There are deployments where the Layer 3 interface on which IS-IS
operates is a Layer 2 interface bundle. Existing IS-IS
advertisements only support advertising link attributes of the Layer
3 interface. If entities external to IS-IS wish to control traffic
flows on the individual physical links which comprise the Layer 2
interface bundle link attribute information about the bundle members
The extension in this document are mostly used for:
1) telemetry applications which build segment-routing stacks such that
child-links of a bundle can get probed.
2) TE to manage the load on child links if there is an imbalance.
Working Group Summary
There was some controversy mostly triggered by
network operators that the use-cases are not clear and
wether IS-IS is the correct place for these extensions.
BGP-LS was suggested as an alternative, mostly
because BGP-LS is a strict northbound protocol
and this would be the precedent-case for a pure-northbound
protocol (= no receive side logic) in IS-IS.
Alia raised awareness in OSPF, IDR, and RTGWG during the IETF Last
Call to see if there were any concerns about this technical path
forward and had a response that this direction can work for OSPF as
well. Given the implications for an l2bundle being an IEEE Link
Aggregate Group (LAG), Alia also raised awareness on the ieee-ietf-
coord about the IETF LC, but without any response.
While the draft shepherd clearly would prefer a different technical
solution, there was clear WG consensus to publish and no discussion or
disagreement at IETF 98.
There is one implementation for Cisco IOS-XR. At IETF 98 ISIS WG,
when this draft was discussed, Les mentioned that Cisco is awaiting
the IANA code-point to ship this feature.
Hannes Gredler (isis-wg co-chair) is the Document Shepherd.
Alia Atlas is the AD.