1、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 for CEPT Administrations to have more precise answers to their spec
2、ific 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 material from CCITT Recommendations, promote and strengthen European
3、 harmonisation, O recommends - to the member Administrations of the CEPT that they evolve their telecommunication networks towards ISDN according to the guidelines and specifications given in the attached text.” CEPT T/GSI*03-04 E 2326434 0005557 7 0 TGS03-04 Page E 1 Recommendation T/GSI 03-04 (Nic
4、e 1985, revised by correspondence, June 1987) CONNECTION TYPES Recommendation proposed by the Special Group Integration (GSI) Revised text of the Recommendation adopted by the “Telecommunications” Commission: “The European Conference of Posts and Telecommunications Administrations, CEPT T/GSI*03-04
5、E W 2326434 0005558 9 T/GSI 03-04 E Page 2 1. 2. 2.1. 2.2. GENERAL The ISDN may be described by a limited set of user-network interfaces (refer to Recommendation T/GSI 04-01) and a limited set of ISDN connection types to support the telecommunications services described in the T/GSI 02 series of Rec
6、ommendations. This Recommendation identifies and defines these connection types insofar as they relate to the provision of particular network capabilities for an ISDN. This Recommendation should be considered in conjunction with other Recommendations in the T/GSI- series, with particular reference t
7、o Recommendations T/GSI 01-02,01-06,02-01,02-02,02-03,03-01,03-02, and 04-01. For definitions of terms used in this Recommendation refer to Recommendation T/GSI 01-03. BASIC CONCEPT OF ISDN CONNECTION TYPES Introduction An ISDN provides a set of network capabilities which enable telecommunication se
8、rvices to be offered to a user (refer to T/GSI 02 series Recommendations). ISDN connection types are a description, using the attribute method of Recommendation T/GSI 01-05, of the basic low layer functions (BLLFs) of the ISDN. The set of possible values of attributes is given in section 3. It is po
9、ssible to select combinations of attribute values which are either impractical or of little use, therefore there is a set of agreed connection types in section 3. An ISDN connection is a connection established between ISDN reference points (see Recommendations T/GSI 03-01 and 04-01). All ISDN connec
10、tions are made to support a request for an ISDN service and are time dependent and of finite duration. All ISDN connections will fall under the category of one or other of the connection types. It follows therefore that an ISDN connection type is a time independent description and an ISDN connection
11、 is an instance of a type. Purpose of ISDN connection types The definition of a set of ISDN connection types provided the necessary input to identify the network capabilities of ISDNs. Other key requirements of an ISDN are contained in other T/GSI Recommendations, in particular in Recommendations T/
12、GSI 03-01, and T/GSI 04-01. In addition to describing network capabilities of an ISDN the identification of ISDN connection types facilitates the specification of network-to-network interfaces. It will also assist in the allocation of network performance parameters. It should be noted that the user
13、specifies only the service required while the network allocates resources to set up a connection of the specific type as necessary to support the requested service. It is further noted that for certain services additional functions (e.g. additional lower layer functions and/or higher layer functions
14、) may be required as depicted in Figure 1 (T/GSI 03-04). For examples of such cases refer to Recommendation T/GSI 03-01. SERVICE OFFERING NETWORK CAPABILITY Telecommunication Service Limited set of ISDN connection type I I I I I Additional network functions where re- I quired to support the service,
15、 e.g., addi- tional lower layer functions, higher layer i functions. Figure (TIGSI 03-04). The role of network capabilities in supporting service offerings. O Edition of October 31, 1987 CEPT T/GSI*03-04 E m 232b4L4 O005559 O m I. TIGSI 03-04 E Page 3 2.3. Functions associated with ISDN connection t
16、ypes Any ISDN connection type involves an association of functions to support telecommunication services. These functions are fully described in Recommendation T/GSI 03-01. 2.4. Applications of ISDN connection types Four situations have been identified thus far to which ISDN connection types apply:
17、- between two ISDN user-network interfaces, Le. between S/T reference points (refer to Figure 2a (Note. There may be a need in certain cases to differentiate between the S and T reference points. This is for further study.) - between an ISDN user-network interface and an interface to a specialized r
