1、CEPT T/GSI*02-01 E 2326434 0005343 T (3 TGs02-01 Page 1 E Recommendation T/GSI 02-01 (Nice 1985, revised by correspondence, June 1987) SERVICE DEFINITION Recommendation proposed by the Special Group Integration (GSI) Text of the Recommendation adopted by the “Telecommunications” Commission : “The Eu
2、ropean Conference of Posts and Telecommunications Administrations, considering - the common CEPT approach to the ISDN and general CEPT assumptions and policies for the evolution towards - the I. Series Recommendations of the CCITT, as well as other CCITT Recommendations on ISDN, to which - the need
3、for CEPT Administrations to have more precise answers to their specific European requirements, i.e. - the need for CEPT Administrations to have as a base a comprehensive set of Recommendations, in order to ISDN, CEPT Administrations have contributed most significantly, to select and further define m
4、aterial from CCITT Recommendations, promote and strengthen European harmonization, O recommends - to the members of the CEPT that they evolve their telecommunication networks towards ISDN according to the following specifications.” CEPT T/GSI*OZ-OL E m 2326434 0005344 3 m T/GSI 02-01 E Page 2 PRINCI
5、PLES OF TELECOMMUNICATION SERVICES SUPPORTED BY AN ISDN 1. 2. 2.1. 2.2. 2.3. 2.4. 2.5. 2.6. 2.7. GENERAL An ISDN will support a wide range of services as described generally in Recommendation T/GSI 01-02. The purpose of this Recommendation is to provide a classification and a method of description o
6、f such services as well as giving a basis for the definition of the network capabilities required by an ISDN. These network capabilities are defined in the series Recommendation T/GSI 03. SERVICE CONCEPT Services supported by an ISDN are the communication capabilities made available to customers by
7、telecommunication service providers. An ISDN provides a set of Network Capabilities which are defined by standardized protocols and functions and enable Telecommunication services to be offered to Customers. A service provision by the network provider to a Customer connected to an ISDN may cover the
8、 whole or only part of the means required to fully support the service. The operational and commercial features associated with provision of the service are included in the service concept. The service classification and descriptions which follow are independent of different possible arrangements fo
9、r ownership and provision to the customer of the means required to support a service. Telecommunication services are described by attributes that define service characteristics as they apply at a given reference point where the customer accesses the service. Recommendation T/GSI 01-05 describes the
10、use of attributes for this purpose. A telecommunication service is composed of - technical attributes as seen by the customer, and - other attributes associated with the service provision, e.g. operational and commercial attributes. Realization of the technical attributes of a telecommunication serv
11、ice requires a combination of network and terminal capabilities and other service providing systems. Telecommunication services are divided into two broad categories, i.e. : - bearer services, and - teleservices as defined in Recommendation T/GSI 01-03. These services are described in Recommendation
12、s T/GSI 02-02 and T/GSI 02-03. A supplementary service modifies or supplements a basic telecommunication service. Consequently, it cannot be offered to a customer as a stand alone service. It must be offered together with or in association with a basic telecommunication service. The same supplementa
13、ry service may be common to a number of telecommunication services. Supplementary services correspond to the concept of user facilities in the X. series of Recommendations. A supplementary service is characterized by appropriate attributes. Their characterization requires further study. The concepts
14、 introduced in this Recommendation are illustrated in Table 1 (T/GSI 02-01). I Telecommunication service I I Bearer service I Teleservice I Basic bearer service + Basic bearer service Supplementary Basic teleservice Basic teleservice + Supplementary services Table 1 (T/GSI 02-0 1). Categorization of
15、 telecommunication services. The combined usage of more than one Telecommunication service during a communication is possible and defined as Multiservice operation (see Appendix 1 for the definition of Multiservice operation). Edition of October 31, 1987 CEPT T/GSI*02-OL E 232b414 0005345 3 T/GS102-
16、01 E Page 3 3. CUSTOMER ACCESS TO TELECOMMUNICATION SERVICES SUPPORTED BY AN ISDN 3.1. Considering the reference configurations defined in Recommendation T/GSI 04-01, customers can access various telecommunication services at different access points. Figure 1 (T/GSI 02-01) shows these points. This f
17、igure takes into account that the service provision by the network provider to a customer connected to an ISDN may cover the whole or only part of the means required to fully support the service. 3.2. Figure 1 (T/GSI 02-01). Customer access to services supported by an ISDN. The definitions of the ac
