decision process

["John G. Scudder" <[e-mail]>]

While perusing draft-ietf-idr-bgp4-03.txt for my last note, I noticed that
this is still in the draft (section 9.1):

      a) Phase 1 is responsible for calculating the degree of preference
      for each route received from a BGP speaker located in a
      neighboring autonomous system, and for advertising to the other
      BGP speakers in the local autonomous system the routes that have
      the highest degree of preference for each distinct destination.

I submit that as far as I know, no one actually disseminates routes which
they don't use via IBGP (or at all).  However, this text calls for what's
sometimes called "best external route" distribution.  The best external
route is not necessarily the selected route.

Given that this is not implemented anywhere as far as I know, I suggest
that the text be trimmed to read

      a) Phase 1 is responsible for calculating the degree of preference
      for each route received from a BGP speaker located in a
      neighboring autonomous system.

and part c should also be modified:

      c) Phase 3 is invoked after the Loc-RIB has been modified. It is
      responsible for disseminating routes in the Loc-RIB to each peer,
      according to the policies contained in the PIB. Route aggregation
      and information reduction can optionally be performed within this
      phase.

(this deletes the "located in a neighboring autonomous system" part)

If someone *has* actually implemented the "best external route" thing *in
BGP* it would be interesting to know about that.  Experience from IDRP
implementations which do this would also be interesting.  I know it was a
lot of work to do in gated IDRP -- it would be interesting to know what, if
any, measured real-world benefit it provides.

--John

--
John Scudder                        email:  [e-mail]
Internet Engineering Group, LLC     phone:  [phone]
122 S. Main, Suite 280              fax:    [phone]
Ann Arbor, MI  41804                www:    http://www.ieng.com