1、ITU-T RECMN*Qm72 73 m 4862571 0584584 875 m INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOM MUN ICATION STANDARDIZATION SECTOR OF ITU Q.72 (03/93) GENERAL RECOMMENDATIONS ON TELEPHONE SWITCHING AND SIGNALLING FUNCTIONS AND INFORMATION FLOWS FOR SERVICES IN THE ISDN STAGE 2 DESCRIPTION FOR PACKET
2、 MODE ITU-T Recommendation Q.72 (Previously “CCITT Recommendation”) ITU-T RECMNtQ.72 73 4862571 0584b88 3TL FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union. The ITU-T is responsible for studying technical, operatin
3、g and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the ITU-T Study Groups which, in their tur
4、n, produce Recommendations on these topics. ITU-T Recommendation Q.72 was prepared by the ITU-T Study Group XI (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). NOTES 1 As a consequence of a reform process within the International Telecommunication Union (ITU), the CCITT ceased
5、to exist as of 28 February 1993. In its place, the ITU Telecommunication Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector. In order not to delay publication of this Recommendati
6、on, no change has been made in the text to references containing the acronyms “CCITT, CCIR or IFRB” or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain the proper terminology related to the new ITU structure. 2 telecommunicatio
7、n administration and a recognized operating agency. In this Recommendation, the expression “Administration” is used for conciseness to indicate both a O ITU 1994 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, incl
8、uding photocopying and microfilm, without permission in writing from the ITU. ITU-T RECMN*Q.72 93 = 48b259L 0584689 238 CONTENTS O General . 1 X.25 virtual call and permanent virtual circuit bearer service . 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.10 Scope References . Definitions Symbols and abbrevia
9、tions . Description (1.232.1) . Derivation of the functional model . Information flows . SDL diagrams for functional entities Functional entity actions (FEAs) Allocation of functions to physical entities 2 Frame mode virtual call and permanent virtual circuit bearer services 2.1 Scope 2.2 References
10、 . 2.3 Definitions 2.4 Symbols and abbreviations . 2.5 Description 2.6 Derivation of the functional model . 2.7 Information flows . 2.8 2.9 2.10 SDL diagrams for functional entities Functional entity actions (FEAs) Allocation of functions to physical entities Recommendation Q.72 (03/93) Page 1 1 1 1
11、 2 2 2 2 4 19 19 23 23 23 25 25 25 26 27 28 32 32 35 i _ ITU-T RECMN+Q.72 93 48b2593 0584b90 T5T SUMMARY This Recommendation provides the stage 2 descriptions for call set-up and release applicable to the packet mode virtual call services supported by an ISDN. The stage 2 descriptions are comprised
12、of the switching functions and signalling information flows. Stage 2, which is defined in detail in Recommendation Q.65, is part of the three stage service description methodology described in Recommendation I. 130. Recommendation Q.72 describes virtual call services which provide the unrestricted b
13、i-directional transfer of user information in a packetized manner over a virtual circuit within a B- or D-channel from one S/T reference point to another. The user information consists of layer 2 frames consistent with the layer 2 definitions of DSS 1. The data units are routed through the network o
14、n the basis of an attached label. This label is a logical identifier with local significance. 11 Recommendation Q.72 (03/93) ITU-T RECMN*:Q*72 93 4862593 0584b9L 996 Recommendation Q.72 STAGE 2 DESCRIPTION FOR PACKET MODE (Helsinki, 1993) O General The purpose of this Recommendation is to provide in
15、formation on the functions in ISDN entities and the information flows between the entities which are required to provide call control and data transfer procedures for packet mode services on the ISDN. Currently, only the ISDN virtual call and permanent virtual circuit bearer services are defined (se
16、e Recommenda- tions 1.232.1 and X.31). The following services have been identified and may be added to this Recommendation at a later date: - - - connectionless bearer service (see Recommendation 1.232.2); user signalling bearer service (see Recommendation 1.232.3); additional packet-mode bearer ser
17、vices (the framework for these services are described in Recommenda- tion I. 122). 1 X.25 virtual call and permanent virtual circuit bearer service 1.1 Scope This Recommendation provides the stage 2 descriptions for call Set-up, call release and data transfer applicable to the X.25 virtual call serv
18、ice and the permanent virtual circuit service supported by an ISDN. Note that permanent virtual circuit service has no call Set-up and release procedures. For ISDN virtual call and PVC bearer services, the emphasis is placed on the access arrangements to packet switching functions provided by an ISD
