1、CEPT T/SF*31-OL*E 232b4L4 0007L83 L T/SF 31 -01 E Page 1 - Recommendation T/SF 31-01 (Cannes 1983, revised in Odense 1986) GENERAL ASPECTS OF AN INTEGRATED SERVICES DIGITAL NETWORK (ISDN) Content 1. GENERAL . 1 2. TYPES OF ISDN SERVICES. 2 3. USER INTERFACES (EXCLUDING ISPBXs) . 3 4. CALL HANDLING P
2、ROCEDURES 3 5. CHANNEL ALLOCATION . 5 6. RATE ADAPTION . 5 7. NUMBERING ADDRESSING AND SERVICE INDICATION ASPECTS . 5 8. DEFINITION OF BUSY IN AN ISDN . 6 Figure 1 (T/SF 31-01): Bearer Service attributes 8 Figure 2 (T/SF 31-01): Illustration of essential differences between Bearer Services, and Tele
3、services 8 Figure 3 (T/SF 31-01): Inter-relationship of Services 9 Figure 4 (T/SF 31-01): Procedural aspects of call offering 10 O 1. GENERAL 1.1. Services Design That, in general, the design of services and the location of their features must aim to meet the service requirements in full, including
4、maintenance, recognise the varying degrees of usage and provide the Service and Supplementary Service. 1.2. flexibility of ISDN Design That the ISDN should be able to respond to new requirements quickly and at reasonable cost. The design should provide flexibility to meet foreseen requirements and t
5、ake advantage of improved technology. Commercial Benefits of the ISDN That Administrations may utilize the technical facilities of the ISDN to provide customers with one or more of a range of services via common access point in their premises. This access point offers the capability to permit the us
6、e of more than one service simultaneously. That this range includes services presented as both Bearer and Teleservices, but Administrations will normally choose whether to offer customers a particular facility in the form of a Bearer Service, a Teleservice or both. 1.3. 1.3.1. O 1.3.2. . 1.3.3. That
7、 the ISDN is seen as a powerful service provision tool for administrations whose main commercial benefits appear to be: - the ease and speed with which the composition of a given customers package of Bearer Services can the ease and speed with which new types of Bearer Services can be offered to a c
8、ustomer once that - the expected improvement in quality of service on calls connected via the ISDN; the eventual attraction when ISDN penetration and availability is more general, of being a subscriber That the customer services that may be offered in the form of Bearer Services available at the net
9、work (T“) interface fall into two groups: Leased Point-to-Point Permanent Circuits (accessed via 64 kbit/s, 384 or 1920 kbit/s); - Access via 64 kbit/s, 384 kbit/s or 1920 kbit/s to one or more of a number of switched services; be altered from time-to-time to take account of changing needs; customer
10、 is served by the ISDN; to a service used by correspondents. 1.3.4. O Edition of January 15, 1988 CEPT T/SF*3L-OL*E , 232b414 0009184 3 T/SF 31-01 E Page 2 1.3.5. 1.4. 1.5. 1.6. 1.7. 1.8. 1.9. 1.9.1. 1.9.2. 1:9.3. 2. 2.1. - Access via 64 kbit/s and 16 kbit/s to packet mode services. That the custome
11、r services that may be offered in the form of Teleservices from a common ISDN access also fall into two groups: - Leased Point-to-Point Permanent Circuits; - Access to one or more of a number of switched services. Teleservices, however, include the terminal apparatus at the customer premises and thi
12、s apparatus may itself introduce a number of further variants in the presentation of the service tothe customer. security That for administrative security reasons, certain sensitive functions (e.g. charging, programming, traffic management) shall be located only inside premises or equipment that is
13、physically secure from interference by persons other than authorised administration staff. Charging That the administration shall have the ability to charge at the outset, during and at the end of a call. Charging requirements may be mainly in accordance with the work done by the network in providin
14、g the service. This needs flexibility and typically requires: (a) processing cost (b) switching cost (c) Transmission cost (d) signalling cost as possible components of charging. Testing That the network should be able to prove remotely whether or not the Network Termination is in working order. It
15、is also desirable to be able to remotely prove whether or not the users terminal equipment is in working order. For further SF study. Power Failure That under conditions of local power failure at least one terminal on the basic access should be operational for basic telephony service. In addition al
16、arm (warning) transmission should also be possible under these conditions. Provision, Removal and Withdrawal of Service That the provision and removal of service and the temporary withdrawal of service under any conditions is covered by the individual service. Physical Connection For Basic Access Te
17、rminals That the ultimate aim should be the standardization of a single universal socket allowing the connexion of any type of terminal with the appropriate interface to the ISDN basic access. For ISPBX Terminals That, where administrations are able to do so, the ultimate aim should be the standardi
