[Lsr] draft-peng-lsr-flex-algo-l2bundles

Peter Psenak <ppsenak@cisco.com> Tue, 09 March 2021 10:08 UTC

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From: Peter Psenak <ppsenak@cisco.com>
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Subject: [Lsr] draft-peng-lsr-flex-algo-l2bundles
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Dear authors,

here are couple of comments to draft-peng-lsr-flex-algo-l2bundles:

1. Flex-algo specification as specified in draft-ietf-lsr-flex-algo only 
uses L3 link information for path computation. This is consistent with 
the regular Algo 0 path computation. My preference would be to keep it 
that way.

2. Flex-algo is not a replacement for SRTE. The problem that you are 
trying to solve can be solved by SRTE with the usage of the L2 Adj-SIDs.

3. Usage of the L2 link data for flex-algo path computation is much more 
complex than defining the L-flag in the FAD. You would need to deal with 
things like:

a) conflicting information in L3 and L2 link information
b) missing information in L3 or L2 link information

which would require to define a strict path computation preference rules 
and conflict resolutions that all routers would need to follow. I would 
argue that this is much easier to be done with SRTE, where the logic to 
select the path is a local matter compared to consistency in path 
selection that is required for distributed calculation used by flex-algo.