Definition of Events for Channel-Oriented Telephony Signalling
RFC 5244
Document | Type |
RFC - Proposed Standard
(June 2008; No errata)
Updates RFC 4733
|
|
---|---|---|---|
Authors | Henning Schulzrinne , Tom Taylor | ||
Last updated | 2015-10-14 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Reviews | |||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 5244 (Proposed Standard) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Cullen Jennings | ||
Send notices to | (None) |
Network Working Group H. Schulzrinne Request for Comments: 5244 Columbia U. Updates: 4733 T. Taylor Category: Standards Track Nortel June 2008 Definition of Events for Channel-Oriented Telephony Signalling 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. Abstract This memo updates RFC 4733 to add event codes for telephony signals used for channel-associated signalling when carried in the telephony event RTP payload. It supersedes and adds to the original assignment of event codes for this purpose in Section 3.14 of RFC 2833. As documented in Appendix A of RFC 4733, some of the RFC 2833 events have been deprecated because their specification was ambiguous, erroneous, or redundant. In fact, the degree of change from Section 3.14 of RFC 2833 is such that implementations of the present document will be fully backward compatible with RFC 2833 implementations only in the case of full ABCD-bit signalling. This document expands and improves the coverage of signalling systems compared to RFC 2833. Schulzrinne & Taylor Standards Track [Page 1] RFC 5244 Channel-Oriented Signalling Events June 2008 Table of Contents 1. Introduction ....................................................2 1.1. Overview ...................................................2 1.2. Terminology ................................................3 2. Event Definitions ...............................................4 2.1. Signalling System No. 5 ....................................6 2.1.1. Signalling System No. 5 Line Signals ................6 2.1.2. Signalling System No. 5 Register Signals ............7 2.2. Signalling System R1 and North American MF .................8 2.2.1. Signalling System R1 Line Signals ...................8 2.2.2. Signalling System R1 Register Signals ...............8 2.3. Signalling System R2 ......................................10 2.3.1. Signalling System R2 Line Signals ..................10 2.3.2. Signalling System R2 Register Signals ..............10 2.4. ABCD Transitional Signalling for Digital Trunks ...........12 2.5. Continuity Tones ..........................................14 2.6. Trunk Unavailable Event ...................................14 2.7. Metering Pulse Event ......................................15 3. Congestion Considerations ......................................15 4. Security Considerations ........................................16 5. IANA Considerations ............................................17 6. Acknowledgements ...............................................20 7. References .....................................................20 7.1. Normative References ......................................20 7.2. Informative References ....................................21 1. Introduction 1.1. Overview This document extends the set of telephony events defined within the framework of RFC 4733 [4] to include signalling events that can appear on a circuit in the telephone network. Most of these events correspond to signals within one of several channel-associated signalling systems still in use in the PSTN. Trunks (or circuits) in the PSTN are the media paths between telephone switches. A succession of protocols have been developed using tones and electrical conditions on individual trunks to set up telephone calls using them. The events defined in this document support an application where such PSTN signalling is carried between two gateways without being signalled in the IP network: the "RTP trunk" application. In the "RTP trunk" application, RTP is used to replace a normal circuit-switched trunk between two nodes. This is particularly of interest in a telephone network that is still mostly circuit-switched. In this case, each end of the RTP trunk encodes Schulzrinne & Taylor Standards Track [Page 2] RFC 5244 Channel-Oriented Signalling Events June 2008 audio channels into the appropriate encoding, such as G.723.1 [13] or G.729 [14]. However, this encoding process destroys in-band signalling information that is carried using the least-significant bit ("robbed bit signalling") and may also interfere with in-bandShow full document text