Audio/Video Transport (avt) H. Schulzrinne Internet-Draft Columbia U. Expires: August 10, 2005 S. Petrack eDial T. Taylor Nortel February 6, 2005 Definition of Events For Channel-Oriented Telephony Signalling draft-ietf-avt-rfc2833biscas-00 Status of this Memo This document is an Internet-Draft and is subject to all provisions of Section 3 of RFC 3667. By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 10, 2005. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This memo updates RFC xxxx (currently draft-ietf-avt-rfc2833bis-07) to add event codes for telephony signals used for channel-associated signalling when carried in the telephony event RTP payload. Schulzrinne, et al. Expires August 10, 2005 [Page 1] Internet-Draft Channel-Oriented Signalling Events February 2005 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 Overview . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Event Definitions . . . . . . . . . . . . . . . . . . . . . . 5 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 . . . . . . . . . . . . . . . . . . . . . 13 2.6 Trunk Unavailable Event . . . . . . . . . . . . . . . . . 13 2.7 Metering Pulse Event . . . . . . . . . . . . . . . . . . . 14 3. Security Considerations . . . . . . . . . . . . . . . . . . . 15 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21 6.1 Normative References . . . . . . . . . . . . . . . . . . . 21 6.2 Informative References . . . . . . . . . . . . . . . . . . 21 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 22 Intellectual Property and Copyright Statements . . . . . . . . 23 Schulzrinne, et al. Expires August 10, 2005 [Page 2] Internet-Draft Channel-Oriented Signalling Events February 2005 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] and indicate requirement levels for compliant implementations. In addition to those defined for specific events, this document uses the following abbreviations: MF Multi-frequency PSTN Public Switched (circuit) Telephone Network RTP Real-time Transport Protocol [2] 1.2 Overview This document extends the set of telephony events defined within the framework of RFC xxxx [3] 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 interworked to signalling 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 audio channels into the appropriate encoding, such as G.723.1 [10] or G.729 [11]. However, this encoding process destroys in-band signalling information which is carried using the least-significant bit ("robbed bit signalling") and may also interfere with in-band signalling tones, such as the MF (multi-frequency) digit tones. In a typical application, the gateways may exchange roles from one call to the next: they must be capable of either sending or receiving each signal in the table. This document defines events related to four different signalling systems. Three of these are based on the exchange of multi-frequency Schulzrinne, et al. Expires August 10, 2005 [Page 3] Internet-Draft Channel-Oriented Signalling Events February 2005 tones. The fourth operates on digital trunks only, and makes use of low-order bits stolen from the encoded media. In addition, this document defines tone events for supporting tasks such as continuity testing of the media path. Implementors are warned that the descriptions of signalling systems given below are incomplete. They are provided to give context to the related event definitions, but omit many details important to implementation. Schulzrinne, et al. Expires August 10, 2005 [Page 4] Internet-Draft Channel-Oriented Signalling Events February 2005 2. Event Definitions Table 1 lists all of the events defined in this document. These events incorporate a considerable number of changes compared with the corresponding set of events in RFC 2833 [9], but it would appear that the changes have not affected any implementations. +-----------------------+------------+-------------+-------+--------+ | Event | Frequency | Event Code | Event | Volume | | | (Hz) | | Type | ? | +-----------------------+------------+-------------+-------+--------+ | MF 0...9 | (Table 2) | 128...137 | tone | yes | | | | | | | | MF Code 11 (SS No. 5) | 700+1700 | 138 | tone | yes | | or KP3P/ST3P (R1) | | | | | | | | | | | | MF Code 12 (SS No. 5) | 900+1700 | 142 | tone | yes | | or KP'/STP (R1) | | | | | | | | | | | | MF KP (SS No. 5) or | 1100+1700 | 