1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T G.799.4 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2014) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital terminal equipments Other terminal equipment Procedures for control of de-jitt
2、er buffers used in PSTN-IP gateways carrying voiceband data Recommendation ITU-T G.799.4 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRAN
3、SMISSION SYSTEMS G.200G.299 INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES G.300G.399 GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES G.400G.449 COORDINATION OF RADIO
4、TELEPHONY AND LINE TELEPHONY G.450G.499 TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 General G.700G.709 Coding of voice and audio signals G.710G.729 Principal characteristics of primary multiplex equipment G.730G.739 Principal characteristi
5、cs of second order multiplex equipment G.740G.749 Principal characteristics of higher order multiplex equipment G.750G.759 Principal characteristics of transcoder and digital multiplication equipment G.760G.769 Operations, administration and maintenance features of transmission equipment G.770G.779
6、Principal characteristics of multiplexing equipment for the synchronous digital hierarchy G.780G.789 Other terminal equipment G.790G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED ASPECTS G.10
7、00G.1999 TRANSMISSION MEDIA CHARACTERISTICS G.6000G.6999 DATA OVER TRANSPORT GENERIC ASPECTS G.7000G.7999 PACKET OVER TRANSPORT ASPECTS G.8000G.8999 ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.799.4 (10/2014) i Recommendation ITU-
8、T G.799.4 Procedures for control of de-jitter buffers used in PSTN-IP gateways carrying voiceband data Summary Recommendation ITU-T G.799.4 describes procedures for the control of de-jitter buffers used in PSTN-IP gateways carrying voiceband data. History Edition Recommendation Approval Study Group
9、Unique ID* 1.0 ITU-T G.799.4 2014-10-14 16 11.1002/1000/12234 Keywords De-jitter buffer, PSTN-IP gateways. _ * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.10
10、02/1000/11830-en. ii Rec. ITU-T G.799.4 (10/2014) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a per
11、manent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establ
12、ishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary stan
13、dards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Rec
14、ommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents
15、 are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed I
16、ntellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not re
17、ceived notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/
18、ipr/. ITU 2015 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T G.799.4 (10/2014) iii Table of Contents Page 1 Scope . 1 1.1 Applicability statements . 1 2 References . 2 3 Definitions 3 3.1 Terms def
19、ined elsewhere 3 3.2 Terms defined in this Recommendation . 4 4 Abbreviations and acronyms 4 5 Conventions 5 6 Overview XoIP emulation services versus applicable de-jitter buffer modes of operation . 5 7 Characteristics of de-jitter buffers 6 7.1 General . 6 7.2 Purpose, operation and environment 7
20、7.3 External enabling of fixed de-jitter buffers 7 8 Activation of de-jitter buffer for VBDoIP 7 8.1 Activation of de-jitter buffer for ISDN bearer service . 11 9 Characteristics of VBD-mode switching of de-jitter buffers 12 9.1 General . 12 9.2 Detector characteristics 13 10 Requirements for config
21、uration of de-jitter buffers 21 10.1 Fixed de-jitter buffers . 21 10.2 Adaptive de-jitter buffers . 21 10.3 Activation procedure into the fixed mode 22 10.4 Transition from VBD to voice mode (ITU-T V.152) 22 10.5 Handling of de-jitter buffer in case of lost or late packets . 23 Annex A De-jitter buf
22、fer facsimile tests . 24 A.1 Measurement method . 24 Appendix I Features of ITU-T V.17 fax and V.34 fax . 53 I.1 Features of V.17 fax (V.17 fax modem) . 53 I.2 V.34 high-speed fax 53 I.2.1 Features . 53 I.3 The ITU-T V.34 fax connection and session 54 I.4 ECM as a mandatory feature 55 I.5 Suitable X
23、oIP emulation services for V.34 fax 56 Bibliography. 57 Rec. ITU-T G.799.4 (10/2014) 1 Recommendation ITU-T G.799.4 Procedures for control of de-jitter buffers used in PSTN-IP gateways carrying voiceband data 1 Scope De-jitter buffers have a major effect on voice and data transmission quality in tel
24、ecommunication networks. They affect the three service categories of public switched telephone network/integrated service digital network (PSTN/ISDN) voice, voiceband data (due to PSTN modem calls) and ISDN circuit mode data. Since the requirements for the settings of de-jitter buffers differ for di
25、fferent services, this Recommendation describes the activation and mode switching procedures of de-jitter buffers, including the requirement for in-band tone activating and other control mechanisms. It is assumed that the clock accuracy of all elements involved is sufficiently high for application o
26、f this Recommendation. This Recommendation covers de-jitter buffer usage in circuit-to-IP media gateways, such as residential, access or trunking gateways in the context of the next generation network/internet protocol multimedia subsystem (NGN/IMS). The notion of circuit relates to a PSTN analogue
27、line or an ISDN 164 bearer channel. 1.1 Applicability statements This Recommendation is a) applicable: a1) to circuit-to-IP media gateways and communication services with a gateway interworking function operating at the level of a synchronous byte-stream, such as: service “voice-over-IP“ (VoIP) with
28、out or with silence suppression; service “voiceband data-over-IP“ (VBDoIP); and service “circuit-mode data-over-IP“ (CMDoIP); a2) to IP-to-IP media gateways for dedicated interworking services between two IP domains, such as: service “IPDV reduction between two IP domains“ with different grade of se