18、cess points introduced in Figure 1 (T/GSI 02-01) are as follows: i) Access points 1 (reference point T) and 2 (reference point S) are the access points for bearer services supported by an ISDN. The choice between access points 1 (T) and 2 (S) depends on the ownership and form of provision (to the cu
19、stomer) of the communications equipment at the customer premises. The service classification and descriptions in the following are independent of different possible arrangements for such provision. At access point 4 (reference point R), depending on the type of terminal adaptors provided, other CCIT
20、T standardized services may be accessed, e.g. according to the X. and V. series of Recommenda- tions. iii) At access points 3 and 5 (user to terminal interface). Teleservices are accessed-the teleservice concept includes the terminal capabilities. ii) 3.3. The following customer entities may be conn
21、ected at access points I and 2: - customer terminals; - customer system, e.g. PABXs, LANs, service vendor system; - private networks. Note. Customer terminals and systems may be private or provided by Administrations or RPOAs. All customer equipment connected to an ISDN interface at one of these acc
22、ess points must meet the specifications of the protocols at that interface for all the layers that are included in the definition of the telecommunication service used. For some telecommunication services, the service definition also covers some terminal functions and characteristics in addition to
23、those specified by the protocols at the interface. 4. CAPABILITIES TO SUPPORT A TELECOMMUNICATION SERVICE 4.1. The capabilities required to fully support a telecommunication service for a customer connected to an ISDN include : - network capabilities; - terminal capabilities, when required; - other
24、service providing capabilities, when required; - operational and commercial features associated with the service provision (i.e. sales or marketing aspects), Edition of October 31, 1987 CEPT T/GSI*OZ-OL E W 232bYL4 O005346 5 Network capabilities specified LLF HLF cation service BLLF ALLF“ BHLF AHLF“
25、 - Bearer service x opt - T/GSI 02-01 E Page 4 Terminal capabilities specified I LLF HLF BLLF ALLF BHLF AHLF - - - - 4.2. Network capabilities are described in detail in Recommendation T/GSI 03-01. Two different levels of ISDN network capabilities are introduced: - low layer capabilities, which rela
26、te to bearer services; - high layer capabilities, which together with low layer capabilities relate to teleservices. The low layer capabilities are defined as a set of low layer functions (LLF) (relating to layers 1-3 in X.200) which provide the capability for the carriage of user information over a
27、n ISDN connection. These functions include: - basic low layer functions (BLLF) supporting the necessary layer 1-3 requirements; - additional low layer functions (ALLF) supporting, in addition to BLLFs, lower layer requirements of High layer capabilities are defined as a set of high layer functions (
28、HLF) generally associated with layers 4 to 7 in X.200. High layer functions are subdivided into basic high layer functions (BHLF) and additional high layer functions (AHLF). Note. Dependent upon national regulations, ALLF, BHLF and AHLF may be provided by Administrations, RPOAs or other suppliers. s
29、upplementary services. Teleservice 4.3. The concept of describing network capabilities in terms of low layer capabilities and high layer capabilities can equally be applied to describe terminal capabilities. In the description of teleservices the HLF and LLF are included in the service definition. I
30、n the case of bearer service definition the terminal capabilities are not included but the terminal must conform to the LLF of the bearer service. Note. The relationships between service categories, network/terminal capabilities and functions are illustrated in Table 2 (TIGSI 02-01). x opt opt opt x
31、 opt x opt X 4.4. The operational service capabilities associated with a service offering may include capabilities for mainte- nance, charging, user control of service features, etc. The use of such capabilities may involve terminal-network communication and may therefore be viewed as specific appli
32、cations. A more precise description of these capabilities and their relationship to Recommendation X.200 needs further study. 5. TELECOMMUNICATION SERVICE CHARACTERIZATION 5.1. A telecommunication service supported by an ISDN is characterized and described by service attributes. They are two groups
33、of service attributes applicable to user information flows: - low layer attributes; - high layer attributes. Bearer services are characterized only by low layer attributes. Teleservices are characterized by both low layer attributes and high layer attributes. The basic characteristics of a telecommu
