[Serdev] contribution: SER module implementing Path extension(RFC 3327)

[Jan Janak]

On 09-06-2005 11:11, Klaus Darilion wrote:
> Juha Heinanen wrote:
> >Klaus Darilion writes:
> >
> > > Nevertheless, the IMS infrastructure deals with distribution and high 
> > > availability. Thus, using IMS concepts for "normal" SIP setups might be 
> > > interesting.
> >
> >the only thing that currently prevents ser to achieve high availability
> >+ redundancy is nat and the fact that we let customers freely choose
> >their terminals, whose quality varies.  can ims terminals sit behind
> >nats?
> 
> If the outboundproxy makes NAT traversal - why not? The Path header 
> ensures that the call will be routed via the OBP which has the NAT binding.
> 
> Of course you still need a solid NAT.

  This would help you to scale the system but it does not make it highly
  available. There isn't much a server can to to ensure that the user
  agent behind NAT stays reachable when either the user agent or the NAT
  are broken. And this is where most troubles come from in real world
  setups.

  IMS is supposed to work in walled gardens without NATs so there are no
  hard HA-issues -- any server can communicate with any user agent.
  That is the way how IMS solves HA issues, in my opinion.

     Jan.