1、CEPT T/CD*08-04*E 7 E 2326414 0004312 5 = T/CD 08-04 E Page 1 Recommendation T/CD 08-04 (Copenhagen 1987) HARMONIZATION OF THE DEDICATED USE OF A CIRCUIT SWITCHED PUBLIC DATA NETWORK FOR TELEMATIC END SYSTEMS Recommendation proposed by Working Group T/WG 1 O “Terminal equipment” (TE) Text of the Rec
2、ornmendation adopted by the “Telecotnmunicatiorzs” Commission: “The European Conference of Posts and Telecommunication Administrations, considering - that European Circuit Switched Data Networks are in service, - that CCIT Recommendations X.2, X.21 and T.70 provide options, - that a harmonization of
3、 Telematic End Systems is needed, - that networks may provide additional options for other applications, recommends to the members of the CEPT that this Functional Standard should be applied for Telematic End Systems implementa- tion as a minimum subset of options provided.” Edition of February 10,
4、1988 CEPT T/CD*08-04*E 87 m 2326434 0004333 7 -1 T/CD 08-04 E Page 2 Table of Contents FUNCTIONAL STANDARD T/41 DIGITAL DATA CIRCUIT (CSDN): FOR TELEMATIC END SYSTEMS PROVISION OF THE OS1 CONNECTION-MODE TRANSPORT IN THE T.70 CASE O . INTRODUCTION . 3 1 . SCOPE AND FIELD OF APPLICATION 3 2 . REFEREN
5、CES 3 2.1. General reference documents . 3 2.2. National network attachment specifications . 4 3 . 3.1. 3.2. 3.3. 3.4. 4 . 5 . 5.1. 5.2. DEFINITIONS 4 Digital Data Circuit . 4 DTE . 4 Functional Standard Option . 4 ABBREVIATIONS . 4 SCENARIO DESCRIPTION AND MODEL DESCRIPTION . 5 Scenario description
6、 . 5 EndSystem 4 Model description 5 6 . CONFORMITY 5 6.1. Conformity principles 5 6.3. Conformity at layer 3 6 6.4. Conformity at layer 2 6 6.5. Conformity at layer 1 6 7 . LAYER4 . 6 7.1. Strategy for implementation . 6 7.2. Options to be used . 7 . 7.3. Recommended parameter values 7 c 6.2. Confo
7、rmity at layer 4 6 7.4. Addressing . : . 7 7.5. Class negotiation 7 7.6. Qualityofservice 7 7.7. Management of network connections 7 7.8. Transport protocol identification . 7 7.9. Use of the Network Service . 7 7.10. Protocol errors . 7 8 . LAYER3 . 7 8.2. Connection establishment phase 7 8.3. Data
8、 transfer phase . 8 8.4. Connection release phase . 8 8.1. Strategy for implementation . 7 9 . LAYER2 . 9.1. Strategy for implementation . 9.2. General Rules . 9.3. Specific Rules . 10 . LAYER1 . 10.1. Strategy for implementation . 10.2. Physical interface 10.3. Data signalling rates 10.4. Connector
9、s . ANNEXES Annex A . Contact points for additional information on circuit switched data networks Annex B . Recommendations for implementation of p.211 9 9 9 9 11 II 11 11 11 12 13 -; Edition of February 10. 1988 I r . . 1 CEPT T/CD*O-O4*E 7 2326434 0004334 9 -1 T/CD 0%-O4 E Page 3 O. INTRODUCTION T
10、he concept and structure of Functional Standard for information systems interconnection are laid down in the CEN/CENELEC/CEPT Memorandum M-IT-O 1. The purpose of a Functional Standard is to recommend when and how certain information technology standards should be used. This Functional Standard speci
11、fies telecommunication function T/41 as defined in the CEN/CENELEC/CEPT Memorandum M-IT-02. 1. SCOPE AND JXELD OF APPLICATION This Functional Standard defines : - the provision of the OS1 Connection-mode Transport Service for Telematic Services between a Telematic End System (?The Reference Telemati
12、c End System?) attached to a Permanent or Switched Data Circuit, and another Telematic End System (?The CompatibleTelematic End System?) which is attached to the same Data Circuit, or indirectly accessible through a Network Interworking function or interwork- ing arrangement providing support for th
13、e Telematic Services. This Transport Service is provided by a protocol which is compatible with that defined in Network Independent Basic Transport Service for the Telematic Services TT.70; - the provision of a connection-mode network service that satisfies the requirement of T,70. Note. See Combine
14、d Functional Standards C/1X3 for its use in the context of such Telematic Services. Note. Conformity to this Functional Standard does not imply provision of all features of the OS1 Connection-mode Network Service, and consequently interworking capabilities are limited outside the Telematic Services
15、(e.g. it does not support the NSAP addressing scheme) with other Functional Standards. This Functional Standard specifies a set of protocols to provide the function defined above. It does not specify total End System capability. The requirements placed on an End System in this Functional Standard ar
16、e solely those necessary for operation of the protocol set specified. 2. REFERENCES 2.1. General reference documents IS0 77761 IS0 80721 IS0 80731 IS0 8073-DAD11 IS0 83481 IS0 8348-AD21 T.70 K.21 m.211 x.2lbis 1x251 rX.751 x. 1211 B.2131 p.2141 p.2241 IV-series Information Processing Systems, Data C
17、ommunications -HDLC -Description of the X.25 LAPB compatible DTE single procedure, Version October 1985-04-19, Information Processing Systems, Open Systems Interconnection Transport Service Definition, Version 1986. Information Processing Systems, Open Systems Interconnection Transport Protocol Spec