139 | tone | yes | | KP1 (R1) | | | | | | | | | | | | MF KP2 (SS No. 5) or | 1300+1700 | 140 | tone | yes | | KP2P/ST2P (R1) | | | | | | | | | | | | MF ST (SS No. 5 and | 1500+1700 | 141 | tone | yes | | R1) | | | | | | | | | | | | ABCD signalling | N/A | 144...159 | state | no | | | | | | | | Continuity check-tone | 2000 | 167 | tone | yes | | | | | | | | Continuity | 1780 | 168 | tone | yes | | verify-tone | | | | | | | | | | | | Metering pulse | N/A | 174 | other | no | | | | | | | | Trunk unavailable | N/A | 175 | other | no | | | | | | | | MFC Forward 1...15 | (Table 4) | 176...190 | tone | yes | | | | | | | | MFC Backward 1...15 | (Table 5) | 191...205 | tone | yes | +-----------------------+------------+-------------+-------+--------+ Table 1: Trunk signalling events Schulzrinne, et al. Expires August 10, 2005 [Page 5] Internet-Draft Channel-Oriented Signalling Events February 2005 2.1 Signalling System No. 5 Signalling System No. 5 (SS No. 5) is defined in ITU-T Recommendations Q.140 through Q.180 [4]. It has two systems of signals: "line" signalling, to acquire and release the trunk, and "register" signalling, to pass digits forward from one switch to the next. 2.1.1 Signalling System No. 5 Line Signals No. 5 line signalling uses tones at two frequencies: 2400 and 2600 Hz. The tones are used singly for most signals, but together for the Clear-forward and Release-guard. (This reduces the chance of an accidental call release due to carried media content looking like one of the frequencies.) The specific signal indicated by a tone depends on the stage of call set-up at which it is applied. No events are defined in support of No. 5 line signalling. However, implementations MAY use the ABCD events described in Section 2.4 and shown in Table 1 to propagate SS No. 5 line signals. If they do so, they MUST use the following mappings. These mappings are based on an underlying mapping equating A=0 to presence of 2400 Hz signal and B=0 to presence of 2600 Hz signal in the indicated direction. o both 2400 and 2600 Hz present: event code 144; o 2400 Hz present: event code 145; o 2600 Hz present: event code 146; o neither signal present: event code 147. The initial event report for each signal SHOULD be generated as soon as the signal is recognized, and in any case no later than the time of recognition as indicated in ITU-T Recommendation Q.141, Table 1 (i.e. 40 ms for "seizing" and "proceed-to-send", 125 ms for all other signals). The packetization interval following the initial report SHOULD be chosen with considerations of reliable transmission given first priority. Note that the receiver must supply its own volume values for converting these events back to tones. Moreover, the receiver MAY extend the playout of "seizing" until it has received the first report of a KP event (see below), so that it has better control of the interval between ending of the seizing signal and start of KP playout. The KP has to be sent beginning 80 +/- 20 ms after the SS No. 5 "seizing" signal has stopped. Schulzrinne, et al. Expires August 10, 2005 [Page 6] Internet-Draft Channel-Oriented Signalling Events February 2005 2.1.2 Signalling System No. 5 Register Signals No. 5 register signalling uses pairs of tones to convey digits and signals framing them. The tone combinations and corresponding signals are shown in the Table 2. All signals except KP1 and KP2 are sent for a duration of 55 ms. KP1 and KP2 are sent for a duration of 100 ms. Inter-signal pauses are always 55 ms. +-----------+-------------------------------------------------------+ | Lower | Upper Frequency (Hz) | | Frequency | 900 1100 1300 1500 1700 | | (Hz) | | +-----------+-------------------------------------------------------+ | 700 | Digit 1 Digit 2 Digit 4 Digit 7 Code 11 | | | | | 900 | Digit 3 Digit 5 Digit 8 Code 12 | | | | | 1100 | Digit 6 Digit 9 KP1 | | | | | 1300 | Digit 0 KP2 | | | | | 1500 | ST | +-----------+-------------------------------------------------------+ Table 2: SS No. 5 Register Signals The KP signals are used to indicate start of digit signalling. KP1 indicates a call expected to terminate in a national network served by the switch to which the signalling is being sent. KP2 indicates a call that is expected to transit through the switch to which the signalling is being sent, to another international