1、 International Telecommunication Union ITU-T H.248.28TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (01/2007) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMSInfrastructure of audiovisual services Communication procedures Gateway control protocol: International CAS packages ITU-T Recommendation H.248.2
2、8 ITU-T H-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
3、 Coding of 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.3
4、69 Supplementary 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 service
5、s H.520H.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 MULTI
6、MEDIA SERVICES Broadband multimedia services over VDSL H.610H.619 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. H.248.28 (01/2007) i ITU-T Recommendation H.248.28 Gateway control protocol: International CAS packages Summary The international CAS package (icas) pr
7、ovides an extension to the basic CAS packages, defining additional line signals and events required for international signalling protocols. For some international protocols, such as some variants of the R2 signalling system, it would typically be necessary to implement the bcas, icas and casblk pack
8、ages to fully support the interface. In addition, register signalling will require support of either the bcasaddr package for non-compelled signalling, or a package to perform compelled signalling. This version of this Recommendation adds new read-only properties containing the current CAS state of
9、the termination, to allow the MGC to resynchronize itself in the event that it loses track of this state. Source ITU-T Recommendation H.248.28 was approved on 13 January 2007 by ITU-T Study Group 16 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. H.248.28 (01/2007) FOREWORD T
10、he International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Re
11、commendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. T
12、he 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 standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Admi
13、nistration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and com
14、pliance 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 are used to express requirements. The use of such words does not suggest that compliance with the Recommendation
15、 is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed
16、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 received notice of intellectual property, protected by patents, which may be required to implement this Recommenda
17、tion. 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/ipr/. ITU 2007 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, with
18、out the prior written permission of ITU. ITU-T Rec. H.248.28 (01/2007) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 1 4 Abbreviations 2 5 International CAS package. 2 5.1 Properties 2 5.2 Events . 3 5.3 Signals 6 5.4 Statistics 8 5.5 Procedures 8 6 CAS blocking package . 8 6.1 Propertie
19、s 9 6.2 Events . 9 6.3 Signals 10 6.4 Statistics 10 6.5 Procedures 10 ITU-T Rec. H.248.28 (01/2007) 1 ITU-T Recommendation H.248.28 Gateway control protocol: International CAS packages 1 Scope The icas package presented in this Recommendation is an extension of the bcas package (as per definition of
20、 package extensions in ITU-T H.248.1). Any termination supporting this package must also support the bcas package. Only signals and events related to generic international CAS signalling operation, both for automatic or semi-automatic working, have been considered for inclusion in the icas package.
21、Some international signalling systems may require new supervisory (line) and call set-up control (register) signals to introduce features such as re-answering, trunk offering, re-ring, operator break-in, etc. As there is no single standard mechanism to implement such features (they vary from country
22、 to country), they have not been considered in this package. If these are required, it is expected they would be implemented by defining additional signals and events in new packages that either extend the bcas package or this icas package. These packages are intended for use in analogue (one-way op
23、eration) or digital transmission systems (one-way or both-ways operations). The MGC should be unaware of the transmission details at the physical layer. The MG shall be provisioned with the actual signalling frequencies for inter-register signalling (for example 2-out-of-n in-band multi-frequency co
24、de with forward and backward compelled signalling for R2) along with their properties such as amplitude, tone duration, cadence, etc., and also their logical significance. Any timers that dictate the inter-register compelling actions shall be provisioned in the MG. For example in R2 the SF, E users
25、of this Recommendation 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 Recommendat
26、ion does not give it, as a stand-alone document, the status of a Recommendation. ITU-T H.248.1 ITU-T Recommendation H.248.1 (2005), Gateway control protocol: Version 3. ITU-T H.248.25 ITU-T Recommendation H.248.25 (/2007), Gateway control protocol: Basic CAS packages. 3 Definitions None. 2 ITU-T Rec
27、. H.248.28 (01/2007) 4 Abbreviations This Recommendation uses the following abbreviations: CAS Channel Associated Signalling E&M Ear and Mouth MG Media Gateway MGC Media Gateway Controller PDN Packet Data Network R2 Signalling System R2 SF Single Frequency 5 International CAS package Package name: I
28、nternational CAS package PackageID: icas (0x007b) Description: This package provides event and signal handling for terminations that support international CAS signalling. Version: 2 Extends: bcas version 2 5.1 Properties 5.1.1 Trunk direction Property name: Trunk direction PropertyID: trdir (0x0001)
29、 Description: Specifies whether the icas termination is an incoming, outgoing or both way trunk circuit. Type: Enumeration Possible values: IC (0x0001) Incoming. OG (0x0002) Outgoing. BW (0x0003) Both ways. Default: Provisioned Defined in: TerminationState descriptor Characteristics: Read only 5.1.2
