1、 ITU-T RECMN*Q-923 95 4862593 Ob01088 898 INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU DIGITAL SUBSCRIBER SIGNALLING SYSTEM No. 1 (DSS 1) Q.923 (02/95) SPECIFICATION OF A SYNCHRONIZATION AND COORDINATION FUNCTION FOR THE NETWORK SERVICE IN AN ISDN ENVIR
2、ONMENT PROVISION OF THE OS1 CONNECTION-MODE ITU-T Recommendation Q.923 (Previously “CCIlT Recommendation”) IT-T RECMNrQ-923 95 H 4862591 Ob03089 724 FOREWORD The ITU-T (Telecommunication Standardization Sector) is a permanent organ of the International Telecommunication Union (ITU). The ITU-T is res
3、ponsible for studying technical, operating and tariff questions and issuing Recommen- dations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by
4、 the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993). ITU-T Recommendation 4.923 was prepared by ITU-T Study Group
5、 11 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 7th of February 1995. NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. O ITU 1995 All rights re
6、served. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. ITU-T RECMN*Q.i23 i5 4862591 b1i 446 CONTENTS 1 Scope and field of application 1 2 Normative refe
7、rences . 1 3 Abbreviations . 1 4 General . 2 5 Model of coordination between the C-plane and U-plane 3 . 6 Sequence of service primitives for coordination of C-plane and U-plane . 6.1 Sequence of primitives at NC endpoint 6.2 Sequence of primitives at N(c)C endpoint 6.3 Sequence of primitives at N(u
8、)C endpoint . 6.3.1 Recommendation X.213 2 type of service . 6.3.2 ISDN U-plane Sub-N-Service . Sequence of primitives at related NC, N(c)C and N(u)C endpoints . 6.4.1 Combined state transition diagram for SCF option 1 in case of Recommen- dation X.213 2 type of service . 6.4.2 Combined state transi
9、tion diagram for SCF option 2 in case of ISDN U-plane Sub- N-Service 6.4 7 9 7 Synchronization and coordination function for C-plane and U-plane . 8 Provision of C-plane Sub-N-Service 13 8.1 C-plane connection and U-plane connection 13 Application of SCF to Permanent Virtual Circuit (PVC) arrangemen
10、t 9.2 Sequence of primitives at N(m)C endpoint 19 10 9 13 9.1 Protocol stack for PVC arrangement . 13 9.3 Sequence of primitives at related NC, N(m)C and N(u)C endpoints 20 9.3.1 Combined state transition diagram for SCF in support of PVC 21 9.4 Synchronization and coordination function in support o
11、f PVC 23 Appendix I - Mapping between N(c)-primitive parameters and information elements of DSS 2 messages specified in Recommendation 4.2931 . 26 Recommendation Q.923 (OZ95) 1 ITU-T RECMNUQ.923 95 m 4862591 0601091 382 SUMMARY In the field of ISDN customer accesses, various protocols were defined f
12、or use in different protocol stacks to suit different needs of a range of services. These different protocol stacks have in common the control-plane, or management-plane if appropriate, and user-plane concept of the ISDN, thus require some coordination between these two planes. This coordination is
13、in particular required, if the OS1 Connection-mode Network Service (OSI-CONS) according to Recommendation X.213 2 is to be provided in an ISDN environment. For the purpose of coordination of the C-plane, or M-plane if appropriate, with the U-plane, Recommendation 1.320 “ISDN Protocol Reference Model
14、 (PRM)” I defines a function called synchronization and coordination function (SCF) and established an architecture for C- and U-plane coordination. This Recommendation specifies a state machine which provides synchronization and coordination capabilities based on the handling of network (N-) primit
15、ives, rather than processing protocol data units (PDU) used by the layer 3 protocols which form a particular stack. Any C-plane service, or M-plane service if appropriate, and U-plane service whose repertoire of (N-) primitives matches the repertoire of (N-) primitives defined in Recommendation X.21
16、3 2 can be coordinated. In addition, the repertoire of (N-) primitives was enhanced in order to make provision in the coordination process, that a connection is released by means of C-plane call control protocol after completion of the disconnection of the U-plane protocols, avoiding premature inter
17、ruption of the U-plane information flow. The SCF offers different coordination functionality which can be selected by means of predicates. This Recommendation does not address the mapping of various cause values in reason parameters contained in primitives and the handling of parameters contained in
18、 primitives. This Recommendation covers Switched Virtual Circuit (SVC) and Permanent Virtual Circuit (PVC) arrangements in the narrow-band and broadband ISDN. It is expected that there will be a growing demand for such a function since also B-ISDN and TMN may have this coordination problem. C-plane