exchange. The end of digit signalling is indicated by the ST signal. Code 11 or Code 12 following a country code (and possibly another digit) indicates a call to be directed to an operator position in the destination country. A Code 12 may be followed by other digits indicating a particular operator to whom the call is to be directed. Implementations using the telephone-events payload to carry SS No. 5 register signalling MUST use the following events from Table 1 to convey the register signals shown in Table 2: o event code 128 to convey Digit 0 o event codes 129-137 to convey Digits 1 through 9 respectively o event code 139 to convey KP1 Schulzrinne, et al. Expires August 10, 2005 [Page 7] Internet-Draft Channel-Oriented Signalling Events February 2005 o event code 140 to convey KP2 o event code 141 to convey ST o event code 138 to convey Code 11 o event code 142 to convey Code 12. The sending implementation SHOULD send an initial event report for the KP signals as soon as they are recognized, and MUST send an event report for all of these signals as soon as they have completed. 2.2 Signalling System R1 and North American MF Signalling System R1 is mainly used in North America, as is the more common variant designated simply "MF". R1 is defined in ITU-T Recommendations Q.310-Q.332 [5], while MF is defined in [8]. Like SS No. 5, R1/MF has both line and register signals. The line signals (not counting Busy and Reorder) are implemented on analogue trunks through the application of a 2600 Hz tone, and on digital trunks by using ABCD signalling. Interpretation of the line signals is state-dependent (as with SS No. 5). 2.2.1 Signalling System R1 Line Signals In accordance with Table 1/Q.311, implementations MAY use the ABCD events described in Section 2.4 and shown in Table 1 to propagate R1 line signals. If they do so, they MUST use the following mappings. These mappings are based on an underlying mapping equating A=0 to presence of 2600 Hz signal in the indicated direction and A=1 to absence of that signal. o 2600 Hz present: event code 144; o no signal present: event code 145. 2.2.2 Signalling System R1 Register Signals R1 has a signal capacity of 15 codes for forward inter-register signals but no backward inter-register signals. Each code or digit is transmitted by a tone pair from a set of 6 frequencies. The R1 register signals consist of KP, ST, and the digits "0" through "9". The frequencies allotted to the signals are shown in Table 3. Note that these frequencies are the same as those allotted to the similarly-named SS No. 5 register signals, except that KP uses the frequency combination corresponding to KP1 in SS No. 5. Table 3 also shows additional signals used in North American practice: KP', KP2P, Schulzrinne, et al. Expires August 10, 2005 [Page 8] Internet-Draft Channel-Oriented Signalling Events February 2005 KP3P, STP or ST', ST2P, and ST3P [8]. +-----------+-------------------------------------------------------+ | Lower | Upper Frequency (Hz) | | Frequency | 900 1100 1300 1500 1700 | | (Hz) | | +-----------+-------------------------------------------------------+ | 700 | Digit 1 Digit 2 Digit 4 Digit 7 KP3P or ST3P | | | | | 900 | Digit 3 Digit 5 Digit 8 KP' or STP | | | | | 1100 | Digit 6 Digit 9 KP | | | | | 1300 | Digit 0 KP2P or ST2P | | | | | 1500 | ST | +-----------+-------------------------------------------------------+ Table 3: R1/MF Register Signals Implementations using the telephone-events payload to carry North American R1 register signalling MUST use the following events from Table 1 to convey the register signals shown in Table 3: o event code 128 to convey Digit 0; o event codes 129-137 to convey Digits 1 through 9 respectively; o event code 139 to convey KP; o event code 141 to convey ST; o event code 142 to convey KP' or STP; o event code 140 to convey KP2P or ST2P; o event code 138 to convey KP3P or ST3P. As with the original telephony signals, the receiver interprets codes 138, 140, and 142 as KPx or STx signals based on their position in the signalling sequence. Unlike SS No. 5, R1 allows a large tolerance for the time of onset of register signalling following the recognition of start-dialling line signal. This means that sending implementations MAY wait to send a KP event report until the KP has completed. Schulzrinne, et al. Expires August 10, 2005 [Page 9] Internet-Draft Channel-Oriented Signalling Events February 2005 2.3 Signalling System R2 International Signalling System R2 is described in ITU-T Recommendations Q.400-Q.490 [6], but there are many national variants. R2 line signals are continuous, out-of-band, link by link, and channel associated. R2 (inter)register signals are multifrequency, compelled, in-band, end to end, and also channel associated. 