more comments...

Marten,

 * 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.

Actually, AS690's as-in is exactly specified by its neighbor ASs.  The
format of that is to use NCAR.  So there is practice that AS configure 
their routers based neighbor's specification and it works well for all
these years.  


 * 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?

Would you tell me that routing protocols people are using and register
with you currently?  EGP and BGP right?  Even EGP has outbound announcement
metric which could be used by its neighbor.

Would you tell me what inter-domain routing protocols people will use
in the next 3 years?  Again EGP, BGP and IDRP. 

In terms of metrics used by IDRP, MED like BGP. 

Other point:

I feel puzzled that why it was decided to have both as-in/as-out and interas-in/
interas-out.  The latter is somesort a superset of the former.  Why define a
system which has redundant attributes.  I was told that interas-in/interas-out
could be used to allow the neighbors to exchange more routing exchange information
including the gateways,etc.  If that is the case, then it REALLY MAKES SENSE to
allow people to specify pref/metric in interas-out.  
 
							--Jessica



-------- Logged at  Tue May 31 17:49:09 MET DST 1994  ---------