nanog mailing list archives
Re: gigabit router (was Re: Getting a "portable" /19 or /20)
From: Craig Partridge <craig () aland bbn com>
Date: Wed, 11 Apr 2001 16:59:54 -0400
In message <20010411164727.B647 () alcor net>, Matt Zimmerman writes:
I think Alex was referring to internal consistency within the router (between linecards), not external consistency. For example, if linecard X believes tha t a packet should be forwarded to linecard Y, but linecard Y's forwarding table is older than X's, Y could misforward the packet, causing a forwarding loop or a dropped packet. Thus, it can be the case that neither the old path nor the new path is taken.
I used to give a course on building high speed routers. A section of the course was entitled "common mistakes to avoid." One of them was precisely this problem. The rule is forward once within a box -- if linecard X has decided how a packet is to be forwarded, linecard Y shouldn't be reconsidering the decision. (And, in fact, if you look at most linecard designs, the output path, from switch to transmission, does not include a forwarding engine -- there's only a forwarding engine on the inbound path). Craig
Current thread:
- Re: Getting a "portable" /19 or /20, (continued)
- Re: Getting a "portable" /19 or /20 Richard A. Steenbergen (Apr 10)
- Re: Getting a "portable" /19 or /20 Greg Maxwell (Apr 10)
- Re: Getting a "portable" /19 or /20 Richard A. Steenbergen (Apr 10)
- gigabit router (was Re: Getting a "portable" /19 or /20) Craig Partridge (Apr 10)
- Re: gigabit router (was Re: Getting a "portable" /19 or /20) Richard A. Steenbergen (Apr 10)
- Re: gigabit router (was Re: Getting a "portable" /19 or /20) alex (Apr 10)
- RE: gigabit router (was Re: Getting a "portable" /19 or /20) David Schwartz (Apr 10)
- RE: gigabit router (was Re: Getting a "portable" /19 or /20) alex (Apr 10)
- RE: gigabit router (was Re: Getting a "portable" /19 or /20) David Schwartz (Apr 11)
- Re: gigabit router (was Re: Getting a "portable" /19 or /20) Matt Zimmerman (Apr 11)
- Re: gigabit router (was Re: Getting a "portable" /19 or /20) Craig Partridge (Apr 11)
- Re: gigabit router (was Re: Getting a "portable" /19 or /20) Brett Frankenberger (Apr 11)
- Re: Getting a "portable" /19 or /20 Greg Maxwell (Apr 10)
- Re: Getting a "portable" /19 or /20 Richard A. Steenbergen (Apr 10)
- Re: gigabit router (was Re: Getting a "portable" /19 or /20) Richard A. Steenbergen (Apr 10)
- Re: gigabit router (was Re: Getting a "portable" /19 or /20) Rafi Sadowsky (Apr 11)
- Re: gigabit router (was Re: Getting a "portable" /19 or /20) Craig Partridge (Apr 10)
- Re: gigabit router (was Re: Getting a "portable" /19 or /20) Greg Maxwell (Apr 10)
- Re: gigabit router (was Re: Getting a "portable" /19 or /20) Richard A. Steenbergen (Apr 10)
- Re: gigabit router (was Re: Getting a "portable" /19 or /20) Peter Galbavy (Apr 11)
- Re: gigabit router (was Re: Getting a "portable" /19 or /20) Bora Akyol (Apr 10)
- Re: gigabit router (was Re: Getting a "portable" /19 or /20) Michael C . Wu (Apr 16)
- Re: Getting a "portable" /19 or /20 Dan Hollis (Apr 10)