2.3.1 Signalling System R2 Line Signals R2 line signals may be analog, one-bit digital using the A bit in the 16th channel, or digital using both A and B bits. Implementations MAY use the ABCD events described in Section 2.4 and shown in Table 1 to propagate these signals. If they do so, they MUST use the following mappings. 1. For the analog R2 line signals shown in Table 1 of ITU-T Recommendation Q.411, implementations MUST map as follows. This mapping is based on an underlying mapping of A bit = 0 when tone is present. * event code 144 (Table 1) is used to indicate the Q.411 "tone-on" condition * event code 145 (Table 1), is used to indicate the Q.411 "tone-off" condition. 2. The digital R2 line signals as described by ITU-T Recommendation Q.421 are carried in two bits, A and B. The mapping between A and B bit values and event codes SHALL be the same in both directions and SHALL follow the principles for A and B bit mapping specified in Section 2.4. Note that the mapping from line states to event codes thus generated differs from the mappings generated for analog signalling. 2.3.2 Signalling System R2 Register Signals In R2 signalling, the signalling sequence is initiated from the outgoing exchange by sending a line "seizing" signal. After line "seizing" signal (and "seizing acknowledgment" signal in R2D), the signalling sequence continues using MF register signals. ITU-T Recommendation Q.441 classifies the forward MF register signals into Groups I and II, the backward MF register signals into Groups A and B. These groups are significant with respect both to what sort of information they convey and where they can occur in the signalling sequence. Schulzrinne, et al. Expires August 10, 2005 [Page 10] Internet-Draft Channel-Oriented Signalling Events February 2005 R2 is a compelled tone signalling protocol, meaning that one tone is played until an "acknowledgment or directive for the next tone" is received which indicates that the original tone should cease. In R2 signalling, the signalling sequence is initiated from the outgoing exchange by sending a forward Group I signal. The first forward signal is typically the first digit of the called number. The incoming exchange typically replies with a backward Group A-1 indicating to the outgoing exchange to send the next digit of the called number. The tones have meaning; however, the meaning varies depending on where the tone occurs in the signalling. The meaning may also depend on the country. Thus, to avoid an unmanageable number of events, this document simply provides means to indicate the 15 forward and 15 backward MF R2 tones (i.e., using event codes 176-190 and 191-205 respectively as shown in Table 1). The frequency pairs for these tones are shown in Table 4 and Table 5. +------------------+------------------------------------------------+ | Lower Frequency | Upper Frequency (Hz) | | (Hz) | 1500 1620 1740 1860 1980 | +------------------+------------------------------------------------+ | 1380 | Fwd 1 Fwd 2 Fwd 4 Fwd 7 Fwd 11 | | | | | 1500 | Fwd 3 Fwd 5 Fwd 8 Fwd 12 | | | | | 1620 | Fwd 6 Fwd 9 Fwd 13 | | | | | 1740 | Fwd 10 Fwd 14 | | | | | 1860 | Fwd 15 | +------------------+------------------------------------------------+ Table 4: R2 Forward Register Signals Schulzrinne, et al. Expires August 10, 2005 [Page 11] Internet-Draft Channel-Oriented Signalling Events February 2005 +------------------+------------------------------------------------+ | Lower Frequency | Upper Frequency (Hz) | | (Hz) | 1140 1020 900 780 660 | +------------------+------------------------------------------------+ | 1020 | Bkwd 1 | | | | | 900 | Bkwd 2 Bkwd 3 | | | | | 780 | Bkwd 4 Bkwd 5 Bkwd 6 | | | | | 660 | Bkwd 7 Bkwd 8 Bkwd 9 Bkwd 10 | | | | | 540 | Bkwd 11 Bkwd 12 Bkwd 13 Bkwd 14 Bkwd 15 | +------------------+------------------------------------------------+ Table 5: R2 Backward Register Signals 