more comments...

Jessica,

Jessica Yu <jyy at merit.edu> writes
 * 
 * There are cases that people do not config a preference when accepting certai
 * n routes
 * and rather they use the MED (Multi Exit Distriminator) information passed al
 * ong with
 * the routes.  So the sending AS actually really specify the preference not th
 * e
 * receiving AS.  Let interas-out to specify its MED is to inform the receiving
 *  AS 
 * the policy it has and how the traffic will flow.  There is no other way exce
 * pt a 
 * phone call to let the receiving AS know.  One of the purpose of routing regi
 * stry 
 * is to reduce the need to have phone such calls.

Well, again I do not agree. If I was to configure my router, I would
NEVER base my configuration on my neighbours as-out lines (or
interas-out for that matter). This is not so much a matter of
translation into configuration or direct mapping into protocols, but
about control. My neighbour can specify whatever he wants in his
as-out, I make the decision (of course after discussing with my
neighbour) HOW I want to receive his announcements. If you accept MED,
you basically say you do not care how your neighbour sends his routes
over multiple links. He can pick and choose whatever he wants, and by
accepting MED you loose control over what he announces where. I
strongly believe that you should only specify what you can enforce.

 * The MED is not just bgp specific.  IDRP has allow to specify that
 * too. So it is not just for BGP.  

Not a fair argument. We all know that IDRP will be  the logical
successor of BGP-4 and is often referred to as BGP-5. Besides, IDRP
can have many more attributes defined (see section 5.2.3 in
draft-hares-idrp-05.txt). Do we include all of these? If not, can
someone pick and choose which of the attributes the one specified in
interas-out is?

There is no way you can generate a complete router configuration
without local information. You will always need this. I believe
outgoing metrics is local/advisory information (again for the control
argument). 

 * How do I express that if I can not specify MED.  I do not suppose I can writ
 * e
 * as-in for AS690.

Noop you cannot. In the same way that you cannot specify that AS690
should accept MEDs on your connections. AS690 has control, not the
neighbour. It is again enforcable versus advisory information. Mixing
the two will give information you cannot base any tools on.

-Marten



-------- Logged at  Mon May 30 11:18:18 MET DST 1994  ---------