18、ification, Version 1986. Information Processing Systems, Open Systems Interconnection, Connection-mode Transport Protocol Specification. Addendum covering the Network Connection Management Subprotocol, Version 1986-02-22. Information Processing Systems, Data Communications-Network Service defini- ti
19、on, Version 1985-03-27. Information Processing Systems, Data Communication- Addendum to the Net- work Service Definition covering Network Layer Addressing, Version 1986. Networkindependent basicTransport Service for the Telematic Services, Version 1984. International data transmission services and o
20、ptional user facilities in Public data network (PDNs), Version 1984. Interface between DTE and DCE for synchronous operation on PDNs, Version 1984. Use on PDNs of DTE which is designed for interfacing to synchronous V-series modems, Version 1984. Interface between DTE and DCE for terminals operating
21、 in the packet mode and connected to PDNs by dedicated circuits, Version 1984. Terminal and transit call control procedures and data transfer system on international circuits between packet switched data network, Version 1984. International numbering plan for Public Data Networks, Version 1984. Netw
22、ork Service Definition for Open System Interconnection for CCLTT Applica- tions, Version 1986. Transport Service Definition for Open Systems Interconnection for CCITT Applica- tions, Version 1984. Transport Protocol Specification for Open Systems Interconnection for CCITT Applications, Version 1984.
23、 Recommendations of the V-series, Version 1984. Edition of February 10, 1988 ! T/CD 08-04 E Page 4 2.2. 3. 3.1. 3.2. 3.3. 3.4. 4. National network attachment specifications/requirements If additional information regarding specific national PDNs or services is required to find out what local options
24、can be used on a specific network, a non-exhaustive list of contact points from which such information can be obtained is given in Annex A to this document. DEFINITIONS Digital Data Circuit In this Functional Standard, a Digital Data Circuit is provided through a CSDN or through a concatenation of C
25、SDNs, and may be switched or permanent. End System The term End System is taken from the OS1 Reference Model terminology and is used to refer to the fiinctionality of the communicating system in an abstract form, independent of the physical realisation. An End System in real world terminology may, t
26、herefore, as an example, be either a simple self-contained system or a group of interconnected main frame computers acting as a whole. All End Systems contain a Transport Layer entity fhnction. Note. This Functional Standard only applies to Telematic End Systems. DTE The term Data Terminal Equipment
27、 (DTE) is used by CCITT to define the users equipment that is con- nected to a Public Data Network (PDN), or a modem in the Public Switched Telephone Network (PSTN) case. Note. In the general case a DTE does not necessarily contain a Transport Layer entity function. Since this Functional Standard is
28、 only concerned with equipment that does contain Transport Layer entities, both terms will be used synonymously. Functional Standard Option Standards and Recommendations support many options. In a Functional Standard based on these Stan- dards and Recommendations such an option may be: - precluded,
29、because it may limit the interworking capabilities; - out of the scope, but it does not limit the interworking capabilities; - kept as an option, in this case it is called a Functional Standard Option and it is clearly referenced; or - supported, which means that its implementation is required. A Fu
30、nctional Standard Option which cannot operate with a mandatory mechanism of the Functional Standard, or two or more Functional Standard Options which cannot operate simultaneously with each other, may be implemented in an End System, but in such cases, a system parameter shall be used to select and
31、indicate the mechanism in use. ABBREVIATIONS CR TPDU CSDN DCE DTE FSO NC NL NS NSAP os1 QOS TPDU TSAP SNPA NCMS TSAP-ID Connect Request Transport Protocol Data Unit CIRCUIT SWITCHED DATA NETWORK DATA TERMINAL EQUIPMENT Functional Standard Option NETWORK CONNECTION NETWORK LAYER NETWORK SERVICE NETWO
32、RK SERVICE ACCESS POINT OPEN SYSTEMS INTERCONNECTION QUALITY OF SERVICE Transport Protocol Data Unit TRANSPORT SERVICE ACCESS POINT TRANSPORT SERVICE ACCESS POINT IDENTIFIER SUBNETWORK POINT OF ATTACHMENT Network Connection Management Subprotocol i DATA CIRCUIT-TERMINATING EQUIPMENT - Edition of Feb
33、ruary IO, 1988 CEPT T/CD*OB-OV*E 7 E 2326434 0004336 2 W - Reference Digital Data Circuit End System (CSDN) TfCD 08-04 E Page 5 , Compatible System End System Intermediate I 5. SCENARIO DESCRIPTION AM) MODEL DESCRIPTION Figure I. Scenario description. Note. The Compatible End System should only rely
