Re: [Sip] PING/PONG

----- Original Message ----- 
From: "Christer Holmberg (JO/LMF)" <christer.holmberg@ericsson.com>

>
> Hi,
>
> >With UDP, the PING will create a new NAT binding and the
> >server can update its mapping for the UA.
>
> So will CRLF, won't it? The difference is that the UA will not be informed
> that the message has reached the destination (since there is no response),
> but the question is if we really would need that information for every
> keep-nat-binding message that we send (ie we use CRLF most of the time,
> and every now and then we use a SIP request to make sure that everything
> really works).

The CRLF does not contain enough information for the server to update its
mapping for the UA. There could be many UAs behind the same NAT, so the
server has no way to know which one it is.

The CRLF will keep an existing binding open in the NAT, but it does not
cover the case of a NAT reset. So the it depends on how long you are willing
to live without a valid binding in the server for the UA, and that would be
how often you would need to send a PING. You would only send CRLF too if
that was longer than the binding lifetime in the NAT.

>
> >With TCP, if you want to be able to detect that the NAT binding is gone
on
> >the order of a transaction timeout, you would need to send a
> >PING every 32 seconds or so. Given that NAT bindings for TCP live longer
> >than that, I don't see what the CRLF buys you.
>
> My point was that using PING you will not be able to detect problems
immediately, since you will have to wait for the transaction timeout before
you can determine that something is wrong.
>
> What I do NOT want to do is to send SIP requests too often, and therefor I
was wondering if it would be possible to also use CRLF :)
>
> Regards,
>
> Christer Holmberg
> Ericsson Finland
>
>
>
> >
> > cheers,
> > (-:bob
> >
> > Robert F. Penfield
> > Chief Software Architect
> > Acme Packet, Inc.
> > 130 New Boston Street
> > Woburn, MA 01801
> > bpenfield@acmepacket.com
> >
> >
> >
>
>

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