nanog mailing list archives
Re: "2M today, 10M with no change in technology"? An informal survey.
From: Florian Weimer <fw () deneb enyo de>
Date: Sun, 26 Aug 2007 10:41:46 +0200
* Deepak Jain:
When it comes to an FIB, there are only say 100-200 destinations on a big router (outbound). Irrespective of the 2M or 20M routes it has. Even though the entire Internet isn't aggregated the way it should be, for FIB purposes, the router knows how it will route out to its 100-200 destinations (ports).
Could be more than that in some MPLS and IXP environments, but in essence, that's true.
Couldn't it just aggregate before it drops routes into its FIB and only import specifics (deagg) if a destination changes for a more specific prefix [like the swamp]? We talk about default-free zones as needing every prefix, and they do (for propagation purposes) but for FIB purposes, they really don't.
My understanding is that there are no known algorithms for fast updates (and particularly withdrawals) on aggregated FIBs, especially if those FIBs are stored in CIDR form. This is the prime reason why all those Cisco 65xx/76xx with MSFC2/PFC2 will be worthless junk in a couple of months. But I'm sure that this is not the end of the story.
For example, a router with only 1 connection (no matter how many routes being sent by its upstream), would only have 1 route entered into its FIB -- because no matter where the route goes, it can go upstream.
This will cause routing loops for unallocated address space.
Current thread:
- Re: "2M today, 10M with no change in technology"? An informal survey., (continued)
- Re: "2M today, 10M with no change in technology"? An informal survey. Simon Leinen (Aug 27)
- Re: "2M today, 10M with no change in technology"? An informal survey. Adrian Chadd (Aug 27)
- RE: "2M today, 10M with no change in technology"? An informal survey. Ross Callon (Aug 26)
- Re: "2M today, 10M with no change in technology"? An informal survey. David Conrad (Aug 27)
- Re: "2M today, 10M with no change in technology"? An informal survey. Rob Evans (Aug 28)
- Re: "2M today, 10M with no change in technology"? An informal survey. bmanning (Aug 28)
- Re: "2M today, 10M with no change in technology"? An informal survey. Brandon Butterworth (Aug 25)
- Re: "2M today, 10M with no change in technology"? An informal survey. Randy Bush (Aug 25)
- Re: "2M today, 10M with no change in technology"? An informal survey. Jared Mauch (Aug 25)
- Re: "2M today, 10M with no change in technology"? An informal survey. Deepak Jain (Aug 25)
- Re: "2M today, 10M with no change in technology"? An informal survey. Florian Weimer (Aug 26)
- Re: "2M today, 10M with no change in technology"? An informal survey. Deepak Jain (Aug 26)
- Re: "2M today, 10M with no change in technology"? An informal survey. Eric Gauthier (Aug 27)
- Re: "2M today, 10M with no change in technology"? An informal survey. Jon Lewis (Aug 27)
- Re: "2M today, 10M with no change in technology"? An informal survey. Deepak Jain (Aug 27)
- Re: "2M today, 10M with no change in technology"? An informal survey. David Conrad (Aug 27)
- Re: "2M today, 10M with no change in technology"? An informal survey. Deepak Jain (Aug 27)
- Re: "2M today, 10M with no change in technology"? An informal survey. Mikael Abrahamsson (Aug 27)
- Re: "2M today, 10M with no change in technology"? An informal survey. Jon Lewis (Aug 27)
- Re: "2M today, 10M with no change in technology"? An informal survey. David Conrad (Aug 27)
- Re: "2M today, 10M with no change in technology"? An informal survey. Jon Lewis (Aug 29)
- Re: "2M today, 10M with no change in technology"? An informal survey. Randy Bush (Aug 25)