1、 International Telecommunication Union ITU-T H.248.62TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (06/2008) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMSInfrastructure of audiovisual services Communication procedures Gateway control protocol: Re-answer package Recommendation ITU-T H.248.62 ITU-T H
2、-SERIES RECOMMENDATIONS AUDIOVISUAL AND MULTIMEDIA SYSTEMS CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS H.100H.199 INFRASTRUCTURE OF AUDIOVISUAL SERVICES General H.200H.219 Transmission multiplexing and synchronization H.220H.229 Systems aspects H.230H.239 Communication procedures H.240H.259 Coding o
3、f moving video H.260H.279 Related systems aspects H.280H.299 Systems and terminal equipment for audiovisual services H.300H.349 Directory services architecture for audiovisual and multimedia services H.350H.359 Quality of service architecture for audiovisual and multimedia services H.360H.369 Supple
4、mentary services for multimedia H.450H.499 MOBILITY AND COLLABORATION PROCEDURES Overview of Mobility and Collaboration, definitions, protocols and procedures H.500H.509 Mobility for H-Series multimedia systems and services H.510H.519 Mobile multimedia collaboration applications and services H.520H.
5、529 Security for mobile multimedia systems and services H.530H.539 Security for mobile multimedia collaboration applications and services H.540H.549 Mobility interworking procedures H.550H.559Mobile multimedia collaboration inter-working procedures H.560H.569 BROADBAND AND TRIPLE-PLAY MULTIMEDIA SER
6、VICES Broadband multimedia services over VDSL H.610H.619 Advanced multimedia services and applications H.620H.629 IPTV MULTIMEDIA SERVICES AND APPLICATIONS FOR IPTV General aspects H.700H.719 IPTV terminal devices H.720H.729 For further details, please refer to the list of ITU-T Recommendations. Rec
7、. ITU-T H.248.62 (06/2008) i Recommendation ITU-T H.248.62 Gateway control protocol: Re-answer package Summary Re-answer call is a particular channel associated signalling (CAS) service, which is deployed in some networks, e.g., in China and Indonesia. If a media gateway (MG) interconnects with such
8、 CAS equipment, it cannot support the re-answer service without the additions defined in the re-answer package. In the re-answer package, the re-answer event and the procedures on how to use this event are defined. Source Recommendation ITU-T H.248.62 was approved on 13 June 2008 by ITU-T Study Grou
9、p 16 (2005-2008) under Recommendation ITU-T A.8 procedure. ii Rec. ITU-T H.248.62 (06/2008) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunicati
10、on Standardization Sector (ITU-T) is a permanent 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 (W
11、TSA), which meets every four years, establishes 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
12、 within ITU-Ts purview, the necessary standards 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 Rec
13、ommendation is voluntary. However, the Recommendation 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 su
14、ch as “must“ and the negative equivalents 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 RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recomme
15、ndation may involve the use of a claimed Intellectual 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 appro
16、val of this Recommendation, ITU had not received 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 p
17、atent database at http:/www.itu.int/ITU-T/ipr/. ITU 2009 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 H.248.62 (06/2008) iii CONTENTS Page 1 Scope 1 1.1 Applicability. 1 1.2 Difference between “an
18、swer“ and “re-answer“ signals 1 2 References. 1 3 Definitions 2 3.1 Terms defined elsewhere 2 3.2 Terms defined in this Recommendation. 2 4 Abbreviations and acronyms 2 5 Conventions 3 6 Re-answer call service 3 7 Re-answer package . 4 7.1 Properties 4 7.2 Events . 4 7.3 Signals 4 7.4 Statistics 4 7
19、.5 Error codes 5 7.6 Procedures 5 Bibliography. 7 iv Rec. ITU-T H.248.62 (06/2008) Introduction In some network architectures where the channel associated signalling (CAS) equipment, such as the public switched telephone network (PSTN), which supports CAS signalling systems (e.g., such as SS R5), ar