34、 on the OS1 Connection-mode Network Service functions which are used by the Telematic End Systems. The Compatible End System may be conforming to either T/31 End System Type A or B, os T/32. 5.2. Model description Figure 2 gives the protocol model of the End System. rSO 80731 Class O T.70 (T.701 sec
35、tion 3.3.3 F.211 (a) r.701 section 3.3.2 F.211 (b) Figure 2. Model description. Notes. (a) The call set-up and clearing procedure defined in p.211 apply to the switched case. (b) Other physical interfaces may apply, Le. pC.21bis and B.221. See section 3.3.1 of p.701. Permanent circuits may for insta
36、nce be provided by means of semi-permanent switched connections in a CSDN. A simplified w.211 procedure for Leased circuit service may apply in those cases (see F.211 section 5.2). Multipoint operation (see F.211 sections 5.3 and 5.4) is not part of this Functional Standard. 6. CONFORMITY 6.1. Confo
37、rmity principles This Functional Standard states requirements placed upon systems for the purpose of achieving interwork- ing. In addition the Functional Standard contains a number of Recommendations and options that are not required for interworking but may affect performance, A claim of conformity
38、 to the Functional Standard is a claim that all requirements in the body of the Standard are satisfied. For each layer, the claim of conformity shall indicate: - the supported FSO defined in the Functional Standard, - the general conformity requirements related to the base standards. Edition of Febr
39、uary 10, 1988 - CEPT T/CD*O-O4*E 7 2326434 0004337 4 * T/CD 08-04 E Page 6 6.2. 6.2.1, 6.2.2. 6.3. 6.3.1, 6.3.2. 6.4. 6.4.1. 6,4.2. 6.5. S.1. 7. 7.1. Conformity at layer 4 Options related to the Functional Standard There is no option. General conformity requirements An End System claiming conformity
40、 to this Functional Standard shall state: - the maximum TPDU (block) size supported (see T.70). Conformity at layer 3 Options related to this Fiinctional Standard The claim of conformity shall indicate: - the list of circuit switched optional user facilities implemented among those qualified as loca
41、l choice in General conformity requirements The claim of conformity shall indicate the supported operational environment: - Circuit Switched Data Network; Table 2 (see Table i). - Permanent Circuit. Table 1. Note. Code I Note c.1.1 2 c. 1.2 1 C.1.3 1 C.1.7 1 C.1.8 1 C.1.18 2 c.2.1 2 c.2.2 2 C.2.6 2
42、C.2.7 1 C.3.1 2 C.3.2 1 (2.3.3 1 c.3.4 1 Implemented I yes/no yes/no yes/no Y4no yes/no yes/no yes/no yes/no yeslno yes/no Y4no yes/no yes/no yes/no ist of Circuit Switched Optional User Facilities. 1. Optional user facility related to interworking capability. 2. Optional user facility related to pe
43、rformance. Conformity at layer 2 Options related to this Ftnctional Standard There is no option. General conformity requirements An End System claiming conformity to this Functional Standard shall indicate: - the supported value of parameter N1 (maximum frame length). Conformity at layer 1 Options r
44、elated to this Fiinctional Standard The claim of conformity shall indicate: - which physical interface(s) is (are) supported; - which connector(s) is (are) supported; - which data signalling rate(s) is (are) supported. LAYER 4 Strategy for implementation The transport service provided is as describe
45、d in IS0 80721 and p.2141. The transport protocol procedures shall be as described in IS0 80731 Class O, B.2241 Class O and T.70 section 5.1.2.3. - -+ Edition of February 10, 1988 CEPT T/CD*O-O4*E 87 232b434 0004338 b = 7.2. 7.3. 7.4. 7.5. 7.6. 7.7. 7.8. 7.9. 7.10. 8. 8.1. 8.2. 8.2.1 T/CD 08-04 E Pa
46、ge 7 Options to be used There is no option. . Recommended parameter values The following values are recommended: - TSl timer: 60 seconds, - TS2 timer: 60 seconds. Note. Timer values should be tunable. The timers should be capable of taking values of the above order of magnitude, which is considered
47、as typical for working over a PDN. Addressing End Systems conforming to this Functional Standard may use Transport Selectors for identification of their TSAPs (Transport Addresses). End Systems shall be capable of transmitting and receiving TSAP-ID fields (calling and called extension addresses para
48、meters) of variable size up to 32 octets. The encoding shall be as described in T.70 section 5.5.4.2. Note. Further detailed study is required and details will be provided in a separate document. Flexibility is recommended in implementations to allow for future developments. Class negotiation Class
49、negotiation takes place as defined in T.70. To be in conformity with the rules described in IS0 80731, a Telematic End System should accept the Transport Connection only if Class O is proposed as the preferred or the alternative class in the CR TPDU (TCR block). Note. A Telematic End System receiving user data in an acceptable CR TPDU may respond either: - with a CC TPDU indicating Class O, the user data being ignored; or - by a connection refusal. Quality of service The exchange of QOS parameters is not presently allowed in p.701.
