Draft of RIPE81++

Marten Terpstra (Marten.Terpstra at ripe.net) on September  7:
> Huh? Why would you in any case want to know addresses of border
> routers you do not peer with? An RS model is no different, and even
> the NEXT_HOP feauture does not change that. I cannot believe there is
> one example where you can configure a peering session without
> knowing both ends of the session.....

I agree with what you say in the above paragraph: The border routers
which peer with an RS know the address of the RS. I just want to
clarify a point though. 

In specifying policies, RS will be transparent.  That is if AS100 and
AS200 peer with an RS, administrators of AS100 specify policies for
AS200, not for RS. If multi-exit discrimination is allowed in this
case, there are two options for administrators of AS100:
	1) only specify local border router, i.e. 
		interas-in: from AS200 local-address - ...
	2) use RS's address, i.e.
		interas-in: from AS200 local-address rs-address ...

There are 4 problems with the second option:
1) RS is not completely transparent. (though RS' AS is).
2) It is confusing since RS is not in AS200.  
3) If the address of the RS changes, many changes by many
   administrators will be necessary in the database even though
   policies stay the same.
4) If it was actually necessary to specify two addresses (i.e. one
   address in AS100 and one in AS200) in expressing policies (e.g. if
   both ASs has two connections to RS, and they want to discriminate
   on each connection), option two can not handle this.

Regards,

Cengiz

-- 
Cengiz Alaettinoglu       Information Sciences Institute
cengiz at isi.edu            University of Southern California




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