19、N or PSPDN, and not on the inter-packet-switch functions. However, future service descriptions may include details of the functional entities and information flows throughout an ISDN. This Recommendation is based on the methodology specified in Recommendation Q.65 3. This Recommendation is applicabl
20、e to the stage 3 standards for the ISDN packet-mode service. The term “stage 3” is also defined in Recommendation 1.130 i. 1.2 References The references are cited at the appropriate places in the text and the publications are listed hereafter. For data references, subsequent amendments to, or revisi
21、ons of, any of these publications apply to this Recommendation only when incorporated in it by amendment or revision, For undated references, the latest edition of the publication referred to applies. CCITT Recommendation I. 130 (1988) Method for the characterization of telecommunication services su
22、pported by an ISDN and network capabilities of an ISDN. CCITT Recommendation 1.1 12 (1988) Vocabulary of terms for ZSDNs. CCIT Recommendation 4.65 (1988) Stage 2 of the method for the characterization of serices supported by an ISDN. CCITT Recommendation 1.232.1 (1988) Virtual call and permanent vir
23、tual circuit bearer service category Recommendation 4.72 (03/93) 1 ITU-T RECMN*Q.72 73 m 4862573 0584672 822 m CCITT Recommendation 4.7 1 (1988) ISDN 64 bits circuit-mode switched bearer service. CCIT Recommendation 1.210 (1988) Principles of telecommunication services supported by an ISDN and the m
24、eans used to describe them. CCITT Recommendation 1.462 (1988) Support of packet mode terminal equipment by an ISDN. CCITT Recommendation X.3 1 Support of packet-mode terminal equipment by an ISDN. Definitions For the purposes of this Recommendation, the following definitions apply: integrated servic
25、es digital network (ISDN): See 2.3I.112 2, definition 308. service: bearer service: See 2.2I.112 2, definition 202. virtual call: See Recommendation 1.232.1 4. permanent virtual circuit: See Recommendation 1.232.1 4. 1.4 Symbols and abbreviations AU DAS FEA ISDN LE NT2 OAS OR TAS TE vc Access Unit D
26、isconnect Access Situation Functional Entity Action Integrated Services Digital Network Local Exchange Network Termination type 2 Originating Access Situation Originating Terminating Access Situation Terminating Virtual Call 1.5 Description (1.232.1) This bearer service category provides the unrestr
27、icted transfer (without alteration) of user information in a packetized manner over a virtual circuit within a B- or D-channel at the S reference point. Signalling information for virtual call and/or possibly OAM information for permanent virtual circuit services arehs transferred via B- or D-channe
28、l as described in Recommendation 1.462 7 (see Recommendation X.3 1 SI). 1.6 Derivation of the functional model The full functional model would be an end-to-end representation of the functions in a virtual call. The functional model in Figure 1-1 represents only the access portion of the full model b
29、ecause the information flows for internal ISDN or PSPDN links are not covered by this Recommendation. The model is a basis for representing the functional entities and information flows for a packet-mode call or data transfer, originated by a user interacting with FE1 and terminating to a user inter
30、acting with FE6. FE6 may transfer data to FEI while the connection is established. The functional model accommodates several access situations (AS), as described below. For each access situation, only a subset of the FES and relationship types may be employed. Each AS may have an information flow di
31、agram. 2 Recommendation Q.72 (03/93) ITU-T RECMNUQ-72 93 48b2571 0584693 769 ISDN a PSPDN T1126040-9QdOl FIGURE 1-1/Q.72 Functional model The CCAP is a functional entity that serves users, that initiates functional requests and interacts with CCs or CCPs. CCs and CCAPs are functional entities that c
32、ooperate with each other to provide the services requested by the CCAPs; rl through r6 are types of relationships between functional entities wherein information flows occur, in order to process call attempts or service requests. See 1.6.1, 1.6.2 and 1.6.3 below. The functional model addresses only
33、the functional entity actions and information flows at the network layer of the Open System Interconnect model. It is assumed that link layer functions exist which provide the necessary communication channels. The term “network layer” refers to information flows which result in Q.931 messages or X.2
34、5 packet layer messages. 1.6.1 Description of the packet call control agent (CCAP) functional entity FE1 and FE6 represent the originating and terminating CCAP functions which access the ISDN service-providing capabilities of the CC entities, using service requests for the establishment, manipulatio
