nanog mailing list archives
Re: Load balancing in routers
From: joe mcguckin <joe () via net>
Date: Mon, 08 Apr 2002 09:21:54 -0700
I don't think flow-caching is necessarily due to CEF. Even on dinky 2500 & 2600 series where you don't run CEF, load balancing over multiple links uses a flow-hashed method. If you want per-packet load distribution you have to specifically enable it by saying "no ip route-cache" on each interface. Paul's statement about CEF is interesting. It's probably the first public statement I've ever heard where someone was praising CEF. Usually discussions about CEF are accompanied by liberal amounts of swearing... Joe On 4/8/02 9:03 AM, "Iljitsch van Beijnum" <iljitsch () muada com> wrote:
On 8 Apr 2002, Paul Vixie wrote:I seem to remember fast switching was per-destination, and CEF was round robin. But it seems CEF is now per-destination as well in IOS 12.2. Round robin is optional.CEF is flow-hashed, and the hash seems to include both source and destination, and seems to include the port numbers. This is by observing the behaviour of flows hitting various members of the F.ROOT-SERVERS.NET set, each of whom sends F's address to several upstream routers using OSPF. CEF works like a charm -- the load is never split by more than 45-55 and that's damn good for wire speed hashing in my view.We used CEF in 11.x and it behaved the same way. It was never round-robin in any way we could observe.You're right. I was thinking of process switching. According to: http://www.ils.unc.edu/dempsey/186s00/reorderingpaper.pdf packet reordering at MAE East was extremely common a few years ago. Does anyone have information whether this is still happening?
Current thread:
- Load balancing in routers abhijit bare (Apr 07)
- Re: Load balancing in routers Stephen J. Wilcox (Apr 07)
- Re: Load balancing in routers Richard A Steenbergen (Apr 07)
- Re: Load balancing in routers Steve Francis (Apr 07)
- Re: Load balancing in routers jeffrey arnold (Apr 07)
- Re: Load balancing in routers Eric Osborne (Apr 08)
- Re: Load balancing in routers Iljitsch van Beijnum (Apr 08)
- Re: Load balancing in routers Lincoln Dale (Apr 08)
- Re: Load balancing in routers Paul Vixie (Apr 08)
- Re: Load balancing in routers Iljitsch van Beijnum (Apr 08)
- Re: Load balancing in routers joe mcguckin (Apr 08)
- Re: Load balancing in routers Stephen Sprunk (Apr 08)
- Re: Load balancing in routers Alex Rubenstein (Apr 08)
- Re: Load balancing in routers Richard A Steenbergen (Apr 08)
- Re: Load balancing in routers Mark Kent (Apr 08)
- Re: Load balancing in routers Stephen J. Wilcox (Apr 08)
- Re: Load balancing in routers Mark Kent (Apr 08)
- Re: Load balancing in routers Stephen Sprunk (Apr 08)
- Re: Load balancing in routers Steve Francis (Apr 07)
- Re: Load balancing in routers Richard A Steenbergen (Apr 08)
- Re: Load balancing in routers Rodney Dunn (Apr 08)
- Re: Load balancing in routers Donn Lasher (Apr 08)