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From: Tony Li (no email)
Date: Fri Dec 02 2005 - 03:41:37 EST
>
> An alternative for sbgp design could be that aggregating ASN would
> create special self-signing cert for such aggregate block and that
> cert would have special attribute(s) indicating list of all sub-
> blocks and reference
> to all certs that "make" this aggregate block. Then verifying router
> in such a case would go through and verify each one of those sub-block
> certs (and those sub-block certs would have to be such that they
> give permission for announcing the block from that sub-block owner
> to aggregating ASN).
>
Advertising an aggregate that is not specifically assigned to you is
known as "proxy aggregation".
William has given a good description of what's required above, but it
needs a further enhancement
in that proxy aggregation will frequently need to happen in several
locations for the aggregate to
have any true impact on routing. In graph theoretic terms, proxy
aggregation must form a
"cut set" topologically around the longer prefixes to contain them
and prevent them from being
distributed throughout the network.
Thus, any security mechanism needs to provide some means for
indicating that
an entire set of ASes may legitimately be advertising a proxy
aggregate prefix. How one
determines the appropriate set of ASes that are authorized is another
interesting administrative
issue that needs to be resolved.
Tony
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