Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Organization: SipXecs Forum In-Reply-To: <[email protected]> X-FUDforum: 08063afcdd00a6e76393c5b9527381e8 <64388> Message-ID: <[email protected]>
Tony, consider a scenario where most phones are connected to wireless modems, and servers are on a public IP. There are no gateways or trunk providers, just extensions are calling extensions. There are many possible applications, but think about application where care is provided to old people at their homes that do not have connection to the internet (most really don't), so the connection is via mobile data network. The case of inherent (by design to save energy)latency in opening a connection on a mobile data network is well described in the following AT&T labs paper http://www.research.att.com/articles/featured_stories/2011_03/201102_Energy_efficient?fbid=0lDQwAs5gdi (see the graphical depiction of the phases of data connection setup). The conclusion is that it takes typically 2.4 seconds, before packets start flowing, and including RT for DNS and RT for first invite and ack it's 2.6 sec. I believe that these numbers are "typical" sometimes less (and this is why sometimes calls get through), and sometimes more. If this is typical, i.e. a "mean" than probably doubling this number would be "safe" timeout, i.e. 5.2sec. Also, in any case, if and when the SIPX gives up after a timeout, it needs to send a disconnect message not leaving the called extension in limbo (currently on timeout the called phone doesn't stop ringing). _______________________________________________ sipx-users mailing list [email protected] List Archive: http://list.sipfoundry.org/archive/sipx-users/