29、rvice (GoS) as e.g., described in b-ITU-T G.799.3; service “RTP PDV reduction between two RTP domains“, which may be the subject of an “RTP transport translator“ topology (see IETF RFC 5117 and ITU-T H.248.88); but IP-to-IP media gateways are basically out of the scope of this Recommendation due to
30、their focus on circuit-to-IP gateway types, and is b) not applicable, because de-jitter buffers are not required: b1) to circuit-to-IP media gateways and communication services with a gateway interworking function operating at the level of individual packets as atomic units (i.e., an asynchronous pa
31、cket-stream), such as: service “facsimile-over-IP“ (FoIP) according to ITU-T T.38; service “text-over-IP“ (ToIP) according to ITU-T V.151; and service “data-over-IP“ (MoIP) according to b-ITU-T V.150.1; 2 Rec. ITU-T G.799.4 (10/2014) b2) to IP-to-IP media gateways in general. 2 References The follow
32、ing ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recomm
33、endation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not g
34、ive it, as a stand-alone document, the status of a Recommendation. ITU-T G.161.1 Recommendation ITU-T G.161.1 (2014), Do-no-harm testing. ITU-T G.168 Recommendation ITU-T G.168 (2012), Digital network echo cancellers. ITU-T H.248.88 Recommendation ITU-T H.248.88 (2014), Gateway control protocol: RTP
35、 topology dependent RTCP handling by ITU-T H.248 media gateways with IP terminations. ITU-T T.38 Recommendation ITU-T T.38 (2010), Procedures for real-time Group 3 facsimile communication over IP networks. ITU-T V.8 Recommendation ITU-T V.8 (2000), Procedures for starting sessions of data transmissi
36、on over the public switched telephone network. ITU-T V.8bis Recommendation ITU-T V.8bis (2000), Procedures for the identification and selection of common modes of operation between data circuit-terminating equipments (DCEs) and between data terminal equipments (DTEs) over the public switched telepho
37、ne network and on leased point-to-point telephone-type circuits. ITU-T V.21 Recommendation ITU-T V.21 (1988), 300 bits per second duplex modem standardized for use in the general switched telephone network. ITU-T V.22 Recommendation ITU-T V.22 (1988), 1200 bits per second duplex modem standardized f
38、or use in the general switched telephone network and on point-to-point 2-wire leased telephone-type circuits. ITU-T V.25 Recommendation ITU-T V.25 (1996), Automatic answering equipment and general procedures for automatic calling equipment on the general switched telephone network including procedur
39、es for disabling of echo control devices for both manually and automatically established calls. ITU-T V.32 Recommendation ITU-T V.32 (1993), A family of 2-wire, duplex modems operating at data signalling rates of up to 9600 bit/s for use on the general switched telephone network and on leased teleph
40、one-type circuits. ITU-T V.32bis Recommendation ITU-T V.32bis (1991), A duplex modem operating at data signalling rates of up to 14 400 bit/s for use on the general switched telephone network and on leased point-to-point 2-wire telephone-type circuits. ITU-T V.151 Recommendation ITU-T V.151 (2006),
41、Procedures for the end-to-end connection of analogue PSTN text telephones over an IP network utilizing text relay. ITU-T V.152 Recommendation ITU-T V.152 (2010), Procedures for supporting voice-band data over IP Networks. Rec. ITU-T G.799.4 (10/2014) 3 ITU-T P.501 Recommendation ITU-T P.501 (2012),
42、Test signals for use in telephonometry. IETF RFC 5117 IETF RFC 5117 (2008), RTP Topologies. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 de-jitter buffer b-ITU-T G.1020: A buffer designed to remove the delay variation (i.e., jitter)
43、in packet arrival times. Data is put into the de-jitter buffer at a variable rate (i.e., whenever they are received from the network), and taken out at a constant rate. 3.1.2 voice-band data mode ITU-T V.152: The transport of voice-band data over a voice channel of a packet network with the encoding
44、 appropriate for modem signals as defined in clause 6 of ITU-T V.152. 3.1.3 G3 facsimile equipment (G3FE) ITU-T T.38: G3FE refers to any entity which presents a communications interface conforming to b-ITU-T T.30, b-ITU-T T.4, and, optionally, b-ITU-T T.6. A G3FE may be a traditional G3 facsimile ma
45、chine, an application with a b-ITU T T.30 protocol engine, or any of the other possibilities mentioned in the network model for IP facsimile. 3.1.4 PSTN modem call b-ETSI TR 183 072: Voiceband data call originating/terminating in a PSTN domain. NOTE The term voiceband data (VBD) is an umbrella term
46、for all kind of teleservices which using a “data-oriented transport“ in the frequency band of the narrowband voice spectrum (which is a 3.1-kHz-band). The data-oriented transport is realized by modem protocols (definition as in clause 3.13 of ITU-T V.152), as defined e.g., within the ITU-T V.x-serie
47、s of Recommendations. Teleservices may be categorized into three major applications areas: facsimile, text-based communication and general data services. 3.1.5 ITU-T T.38/G3 ITU-T T.38: ITU-T T.38/G3 refers to an ITU T T.38 endpoint that supports G3FE, but excludes the ITU-T T.30/ITU-T V.34 procedur
48、es. 3.1.6 ITU-T T.38/ITU-T V.34G3 ITU-T T.38: ITU-T T.38/ITU-T V.34G3 refers to an ITU-T T.38 endpoint that supports G3FE and includes the ITU-T T.30/ITU-T V.34 half-duplex procedures. 3.1.7 VBD gateway ITU-T V.152: A media gateway that is compliant with ITU-T V.152. 3.1.8 XoIP emulation service (fo
49、r PSTN modem calls) b-ETSI TR 183 072: Emulation service in IP networks, based on appropriated gateway technologies for interworking voiceband data information between the PSTN and IP networks. NOTE Example emulation services for the three main VBD application areas, which may be summarized as (by using notation “application/transport“): Facsimile/modem: Gateway technologies for PSTN-to-IP interworking see e.g., ITU-T
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