draft-ietf-ospf-segment-routing-msd-07.txt   draft-ietf-ospf-segment-routing-msd-08.txt 
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Internet-Draft Individual Internet-Draft Individual
Intended status: Standards Track U. Chunduri Intended status: Standards Track U. Chunduri
Expires: June 17, 2018 Huawei Technologies Expires: June 17, 2018 Huawei Technologies
S. Aldrin S. Aldrin
Google, Inc Google, Inc
P. Psenak P. Psenak
Cisco Systems Cisco Systems
December 14, 2017 December 14, 2017
Signaling MSD (Maximum SID Depth) using OSPF Signaling MSD (Maximum SID Depth) using OSPF
draft-ietf-ospf-segment-routing-msd-07 draft-ietf-ospf-segment-routing-msd-08
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 OSPF supported by a node at node and/or link granularity by an OSPF
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 impose the SID by the head-end at node and/or link granularity to impose the SID
stack of an appropriate depth. MSD is relevant to the head-end of a stack of an appropriate depth. MSD is relevant to the head-end of a
SR tunnel or Binding-SID anchor node where Binding-SID expansions SR tunnel or Binding-SID anchor node where Binding-SID expansions
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appropriate depth, so it could be read by transit nodes. MSD in appropriate depth, so it could be read by transit nodes. MSD in
contrary signals ability to impose SID's stack of a particular depth. contrary signals ability to impose SID's stack of a particular depth.
MSD of type 1 (IANA Registry), called Base MSD is used to signal the MSD of type 1 (IANA Registry), called Base MSD is used to signal the
total number of SIDs a node is capable of imposing, to be used by a total number of SIDs a node is capable of imposing, to be used by a
path computation element/controller. In case, there are additional path computation element/controller. In case, there are additional
SIDs (e.g. service) that are to be imposed to the stack - this would SIDs (e.g. service) that are to be imposed to the stack - this would
be signaled with an another MSD type (TBD), no adjustment to the Base be signaled with an another MSD type (TBD), no adjustment to the Base
MSD should be made. In the future, new MSD types could be defined to MSD should be made. In the future, new MSD types could be defined to
signal additional capabilities: entropy labels, SIDs that can be signal additional capabilities: entropy labels, SIDs that can be
imposed thru recirculation, or another dataplane e.g IPv6. imposed 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
OSPF: Open Shortest Path First OSPF: Open Shortest Path First
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Figure 2: Link MSD Sub-TLV Figure 2: Link MSD Sub-TLV
The Type (2 bytes) of this TLV: The Type (2 bytes) of this TLV:
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], and has Sub-TLV of OSPFv2 Extended Link TLV as defined in [RFC7684], and has
value of 6. value of 6.
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], and has value of 3 (Suggested [I-D.ietf-ospf-ospfv3-lsa-extend], and has value of 16 (Suggested
value - to be assigned by IANA). 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 LSA as specified for 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 OSPFv2 and OSPFv3. Link MSD is a number in the range of 0-254. 0
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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 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]. For Router Information (RI) TLVs Registry as defined by [RFC4970]. For
THE link MSD, we request IANA to allocate new sub-TLV codes as the link MSD, we request IANA to allocate new sub-TLV codes as
proposed in Section 4 from OSPFv2 Extended Link TLV Sub-TLVs registry proposed in Section 4 from OSPFv2 Extended Link TLV Sub-TLVs registry
and from Router-Link TLV defined in OSPFv3 Extend-LSA Sub-TLV and from Router-Link TLV defined in OSPFv3 Extend-LSA Sub-TLV
registry. registry.
This document also requests IANA to create a new Sub-type registry as This document also requests IANA to create a new Sub-type registry as
proposed in Section 3, Section 4. proposed in Section 3, Section 4.
Value Name Reference Value Name Reference
----- --------------------- ------------- ----- --------------------- -------------
0 Reserved This document 0 Reserved This document
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