A call for the future. Was: Re: Verio Decides what parts of the internet to drop

In the design of contemporary core routers, table maintenance and packet
processing are discrete functions.

The maintenance of comprehensive routing information that includes a superset of
best paths is common practice, with proven benefits. However, it is neither
necessary nor desirable to consult this database for a forwarding decision.
Instead, the fastpath need only have knowledge of the best next hop matching a
DA prefix.

Whatever changes we believe to be in store for the table population, this is
unlikely to affect the typical number of adjacencies for a core router. Assuming
also that we continue to use IPv4 for a while, the "input length" of composite
information for the FIB could be less than 7 bytes for unicast routes. For the
2.5E5 best paths discussed, this equates to approximately 1.4MB.

Also, since the matching (ideally) yields a singular, exclusive result, this
matching operation is easily "parallelized" , in hardware or otherwise; observed
work need not even be linear with FIB size.

In short, the technical obstacles presented by high table / route population are
no greater for forwarding logic than for the control plane.

Andrew Bender
Total Network Solutions, Inc.