Subject: [bess] About draft-dskc-bess-bgp-car

From: "Rabadan, Jorge (Nokia - US/Mountain View)" <[email-masked]>
Date: Wed, 10 Mar 2021 15:01:32 +0000

DJ, Swadesh,

Thanks for your time about these two drafts during the BESS session.
I just wanted to follow up on the two comments I made:

1) About this and the security section

   “The indication of the key length enables BGP Speakers to determine
   the key portion of the NLRI and use it along with the NLRI Type field
   in an opaque manner for handling of unknown or unsupported NLRI
   types.  This can help Route Reflectors (RR) to propagate NLRI types
   introduced in the future in a transparent manner.”

As discussed, this brings a potential security risk, since, for unknown route types, the RR only validates the key length without understanding if the content is wrong or not for the route type. I think DJ agreed this has to be discussed into the Security section (which by the way does not exist in the document in rev 01 __).

2) About the srv6 tlv and transposition:

"o  SRv6 SID Information: field of size as indicated by the length
      that either carries the SRv6 SID(s) for the advertised color-aware
      route as one of the following:

      *  A single 128-bit SRv6 SID or a stack of 128-bit SRv6 SIDs

      *  A transposed portion (refer [I-D.ietf-bess-srv6-services]) of
         the SRv6 SID that MUST be of size in multiples of one octet and
         less than 16."

@Swadesh, in the srv6-services draft, transposition is used for efficient packing, which *should not* be an issue here since the srv6 tlv is part of the NLRI (at least for 1 SID). I 'suspect' the use case here is to *save* some bytes when a stack of SIDs need to be advertised with the BGP CAR route, and those SIDs have a few common bytes in the locator part? it would be good if you can clarify please.

Thank you!
Jorge