18、zation of the same socket for connexion of terminals connected to ISPBXs. That the terminals connected to the ISDN basic access and behind the ISPBX should be compatible. TYPES OF ISDN SERVICES Service Types That the ISDN shall provide a set of Bearer Services and a range of Teleservices. The ISDN s
19、hould also provide Supplementary Services. Standardized Teleservices are listed in Recommendation T/SF 3 1-02. Edition of January IS, 1988 CEPT T/SF*33-O1*E W 2326414 0009385 5 2.2. 2.3. 2.4. 3. 3.1. 3.1.1. 3.1.2. 3.1.3. 3.1.4. 3.2. 3.2.1. 3.2.2. 3.2.3. 3.3. 3.3.1. 3.3.2. 3.4. T/SF 31-01 E Page 3 Be
20、arer Service That a set of internationally standardized Bearer Services should be offered by administrations. A list of Bearer Services is given in Recommendation T/SF 31-02. The Circuit-mode bearer services are typically characterized by the provision of user information over one type of channel an
21、d signalling over another type of channel. The packet-mode bearer services involve packet handling functions. Note: The multiplexing of multiple sub-rate information streams made by users are their own responsibility. Description of Bearer Services Bearer Services are described by a number of attrib
22、utes. These attributes are described and defined in CCITT Recommendation 1.2 11. Introduction of New Services That the introduction of new services should not prejudice telephony or cause any significant penalties to be incurred by the major services in the network. USER INTERFACES (EXCLUDING ISPBXs
23、) Basic Access Capabilities That for the basic access the capability of carrying at least 2 simultaneous calls should be provided. These may use one or more channels provided exclusively for the transfer of user information and a channel whose primary use is for user-to-network signalling. That the
24、bothway signalling system between the users premises and the network shall be adequate to support existing services and also provide the capability of introducing new services on the basic access without adversely affecting the existing or new services. That the user should be given the possibility
25、to ascertain the state of his access channels, for instance whether a channel is busy or whether a channel is allocated to a particular service. This may be provided automatic- ally. That the user should be able to employ his access to the network for the operation of one or more teminals of either
26、the same or different type either sequentially or simultaneously, using the same links between his premises and the local switching node. The number may be restricted by the number of parts on the Network Termination. Connection of More than One Terminal That it would be possible to connect up to an
27、y mixture of terminals up to a maximum of 8 terminals to thesame basic access. That for voice communication it should be possible for up to 2 telephone terminals at each destination to be used by the same call. That for the connexion of more than one non-voice terminal to be used on the same call fu
28、rther study is required. Electrical and Protocol Characteristics Basic Access That one interface (the “S/T” interface) exhibiting standardized electrical and protocol characteristics shall be adopted for the ISDN Basic Access. Note: It is recognised that administrations may wish to offer other stand
29、ardized interfaces vice Terminal Adaptor e.g. X.21, X.25, standardized interfaces vice Terminal Adaptor e.g. X.21, X.25, V Series, analogue telephony, telex for an iterim period in order to make ISDN attractive to users. Primary Rate That one interface exhibiting standardized electrical and protocol
30、 characteristics shall be adopted for the ISDN Primary Rate Access. The Primary Rate Access interface should permit: - any number of subscriber channels from a small number (greater than one to be agreed by administra- - one or more signalling channels as dictated by trafic characteristics. Terminal
31、 Intercommunication That it is desirable to be able to communicate between terminals connected to the same network termination without placing a call towards the public network. tions) but with no upper limit; Edition of January 15, 1988 CEPT T/SF*31-OL*E !D 232b434 0009386 i-= - T/SF 31-01 E Page 4
32、 4. 4.1. 4.1.1. 4. I .2. 4.1.3. 4.1.4. 4.2. 4.2.1. 4.2.2. 4.2.3. 4.3. 4.3.1. 4.4. 4.4.1. 4.4.2. 4.5. 4.6. CALL HANDLING PROCEDURES User Control Procedures That it should be possible to Set-up, cleardown and manipulate calls separately on each channel. That in the long term and where services make us
33、e of network based resources, a common user control procedure shall apply to Services and Supplementary Services as far as is praticable. That it should be recognised that the existing control procedures for Services and Supplementary Services (as described in the SF Handbook and appropriate CCITT R
