an enquiry

Yuko Murayama in Tokyo <murayama@nc.u-tokyo.ac.jp> Wed, 25 November 1992 09:07 UTC

Received: from ietf.nri.reston.va.us by IETF.CNRI.Reston.VA.US id aa00862; 25 Nov 92 4:07 EST
Received: from CNRI.RESTON.VA.US by IETF.CNRI.Reston.VA.US id aa00858; 25 Nov 92 4:07 EST
Received: from PIZZA.BBN.COM by CNRI.Reston.VA.US id aa02524; 25 Nov 92 4:08 EST
Received: by PIZZA.BBN.COM id aa17628; 25 Nov 92 4:07 EST
Received: from pizza by PIZZA.BBN.COM id aa17403; 25 Nov 92 3:32 EST
Received: from BBN.COM by PIZZA.BBN.COM id aa17399; 25 Nov 92 3:29 EST
Received: from angora.nc.u-tokyo.ac.jp by BBN.COM id aa13965; 25 Nov 92 3:29 EST
Received: from localhost by angora.nc.u-tokyo.ac.jp (5.65/2.7W-1.2) id AA23845; Wed, 25 Nov 92 17:29:36 +0900
Return-Path: <murayama@nc.u-tokyo.ac.jp>
Message-Id: <9211250829.AA23845@angora.nc.u-tokyo.ac.jp>
To: idpr-wg@bbn.com
Cc: motonori@kuis.kyoto-u.ac.jp, sone@hitachi-cable.co.jp, murayama@angora.nc.u-tokyo.ac.jp
Subject: an enquiry
Date: Wed, 25 Nov 92 17:29:36 +0900
Sender: ietf-archive-request@IETF.CNRI.Reston.VA.US
From: Yuko Murayama in Tokyo <murayama@nc.u-tokyo.ac.jp>

We have a working group of policy routing at WIDE Project, Japan, 
starting studying IDPR.

We have a small policy-routing problem which is termed 
"the Motonori Problem," because it was first defined 
clearly by Motonori Nakamura at Kyoto University.

The problem is: how can one enforce the preference of transits?
Suppose that we have two transit ADs, A and B between the source AD X
and the destination AD Y.  There are more than one interface (VG)
between A and B as follows:


Y1                    AS Y (destination)
|                  
---------------------
|                   |
|       AS B        |
|                   |
---B1----B2----B3----
   |     |     |
   |L1   |L2   |L3
   |     |     |
---A1----A2----A3----  
|                   |
|       AS A        |
|                   |
---------------------
                  |
                  X1  AS X (source)    

When one at AD X wants to send a message to someone at AD Y,
how can one say, "packets should go through AD A as much as possible,
and pass through B as less as possible due to some cost parameter" ?
Does a local route server at X have knowledge on locations of VGs, L1, L2, 
and L3, so that pakcets from X to Y would take L1?

Using BGP one could implement this policy to some extent, but not exactly
because, if my memory is correct, B has to
advertise each interface with different preference for the sake of A/X...which 
is not necessarily B's own policy.

Yuko