Subject: Proxy: comments on section 9.1.3

From: Alex Zinin <[email-masked]>
Date: Fri, 6 Sep 2002 15:07:40 +0200

Proxy-fwd below.

--
Alex

I'm looking for clarification to wording in section 9.1.3 Phase 3: Route
Dessemination of draft-ietf-idr-bgp4-17.txt.

My understanding is that a BGP route should not be advertised to a peer if
that route is not also in the Routing Table (e.g. FIB).  I was looking for
wording to support this, but am now starting to second guess myself.

"All routes in the Loc-RIB shall be processed into Adj-RIBs-Out according to
configured policy. This policy may exclude a route in the Loc-RIB from being
installed in a particular Adj-RIB-Out."

This seems clear.  I'm interpreting "configured policy" as routes can be
filtered prior to being sent (and thus not sent) to a peer.

"A route shall not be installed in the Adj-Rib-Out unless the destination
and NEXT_HOP described by this route may be forwarded appropriately by the
Routing Table."

This covers the case when local policy keeps a route in Loc-RIB from being
placed into the Routing Table and there is no other way for the route to get
in the Routing Table.  Even though the route is in Loc-RIB, it will not be
sent to the peer.

What if the route in Loc-RIB would have been placed in the Routing Table,
except local policy (e.g. lower Administrative Distance) placed an IGP route
there instead?   Durring Phase 3, both the destination and NEXT_HOP
described by the route in Loc-RIB could be "forwarded appropriately" (but
perhaps to the wrong place.)   In this case, should the Loc-RIB be placed in
Adj-RIB-Out?

The text doesn't say that both Loc-RIB and the Routing Table (the route the
local speaker itself uses) must have the same route.  It reads as if only
route in Loc-RIB need be considered.  In the description of earlier phases,
"local policy" is mentioned in the text describing what to do.  In this
phase, the impact of any "local policy" should be called out.

---

From: Mathew Richardson <[email-masked]>
Date: Fri, 6 Sep 2002 09:42:14 -0400

> Alex Zinin <[email-masked]> [Fri, Sep 06, 2002 at 03:07:40PM +0200]:
>Proxy-fwd below.
>
>--
>Alex
>
>there instead?   

From section 3.1:

   Routes that will be used by the local BGP speaker must be
   present in the Loc-RIB ...

From section 9.1.2:

  The local speaker SHALL then install that route in the Loc-RIB,
  replacing any route to the same destination that is currently being
  held in the Loc-RIB. 

So, the Loc-RIB contains only one route per-destination, and routes
that will be used by the local BGP speaker must be present in the
Loc-RIB.

>Durring Phase 3, both the destination and NEXT_HOP

I agree that this could use some clarification.  How about adding
to b) in section 9.1:

  The Loc-RIB must contain only one route per destination; further, it
  must include all routes that the BGP speaker is using.

changing c) in section 9.1.2 to:

  c) is selected as a result of the Phase 2 tie breaking rules specified
  in 9.1.2.2, or

and adding

  d) when routing protocols other than BGP are in use, is determined by
  some other local means to be the route that will actually be used to
  reach a particular destination.

mrr