Niels, thanks for the response. My description was pretty poor, as I look back over it. I am not questioning whether the load balancing algorithm is working or not; but my concern is the way it treats an ICMP traceroute. If I originate an ICMP traceroute from behind the router to a destination on the internet for which the XMR has two equal cost routes (or paths, especially in the case of "multipath multi-as"), it appears to do per-packet load balancing. If my customer has a problem, he is going to conduct a traceroute and the XMR will send the packets out different paths. He will infer that this is the problem (i.e. per-packet load balancing, which could cause latency and packet re-ordering, etc.) when in fact it may not be the case since the XMR does the "4 tuple" load balancing on TCP and UDP flows.
If I conduct a traceroute (ICMP) that originates from the XMR to a destination with two equal cost paths, it always keeps that traceroute on one path. That seems to me to be very inconsistent. I am in discussions with Foundry currently on this, but I am not getting much help explaining why this is the way it should be. Also, I didn't think there was a way to change the load balancing algorithm. I thought it was either on with "ip load-sharing <num>" or off with "no ip load-sharing". By the way, I really want to use the load balancing across multiple AS'es with the "multipath multi-as", but I can't right now because of the "perceived" (i.e. per-packet load balancing) issue. Thanks, Jason On 5/28/07, Niels Bakker <niels=foundry-nsp at bakker.net> wrote: > * boards188 at gmail.com (Jason Pope) [Sun 27 May 2007, 21:29 CEST]: > >Has anyone experienced problems with the XMR and load balancing? > > [snip description of XMR load-balancing working] > > I'm not sure I see anything wrong with your description. Generally, > load-balancing algorithms use src and dst IP addresses and TCP/UDP port > numbers or ICMP sequence. Not all equipment balances IPv6 and multicast > traffic as nicely as most do IPv4. > > Given a recent amount of entropy, hash-based load-balancing works quite > well, in my experience. The XMR can do per-packet too. Just be aware > that that might in some cases lead to packet reordering. And stay away > from "switch trunks" (support for which the XMR deprecates). > > > -- Niels. > > -- > _______________________________________________ > foundry-nsp mailing list > foundry-nsp at puck.nether.net > http://puck.nether.net/mailman/listinfo/foundry-nsp >