18、esource (refer to Figure 2b - between an ISDN user-network interface and a network-to-network interface (refer to Figure 2c - between two ISDN-to-other network interfaces (refer to Figure 2d (T/GSI 03-04). (T/GSI 03-04); (T/GSI 03-04); (T/GSI 03-04); ISDN CONNECTION 4 b ISDN CONNECTION 4 ISDN CONNEC
19、TION ISDN CONNECTION 4 b Note I. The location of reference points used in this figure is detined in Recommendations T/GSI 03-03 and 04-01. Note 2. This reference point becomes reference point M if the network specialized resource is outside the ISDN. Note 3. This box represents a network specialized
20、 resource. The use of a network specialized resource originates from a service request or is for internal administrative purposes. Some examples are: 1. a network node incorporating additional lower layer functions (ALLFs) and/or higher layer functions (HLFs) (refer to Recommendation T/GSI 03-01); 2
21、. a network provided database (which may also be used to fulfil network functions); 3. an operation or management centre. Note 4. This box represents either an existing telephone network or a dedicated network. Figure 2 (T/GSI 03-04). Applications of ISDN connection types. h CEPT T/GSI*03-04 E 3. In
22、formation Transfer Susceptance = 2326434 0005560 7 W Speech processing equipment, e.g. LRE/speech interpolation/ p. A conversion, Echo Sup- pression Equipment, null i Unidirectional, Bidirectional Symmetric, Bidirectional Asymmetric Attribute Unidirectional, Bidirectional Unidirectional, Bidirection
23、al Symmetric, Bidirectional Symmetric, Bidirectional Asymmetric Asymmetric 1. Information Transfer Mode 2. Information Transfer Rate Layer 1 Layer 2 Layer 3 8 kHz Integrity, Unstructured SDU integrity, Unstructured SDU integrity, Unstructured I National or International Connection Element Access Con
24、nection Element 8 kHz Integrity, Unstructured SDU integrity, Unstructured SDU integrity. Unstructured 8 kHz Integrity. Unstructured SDU integrity, Unstructured SDU integrity, Unstructured 64, 384, 1,536 (5), 1,920 16, 32, 64, 384, 1,536 (5), 1,920 D(16), D(64), B(64), H0(394), H12( i ,920) W6), DW)
25、Overall Connection Type Circuit, Packet 64, 1,536 (5), 1,920, analogue Common Channel Signalling (16, 32) 64, 384, 1,536 (5), 1,920 T/GSI 04-02/1, 1.431 T/GSI 04-02/2, X.25 link level (3,4) 1.451, X.25 packet level (3,4) Throughput options for FS Throughput options for FS 4.702, X.75 physical level
26、(3) 4.703, X.75 link level (3) X.25 link level (3) Q.704+SCCP, X.75 packet level (3), X.25 packet level (3) 4.704 + ISUP 1.430, 1.431, G.711 1.441, X.25 link level (3) or null 1.451, X.25 packet level (3) or null Speech processing equipment, e.g. LRE/speech interpolation/ 1. A conversion, Echo Sup-
27、pression Equipment, multi sa- tellite hops, null G.711. 4.702, X.75 physical level 4.703, X.25 link level (3) X.75 link level (3) or null X.25 packet level (3) X.75 packet level (3) 0.704+ISUP or null Unrestricted digital informa- tion Speech, 3.1 kHz Audio, or video I I. Performance (2) Error Perfo
28、rmance Slip Performance 12. Intenvorking 13. Operations and Management 4. Establishment of Switched, Semi-permanent, Switched, Semi-permanent, Switched, Semi-permanent, Connection Permanent Permanent Permanent G.821 G.821 G.822 G.822 5. Symmetry 6. Connection Configuration Topology Uniformity Dynami
29、cs Point-to-point (simple, tandem or parallel) Uniform, Non-Uniform Not Applicable Point-to-point (simple, tandem or parallel) multi-point Uniform, Non-Uniform Not Applicable Local, National, International multi-point Not Applicable Concurrent, Sequential, add/rem. 7. Structure Layer 1 Layer 2 Layer
30、 3 8. Channel (Rate) Information Channel Signalling Channel I System Packet 9. Connection Control Protocol (i) Layer 1 Layer 2 Layer 3 IO. Information Transfer Coding/Protocol (i) Layer 1 Layer 2 Layer 3 Table 1 (T/GSI 03-04). So far identified values for attributes for connection elements and conne
31、ction types. Edition of October 31, 1987 CEPT T/GSI*03-04 E = 232b4L4 0005561 9 T/GSI 03-04 E Page 5 Notes. (i) Where there are two or more S/T interfaces different values of access attributes (attributes 8, 9 and 10) may occur at each interface. Values need to be specified for each channel of the i
32、nterface structure. The role of the access attributes in determining connection types is for further study. Interfaces to network specialised resources and to other networks are for further study. - call and packet processing delays; - probability of call failure due to congestion; probability of ca
33、ll failure due to network malfunction or packet mishandling; - information transfer delay; - error performance (including attributes li(a) and ll(b) in Table I. (2) Examples of the additional performance attributes which may be defined are: (3) Use of X.25 and X.75 in ISDN can be found in X.31. (4)
34、Packet connection establishment/release may be a two stage process, stage 1 the selection of a B-Channel, stage 2 (5) 1,536 is not supported by European networks. the setting up of a packet connection. For further details see X.31. 2.5. ISDN connection involving several networks An ISDN connection m
