Internet Backbone Index

Mon Jul 14 16:28:52 UTC 1997

Stephen Balbach <stephen at clark.net> writes:

> Routes the first packets and switches the rest based on
> "flows".

How is this conceptually different from cisco
fastswitching wherein the slow path is used for the first
packet towards a destination and all subsequent packets
use a cache-based fast path?   

In both cases you have a slow cache-set-up path and a
finite cache.

There are significant disadvantages to using a cache in 
core routers (look up Dennis Ferguson's comments in your
local NANOG archive, nobody I can think of can improve on
them).

The only principal advantage to cache-based routing is
when you haven't got the power to process all packets
through the same path without drops or mishandling of
things like options and filters, but you do have the power
to do some sort of hashed cache lookup.  With luck, this
will not be the case in future routers.

	Sean.