2.4 ABCD Transitional signalling For Digital Trunks ABCD is a 4-bit signalling system used by digital trunks, where A, B, C, and D are the designations of the individual bits. For N-state (N<=16) signalling, the first N values are used. ABCD signalling events are all mutually exclusive states. The most recent state transition determines the current state. When using Extended Super Frame (ESF) T1 framing, signalling information is sent as robbed bits in frames 6, 12, 18, and 24. A D4 superframe only transmits 4-state signalling with A and B bits. On the CEPT E1 frame, all signalling is carried in timeslot 16, and two channels of 16-state (ABCD) signalling are sent per frame. The meaning of ABCD signals varies with the application. One example of a specification of ABCD signalling codes is T1.403.02 [13], which reflects North American practice for "loop" signalling as opposed to the trunk signalling discussed in previous sections. Since ABCD information is a state rather than a changing signal, implementations SHOULD use the following triple-redundancy mechanism, similar to the one specified in ITU-T Rec. I.366.2 [12], Annex L. At the time of a transition, the same ABCD information is sent 3 times at an interval of 5 ms. If another transition occurs during this time, then this continues. After a period of no change, the ABCD information is sent every 5 seconds. As shown in Table 1, the 16 possible states are represented by event codes 144 to 159 respectively. Implementations using these event codes MUST map them to and from the ABCD information based on the Schulzrinne, et al. Expires August 10, 2005 [Page 12] Internet-Draft Channel-Oriented Signalling Events February 2005 following principles: 1. State numbers are derived from the used subset of ABCD bits by treating them as a single binary number, where the A bit is the high-order bit. Unused bits are ignored. As examples: if only A and B bits are used, A=0, B=1, then C and D are ignored and the state number is 1 (binary 01); if all four bits are used and A=0, B=1, C=0, D=1, then the state number is 5 (binary 0101). 2. State numbers map to event codes by order of increasing value (i.e., state number 0 maps to event code 144, ..., state number 15 maps to event code 159). 2.5 Continuity Tones Continuity tones are used for testing circuit continuity during call setup. Two basic procedures are used. In international practice, clause 7 of ITU- T Recommendation Q.724 [7] describes a procedure applicable to four-wire trunk circuits, where a single 2000 +/- 20 Hz check-tone is transmitted from the initiating telephone switch. The remote switch sets up a loopback, and continuity check passes if the sending switch can detect the tone on the return path. Q.724 clause 8 describes the procedure for two-wire trunk circuits. The two-wire procedure involves two tones: a 2000 Hz tone sent in the forward direction, and a 1780 +/- 20 Hz tone sent in response. If implementations use the telephone-events payload type to propagate continuity check-tones, they MUST map these tones to event codes as follows: o For four-wire continuity testing, the 2000 Hz check-tone is mapped to event code 167. o For two-wire continuity testing, the initial 2000 Hz check-tone Hz tone is mapped to event code 167. The 1780 Hz continuity verify tone is mapped to event code 168. 2.6 Trunk Unavailable Event This event indicates that the trunk is unavailable for service. The length of the downtime is indicated in the duration field. The duration field is set to a value that allows adequate granularity in describing downtime. A value of 1 second is RECOMMENDED. When the trunk becomes unavailable, this event is sent with the same timestamp three times at an interval of 20 ms. If the trunk persists in the unavailable state at the end of the indicated duration, then the event is retransmitted, preferably with the same redundancy scheme. Schulzrinne, et al. Expires August 10, 2005 [Page 13] Internet-Draft Channel-Oriented Signalling Events February 2005 Unavailability of the trunk might result from a failure or an administrative action. This event is used in a stateless manner to synchronize trunk unavailability between equipment connected through provisioned RTP trunks. It avoids the unnecessary consumption of bandwidth in sending a continuous stream of RTP packets with a fixed payload for the duration of the downtime, as would be required in certain E1-based applications. In T1-based applications, trunk conditioning via the ABCD transitional events can be used instead. 