[Idr] [draft-ietf-idr-segment-routing-te-policy] Error handling for Explicit NULL Label Policy Sub-TLV

Nandan Saha <nandan@arista.com> Thu, 16 May 2019 07:42 UTC

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From: Nandan Saha <nandan@arista.com>
Date: Thu, 16 May 2019 13:12:39 +0530
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To: draft-ietf-idr-segment-routing-te-policy@ietf.org, "Ketan Talaulikar (ketant)" <ketant@cisco.com>, Paul Mattes <pamattes@microsoft.com>, Przemyslaw Krol <pkrol@google.com>
Cc: idr@ietf.org, Manoharan Sundaramoorthy <manoharan@arista.com>
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Subject: [Idr] [draft-ietf-idr-segment-routing-te-policy] Error handling for Explicit NULL Label Policy Sub-TLV
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Hi folks,
 There error handling for the ENLP sub-TLV isn't defined in
draft-ietf-idr-segment-routing-te-policy-05 [1].

There are 2 things that need to be clarified:-

1. The behavior when ENLP sub-TLV occurs more than once:
  For this, my preference is to add text like we have for policy
priority sub-TLV [2] (and some other sub-TLVs), mandating only one
occurrence and treat-as-withdraw when present more than once.

2. Behavior when ENLP value is either 0 or >= 5.
  The only meaningful/legal values defined now are 1-4. My preference is to
2a: mark other values as reserved for future use. (We could mark them
illegal but that'll rule out trying to extended them if ever needed)
and
2.b: Upon receipt ENLP = 0 || >=5 the headend call fall back to local
policy. (If we go down the route of marking 0 || >= 5 as illegal, we
can do TAW)

Please let me know what you think, and if this seems reasonable.

[1] - https://tools.ietf.org/html/draft-ietf-idr-segment-routing-te-policy-05#section-2.4.4
[2] - https://tools.ietf.org/html/draft-ietf-idr-segment-routing-te-policy-05#section-2.4.5

Thanks,
Nandan