North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: gigabit router (was Re: Getting a "portable" /19 or /20)
In message <[email protected]>, 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
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