2.7 Metering Pulse Event The metering pulse event may be used to transmit meter pulsing for billing purposes. Since the metering pulse is a discrete event, each metering pulse event report MUST have both the 'M' and 'E' bits set. Meter pulsing is normally transmitted by out-of-band means while conversation is in progress. Senders MUST therefore be prepared to transmit both the telephone-event and audio payload types simultaneously. Metering pulse events MUST be retransmitted as recommended in section 2.5.1.4 of RFC xxxx [3]. It is RECOMMENDED that the retransmission interval be the lesser of 50 ms and the pulsing rate, but no less than audio packetization rate. Schulzrinne, et al. Expires August 10, 2005 [Page 14] Internet-Draft Channel-Oriented Signalling Events February 2005 3. Security Considerations Because the events for which event codes are provided in this document relate directly to the setup, billing, and takedown of telephone calls, they may be used to commit toll fraud in the PSTN. Thus PSTN gateways MUST authenticate the source of trunk signalling event reports and ensure that the authenticated entity is authorized to originate them. Additional security considerations are described in RFC xxxx [3]. Schulzrinne, et al. Expires August 10, 2005 [Page 15] Internet-Draft Channel-Oriented Signalling Events February 2005 4. IANA Considerations This document defines the event codes shown in Table 6. These events are additions to the telephone-event registry established by RFC xxxx [3]. +-----------+-------------------------------------+-----------------+ | Event | Event Name | Reference | | Code | | | +-----------+-------------------------------------+-----------------+ | 128 | SS No. 5 or R1 digit "0" | | | | | | | 129 | SS No. 5 or R1 digit "1" | | | | | | | 130 | SS No. 5 or R1 digit "2" | | | | | | | 131 | SS No. 5 or R1 digit "3" | | | | | | | 132 | SS No. 5 or R1 digit "4" | | | | | | | 133 | SS No. 5 or R1 digit "5" | | | | | | | 134 | SS No. 5 or R1 digit "6" | | | | | | | 135 | SS No. 5 or R1 digit "7" | | | | | | | 136 | SS No. 5 or R1 digit "8" | | | | | | | 137 | SS No. 5 or R1 digit "9" | | | | | | | 138 | MF Code 11 (SS No. 5) or KP3P/ST3P | | | | (R1) | | | | | | | 139 | MF KP (SS No. 5) or KP1 (R1) | | | | | | | 140 | MF KP2 (SS No. 5) or KP2P/ST2P (R1) | | | | | | | 141 | MF ST (SS No. 5 and R1) | | | | | | | 142 | MF Code 12 (SS No. 5) or KP'/STP | | | | (R1) | | | | | | | 144 | A bit signalling state '0' or AB | | | | state '00' or ABCD state '0000' | | | | | | | 145 | A bit signalling state '1' or AB | | | | state '01' or ABCD state '0001' | | | | | | Schulzrinne, et al. Expires August 10, 2005 [Page 16] Internet-Draft Channel-Oriented Signalling Events February 2005 | 146 | AB signalling state '10' or ABCD | | | | state '0010' | | | | | | | 147 | AB signalling state '11' or ABCD | | | | state '0011' | | | | | | | 148 | ABCD signalling state '0100' | | | | | | | 149 | ABCD signalling state '0101' | | | | | | | 150 | ABCD signalling state '0110' | | | | | | | 151 | ABCD signalling state '0111' | | | | | | | 152 | ABCD signalling state '1000' | | | | | | | 153 | ABCD signalling state '1001' | | | | | | | 154 | ABCD signalling state '1010' | | | | | | | 155 | ABCD signalling state '1011' | | | | | | | 156 | ABCD signalling state '1100' | | | | | | | 157 | ABCD signalling state '1101' | | | | | | | 158 | ABCD signalling state '1110' | | | | | | | 159 | ABCD signalling state '1111' | | | | | | | 167 | Continuity check-tone | | | | | | | 168 | Continuity verify-tone | | | | | | | 174 | Metering pulse | | | | | | | 175 | Trunk unavailable | | | | | | | 176 | MFC forward signal 1 | | | | | | | 177 | MFC forward signal 2 | | | | | | | 178 | MFC forward signal 3 | | | | | | | 179 | MFC forward signal 4 | | | | | | | 180 | MFC forward signal 5 | | | | | | Schulzrinne, et al. Expires August 10, 2005 [Page 17] Internet-Draft Channel-Oriented Signalling Events February 2005 | 181 | MFC forward signal 6 | | | | | | | 182 | MFC forward signal 7 | | | | | | | 183 | MFC forward signal 8 | | | | | | | 184 | MFC forward signal 9 | | | | | | | 185 | MFC