20、e connected to 3G, public land mobile network (PLMN), next generation network (NGN) circuit-switched (CS) core network domains, the bearer between the media gateway (MG) and the CAS equipment can be time division multiplexing (TDM), as shown in Figure 1. When an NGN user (the caller, such as a mobil
21、e terminal) makes a call to a CAS user (the callee, such as a telephone subscriber), and the call enters the session state, the CAS user cannot initiate a re-answer call after the hook-on operation is done. The primary reason is that the re-answer signal information cannot be transferred to the MGC
22、depending on the current interface between the MG and the media gateway controller (MGC). However, the re-answer call function is required sometimes. Rec. ITU-T H.248.62 (06/2008) 1 Recommendation ITU-T H.248.62 Gateway control protocol: Re-answer package 1 Scope This Recommendation defines an H.248
23、 package in order to request the MG to detect re-answer line signal on a particular TDM termination which supports CAS signalling, and to notify the MGC when the signal is detected. The re-answer capability supplements the basic call service and belongs, thus, to a supplementary service. Such a supp
24、lementary service was supported in legacy PSTN, leading to particular call control signalling information elements at the network-to-network (NNI) interface, such as CAS-based NNIs or CCS-based NNIs (e.g., SS7 telephone user part; TUP according to ITU-T Q.723, ITU-T Q.724). This H.248 package allows
25、 the support of emulation of such a service in NGN environments (like e.g., a PSTN emulation subsystem). RAN CS core networkMGMGCCAS-equipmentsH248RNCNodeBNodeBUEUETDMNOTE Left side of MG: radio access network of the 3GPP defined 3G PLMN: Right side: legacy PSTN with a CAS-based NNI; Middle: 3GPP R3
26、+ CS CN domain with Mc reference point between MSC server (MGC role) and CS-MGW. Figure 1 Logical network architecture 1.1 Applicability The application of the re-answer package is limited on H.248 TDM terminations controlled via CAS or SS7 TUP call control signalling. 1.2 Difference between “answer
27、“ and “re-answer“ signals The semantic difference is indicated by the signal definitions in clauses 3.1.1 and 3.1.2. The syntactical difference is dependent on the encoding format of the correspondent call control signalling protocol. 2 References The following ITU-T Recommendations and other refere
28、nces 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 Recommendation are therefore encouraged to inves
29、tigate 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 give it, as a stand-alone document, the sta
30、tus of a Recommendation. 2 Rec. ITU-T H.248.62 (06/2008) ITU-T H.248.1 Recommendation ITU-T H.248.1 v3 (2005), Gateway control protocol: Version 3. ITU-T H.248.25 Recommendation ITU-T H.248.25 (2007), Gateway control protocol: Basic CAS packages. ITU-T Q.722 Recommendation ITU-T Q.722 (1988), Genera
31、l function of telephone messages and signals. ITU-T Q.723 Recommendation ITU-T Q.723 (1988), Telephone user part formats and codes. ITU-T Q.724 Recommendation ITU-T Q.724 (1988), Telephone user part signalling procedures. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the followi
32、ng terms defined elsewhere: 3.1.1 answer signal: (see clauses 3.5.2, 3.5.3 and 3.5.4 in ITU-T Q.722) A signal sent in the backward direction indicating that the call is answered. 3.1.2 re-answer signal: (see clause 3.5.6 in ITU-T Q.722) A signal sent in the backward direction indicating that the cal
33、led party, after having cleared, again lifts his receiver or in some other way reproduces the answer condition, e.g., switch-hook flashing. 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 ADD.req: H.248.1 add command request. 3.2.2 MOD.req: H.248.1 mod
34、ify command request. 3.2.3 NOT.req: H.248.1 notify command request. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: 3GPP Third Generation Partnership Project CAS Channel Associated Signalling CCS Common Channel Signalling CN Core Network CS Circuit Swi
35、tch MG Media Gateway MGC Media Gateway Controller NGN Next Generation Network MSC Mobile Switching Centre NNI Network-to-Network Interface PLMN Public Land Mobile Network PSTN Public Switched Telephone Network Rec. ITU-T H.248.62 (06/2008) 3 RA Re-Answer RAN Radio Access Network RNC Radio Network Co