34、ecommendations) should be retained for a interim period. However, new control procedures designed to take advantage of the ISDNs separate channel signalling capability should be defined for all existing services. That the administration shall have the option to introduce the new control procedures f
35、or all customers co-incident with the opening of an ISDN exchange which would, for example, provide the opportunity to show the ISDN to its best advantage. Priority That an incoming call be afforded priority under call collision conditions. (It is assumed that adequate measures such as “time-outs” w
36、ill be available to avoid malicious “blocking” problems.) Outgoing Culls That, in the case of outgoing calls, the network should not offer priority of one service over another, unless this is specifically requested by the user or administration, in which event it shall remain under the control of th
37、e administration. That terminals providing for more than one service shall not offer a priority of one service over another, for calls unless this is specially requested by the user or the administration, in which event it shall remain under the control of the administration. Incoming Calls to a Loc
38、ally Busy Terminal That where a terminal is not in use on an outgoing call, but is in use on some local task for the user, an incoming call should be treated by the users terminal as follows. Voice Terminal An incoming call should normally not be allowed to interrupt the local task, but an indicatio
39、n that there is an incoming call waiting may be given. Auto Repeat Attempts That where call data is stored at a terminal and calls (to the same destination) are initiated at a later time, the Automatic repeat call facility shall be limited to make up to 4 calls at intervalls as agreed by individual
40、administrations. A preferred method of meeting this requirements would be to utilise the Completion of Calls Meeting Busy service. In order to minimise increasing congestion in the network it is desirable that the network shall be able to protect itself against uncontrolled auto repeat call attempts
41、 for example by the use of an appropriate charging method. Other methods are for further study. Validation of Network Requests That the ISDN should validate all signals that affect the handling of a call within the network, e.g. Basic Call Demands, Supplementary Services Demands, Activation/Deactiva
42、tion and Call Release. Change of Service During an Established Cali That it should be possible to change between the service offered by administrations during an established call. Whether this applies to Bearer and/or Teleservices requires further study. Note: In the case of Bearer Services it shoul
43、d be recognised that, at least in the early stages of ISDN, it is likely that declaration of the intention to change services during a call, before the call is made, will be required for technical reasons. However, when this is available, the following should occur during or after an attempt change.
44、 (a) the original service not be disconnected before the substituting service is available; (b) the user should receive a suitable indication when the required service is available; (c) the user should receive a suitable indication when the required service is not available. Edition of January 15, 1
45、988 4.7. 5. 5.1. 5.2. 5.2.1. 5.2.2. 5.2.3. 5.2.4. 6. 6.1. 6.2. 7. 7.1. 7.2. CEPT T/SF*31-OL*E 2326434 O009187 9 = T/SF 31-01 E Page 5 Sequential changes between Services That where a sequential change from one service to another is required this should be possible at any time during the progress of
46、the call. However, during the early stage of ISDN when ISDN and existing networks are interworking, the subscriber will be required to indicate the possibility of a sequential change from one service to another at the time of the call set-up by means of a request for a suitable Bearer Service. CHANN
47、EL ALLOCATION Subscriber Control of Channel Allocation That administrations shall be able to allow users to exercise some options over the ISDN channel allocations made in relation to trafic type and direction but administrations should control at least the technical function of signalling and chann
48、el allocation in subscribers premises served by an ISDN; Rules for Channel Allocation That rules should be applied to channel allocation, and these may not be identical for both incoming and outgoing trafic on the same access; That the General Rules should be: i) the operation of the rules should no
49、t restrict unduly the quantity of traffic that a user can offer to the Network; ii) the operation of rules should not allow the completion of incoming calls to be unduly obstructed; iii) the administration should apply standard rules for channel allocation. This would be part of the access and should be included in the basic charge for access to an ISDN. That users should be able to choose options within the channel allocation rules, e.g. to take account of time periods or variations of terminal equipment; That administrations should be able to gain access to a record of all ch
