Remove the text which suggests that many balance_rr links feeding into a single uplink will not experience packet reordering.
More up-to-date tests, with 1G links feeding into a switch with a 10G uplink, using a 2.6.23-rc8 kernel on the system on which the 1G links were bonded with balance_rr (mode=0) shows that even a many to one link configuration will experience packet reordering and the attendant TCP issues involving spurrious retransmissions and the congestion window. This happens even with a single, simple bulk transfer such as a netperf TCP_STREAM test. A more complete description of the tests and results, including tcptrace analysis of packet traces showing the degree of reordering and such can be found at: http://marc.info/?l=linux-netdev&m=119101513406349&w=2 Also, note that some switches use the term "trunking" in a context other than link aggregation. Signed-off-by: Rick Jones <[EMAIL PROTECTED]> --- diff -r 35e54d4beaad Documentation/networking/bonding.txt --- a/Documentation/networking/bonding.txt Wed Oct 24 05:06:40 2007 +0000 +++ b/Documentation/networking/bonding.txt Mon Oct 29 03:47:19 2007 -0700 @@ -1696,23 +1696,6 @@ balance-rr: This mode is the only mode t interface's worth of throughput, even after adjusting tcp_reordering. - Note that this out of order delivery occurs when both the - sending and receiving systems are utilizing a multiple - interface bond. Consider a configuration in which a - balance-rr bond feeds into a single higher capacity network - channel (e.g., multiple 100Mb/sec ethernets feeding a single - gigabit ethernet via an etherchannel capable switch). In this - configuration, traffic sent from the multiple 100Mb devices to - a destination connected to the gigabit device will not see - packets out of order. However, traffic sent from the gigabit - device to the multiple 100Mb devices may or may not see - traffic out of order, depending upon the balance policy of the - switch. Many switches do not support any modes that stripe - traffic (instead choosing a port based upon IP or MAC level - addresses); for those devices, traffic flowing from the - gigabit device to the many 100Mb devices will only utilize one - interface. - If you are utilizing protocols other than TCP/IP, UDP for example, and your application can tolerate out of order delivery, then this mode can allow for single stream datagram @@ -1720,7 +1703,9 @@ balance-rr: This mode is the only mode t to the bond. This mode requires the switch to have the appropriate ports - configured for "etherchannel" or "trunking." + configured for "etherchannel" or "aggregation." N.B. some + switches might use the term "trunking" for something other + than link aggregation. active-backup: There is not much advantage in this network topology to the active-backup mode, as the inactive backup devices are all - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
