Load Balancing Outgoing, its possible ?

[Rob Viau]

> On Fri, 2005-10-28 at 17:19 +0200, G Bryant wrote:
>> Daniel Dias Gonçalves wrote:
>>
>> >
>> > It is possible to make this balancing with the PF ? Exists some
>> > software that I make this ? Zebra can help me?
>> > This type of balancing gives to problems with the navigation of the
>> > user of NAT or IP valid ?
>> > If it is possible, wanted to see examples with rules.
>> >
>
> It would be much better to do per flow load balancing then per packet.
> With per packet your TCP flows will arrive out of order which is a bad
> situation since it will lead to a large number of retransmissions and
> zero-window acknowledgments.
>
> The only tunable to help correct that is to allow selective
> acknowledgments.
>
> You are going to get much higher utilization on your load balanced lines
> by using per flow with multiple TCP connections.
>
> Anybody know how to implement per flow load balancing in FreeBSD?  Are
> multiple default routes supported?
>
> It would be beautiful if you could put multiple routes with the same
> metric into the kernel and then the kernel would enable per flow load
> balancing of the routes...
>
> -Corey Smith
> _______________________________________________
> freebsd-pf at freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-pf
> To unsubscribe, send any mail to "freebsd-pf-unsubscribe at freebsd.org"
>

I believe pf is per-flow.  If it was not, then not only would your packets
arrive out-of-order, but also with different source IPs when you were
NATing to different interfaces on different ISPs (without your own block)
which is something I was able to do with 3 links (with three different IP
addresses) from 2 different providers.