Initial taxonomy draft comment

Joel M. Halpern joel at
Thu Mar 15 23:43:12 UTC 2001

I was reading the taxonomy, and there appeared to be an unstated assumption 
in the description of "covered" cases.

If I am reading the document correctly, when AS (holding a long prefix, 
wants to multi-home with an address from AS2's block, you would like to see: from 7 2 from 1 11 3
rather than having AS2 advertise 198/108.1.0/24 as well. In fact, early on 
you say that such an advertisement should have been aggregated by AS2.

This seems to mean that remote AS are to treat AS2s announcement as 
providing comparable coverage to that of AS3 itself. [The assumption I am 
concerned about.]

This would seem to have two implications:

Firstly, this is a major change from the routing assumptions to date. We 
currently assume that a longer match is "better". If there were no loss of 
functionality, removing this assumption might well be good, but should be 

Secondly, this would mean that there would be no way for AS2 to arrange 
that the traffic for AS3 did NOT come to it if the connection between AS2 
and AS3 went down. This seems to undermine one of the basic purposes of 

Have I misread the intentions of the document? They seem pretty clearly 
stated in the taxonomy section on CD - (SO, DN) where it states that AS2 
should aggregate.

Joel M. Halpern

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