T.38

from Wikipedia, the free encyclopedia

T.38 Procedures for real-time Group 3 facsimile communication over IP networks or Fax over IP (FoIP) is a recommendation of the ITU-T for the transmission of fax documents over the Internet .

overview

The T.30 protocol ( analog fax ) in connection with the digital transport route of the T.38 protocol (combined via gateways)

Due to the compression method and the fluctuations in runtime in IP telephony , it is not possible to transmit faxes without interference in accordance with the ITU transmission standards G2 and G3 . With T.38, the information is not transmitted with tones as in normal telephone network, but with the on UDP or TCP and IP -engaging network protocol Internet Protocol Facsimilé (IFP).

Unlike T.37 , in which the faxes are sent as e-mail using SMTP , T.38 is a real-time system that transmits the faxes without delay. In order to be able to transmit a fax sent with T.38 to a standard fax machine, gateways between the two incompatible transmission types are required. Many providers of IP telephony now operate such gateways. To operate a normal fax machine on a T.38-capable VoIP connection, the ATA used (or the router with integrated telephone function or the IAD ) must also contain a T.38 gateway.

Alternatives

Some providers of NGN connections do not implement T.38 because, in addition to the VoIP connections, they can also adequately control the quality of service (see Quality of Service # QoS in IP networks ) with regard to latency and packet loss in their own network. This is v. a. with regard to the migration from ISDN to IP connections (e.g. M-net and Telekom, see list of receipts below).

Since the official information on the supported protocols is often insufficient, there is speculation in provider forums about the protocol implementation. The activation of T.38 is sometimes recommended (and apparently practiced successfully), although the protocol is still not used by the modem. M-Net points out that it may a. Due to the "different versioning and insufficiently implemented fallback functions in transmissions with T.38 permanent transmission difficulties" could arise, d. H. the users have no control over the transmission mode actually used. Some providers refer to firmware updates for certain modem models. Telekom points out that the T.38 protocol is transparently passed through in its own network. However, in order to be able to offer T.38 for connections to other networks without T.38 support ( interconnection ) or for connections from or to pure voice connections, i.e. analog, ISDN or MSAN-POTS (new IP-based voice connections), gateways would be required that convert between T.38 and other protocols or analog signals. This conversion is not supported and forces the communication partner to fall back on G.711. Such information is missing from other providers, but the problem is often very similar.

Often attempts are made to operate fax machines on a VoIP connection that is not officially supported. This can work, but is by no means guaranteed. The chances of success are best with uncompressed audio codecs (such as G.711 ) and a stable Internet connection with consistently low latency and low packet loss. In these cases, usually no more than five pages can be transferred. In these cases, the providers of IP telephony explicitly point out the experimental character and usually officially exclude fax transmission from their service description. Some providers offer T.38 as an option (possibly at an additional cost).

Support from telecommunications providers in Germany

providers Support T.38 Explanations and (own) receipts
1 & 1 Yes
bluePBX Yes
blueSIP Yes only in the paid premium tariff
Colt Technology Services Yes
Congstar unknown
German Telephone (DTST) Yes Only the SIP PBX CentrexX product is supported, and server-supported "E-Fax services" are also offered
dus.net Yes
DW telephone services (VoIP2GSM) Yes only sending, receiving via Fax2Mail
Ecotel Communication (easyBell) Yes
Equada (PBX network or personal Voip) Yes
envia Tel No
EWE Tel Yes
HFO Telecom (HFO NGN) Yes Alternatively, G.711 is also supported with sufficient quality of service.
HTP No Only G.711 is supported.
inopla Yes T.38 and / or G.711 - the optimal transmission method is negotiated between the two remote stations before transmission.
Cable & Media Service (cablefon) No
M-net No only G.711 (official)
NetCologne Yes
NeXXt mobile (simply VOIP) No
O2 Yes
Placetel Yes
Plusnet Yes Only with IPfonie "extended" and "basic"
sipbase Yes
Sipgate No
TeamFON Yes
Tele2 No Information on customer care by email from January 27, 2015
Telekom Germany Yes Only transparent transmission, no transcoding in the network. MSAN-POTS and PSTN gateways do not use T.38.
Unitymedia (Baden-Württemberg) No The statement declared as correct by the support in the forum is that Unitymedia does not support T.38.
Versatel Yes Generally and explicitly for system connections with fallback option according to G.711 (depending on the support of the PBX used)
vio: networks Yes
Vodafone Yes (depending on the device) No information is officially available. While G.711 has been pointed out for years in the online help desk that the introduction of T.38 is being “worked on under high pressure”, the most recently published information is inconsistent. T.38 is not available, but the recommendation of support is: "Activate protocol T.38". The recommendation applies to certain Fritzbox models.
Vodafone Kabel Germany No Official information does not exist, but in the forum of Vodafone and Kabel Deutschland the support is denied and it is pointed out that faxing without T.38 requires certain firmware versions depending on the model.
Vortel Yes