forward signal 10 | | | | | | | 186 | MFC forward signal 11 | | | | | | | 187 | MFC forward signal 12 | | | | | | | 188 | MFC forward signal 13 | | | | | | | 189 | MFC forward signal 14 | | | | | | | 190 | MFC forward signal 15 | | | | | | | 191 | MFC backward signal 1 | | | | | | | 192 | MFC backward signal 2 | | | | | | | 193 | MFC backward signal 3 | | | | | | | 194 | MFC backward signal 4 | | | | | | | 195 | MFC backward signal 5 | | | | | | | 196 | MFC backward signal 6 | | | | | | | 197 | MFC backward signal 7 | | | | | | | 198 | MFC backward signal 8 | | | | | | | 199 | MFC backward signal 9 | | | | | | | 200 | MFC backward signal 10 | | | | | | | 201 | MFC backward signal 11 | | | | | | | 202 | MFC backward signal 12 | | | | | | | 203 | MFC backward signal 13 | | | | | | | 204 | MFC backward signal 14 | | | | | | Schulzrinne, et al. Expires August 10, 2005 [Page 18] Internet-Draft Channel-Oriented Signalling Events February 2005 | 205 | MFC backward signal 15 | | +-----------+-------------------------------------+-----------------+ Table 6: Channel-oriented signalling events to be added to the audio/telephone-event event code registry Schulzrinne, et al. Expires August 10, 2005 [Page 19] Internet-Draft Channel-Oriented Signalling Events February 2005 5. Acknowledgements The complete list of acknowledgements for contribution to the development and revision of RFC 2833 is contained in RFC xxxx [3]. The Editor believes that the following people contributed specifically to the present document: Flemming Andreasen, Rex Coldren, Bill Foster, Rajesh Kumar, Oren Peleg, Moshe Samoha, Adrian Soncodi, and Yaakov Stein. Schulzrinne, et al. Expires August 10, 2005 [Page 20] Internet-Draft Channel-Oriented Signalling Events February 2005 6. References 6.1 Normative References [1] Bradner, S., "Key words for use in RFCs to indicate requirement levels", RFC 2119, March 1997. [2] Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", RFC 3550, STD 0064, July 2003. [3] Schulzrinne, H., Petrack, S. and T. Taylor, "RTP Payload for DTMF Digits, Telephony Tones and Telephony Signals", Work in progress: draft-ietf-avt-rfc2833bis-07.txt, January 2005. [4] International Telecommunication Union, "Specifications for signalling system no. 5", ITU-T Recommendation Q.140-Q.180, November 1988. [5] International Telecommunication Union, "Specifications of Signalling System R1", ITU-T Recommendation Q.310-Q.332, November 1988. [6] International Telecommunication Union, "Specifications of Signalling System R2", ITU-T Recommendation Q.400-Q.490, November 1988. [7] International Telecommunication Union, "Telephone user part signalling procedures", ITU-T Recommendation Q.724, November 1988. [8] Telcordia Technologies, "LSSGR: signalling for Analog Interfaces", Generic Requirement GR-506, June 1996. 6.2 Informative References [9] Schulzrinne, H. and S. Petrack, "RTP Payload for DTMF Digits, Telephony Tones and Telephony Signals", RFC 2833, May 2000. [10] International Telecommunication Union, "Speech coders : Dual rate speech coder for multimedia communications transmitting at 5.3 and 6.3 kbit/s", ITU-T Recommendation G.723.1, March 1996. [11] International Telecommunication Union, "Coding of speech at 8 kbit/s using conjugate-structure algebraic-code-excited linear-prediction (CS-ACELP)", ITU-T Recommendation G.729, March 1996. Schulzrinne, et al. Expires August 10, 2005 [Page 21] Internet-Draft Channel-Oriented Signalling Events February 2005 [12] International Telecommunication Union, "AAL type 2 service specific convergence sublayer for trunking", ITU-T Recommendation I.366.2, February 1999. [13] ANSI/T1, "Network and Customer Installation Interfaces -- DS1 Robbed-Bit signalling State Definitions", American National Standard for Telecommunications T1.403.02-1999, May 1999. Authors' Addresses Henning Schulzrinne Columbia U. Dept. of Computer Science Columbia University 1214 Amsterdam Avenue New York, NY 10027 US Email: schulzrinne@cs.columbia.edu Scott Petrack eDial 266 Second Ave Waltham, MA 02451 US Email: scott.petrack@edial.com Tom Taylor Nortel 1852 Lorraine Ave Ottawa, Ontario K1H 6Z8 CA Email: taylor@nortel.com Schulzrinne, et al. 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Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Schulzrinne, et al. Expires August 10, 2005 [Page 23]