Deprecation of BGP Path Attribute values 30, 31, 129, 241, 242, and 243
NTT Communications
Theodorus Majofskistraat 100
1065 SZ
Amsterdam
NL
job@ntt.net
Routing
IDR
BGP
This document requests IANA to mark BGP path attribute
values 30, 31, 129, 241, 242, and 243 as "deprecated".
It has been discovered that certain BGP Path Attribute values
have been used in BGP implementations which have been deployed
in the wild while not being assigned by the IANA for such
usage. Unregistered usage of BGP Path Attribute values can lead to
deployment problems for new technologies.
The use of these unregistered values was noticed when BGP Large
Communities attribute
was initially assigned value 30 by IANA. It was subsequently
discovered that a widely-deployed BGP-4
implementation had released code which used path attribute 30
and which applied a "Treat-as-withdraw"
strategy to routes containing a valid Large Community
attribute, since it was expecting a different data structure.
Because these routes were dropped, early adopters of Large
Communities were unreachable from parts of the Internet. As a
workaround, a new Early IANA Allocation was requested.
The squatting of values 30, 31, 129, 241, 242 and 243 has been
confirmed by the involved vendors or through source code
review.
Per this document, IANA is requested to mark values 30, 31,
129, 241, 242, and 243 as "deprecated" in the "BGP Path
Attributes" registry under the "Border Gateway Protocol (BGP)
Parameters" group. The marking "deprecated" meaning "use is not
recommended" ().
There are no meaningful security consequences arising from this
registry update.
The author would like to gratefully acknowledge Marlien
Vijfhuizen who helped discover the squatting of value 30, and
Nick Hilliard for editorial feedback.