19、CONS ISDN M-plane NC NS OSI-CONS PRM PVC SCF svc U-plane Keywords Control plane Connection-mode Network Service Integrated Services Digital Network Management plane Network connection Network Service OS1 Connection-mode Network Service Protocol Reference Model Permanent Virtual Circuit Synchronizati
20、on and Coordination Function Switched Virtual Circuit User plane 11 Recommendation Q.923 (02495) Recommendation Q.923 SPECIFICATION OF A SYNCHRONIZATION AND COORDINATION FUNCTION FOR THE PROVISION IN AN ISDN ENVIRONMENT OF THE OS1 CONNECTION-MODE NETWORK SERVICE (Geneva, 199s) 1 Scope and field of a
21、pplication The intent of this Recommendation is to specify a function which is used to provide the OS1 Network Service in an ISDN environment. Recommendation 1.320 11 identifies this function as Synchronization and Coordination Function (SCF). This Recommendation specifies the provision of the OS1 N
22、etwork Service in terms of the interrelationship between primitives at the upper and lower boundary of the Synchronization and Coordination Function (SCF) and is applicable to an ISDN customer access using an ISDN access signalling system such as the DSS 1 within the C-plane for the provision of a S
23、witched Virtual Circuit (SVC), and Permanent Virtual Circuit (PVC) arrangements. This Recommendation does not require a particular protocol within the U-plane, but rather relies on Service Data Units (SDUs) to be exchanged between the SCF as service user and the U-plane as service provider. The SCF
24、performs the synchronization between C-plane, or M-plane if appropriate, and U-plane on a per NC basis and is not concerned with any functionality which is required, if multiplexing within U-plane underlying layers is used. 2 Normative references The following Recommendations and other references co
25、ntain 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: all users of this Recommendation are therefore encouraged to investig
26、ate 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. I CCITT Recommendation 1,320 (1988), ISDN protocol reference model. Blue Book, Fascicle 111.8. 12) CCITT Recom
27、mendation X.213 (1992), Information technology - Network service definition for Open Systems Interconnection. 3 Abbreviations For the purposes of this Recommendation, the following abbreviations are used: CES Connection Endpoint Suffix CONS Connection-mode Network Service DC Disconnect Control DLCI
28、Data Link Connection Identifier FMBS Frame Mode Bearer Service ISDN Integrated Services Digital Network N- N(c)- Primitive between SCF and Transport Layer, Network Layer Primitive Primitive between SCF and C-plane Network Entity Recommendation Q.923 (02/95) 1 ITU-T RECMN*Q=923 95 9 4862591 Ob03093 1
29、55 Primitive between SCF and M-plane Network Entity Primitive between SCF and U-plane Network Entity Network Connection Network Connection within C-plane Network Connection within M-plane Network Connection within U-plane Network Service Network Service provided by C-plane Network Service provided b
30、y M-plane Network Service provided by U-plane Open Systems Interconnection OS1 Connection-mode Network Service Protocol Data Unit Protocol Reference Model Permanent Virtual Circuit Synchronization and Coordination Function Service Data Unit Switched Virtual Circuit 4 General An ISDN customer access
31、consists of one protocol stack which incorporates protocols of different layers within C-, or M-plane if appropriate, and U-plane. The relationship between protocols of adjacent layers within one plane is defined in form of interactions between these layers making use of primitives, whereby as a res
32、ult of the exchange of primitives protocol data units are exchanged between peer entities. In order to define the relationship between C-, or M-plane if appropriate, and U-plane, a Synchronization and Coordination Function (SCF) is required which relates procedures of the C-plane, or M-plane if appr
33、opriate, to the procedures of the U-plane and vice versa. The function SCF can also include a specification for the provision of the OS1 Connection-mode Network Service (CONS) in an ISDN control- plane, or management-plane if appropriate, and user-plane environment. This Recommendation is based on t
34、he ISDN Protocol Reference Model (PRM) contained in Recommendation 1.320 “ISDN Protocol Reference Model” i. The ISDN PRM identifies a Synchronization and Coordination Function (SCF) which performs the coordination between C-, or M-plane if appropriate, and U-plane of the ISDN. The model used in this
