Re: SIP support in NAT

[Jakob Schlyter <jakob () crt se>]

On Tue, 11 Dec 2001, K K Palei wrote:

>  All, Here is a doubt regarding SIP support in NAT. As per NAT, an
> external host (having a global ip address) can not access the local host
> behind NAT. If the local host has started a session, then packets from
> external host for this particular session should be allowed. If this is
> the case then calling from external host to local users behind NAT will
> never possible.  In case of SIP/MGCP/H.323 only local users can make
> call and never will be able to receive calls. How should this problem
> can be overcome, please suggest.

there are several sip application level gateway on the market (e.g.
intertex, ingate, aravox). I also know of other firewall vendors planning
support for sip in the near future.

in addition to these, there are several proposals within the ietf sip gw
to make sip more friendly to nat.

        jakob

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