TCP/IP redundant connections

[Ivan Voras]

Artem Kazakov wrote:

> So I want to utilize IP-sharing and TCP-connection synchronization
> (which is not yet implemented by anyone as far as I know).  I want it
> in case of failure seamlessly to switch to the other machine. As far
> as the internal state is synchronized, if it is possible to
> synchronize open connections as well(and all the low level stuff as
> packet sequence numbers and so on) it would allow to make switch-over
> to the back-up server in a matter of seconds, and the clients would
> stay connected.

I don't know if you already considered this, but the above looks like 
both machines would simultaneously process a single TCP connection. So, 
when a TCP connection request (handshake) arrives, you want both of the 
machines to respond?

Further on: You'll confuse the remote application and waste bandwidth if 
you send two responses to every TCP packet you receive.

And on: What about the applications running on the two machines: if the 
remote client send e.g. a request to delete a resource (just an 
example): would both servers receive and respond to the request?

etc, etc.

Have you read the manual for carp(4) and why isn't CARP good enough for 
what you need?

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