Subject: [Sip] outbound question

From: Paul Kyzivat <[email-masked]>
Date: Thu, 31 Jul 2008 15:11:37 -0400

I haven't been following outbound closely for awhile now. I hope I 
haven't just overlooked the answer to this question.

I recently received a question about implementing the ping/pong 
mechanism from outbound. So I went and looked to see exactly what the 
definition was. I come away having some questions:

Must a ping always be responded to with a pong? Or is the ping just 
there to solicit *some* response? Namely, if when the ping is received 
there is other output going on the connection, must a pong still be 
sent? (It will have to be when the is a message break of course.) It 
would seem that the presence of output is sufficient evidence that the 
connection is alive. (If the pong is required, then I guess we will have 
to hope that it doesn't take 10 seconds to send the current message that 
is going out. Normally that shouldn't be a problem.)

And, must the be a matching pong for every ping? If several pings are 
received before it is possible to send a pong, must a corresponding 
number of pongs be sent? Or only one? If I have received two pings 
before I can send pong, and I am required to send two pongs, then that 
will look like a ping. That would seem to be bad.

Or is it illegal to send multiple pings before receiving a pong?

	Thanks,
	Paul
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