Re: [load balancing] client response time

From: Iztok Umek <iztok [izzat] si-con.com>
Date: Thu Mar 29 2007 - 08:23:08 EDT

I would assume you would only use this for load balancing ISPs, right?
Because that is the only time where this matters.

There are ISP load balancers on the market that offer that. Look for
"network proximity". It includes combination of response time, number of
hops, load on the link ... I am pretty sure that Radware even has a
patent on this thing.

Other option where "network proximity" would be in use is when you have
multiple data centers across the globe and you want best one (closest
network wise) to serve your client as well.

Bare in mind that all this is not really response time to client but
client's DNS server as at the time this is the only information of
incoming request that load balancer has to decide where to load balance to.

It gets interesting when you have multi-site (global solution) load
balancing in active-active mode and you either don't have a way to
redirect to another site (i.e. not HTTP, RTSP) and client for a reason
chances DNS server in the middle of the session. Not many load balancers
can handle that properly and will fail if client ends up at the wrong
site (due to changed DNS it uses). Resolution is "global triangulation"
where load balancer of the wrong data center sends the request to
correct one and right one then responds directly. This gives you the
ability to actually preserve original source IP of the client and
preserves your session that would be broken. This is also important if
you want to keep the uniform URL for all sites and don't want to do HTTP
redirects.

Ravi Kumar wrote:
> Hi,
> Did any one know about a load balancer that has client
> response time as metric?
> I know that server response time used as metric. But,
> client response time is hard to assume.
> If client response time is also treated as metric, how
> exactly it works?

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Received on Thu Mar 29 08:23:38 2007

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