Extended Link TLV as defined in [RFC7684], and the
value is 5 (Suggested value - to be assigned by IANA)
For OSPFv3, the Link level MSD value is advertised as an optional For OSPFv3, the Link level MSD value is advertised as an optional
Sub-TLV of the Router-Link TLV as defined in Sub-TLV of the Router-Link TLV as defined in
[I-D.ietf-ospf-ospfv3-lsa-extend]. [I-D.ietf-ospf-ospfv3-lsa-extend], and the value is 3 (Suggested
value - to be assigned by IANA).
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
octet value.
Sub-Type 1 (IANA Section), MSD and the Value field contains Link MSD
of the router originating the corresponding LSA as specified for
OSPFv2 and OSPFv3. 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 represents that of the particular link MSD value.
Other Sub-types other than defined above are reserved for future
extensions.
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. Acknowledgements 6. IANA Considerations
TBD
7. IANA Considerations
This document includes a request to IANA to allocate TLV type codes This document includes a request to IANA to allocate TLV type codes
for the new TLV proposed in Section 3 of this document from OSPF for the new TLV proposed in Section 3 of this document from OSPF
Router Information (RI) TLVs Registry as defined by [RFC4970]. Also Router Information (RI) TLVs Registry as defined by [RFC4970]. Also
for link MSD, we request IANA to allocate new sub-TLV codes as for link MSD, we request IANA to allocate new sub-TLV codes as
proposed in Section 4 from OSPFv2 Extended Link Opaque LSAs Extended proposed in Section 4 from OSPFv2 Extended Link Opaque LSAs Extended
Link TLV registry and from Router-Link TLV defined in OSPFv3 Extend- Link TLV registry and from Router-Link TLV defined in OSPFv3 Extend-
LSA Sub-TLV registry. LSA Sub-TLV registry.
8. Security Considerations This document also request IANA to create a new Sub-type registry as
proposed in Section 3, Section 4.
This document describes a mechanism for advertising Segment Routing Value Name Reference
SID depth supported at node and link level information through OSPF ----- --------------------- -------------
LSAs and does not introduce any new security issues. 0 Reserved This document
1 MSD This document
2-250 Unassigned This document
251-254 Experimental This document
255 Reserved This document
9. References Figure 3: MSD Sub-type Codepoints Registry
9.1. Normative References 7. Security Considerations
This document describes a mechanism to signal Segment Routing MSD
supported at node and/or link granularity through OSPF LSA's and does
not introduce any new security issues.
8. Contributors
The following people contributed to this document:
Les Ginsberg
Email: ginsberg@cisco.com
9. Acknowledgements
The authors would like to thank Stephane Litkowski and Bruno Decraene
for their reviews and valuable comments.
10. 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>.
[RFC4970] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and [RFC4970] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
S. Shaffer, "Extensions to OSPF for Advertising Optional S. Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 4970, DOI 10.17487/RFC4970, July Router Capabilities", RFC 4970, DOI 10.17487/RFC4970, July
2007, <http://www.rfc-editor.org/info/rfc4970>. 2007, <http://www.rfc-editor.org/info/rfc4970>.
9.2. Informative References 10.2. Informative References
[I-D.ietf-ospf-mpls-elc] [I-D.ietf-ospf-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 Litkowski, "Signaling Entropy Label Capability Using
OSPF", draft-ietf-ospf-mpls-elc-03 (work in progress), OSPF", draft-ietf-ospf-mpls-elc-04 (work in progress),
October 2016. November 2016.
[I-D.ietf-ospf-ospfv3-lsa-extend] [I-D.ietf-ospf-ospfv3-lsa-extend]
Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3 Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3
LSA Extendibility", draft-ietf-ospf-ospfv3-lsa-extend-13 LSA Extendibility", draft-ietf-ospf-ospfv3-lsa-extend-13
(work in progress), October 2016. (work in progress), 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.,
Raszuk, R., Lopez, V., Tantsura, J., Henderickx, W., and Raszuk, R., Lopez, V., Tantsura, J., Henderickx, W., and
J. Hardwick, "PCEP Extensions for Segment Routing", draft- J. Hardwick, "PCEP Extensions for Segment Routing", draft-
ietf-pce-segment-routing-08 (work in progress), October ietf-pce-segment-routing-08 (work in progress), October
2016. 2016.
[I-D.tantsura-bgp-ls-segment-routing-msd] [I-D.tantsura-idr-bgp-ls-segment-routing-msd]
Tantsura, J., Mirsky, G., Sivabalan, S., and U. Chunduri, Tantsura, J., Chunduri, U., Mirsky, G., and S. Sivabalan,
"Signaling Maximum SID Depth using Border Gateway Protocol "Signaling Maximum SID Depth using Border Gateway Protocol
Link-State", draft-tantsura-bgp-ls-segment-routing-msd-02 Link-State", draft-tantsura-idr-bgp-ls-segment-routing-
(work in progress), January 2016. msd-02 (work in progress), January 2017.
[RFC5838] Lindem, A., Ed., Mirtorabi, S., Roy, A., Barnes, M., and [RFC5838] Lindem, A., Ed., Mirtorabi, S., Roy, A., Barnes, M., and
R. Aggarwal, "Support of Address Families in OSPFv3", R. Aggarwal, "Support of Address Families in OSPFv3",
RFC 5838, DOI 10.17487/RFC5838, April 2010, RFC 5838, DOI 10.17487/RFC5838, April 2010,
<http://www.rfc-editor.org/info/rfc5838>. <http://www.rfc-editor.org/info/rfc5838>.
[RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", RFC 7684, DOI 10.17487/RFC7684, November Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
2015, <http://www.rfc-editor.org/info/rfc7684>. 2015, <http://www.rfc-editor.org/info/rfc7684>.
skipping to change at page 6, line 29 skipping to change at page 8, line 24
<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
Individual Huawei Technologies
Email: uma.chunduri@gmail.com Email: uma.chunduri@huawei.com
Sam Aldrin
Google, Inc
Email: aldrin.ietf@gmail.com
Peter Psenak
Cisco Systems
Email: ppsenak@cisco.com
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