[Pce] Implementation option of draft-ietf-pce-stateful-interdomain-01.txt

olivier.dugeon@orange.com Mon, 22 February 2021 18:35 UTC

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Subject: [Pce] Implementation option of draft-ietf-pce-stateful-interdomain-01.txt
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Dear all,

According to the remark about implementation we got during the WG call
for adoption, we would start a new thread to discuss this point.
The goal isto prepare the discussion for next IETF meeting and reach a
consensusin order to edit revision 2 of the draft.

The stitching label principle requires at least a certain number of
modifications in the current PCEP version:

 a) A new PCE Capability to announce the inter-domain behaviour
 b) A new PCE Association Group to associate the local paths identifier
    to the inter-domain identifier
 c) new PCEP Errors to manage the Stitching Label exchange
 d) A mechanism to convey the Stitching Label

If there is no other choice than to reuse existing PCEP Objects by
allocating new code points for modifications a-c,there is several
options for point d, which we have tried to list below:

 d1) Use ERO and RRO in conjunction to new Path Setup code points as
     described in version 01 of the draft. It is the simplest
     implementation but as mention by Dhruv, each time a new path
     enforcement appear, a new PST code point must be allocated.
     For example, when Segment Routing v6 will be standardized, we must
     allocate a new Stitching label PST code point for SRv6.
 d2) Use ERO and ERO in conjunction to a new flag in LSP. Simple as for d1,
     but need to use the LSP Extended Flag draft as all LSP flags have been
     already allocated.
 d3) Same as d2 but find another place for the flag e.g. SRP or LSPA Object.
 d4) Define a new PCEP sub-Objet TLV within the LSP Object to convey the
     stitching label. This is more independent but need extra parsing from
     an implementation point of view.

Please, give us your opinion about these different options and don't hesitate
to propose others.


Olivier on be-half of co-author's


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