34、nication service are described by the basic service attributes. The additional characteristics of a supplementary service are described by additional service attributes. Edition of OAober 31,-1987 Commercial features/ operational capabilities X CEPT T/GSI*OZ-OL E W 232b414 0005347 7 T/GSI 02-01 E Pa
35、ge 5 The relationship between telecommunication service attributes and low/high layer functions is illustrated in Table 3 (T/GSI 02-01). services Basic service attribute i attributes (Note 1 ) i Supplementary Supplementary low layer high layer attributes attributes (Note 2) (Note 2) Basic low Basic
36、high layer attributes layer attributes J J Service attributes (Teleservice (Teleservice only) only) _-_- - Corresponding or terminal * p;:y Fj FI Norr I. A supplementary service cannot be otered as a stand alone service. This attribute is mainly concerned with supplementary services associated with
37、basic telecommunications services. It could be split into sub-attributes depending on results of further studies. Supplementary services could also have an influence on some attributes characterizing basic telecommunication services. Nofe 2. The characterization of supplementary services with attrib
38、utes requires further studies. Table 3 (T/GSI 02-0 i). Relationship between service attributes and low/high layer functions. 5.2. 5.2.1. Bearer services supported by an ISDN Bearer services supported by an ISDN provide the capability for information transfer between ISDN access points 1 or 2 and inv
39、olve only low layer functions. The customer may choose any set of high layer (at least 4-7) protocols for his communication, and the ISDN does not ascertain compatibility at these layers between customers. An example of a bearer service is a circuit-mode 64 kbit/s unrestricted 8 kHz structured beare
40、r service category. Bearer services are characterized by a set of low layer attributes in Recommendation T/GSI 02-02. These attributes are classified into three categories: - information transfer attributes; - access attributes; and - general attributes, including operational and commercial attribut
41、es. The bearer capability defines the technical features of a bearer service as they appear to the user at the appropriate access points (1 or 2). For the time being, the bearer capability is characterized by information transfer and access attributes. A bearer capability is associated with every be
42、arer service. Note. It is likely that some quality of service parameters (attributes corresponding to Recommendation T/GSI 02-02) -such as error rate or call set-up delay-should be extracted in order to form a new attribute allocated to the information transfer category. Identification and the defin
43、ition of those parameters are under study. 5.2.2. Edition of October 31, 1987 CEPT T/GSI*OZ-OL E 232bYLY 00053Y8 9 T/GSI 02-01 E Page 6 5.2.3. A bearer service provides the user with the possibility of gaining access to various forms of communication, covering for example: - information transfer bet
44、ween users employing the same access points (1 or 2) and access attributes (see - information transfer between users employing different access attributes at the access points (1 or 2) - information transfer between a user and a separate resource providing high layer functions (see Figure 2c Figure
45、2a (T/GSI 02-01); involved (see Figure 2b (T/GSI 02-01); (T/GSI 02-01). Access attributes A Access attributes A Access attributes B Access attributes B v - Scope of bearer service. _ Defined by information transfer attributes. *Access point to be defined but not necessarily subject to CEPT Recommend
46、ations (see Recommendation T/GSI 03-01). Note 1. Further study is required on bearer services extending beyond the ISDN. Note 2. Further study is required on possible communications involving bearer services with different values allocated to information transfer attributes. Figure 2 (T/GSI 02-01).
47、Examples of bearer service operation. 5.2.4. A bearer service may be used to convey various user types of information within an established information transfer path. This particular usage is defined as a multimedia application (see Appendix 1 for further information). 5.3. 5.3.1 Teleservices suppor
48、ted by an ISDN Teleservices provide the full capacity for communication by means of terminal and network functions and possibly functions provided by dedicated centres. A teleservice supported by an ISDN should use only one (or a small number of) bearer capability recommended by CCITT. It should be
49、noted that in the case where more than one of the recommended bearer capabilities is used for a given teleservice, network interworking functions may be required under the responsibility of the teleservice provider. However, a user operating a specific application is not prevented from using a terminal compatible with a given teleservice in association with a bearer capability not recommended for this teleservice. Examples of teleservices are telephony, Teletex, Videotex and message handling. 5.3.2. Teleservices are characterized by a set of low layer attributes, a set of high
