Re: Network load balancing problem

From: Karthic [MSFT] (karthicn_at_online.microsoft.com)
Date: 05/24/04 

Date: Mon, 24 May 2004 12:16:14 -0700

Roger,
    When affinity is set to Single, NLB uses the client IP address only to
determine which server will accept the connection. So, it is expected that
connections from a given client IP address will always go to the same
server. When you set the affinity to None, NLB will also use the client
TCP/UDP port (in addition to the client IP address) to decide on which
server should take the connection. As multiple ongoing connections from a
given client IP address would NOT have the same TCP/UDP port, the chances of
them taken by different servers are maximized. But, as I said, you are only
increasing the chances....NLB does not follow a deterministic algorithm like
least used or round-robin. However, given a large client population, you
should see even load balance. Please be aware that if the application hosted
on the NLB cluster relies on client session affinity where it assumes all
TCP connections from a given client IP address belonging to an ongoing
"application session" will go to the same server, setting Affinity to None
will break that. Let me know if this explanation is not clear and I will try
to present it differently. Feel free to ask questions. 

-- 
Thanks,
Karthic
Software Design Engineer
Windows Server Group
Microsoft Corporation.
This posting is provided "AS IS" with no warranties, and confers no rights.
"Roger" <anonymous@discussions.microsoft.com> wrote in message
news:462C9FDA-76E2-41FB-99F9-EC497E94DA17@microsoft.com...
> Karthic
> I am experiencing pretty much the same symptoms as Naresh.  I have 3 W2K
servers with approx 110 people connecting to them using ICA clients on
Winterms.  I have the NLB set to Multicast Enabled.  I have even reset their
IP addresses to be released after 1 minute (where it was set for a 7 day
lease).  The affinity is set to Single.  I find that the IP address
reconnects to the last server it was connected to so it doens't go to the
'least used' server - which is what I would prefer.  Should I set the
affinity to None and what implications will that have?
> regards
> Roger

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