North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Gordius has left the building. Was: RE: The Gorgon's Knot.
Deepak Jain wrote: > The problem is where the RIB, or forwarding table is exported to > the line cards which frequently have less than 128MB of usable > RAM/SRAM/memory storage/etc. This essentially means that the line > cards can only directly talk to other line cards for a specified, > limited number of routing prefixes. I do not know the algorithms > used when the line card is out of memory, but in many cases this > memory is not field upgradeable beyond a certain point. Srinivasan, Vargese, and others have demonstrated / observed that space is not a material problem for the architecture you describe. Rather, it is the time to complete a longest-match (or equivalent) operation for each forwarding event, especially for high(er) interface speeds. Regardless, 128MB is a LOT of table memory, especially when it is virtually unknown to see anything larger than 10-20Mbit CAMs; prior to reduction / expansion / etc, there's scarcely 11B of unique information in an IPv4 route. Adding in some bytes for mysterious 'other stuff', this is easily 4-8MM routes. We'll have to see another knee in route proliferation before this becomes a problem, and space exhaust would most certainly prevent this from happening. > Many smaller networks can and do use PCs for BGP and for > forwarding because their total forwarding needs at their core are > say sufficiently less than 800mb/s upto which PCs seem to handle. > However, the desires and models of these smaller networks don't > scale much beyond this level with currently available PC > technology. Agreed... as regards PCs lets remember that history has offered certain commentary on the non-role of PCs (indeed general purpose computers) in network infrastructure... viz. there aren't many GRFs / DDP516Rs / etc. around anymore. I doubt this is an 'interesting problem' for the op or planning community. Regards, Andrew Bender taqua.com
|