[H-GEN] Load balancing

David Jericho davidj at pisoftware.com
Tue Jul 8 19:55:05 EDT 2003


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On Tue, Jul 08, 2003 at 01:11:01PM -0400, Robert Brockway wrote:
> Incoming return packets need not travel anything like the path the
> original outgoing packets took.

Unfortunately this is not quite correct. While is is true that at a
conceptual level, packets need not return the same path they came, _BUT_
they should unless you've come to special arrangements with your
bandwidth providers.

All good ISPs should have filters in place to prevent packets from 
addresses they not are owners of leaving their network.

This includes everything from the private address blocks (RFC 1918), to
the special use address blocks (RFC 3330) to everything they don't route
for.

Back to the original question... 

It's probably best to have a good talk with one of the more senior
networking guys from your bandwidth providers before you attempt round
robin balancing on your outbound links.

In anycase, usually you won't actually gain performance this way as one
path will often be slower than the other.

If you're really interested in making sure clients connect to the
cloest IP address, there are other solutions. One that comes to mind
right away is Source AS based name resolution.

The basic gist of it is that when you do an address lookup on my
hostname, I have a look at which network you're coming from. Using my
(normally) precomputed table of information, I find that you're closer
to link X, instead of link Y. Therefore I hand out link X's address.

-- 
David Jericho
Systems Administrator, Plugged In Software

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