Routing server traffic thru two external ips.

[Network Administration]

   Date: Tue, 20 Feb 2001 14:03:07 +0100
   From: Martin Mares <mj at atrey.karlin.mff.cuni.cz>

   > It probably doesn't matter if the same provider is involved and in
   > fact, different providers are preferred as that allows some limited
   > multi-homing.  Load balancing should be employed in any case.  Simply
   > declaring 2 default routes in Cisco IOS accomplishes that and I
   > believe that something similar is available in the 2.4 networking.

   Accomplishes that, but unless the two paths have very similar timing
   (which happens usually only if their load is minimal [which implies
   balancing is useless anyway] or if they are parallel links), route
   level load balancing leads to terribly bad results due to TCP being
   unable to cope with such a high variance of RTT's. Hence, per-connection
   balancing using DNS or redirects leads to much better results.


I suppose that's why IOS maintains a "short term memory" and tends to
send all packets to a particular destination over the same interface
for a few minutes.  The Cisco docs mention this someplace.  I remember
being called upon to explain "why doesn't multi-homing work" when
testers would run the same traceroute repeatedly and found that only a
single path was shown.  A small period of no tracerouting, then trying
again usually showed the other route eventually.  I always wondered
why and hadn't thought of the problem you point out, thank you.

Simple ping statistics should show if the problem you describe is
present, as no upstream provider ever has minimal load these days.
Running an FTP mirror would also pick it up.  I wonder if your concern
is handled in the 2.4 networking however, as I don't recall seeing any
mention of that situation.


DNS RR solves an incoming balance problem nicely, but does nothing for
outgoing traffic.  Game server traffic is primarily outgoing, the
server tells the client about the game state while the client merely
returns the single players actions.

Server redirects seem to be an exclusive feature of high volume custom
servers, I've never heard of a general user program that attempted to
take advantage of a multiple network interface enviroment.  Perhaps I
don't understand what you mean...