Kyle McDonald wrote: > Hi all, > > I'm sure there's a technical reason why it can't be done (I imagine it > would have been if possible.) but I'd love to educate myself on what the > reason is why LACP Load balancing doesn't have a 'round-robin' option in > addition to the L2,L3,L4 src/dst options it has now? > > It seems to me that sending each new packet out the least recently used > interface would be a useful option for distributing the load accross the > aggregated interfaces? Why can't this be done? > > Right now I'm watching (with dladm show-aggr -s -i 5) a large FTP of > several 4GB ISO's. Since L3/4 src/dst load balancing is in use on both > machines, each time FTP starts a new file it picks a new port, and that > generally means that LACP picks a new interface, but since FTP is only > sending 1 file at a time, LACP is only keeping 1 interface going at a time. > > Wouldn't it help if each new packet were sent down a new interface in a > round robin pattern? > > What am I missing?
Hi Kyle, The IEEE 802.3ad link aggregation spec requires preserving the "temporal order" of packets. Using a round robin policy would violate that. No doubt this is to avoid performance bottlenecks. SunTrunking has a round robin policy (which predates the IEEE spec). It worked okay for 100Mb/sec aggregations and was used quite a bit then. In the the gigabit world the results are quite different. When the data rate nears 1Gb/sec, the overhead of "re-ordering" incoming data becomes a serious bottleneck - throughput never increases (frequently goes down). More CPU utilization with less throughput - not a winning combination. So, round robin was rightly avoided with "Native Link Aggregation" (dladm). Cheers, - Neil _______________________________________________ networking-discuss mailing list [email protected]
