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

[Nandan Saha <[e-mail]>]

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