Re: CSS functionality question

mjsully · ‎10-13-2006

Let's say I have a pair of CSS 11050 switches, one of them being redundant. I have them load balancing a pair of web servers. If one of the web servers goes down, what happens to the open and active connections that were established to this server? Does the CSS have any fail over functionality in which the connections can be moved to the other web server transparent to the user, or is there simply no way to make this happen? Thanks

Gilles Dufour · ‎10-13-2006

there is no way to move the connections to the remaining servers.

The reason we did not implement the feature is that a TCP connection can only be moved to another server if the servers are stateful.

This means, each server needs to be ready to accept connections from the other server and continue them where it stoped - so sequence number and ack number must be shared between servers.

Since very few servers have this functionality, we did not think it would be useful to implement the feature.

However, new loadbalancers like the CSM and ACE have this feature.

Gilles.

mjsully · ‎10-13-2006

Thank you.

d.hickie · ‎10-20-2006

How are the existing TCP connections to the failed server teminated? does the CSS time it out? and do users then have to re-establish the connection in order to continue?

Gilles Dufour · ‎10-20-2006

the CSS does nothing.

The application should have a mechanism to detect dead servers or dead client or broken network and recover.

Gilles.