35、n and release of access channel connections for a single call; establish, manipulate and release virtual calls over the established access channels; receive information relating to the ISDN call or use of facilities from the CC entity and relay them to the user: maintain ISDN call state information
36、as perceived from this functional end-point of the service (Le. a single ended view of the ISDN virtual call). 1.6.2 Description of the call control (CC) functional entity The CC functional entity supports the functionality to a) establish, manipulate and release switched access to a packet handler
37、capability or use of facilities (upon request of the CCA entity); b) associate and relate the CCAP entities that are involved in access for a particular call and/or service; c) manage the relationship between the CCAP entities involved in an ISDN call or use of facilities (i.e. reconcile and maintai
38、n the overall perspective of the call andfor service). NOTE - The CC functional entity does not support packet handling functions. Recommendation Q.72 (03/93) 3 ITU-T RECMN+Q-72 93 486259L 0584694 bT5 W r3 - FE2 - r3 - r2 _ cc _ SETUP req. SETUP-vc (Note) L r 1.6.3 Description of the call control pa
39、cket handler (CCP) functional entity FE3 CCP The CCP functional entity supports the functionality to req. ind. 300 a) establish, manipulate and release switched access to an integral ISDN packet-handling capability; SETUP-vc b) establish, manipulate and release virtual calls over established access
40、channels; c) associate and relate the CCAP entities that are involved in a particular virtual call; d) manage the relationship between the CCAP entities involved in a virtual call (Le. reconcile and maintain the overall perspective of the virtual call). 1.7 Information flows 1.7.1 Information flow d
41、iagrams for call Set-up and release The information flow diagrams for call Set-up and release for a virtual call within an ISDN or to a packet switched public data network are shown in Figures 1-2 to 1-1 1. NOTE - The absence of line across an FE indicates no involvement of the FE. FIGURE 1-UQ.72 Or
42、iginating access situation, access channel established (OAS1) 4 Recommendation Q.72 (03/93) # I SETUP req- r SETUP-OR 102 1 req. ind. II REPORT PROCEEDING req. ind. - FE2 cc 201 - 203 SETUP-OR I req. ind SETUP-OR resp. cmf. SETUP-vc ind. SETUP-vc resp. T1134000-91/603 FIGURE 1-3tQ.72 Originating acc
43、ess situation, B-channel required (OAS2) FE6 CCAP ind. 1 FIGURE 1-4tQ.72 Terminating access situation, access channel established and selected, no notification (TAS1) or conditional notification (TAS2) Recommendation Q.72 (03/93) 5 SETUP-vc req. ITU-T RECMNUQ-72 93 m 48b259L 0584b9b 478 m FE4 CCP 35
44、2 - - 353 - - 351 SETUP-TE req. ind. I SETU P-TE resp. conf. SETUP-vc req. ind. FE5 cc - 202 - r SETUP-TE r 103 req. ind. I SETU P-TE 1107 resp. conf. SETUP-vc conf. FIGURE 1-5JQ.72 Terminating access situation, no access channel established, or established channel not selected conditional notificat
45、ion (TAM) or unconditional notification (TAS3) SETUP ind. SETUP resp. SETUP ind. SETUP resp. 6 Recommendation Q.72 (03/93) ITU-T RECMN*Q.72 93 m 4862591 0584697 304 m 1 r4 - .- cc SETUP-TE req. ind. b t SETUP-TE resp. conf. RELEASE req. ind. I RELEASE resp. conf. SETUP-vc req. ind. 4 205 - - 206 I 2
46、07 208 RELEASE rq. ind. SETUP req. SETUP resp. SETUP ind. SETUP 7 resp. T1134030-91/406 a) These information flows are for user notification and are not associated with any established channel. FIGURE 1-6/Q.72 Terminating access situation, access channel established and selected, unconditional notif
47、ication (TAS3) Recommendation Q.72 (03/93) RELEASE req. DISCONNECT ind. DISCONNECT - req. ITU-T RECMNmQ.72 93 W 4862591 0584698 240 W FE1 CCAP 180 - - 181 182 183 185 RELEASE-VC req. ind. DISCONNECT req. ind. RELEASE req. ind. I RELEASE resp. conf. FE2 cc - 280 - 281 - RELEASE-VC resp. conf. Timer D
48、ISCONNECT 7 req. ind. FE3 CCP - 380 381 382 NOTE -The CCP functional entity ascertains that no other virtual calls are present on the affected B-channel. FIGURE 1-7/Q.72 Disconnect access situation 1, calling access, calling user releases virtual call RELEASE-VC ind. 8 Recommendation Q.72 (03/93) RE
49、LE SE. - req. C - ITU-T RECMNMQm7Z 93 = 48b259L 0584699 I187 FE4 CCP - 385 386 382 RELEASE-VC req. ind. I Timer DISCONNECT req. ind. I FE5 cc 280 281 - I n I I RELEASE ind. RELEASE-VC resp. cmf. II DISCONNECT req. RELEASE I 183 I- req. ind. RELEASE resp. cmf. T113405091/dO8 FIGURE 1-WQ.72 Disconnect access situation 1, called access, calling user releases virtual call Recommendation Q.72 (03/93) 9 RELEASE-VC ind. FE4 CCP - 380 381 382 ITU-T RECMNlkQ.72 73 m 4862593 0584700 729 m RELEAS E-VC resp. conf. Timer v
