RE: [Sip] PING/PONG

["Christian Stredicke" <[e-mail]>]

True. For that purpose, use e.g. INFO messages with no body. These
messages keep the dialog "alive". 
 
However, the goal of the PING/PONG keep-alive messages is to keep the
NAT-binding alive. So that you are able to receive the first INVITE!
 
CS


________________________________

	From: [e-mail] [mailto:[e-mail]] On
Behalf Of Steve Langstaff
	Sent: Wednesday, November 10, 2004 5:16 AM
	To: Christian Stredicke; Chris Boulton; Christer Holmberg
(JO/LMF); [e-mail]
	Cc: [e-mail]
	Subject: RE: [Sip] PING/PONG
	
	
	(CS) OPTIONS has the problem that it is relatively expensive
(size and CPU) and might result in responses that exceed the UDP
fragmentation limit (there are many DSL routers that treat UDP
fragmentation as security problem including the one that I have at
home). Therefore I think it would not hurt to have a specific message
that is designed only for the keep-alive job.
	 
	...but if you want your keep alive message to be routed over the
same path and transports as your original INVITE (and hence keep them
alive), don't you need most of the "expensive" content of (say) the
OPTIONS message - e.g. the vias.

	-- 
	Steve Langstaff. 

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