Subject: [mpls] draft-kini-mpls-entropy-label-src-stacked-tunnels

From: <[email-masked]>
Date: Fri, 31 Jan 2014 15:11:45 +0100

Hi Authors,

I would like to know if you are progressing on this draft ?
Entropy label support for stacked tunnels would be mandatory for us, so I would like to support the work on this topic to have a working solution as soon as possible.

Regarding the solutions you are proposing in the current version, there is none perfect one, and unfortunately all have drawbacks.
The compatibility (on LSR) with current generation of hardwares may be "good" (mandatory ?) for the target solution.

In your document , solution §3.3 "re-usable EL for a stack of tunnels" sounds for me to be the best base idea. I'm just wondering what would be the hardware impact of doing the reinsertion of ELI at tunnel end . Could this be done in one pass ? (IMHO, this may be possible, as today we are able to pop or swap + push FRR headers) As you are three different vendors as co-author, did you already evaluate such impact on your hardwares ? (I'm not expecting details on the mailing list, but I would be interested by details unicast to me and just yes/no on the the list)

To be exhaustive in listing solutions, did you think about leaving the EL/ELI at top of the stack ? I think there is already a case where a special label may be kept at top of the stack (MPLS Router alert).
What would be needed :

-          each hop need to advertise is ability to process EL, if nexthop cannot process EL, it should be removed when forwarded to nexthop (there should be the same requirement for re-usable EL)
I don't think this is really different from re-usable EL in the concept :

-          reusable EL : process top level forwarding label, if popped and next label is EL, pop ELI/EL and next label L, push pack ELI/EL and then L (we need to swap positions between ELI/EL and L) if nexthop is able to process EL.

-          top level EL : process top level ELI, ELI is recognized, ELI/EL is removed, forwarding is done on forwarding label, ELI/EL is pushed back in nexthop is able to process EL.

In term of operations, I think that top level EL may be simpler , but as I'm not hardware coder, may be I'm wrong ... moreover it may be similar to MPLS Router alert processing.

Your thoughts ?

Stephane

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