On Tue, Aug 08, 2006 at 02:09:16PM -0700, Tom Samplonius wrote: > > Strictly speaking, Cisco CEF is just a way to store a forwarding table > for fast lookups. The storage could be in some kind of content addressable > memory, and looked up by an ASIC, or it could be in RAM and looked up by > the the router's CPU.
CEF originally implied a software data structure (an mtrie) which was dedicated to doing forwarding lookups only (a FIB), and which was pre-populated to deliver deterministic lookup speeds whether the packet was the first in a flow (or first to a destination) or not. Some later techniques in hardware looked pretty much like this, others did not, but the marketing term stuck. :) > So Foundry made the jump to putting the full routing table in CAM with > the MLX? Juniper has always operated this way, so why have some > respondants talked about replacing Juniper's with MLXs? Other than that > some of the old processing engines on the Juniper's lacked enough memory > for some features, there should be little difference at the L2/L3 > forwarding level these days? Sure, but prepopulating the CAM with a full table is "building a router 101", and has almost nothing to do with the success or failure of replacing a Juniper. Like I said before, doing a bazillion lookups/sec or moving a bazillion bits/sec is trivial, in L2 or L3. It is a problem that has been solved, the hw is a commodity. The difference between a crappy box and a good box is software, software, software. -- Richard A Steenbergen <ras at e-gerbil.net> http://www.e-gerbil.net/ras GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)
