nanog mailing list archives
Routing vs Switching (was Re: Another UUNET Explanation)
From: smd () clock org (Sean M. Doran)
Date: 02 Jul 1997 02:09:57 -0400
"Chris A. Icide" <chris () nap net> writes: smd> A clumsy tech or a backhoe takes out a physical path smd> between two POPs, each of which contains several routers smd> that form part of this flat network. smd> What happens now?
Layer 2 heals itself, without the knowledge of layer 3. Layer 3 experiences a latency increase between certain paths. Sorry, had to do it. *duck*
Well, this is certainly the obvious approach, and is certainly in line with the generally reasonable philosophy of "degraded performance rather than no performance" response to partitions, assuming the routers don't notice a topology change. There are some interesting issues with respect to convergence at the L2 layer (rerouting VCs takes time too), and I've seen problems where the fast-packet layer converged slowly enough that IS-IS adjacencies were lost, causing really neat routing slosh as the VC went and came back. (To augment one of my own questions, when you have two routers in a full mesh (FR, ATM, whatever using VCs) and the VC between N-1 and N-2 goes out of service, how do N-1 and N-2 decide what path(s) to use to talk to each other? Feel free to consider a network using any commonly available IGP and the iBGP hack.) I also have some anecdotes about VCs improperly travelling along the same path for long periods of time because of configuration errors or unnoticed physical disconnectivities between switches. There have also been neat tales of VCs going simplex from time to time. Monitoring two networks simultaneously, fun fun fun... :) I'm sure there are people here with practical experiences who might be willing to share what they've learned.
however, in this fast paced industry, will we ever have the "perfect" protocol (okay, ever is a big word).
IPv6 over ATM/LANE with RSVP will someday change the world. Sean. - -- Sean Doran <smd () ab use net> "Boy, you obviously don't have a clue!" -- Chad Skidmore, Data Source L.L.C.
Current thread:
- Re: Another UUNET Explanation, (continued)
- Re: Another UUNET Explanation Dorian R. Kim (Jul 02)
- Re: Another UUNET Explanation John Leong (Jul 01)
- Re: Another UUNET Explanation Nathan Stratton (Jul 01)
- Re: Another UUNET Explanation Ehud Gavron (Jul 01)
- Re: Another UUNET Explanation Martin J. Hannigan (Jul 01)
- Re: Another UUNET Explanation John Leong (Jul 02)
- Re: Another UUNET Explanation Steve Mansfield (Jul 02)
- Re: Another UUNET Explanation jprovo (Jul 01)
- RE: Another UUNET Explanation Chad Skidmore (Jul 01)
- RE: Another UUNET Explanation Chris A. Icide (Jul 01)
- Routing vs Switching (was Re: Another UUNET Explanation) Sean M. Doran (Jul 01)
- Re: Routing vs Switching (was Re: Another UUNET Explanation) Craig A. Huegen (Jul 02)
- Routing vs Switching (was Re: Another UUNET Explanation) Sean M. Doran (Jul 01)
- FW: Another UUNET Explanation Jan Novak (Jul 02)
- Re: Another UUNET Explanation Mat Miller (Jul 02)
- Re: Another UUNET Explanation Wolfgang Henke (Jul 02)