Re: High Speed Firewalls

[Bennett Todd <bet () rahul net>]

It's been a while since I read the specs on BigIP, but I definitely
remember failing to find anything about tracking the performance of
individual servers in the farm, to adaptively balance load to fit.
Perhaps this has been added since?

In some settings this won't matter, and in those settings a
LocalDirector is overpriced (and hits the wall sooner than some of
its competition).

If there's another load balancer that keeps track of the performance
of each server in its farm, and adapts the load to always
preferentially send traffic to the then-fastest server, I'd love to
learn about it.

While I do try and specify identically-configured servers in the
farm, I still really enjoy the LocalDirector's behavior. It gives me
the freedom to inflict some significant processing load on servers
within the farm, with the confidence that the LocalDirector will
back off the loaded servers if I manage to hit 'em hard enough so
they're no longer keeping up with their brethren. I end up taking
advantage of this for content replication, database rebuilds,
backups, etc.

So until I hear about another load balancer that adapts to varying
server capacity, I'll continue to prefer LocalDirector, without even
having tried the others --- just on specs alone.

I haven't yet had to try and actually implement a distributed
load-balancing solution, one for spreading traffic among multiple
server farms scattered about different backbones. I'd love to learn
if anything out there actually does a great job of this; it's a
wicked hard problem.

I really wish there were support built right into DNS, implemented
in most clients, for load-balancing; then we'd be sitting pretty.
Introduce a special load-balancing record type, where the returned
value from a query contains a list of IP addresses, and the client
is encouraged to send its first queries to all the addresses in the
list, and keep sending them to all addresses until it gets an answer
back, then prefer the first one that answered, or maybe round-robin
among the first N if several answered really quickly.

Without such support, the job of routing a given client to the best
server is impossible, and simply trying to route them to a good
choice is fiendishly difficult in the face of network congestion
and outages constantly changing the relative "nearness" of various
points to each other.

-Bennett

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