T.38 is an ITU standard for sending FAX across IP networks in a real-time mode.
FAX messages are sent as UDP or TCP/IP packets.
From RFC 3362:
ITU-T Recommendation T.38 T.38 describes the technical features necessary to transfer facsimile documents in real-time between two standard Group 3 facsimile terminals over the Internet or other networks using IP protocols. The Recommendation allows the use of either TCP or UDP depending on the service environment.
ITU-T Recommendation T.38 T.38 Annex D describes system level requirements and procedures for internet aware facsimile implementations and internet aware facsimile gateways conforming to ITU-T T.38 to establish calls with other ITU-T T.38 implementations using the procedures defined in IETF RFC 2543 SIP-99 and IETF RFC 2327 SDP.
Note that ITU-T T.38 Recommendation T.38 (04/02) T.38 is an aggregation of the original ITU-T Recommendation T.38 (06/98)T.38-98 and all of the subsequent Amendments and Corrigendum including T.38D-00. While T.38 and T.38D-00 describe SIP procedures per SIP-99, the procedures can also be applied to the revised Session Initiation Protocol specification SIP.
Remarkably, many T.38 implementations, including those of top tier carriers such as Level3, XO, Verizon etc have explicitly disabled ECM error correction. This problem is discussed in detail here. Don't make this mistake! Be sure to enable ECM and insist your provider or PBX vendor do the same!
Want to check to make sure you have ECM enabled? This handy ECM self-test tool can tell you in minutes.
Fax Voip application operates with T.38 faxes via standart COM port interface.
What is Voip? For your fax or voice application, it's a Voice Fax Modem. ...
FAX messages are sent as UDP or TCP/IP packets.
From RFC 3362:
ITU-T Recommendation T.38 T.38 describes the technical features necessary to transfer facsimile documents in real-time between two standard Group 3 facsimile terminals over the Internet or other networks using IP protocols. The Recommendation allows the use of either TCP or UDP depending on the service environment.
ITU-T Recommendation T.38 T.38 Annex D describes system level requirements and procedures for internet aware facsimile implementations and internet aware facsimile gateways conforming to ITU-T T.38 to establish calls with other ITU-T T.38 implementations using the procedures defined in IETF RFC 2543 SIP-99 and IETF RFC 2327 SDP.
Note that ITU-T T.38 Recommendation T.38 (04/02) T.38 is an aggregation of the original ITU-T Recommendation T.38 (06/98)T.38-98 and all of the subsequent Amendments and Corrigendum including T.38D-00. While T.38 and T.38D-00 describe SIP procedures per SIP-99, the procedures can also be applied to the revised Session Initiation Protocol specification SIP.
- Commetrex has completed significant interoperability testing in the T.38 Interoperability Test Lab. http://www.commetrex.com
- Dialogic White Paper: How does FoIP Work?
- Dialogic White Paper: Considerations for using T.38 versus G.711 for Fax Over IP
The Importance of T.30 ECM Error Correction Mode (ECM) in T.38 Deployments
One of the most important features of the traditional facsimile standard (T.30) is ECM error correction. The inventors of fax recognized that the audio quality of PSTN phone lines could not be trusted to be 100% error free - it was not uncommon to hear static, or the occasional pop or crackle on some fax calls. ECM error correction allows the sending and receiving terminals to compare notes at the end of each page, and selectively retransmit any data that was not received the first time around. This retransmission process is continued until the received page is certified error free, and the transmission of the next page begins.Remarkably, many T.38 implementations, including those of top tier carriers such as Level3, XO, Verizon etc have explicitly disabled ECM error correction. This problem is discussed in detail here. Don't make this mistake! Be sure to enable ECM and insist your provider or PBX vendor do the same!
Want to check to make sure you have ECM enabled? This handy ECM self-test tool can tell you in minutes.
T.38 with Fax Voip T38 Fax & Voice
FaxVoip Software develops solutions for the transmission of a fax via the Internet Telephony (FOIP). The main emphasis has been placed on the transfer T.38 and audio via SIP, H.323 and ISDN CAPI 2.0.Fax Voip application operates with T.38 faxes via standart COM port interface.
What is Voip? For your fax or voice application, it's a Voice Fax Modem. ...