35、ay comprise a number of tandem network connections. Figure 3 (T/GSI 03-04) shows an example in which each end network is an ISDN. The intermediate networks may or may not be ISDNs but they offer the appropriate network capabilities for the service supported by the (overall) ISDN connection. Other co
36、nfigurations are for further study. In (overall) ISDN connections involving several networks, each network provides a part of the connection and may be categorised by different attribute values. In such cases, the characterization of the performance for the overall TSDN connection is for further stu
37、dy. (OVERALL) ISDN CONNECTION 4 b ISDN CONNECTION NETWORK NETWORK ISDN 4 LA WT CONNECTION - CONNECTION CONNE CTI ON Note. Reference points are defined in Recommendations T/CiSI 03-01 and 04-01. Reference point O may or may not be an ISDN defined reference point. Figure 3 (T/GSI 03-04). Example of an
38、 ISDN connection involving several networks. 3. ISDN CONNECTION TYPES AND THEIR ATTRIBUTES O 3.1. Attributes and their values ISDN connection types are characterized by a set of attributes. Each attribute has a set of admissible values. The definitions of these attributes are given in Recommendation
39、 T/GSI 01-05. Table 1 (T/GSI 03-04) of this Recommendation lists the set of attributes and their possible values for connection types and connection elements . The concept of connection elements is explained in detail in section 4. The attributes which are associated with ISDN connection types have
40、a similarity to those used to define telecommunication services in Recommendations T/GSI 02-02 and 02-03. However, the two sets of attri- butes differ in several important aspects. For example: (a) ISDN connection types represent the technical capabilities of the network and are a means to ensure de
41、fined performance and interworking between networks. Telecommunications services supported by the ISDN are the packages offered to customers and the definition of their attributes is the means to standardize the service offerings worldwide. (b) Quality of service and commercial attributes are releva
42、nt to telecommunication services, whereas network performance, network operation and maintenance attributes are relevant to connection types. Edition of October 3 1. 1987 CEPT T/GSI*03-04 E 2326434 0005562 O T/GSI 03-04 E Page 6 3.2. Rules of association for the attribute values of connection elemen
43、ts and connection types This section describes the relationship between the attribute values of connection elements and connection types. Attribute values for connection elements: - Circuit, or Packet. Attribute values for overall connection type: - Circuit, or Packet. Association Law: - Due to the
44、nature of current packet systems the use of packet mode in any connection element would 3.2.1. Information transfer mode make the overall connection type packet. 3.2.2. Information transfer rate (kbit/s) Attribute values for connection elements: - 16 or 32 or 64 or 384 or 1,536 (*) or 1,920 Attribut
45、e values for overall connection type : - (16 or 32) or 64 or 384 or 1,536 (*) or 1,920 Association Law: - The value for the overall connection type will be equal to the lowest value of any of its connection (*) This information transfer rate will not be used to support calls between customers belong
46、ing to different European ISDNs as well as customers belonging to one European ISDN. Attribute values for connection elements: - Speech processing equipment (e.g. Low Rate Encoding equipment (LRE), speech interpolation, p/A Law The exact means of specification of the attribute is for further study.
47、Attribute values for overall connection types: - Unrestricted digital information or 3.1 kHz Audio or Speech or video. Association Law: - for an overall connection type to have the value Unrestricted digital no connection element may contain speech processing equipment or echo suppression equipment;
48、 - for an overall connection type to have the value 3.1 kHz Audio no connection element may contain circuit multiplication equipment (CME) or echo suppression equipment, or it has to disable them prior to information transfer. It must, however, contain p/A Law conversion equipment when appropriate;
49、- for an overall connection type to have the value speech it must contain p/A Law conversion equipment and echo suppression equipment when appropriate. (Values 16, and 32 are not allowed in the access connection element.) elements. 3.2.3. Information transfer susceptance conversion) and/or Echo suppression equipment and/or Multiple satellite hops or null. 3.2.4. Establishment of connection Attribute values for connection elements: - Switched or Semi-permanent or Permanent. Attribute values for overall connection type : - Switched or Semi-permanent or Permanent. Association L
