Definition of Events for Modem, Fax, and Text Telephony Signals
RFC 4734
Document | Type |
RFC - Proposed Standard
(December 2006; No errata)
Obsoletes RFC 2833
Updates RFC 4733
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Last updated | 2013-03-02 | ||
Stream | IETF | ||
Formats | plain text pdf htmlized bibtex | ||
Reviews | |||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 4734 (Proposed Standard) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Cullen Jennings | ||
Send notices to | csp@csperkins.org, magnus.westerlund@ericsson.com |
Network Working Group H. Schulzrinne Request for Comments: 4734 Columbia U. Obsoletes: 2833 T. Taylor Updates: 4733 Nortel Category: Standards Track December 2006 Definition of Events for Modem, Fax, and Text Telephony Signals Status of This Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The IETF Trust (2006). Abstract This memo updates RFC 4733 to add event codes for modem, fax, and text telephony signals when carried in the telephony event RTP payload. It supersedes the assignment of event codes for this purpose in RFC 2833, and therefore obsoletes that part of RFC 2833. Schulzrinne & Taylor Standards Track [Page 1] RFC 4734 Modem, Fax, and Text Telephony Events December 2006 Table of Contents 1. Introduction ....................................................3 1.1. Terminology ................................................3 1.2. Overview ...................................................3 2. Definitions of Events for Control of Data, Fax, and Text Telephony Sessions ..............................................5 2.1. V.8 bis Events .............................................5 2.1.1. Handling of Congestion ..............................9 2.2. V.21 Events ...............................................10 2.2.1. Handling of Congestion .............................11 2.3. V.8 Events ................................................12 2.3.1. Handling of Congestion .............................15 2.4. V.25 Events ...............................................15 2.4.1. Handling of Congestion .............................17 2.5. V.32/V.32bis Events .......................................18 2.5.1. Handling of Congestion .............................19 2.6. T.30 Events ...............................................19 2.6.1. Handling of Congestion .............................23 2.7. Events for Text Telephony .................................23 2.7.1. Signal Format Indicators for Text Telephony ........23 2.7.2. Use of Events with V.18 Modems .....................27 2.8. A Generic Indicator .......................................28 3. Strategies for Handling Fax and Modem Signals ..................29 4. Example of V.8 Negotiation .....................................30 4.1. Simultaneous Transmission of Events and Retransmitted Events Using RFC 2198 Redundancy ............35 4.2. Simultaneous Transmission of Events and Voice-Band Data Using RFC 2198 Redundancy ............................37 5. Security Considerations ........................................39 6. IANA Considerations ............................................40 7. Acknowledgements ...............................................42 8. References .....................................................43 8.1. Normative References ......................................43 8.2. Informative References ....................................44 Schulzrinne & Taylor Standards Track [Page 2] RFC 4734 Modem, Fax, and Text Telephony Events December 2006 1. Introduction 1.1. Terminology In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in RFC 2119 [1]. In addition to those defined for specific events, this document uses the following abbreviations: Fax facsimile HDLC High-level Data Link Control PSTN Public Switched (circuit) Telephone Network 1.2. Overview This document extends the set of telephony events defined within the framework of RFC 4733 [5] to include the control events and tones that can appear on a subscriber line serving a fax machine, a modem, or a text telephony device. The events are organized into several groups, corresponding to the ITU-T Recommendation in which they are defined. Their purpose is to support negotiation, start-up and takedown of fax, modem, or text telephony sessions and transitions between operating modes. The actual fax, modem, and text payload is typically carried by other payload types (e.g., V.150.1 [32] modem relay, voice-band data as formalized in ITU-T Rec. V.152 [33],Show full document text