30、 CAS near-end line state Property name: CAS near-end line state PropertyID: nels (0x0002) Description: Specifies the current CAS near-end line state of the termination by reflecting the last applied line signal. Type: Enumeration ITU-T Rec. H.248.28 (01/2007) 3 Possible values: Idle (0x01) The CAS t
31、ermination near-end is in the idle state. Seize (0x02) The CAS termination near-end is in the seize state. SeizeAck (0x03) The CAS termination near-end is in the seize acknowledge state. Answer (0x04) The CAS termination near-end is in the answer state. ClearFwd (0x05) The CAS termination near-end i
32、s in the clear forward state. ClearBack (0x06) The CAS termination near-end is in the clear back state. RelGrd (0x07) The CAS termination near-end is in the release guard state. Default: The last applied line signal. If no line signal has been applied by the MGC, idle. Defined In: TerminationState d
33、escriptor Characteristics: Read only 5.1.3 Far-end line state Property name: CAS far-end line state PropertyID: fels (0x0003) Description: Specifies the current CAS far-end line state of the termination by reflecting the last detected line event. Type: Enumeration Possible values: Idle (0x01) The CA
34、S termination far-end is in the idle state. Seize (0x02) The CAS termination far-end is in the seize state. SeizeAck (0x03) The CAS termination far-end is in the seize acknowledge state. Answer (0x04) The CAS termination far-end is in the answer state. ClearFwd (0x05) The CAS termination far-end is
35、in the clear forward state. ClearBack (0x06) The CAS termination far-end is in the clear back state. RelGrd (0x07) The CAS termination far-end is in the release guard state. Default: The last detected line event. If no line event has been deected by the MGC, idle. Defined in: TerminationState descri
36、ptor Characteristics: Read only 5.2 Events 5.2.1 Subscriber line status Event name: Subscriber line status EventID: sls (0x0006) Description: Reports the line status of the called subscriber. EventsDescriptor parameters: None 4 ITU-T Rec. H.248.28 (01/2007) ObservedEventsDescriptor parameters: Subsc
37、riber line condition Parameter name: Subscriber line condition ParameterID: lsts (0x0001) Description: Line conditions of the called subscriber. Type: Enumeration Optional: No Possible values: SLB (0x0001) Subscriber line busy. SLFC (0x0002) Subscriber line free, charge. Default: None 5.2.2 Clear fo
38、rward Event name: Clear forward EventID: cf (0x0007) Description: This event applies to an incoming interface and is reported when a “clear“ line signal occurs on the termination. The event is reported by the MG if either the timed transition to this line signal is detected or the line signal alread
39、y exists. The condition against which the signal is verified is provisioned in the MG. The parameter “clear guard timing“ can optionally be included. EventsDescriptor parameters: Clear guard timing Parameter name: Clear guard timing ParameterID: clgdt (0x0001) Description: Specifies whether the MG s
40、hall start a clear guard timer for the receipt of the clear forward signal. If the clear guard timer expires prior to the detection of clear forward signal and the CAS failure event is active, the MG shall report a CAS failure event with a “cfto“ error code. The timer value is provisioned on the MG.
41、 Type: Boolean Optional: Yes Possible values: On when the clear guard timing is requested. Off when the clear guard timing is turned off. Default: Off ObservedEventsDescriptor parameters: None 5.2.3 Clear back Event name: Clear back EventID: cb (0x0008) ITU-T Rec. H.248.28 (01/2007) 5 Description: T
42、his event applies to an outgoing interface and is reported when a “clear back“ line signal occurs on the termination. The event 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 i
43、s provisioned in the MG. The parameter “clear guard timing“ can optionally be included. EventsDescriptor parameters: Clear guard timing Parameter name: Clear guard timing ParameterID: clgdt (0x0001) Description: Specifies whether the MG shall start a clear guard timer for the receipt of the “clear b
44、ack“ signal. If the clear guard timer expires prior to the detection of clear back signal and the CAS failure event is active, the MG shall report a CAS failure event with a “cbto“ error code. The timer value is provisioned on the MG. If the clgdt parameter is not provided, the MG does not perform t
45、iming by default. Type: Boolean Optional: Yes Possible values: On when the clear guard timing is requested. Off when the clear guard timing is turned off. Default: Off ObservedEventsDescriptor parameters: None 5.2.4 CAS failure Event name: CAS failure EventID: casf (0x0005) Description: Extends the
46、bcas casf event to handle general failure or abnormal line and register signalling conditions associated with this package. EventsDescriptor parameters: None ObservedEventsDescriptor parameters: Error code Parameter name: Error code ParameterID: ec (0x0001) Description: Describes the CAS failure rea
47、son. Type: Enumeration Optional: No 6 ITU-T Rec. H.248.28 (01/2007) Possible values: CFTO (0x0006) Clear forward time out. CBTO (0x0007) Clear back time out. CNG (0x0008) Congestion: Encountered network congestion. DISC (0x0009) Information signalled by the MGC is inappropriate at the compelling sta
48、ge at MG and hence discarded. Default: None 5.2.5 Release guard Event name: Release guard EventID: rlg (0x0009) Description: This event applies to an incoming interface and is reported when a “release guard“ line signal occurs on the termination. The event is reported by the MG if either the timed t
49、ransition 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. EventsDescriptor parameters: None ObservedEventsDescriptor parameters: None 5.2.6 Congestion Event name: Congestion EventID: cng (0x000a) Description: This event applies to an outgoing interface and is reported when a “network congestion“ line signal occurs on the termination. The event is reported by the MG if either the timed transition to this line signal is detected or the line signal already exists. The c
