CSS11500- Service configuration.

Unanswered Question
Nov 17th, 2007

Hi,

We plan to use CSS11500 series load balancer. We are having two identical servers which we need to load balance for client request. We are having only one client which will use these two servers. If we use only one server, we are facing some delay at client. So plan to use load balancer. Our connectivity is like this, single client makes two TCP connections with this server continously. ( one on 9530 port and another 9531 port ). That it is a single session established with server from client. We checked it using netstat command and from the PIX firewall.so far so good. ( One client one server working ok but with delay ).

Now if we add loan balancer in between with VIP, cleint will make request to this VIP . Then these packets will undergo IP address translation ( source will be that of CSS ip address and destination will be indivisual server ip address ). Servers will replay to this packet, this packet will be received by CSS , it will put the VIP as source address and will replace the destinatin address as client address will sent the packet back to client. This is at layer 3 working fine. But as our client is making only one session with VIP ( earlier with only one server with two ports). After adding load balancer , it will send packets to two different servers in a round robin algorith. But will the second server work properly as packets received on this may have been processed by another server in the existing session. so what is the application prerequisite so support load balancer ( which send packets to each server in round robin algorithm ). How application will need to support the layer three load balancing. If application is just a static pages on webserver , I think it will work. As each packet contents will be checked by each indivisual server and the corresponding page will be sent to client. But for complex application like what we have , ( database , user authentication, accounting and lots more ). how will application or CSS.

In a nut-shell if only one client makes a continuous connection with server, can loand balancer ( layer three load balanceing ) be made to work ?

Thankx in advance.

Subodh

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paul.matthews Mon, 11/19/2007 - 00:37

This would better be placed in the datacentre/application networking forum, but basically can it work? it all depends upon how the application works. Some applications need the user to remain associated with a single server. That is configured using the various options for sticky.


If you only have one user, and need the user to remain associated with one server, the load balancer can only really provide a resilience option rather than a performance benefit - ie if the server fails, it will pass traffic to the other.


It does not load balance individual packets across the servers (unless you are using UDP) but it load balances connections.


P.

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