BEN> What redundancy do you expect to get? What will you
BEN> be able to do that we cannot do today? You mean
BEN> keeping two stacks in sync across two different machines, so
BEN> that you can hot-swap processes or something?
San> Yes, to be more precise, this will be a part of a big VoIP project
San> and thats the world i belong to
San> the idea of the project is to have a redundant VoIP entity (may be MG
/Switch /or MGControllers)
San> where there will be a Single floating IP, and the whole entity will be a
San> unit to the outside world. For UDP there is no problem implementing this ,
but with TCP
San> the stack has to be modified or what i think other ideas like
San> a net-filter or going for hacking packets at the interface rather than
San> allowing them to float to stack are also good.
Ben Greear <greearb@xxxxxxxxxxxxxxx> on 06/01/2001 09:25:20 PM
To: Sandeep Kalra/HSS@HSS
cc: netdev@xxxxxxxxxxx, Rajiv Roy/HSS@HSS
Subject: Re: regarding Redundancy in TCP / IP Stack
> hi all , list
> We am novice to the Linux TCP / IP stack arch,
> At present i want to implement redundancy
> at socket level in the Stack.. Can you please
> help me with some docs, information in this regards
What redundancy do you expect to get? What will you
be able to do that we cannot do today? You mean
keeping two stacks in sync across two different machines, so
that you can hot-swap processes or something?
I thought about this w/regard to building a VOIP box that
could handle failover w/out dropping calls, but I decided
that it was an intractable problem, and that there were probably
other ways to get the functionality better.
For example, on failover, grab packets right off the interface
instead of letting them go up the stack and implement your own
hacked up TCP/IP stack in user-space that is specifically designed
to do what you want. This is pretty damn ugly, of course, but
you might could keep the connections together. For VOIP in particular,
most of your traffic is UDP anyway, so your problem is much more easily
> we want to know
> 1. The Data structures that are kept by the system for maintaining the
> 2. Kernel related data structures that are part of the TCP / IP stack.
> 3. Any Documents, Links that can help us in getting with the procedure .as to
> how it can be implemeted efficiently.
> 4. Pros & cons in implementing such redundancy.
> 5. kernel related other information as to which modules are interdependent to
> this (If any).
> 6. If any work is going in this regards, then what is the present status. &
> more detail whom shall then we refer to.
> Sandeep , Rajiv
Ben Greear <greearb@xxxxxxxxxxxxxxx> <Ben_Greear@xxxxxxxxxx>
President of Candela Technologies Inc http://www.candelatech.com
ScryMUD: http://scry.wanfear.com http://scry.wanfear.com/~greear