36、ntroller TDM Time Division Multiplexing TUP Telephone User Part R2 R2 line signalling and R2 register signalling SS Signalling System SS7 Signalling System 7 UE User Equipment 5 Conventions None. 6 Re-answer call service Re-answer call, as a supplementary service capability, may be applied in the ac
37、tive call phase, i.e., after the caller and the callee enter the speech state, as follows: Figure 2 Example of re-answer call procedure The caller starts a delay timer to wait for the caller to hook on after the callee hooked on, during this time the line (see Note) between the caller and the callee
38、 is kept. If the callee hooks off before the timer expires, the caller can talk with the callee again, and the timer is cancelled. NOTE “Line“ relates to the H.248 context in the MG with the H.248 TDM termination serving as the “line“. Such a type of functionality is optional but is required sometim
39、es according to related call configurations. In some network architectures, such as Figure 1, the CAS equipment access NGN CS core networks, the CAS protocol applied between the MG and the CAS equipment can be the international signalling system R2 protocol, and so on. The MG receives the CAS signal
40、s sent by 4 Rec. ITU-T H.248.62 (06/2008) the CAS equipment, which are subsequently interpreted and reported to the MGC through the H.248 protocol interface, such as sz, sza events in the bcas package ITU-T H.248.25. However, the re-answer signal sent by the CAS equipment cannot be transferred to th
41、e MGC depending on the existing interface between the MG and the MGC. Therefore, the CAS user, as a callee, cannot initiate a re-answer call after the hook on/off operation is done, as in Figure 2, and such a type of call functionality is required sometimes, even if the MG can detect a re-answer lin
42、e signal over the TDM interface. The package in this Recommendation provides a mechanism for the MGC to request the MG to detect the re-answer signal. The MGC can then perform subsequent processing after the re-answer signal is reported to the MGC. It is assumed that the MG has the ability to detect
43、 the re-answer signal on the TDM interface. 7 Re-answer package Package name: Re-answer package Package ID: ra (0x00e2) Description: This package defines an event to enable re-answer functionality for physical terminations which support CAS protocols. Once the event is reported, the MGC may initiate
44、 the appropriate call-dependent procedures. Version: 1 Extends: None 7.1 Properties None. 7.2 Events 7.2.1 Re-answer Event name: Re-answer Event ID: ra (0x0001) Description: This event applies to an outgoing interface, and is reported when a “Re-answer“ line signal occurs on the termination. The eve
45、nt is reported by the MG if either the timed transition to this line signal is detected or the line signal already exists. The condition against which the signal is verified is provisioned in the MG. 7.2.1.1 EventsDescriptor parameters None. 7.2.1.2 ObservedEventsDescriptor parameters None. 7.3 Sign
46、als None. 7.4 Statistics None. Rec. ITU-T H.248.62 (06/2008) 5 7.5 Error codes None. 7.6 Procedures 7.6.1 Overview Example scenario The re-answer call procedure is illustrated in Figure 3. It should be noted that the caller side illustrated in Figure 3 means a TDM termination on the MG, but actually
47、 it may be a mobile terminal of the NGN radio network. This figure only shows the simple interactions between the MGC/MG in NGN CS core network and the CAS equipment, and the details depend on the implementation. Figure 3 Re-answer call procedure 7.6.2 Individual procedural steps P1, P2: When a call
48、 is initiated by the NGN side, the MGC interacts with the MG over the H.248 interface, and the MG interacts with the CAS equipment over CAS signalling interface (using, e.g., packages of ITU-T H.248.25). In procedure P1, the MGC should perform an H.248 ADD.req or MOD.req on the MGs TDM termination,
49、with event Re-answer (ra) to request the MG to detect the re-answer signal that may occur in subsequent call procedures. P3: When the callee is found available, the callee rings until the callee performs a hook-off operation, then the call between the caller and the callee enters speech state after the appropriate P1 and P2 procedures. P4: A hook-on backward signal is sent to the MG as the signal is detected on the callee side. P5: The MG subsequently performs an H.248 NOT.req command on the TDM termination, with event Clear Back (