Web links

Individual evidence

  1. ↑ a b Technical information SIP trunk (section 5.11.1 Codec for fax transmission) from October 13, 2016; see. speculative conflicting experiences in the same forum
  2. ↑ a b Tips & Tricks for sending faxes on the IP-based connection of Telekom. (PDF) Business customer support from Telekom, April 16, 2018
  3. ↑ T.38 at Voip-Information.de (date unknown, there is a reference in the text to an announcement for the beginning of 2007)
  4. ↑ 1 & 1 Help Center - Codecs and protocols for 1 & 1 telephony .
  5. ↑ Description of services .
  6. ↑ blueSIP features .
  7. ↑ SIP trunking data sheet. (PDF) Colt Technology Services GmbH, accessed on January 15, 2020 (English).
  8. ↑ Description for CentrexX on the provider's homepage
  9. ↑ dus.net
  10. ↑ IP telephony - make cheap calls with us. (PDF) Description of the manufacturer's services
  11. ↑ Which audio codecs are supported for Internet telephony? . Easybell. February 11, 2016. Retrieved December 11, 2017.
  12. ↑ VOIP trunk - the business IP system connection - equada .
  13. ↑ PERSONAL VOIP - Support .
  14. ↑ Technical guideline IP system connection - envia TEL
  15. ↑ What other technical settings do I have to make in my router? (In: FAQ at ewe.de)
  16. ^ HFO Telecom AG . Archived from the original on October 26, 2016. Retrieved October 26, 2016.
  17. ↑ HTP SIP trunk technical data. (PDF) HTP, accessed June 25, 2019 .
  18. ↑ Urs Mansmann: Cloud mediation. Virtual telephone systems as an ISDN replacement . In: c't 2016 . tape 8 . heise, S. 128–131 , here p. 130 : "Fax2Mail, Mail2Fax, T.38"
  19. ↑ Send and receive faxes without a fax machine. In: inopla.de. inopla GmbH, accessed on March 6, 2020 .
  20. ↑ provider: cablefon: start. (No longer available online.) In: IP-Phone-Forum Wiki. Archived from the original on November 26, 2016 ; accessed on December 11, 2017 .
  21. ↑ Surf & Fon service description (PDF) from August 2016
  22. ↑ netcologne.de .
  23. ↑ provider: Einfachvoip: start . Archived from the original on August 11, 2016. Retrieved November 4, 2014.
  24. ↑ Welcome - o2 Community . Archived from the original on November 5, 2014. Retrieved November 4, 2014.
  25. ↑ All products at a glance - Placetel. Retrieved April 14, 2019 .
  26. ↑ Description of services Plusnet product IPfonie. Retrieved April 5, 2020 .
  27. ↑ Voip telephone system ǀ Voip provider ǀ Telephone system and details . sipbase. Retrieved December 11, 2017.
  28. ↑ Support of the fax protocol T.38 . sipgate. Retrieved December 11, 2017.
  29. ↑ Thomas Kupec: functions .
  30. ↑ This is how your fax is ready for the future. Deutsche Telekom, accessed on April 20, 2018 : "The transparent transmission of the T.38 fax protocol has also been implemented in the telecommunications network."
  31. ↑ hajodele on the question: "Does fax run via pulse or tone dialing ?!" 2016, accessed on October 17, 2017 : "Another problem could be that UM does not support the T.38 protocol."
  32. ↑ Howto: Germany - Versatel - SIP Provider . Archived from the original on December 7, 2014. Retrieved November 4, 2014.
  33. ↑ Description of services VT voice ( Memento from November 5, 2014 in the Internet Archive ) [flexible] ngn SIP variant
  34. ↑ Reliable faxing with VoIP and T.38. In: vionetworks.de. Retrieved June 14, 2019 .
  35. ↑ SuperUser "Helpnick" on June 30, 2010 - forum for fixed network / LTE users
  36. ↑ Fritzbox 7490 - activate fax switch + T.38 (see bold note from the moderators at the top right) - forum for landline / LTE users, accessed on November 1, 2016
  37. ↑ VF_Enrico (moderator) on November 6, 2013 - Forum for users of cable connections
  38. ↑ FAQ . Inter.net Germany GmbH. Retrieved December 11, 2017.