Voice Is Easy! Voice is generally the default Agree on a codec Enable the media stream Take care of jitter-buffer management Get rid of echo Youre done! Call set-up timing not critical.
Timing is everything. But in Fax…
FoIP…Added Complexity Computer-to-computer protocol (T.30) w/ timing requirements Synchronous modems (not just a different codec) with timing requirements For T.38, codec/media must be renegotiated and switched to SIP Timing is everything!
Is T.38 the Culprit?
10 T.38 Interoperability Lab
The Challenge: Fax calls begin as voice. Negotiation takes time: G.711 pass-through fax? T.38? Can we switch to T.38 in time?
In a Recent Broadcast Test 200 out of 2000 calls had late-arriving T.38 re-Invites.
Session Border Controller
Just Kiddin SBC
The Slow-SIP Problem
Known Issues T.38 can be clearer about some parms V.34-SIP integration is complex Slow SIP leads to T.38 re-Invite failures
Participants to date Deutsche Telekom iBasis SFT OTEGLOBE TATA Telkom SA WIS Telekom Italia Sparkle Telecom Poland Telefonica Reach FSB Telenor
Testing Objectives 1.G.711 or T.38? 2.Percentage successful image transfer 3.Time of the T.38 re-Invite 4.Relationship between the re-Invite delay and call success. 5.Image errors and their reasons. 6.Connect times and image-transfer times/speeds. 7.ECM? 8.FEC or Redundancy & depth 9.Call route and success rate correlation
Test Plan Ready International Routing T.38 Problems Connection Installation