Subject: [Idr] Comments on draft-ietf-idr-bgp-open-policy

From: Jeffrey Haas <[email-masked]>
Date: Wed, 5 Jan 2022 20:42:20 -0500

A few comments from things I noticed while reviewing the open-policy draft
while working through current threads:

Section 4.2:

:    2.  If a route with the OTC Attribute is received from a Peer and at
:        least one of the OTC Attributes has a value that is not equal to
:        the remote (i.e., Peer's) AS number, then it is a route leak and
:        MUST be considered ineligible.

By the definition of the path attribute's length field, there can only be
one of them.

The text recognizes this point later:

:    If an eBGP speaker receives an UPDATE with an OTC Attribute with a
:    length different from 4 octets, then the UPDATE SHALL be considered
:    malformed.  If malformed, the UPDATE message SHALL be handled using
:    the approach of "treat-as-withdraw" [RFC7606].

But:

:    Correct implementation of the procedures specified in this document
:    is not expected to result in the presence of multiple OTC Attributes
:    in an UPDATE.  However, if an eBGP speaker receives multiple OTC
:    Attributes with a route, then the only difference in the processing
:    is in Step 2 of the ingress policy.

This is already a fault per RFC 4271, Section 6.3:

:    If any attribute appears more than once in the UPDATE message, then
:    the Error Subcode MUST be set to Malformed Attribute List.

My recommendations:
- In 4.2, change the voicing to say "the OTC Attribute has a value"
- Delete the "Correct implementation" paragraph as unnecessary text.

-- Jeff