35、 Recommendation is consistent with the model defined in Recommendation 1.320 I. This Recommendation specifies the SCF functionality in order to provide an OS1 Network Service according to X.213 2 in an ISDN control- plane, or management-plane if appropriate, and user-plane environment. The SCF is sp
36、ecified in form of a state machine which provides synchronization and coordination capabilities for different C-plane call control procedures, or M-plane management capabilities if appropriate, and distinct U-plane Sub-N-Services. The desired SCF functionality can be selected by means of predicates
37、in order to accommodate the needs for the coordination of C-, or M-plane if appropriate, and U-plane protocols. The objectives of this Recommendation are: - to specify the SCF which handles primitives at three connection endpoints (C-plane, or M-plane if appropriate, U-plane and Network) for the pur
38、pose of coordination; - to provide at a “coordinated network connection endpoint” a Network Service consistent with Recommendation X.213 2; to avoid that SCF has to handle Protocol Data Units (PDUs) used by C- or U-protocol blocks in order to minimize impact of protocols on SCF; to avoid that SCF ha
39、s to handle parameters contained in primitives; - - 2 Recommendation Q.923 (0195) - to provide a comprehensive description of the relationship between peer-to-peer procedures at various layers within C- and U-plane for the purpose of conformance testing of endsystems connected to the ISDN. The SCF s
40、pecified in this Recommendation is in principle able to coordinate any C-, or M-plane if appropriate, and U-plane protocol which conforms to the primitive procedures specified at the appropriate connection endpoint. The major impact of protocols and services on SCF is caused by: - the capability of
41、the call control protocol within the C-plane to convey information relevant for Network Service (NS) users allowing the NS user to participate at C-plane connection establishment; - the characteristics of the release service within the U-plane with respect to avoidance of premature release of the C-
42、plane connection. 5 Model of coordination between the C-plane and U-plane This Recommendation specifies the provision of the network service according to Recommendation X.213 2 to the (N+ 1)-Layer at the boundary between the network layer of the ISDN and the (N + 1)-Layer. It provides for the design
43、ers of Network protocols a definition of the Synchronization and Coordination Function (SCF) in order to coordinate the Control-plane (C-plane) and User-plane (U-plane) Network protocols for the provision of an ISDN network service through the action of service primitives and the related C-plane and
44、 U-plane network protocols over the underlying services. This relationship is illustrated in Figure 1. (N + 1)-Layer ISDN network Service according to Recommendation X.213 .- c N-Service user E N-Service provider .- ._ TI 153930-93/401 FIGURE UQ.923 Relationship of the network service to the service
45、s provided by C-plane Sub-N-Layer and U-plan Sub-N-Layer Recommendation Q.923 (02/95) 3 - ITU-T RECMN*d*923 95 = 4862591 Ob03095 T28 The model adopts a concept where primitive procedures at three connection endpoints “coordinated Network Connection NC”, “C-plane Network Connection N(c)C” and “U-plan
46、e Network Connection N(u)C” are defined, in order to specify the SCF state machine as a coordination process of the three primitive procedures. At the NC endpoint the SCF provides a network service according to Recommendation X.213 21, while the primitive procedures at the two other connection endpo
47、ints depend on the capabilities of the underlying protocol blocks. The SCF state machine provides synchronization and coordination capabilities for different C-plane call control procedures and distinct U-plane Sub-N-Services, including confirmed N(u)C release. The desired SCF functionality can be s
48、elected by means of predicates in order to accommodate the needs for the coordination of C- and U-plane protocols. This Recommendation covers two options of the SCF: i) option 1 does not involve the NS user in the call establishment within the C-plane; ii) option 2 involves the NS user in the call e
49、stablishment within the C-plane. Option 1 applies to scenarios where the C-plane call control does not provide the capability to convey all the parameters for the support of a network service according to Recommendation X.213 2, while option 2 requires the conveyance of all parameters as part of C-plane call control. 6 Sequence of service primitives for coordination of C-plane and U-plane According to the model, a Network Connection (NC) provided to the Network Service (NS) user, which is the (N + 1)-Layer, is composed of a network connection provided
