1、CEPT T/TE*OB-O4*E 9 = 2326434 OOLL7bO 7T0 TTE Page E 1 Recommendation T/TE 08-04 (Copenhagen 1987, revised in Edinburgh 1988) HARMONIZATION OF THE DEDICATED CSE OF A CIRCCIT SWITCHED PCBLIC DATA NETWORK FOR TELEMATIC END SYSTEMS Recommendation proposed by Working Group T WG 10 “Terminal equipment“ (
2、TE) Text of the Recornmendation adopted bx the “Telecommirtiications“ Commi.nion: “The European Conference of Posts and Telecommunication Administrations. considering - that European Circuit Switched Data Setworks are in service. - that CCITT Recommendations X.2. X.21 and T.70 provide options. - tha
3、t a harmonization of 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.“ Edit
4、ion of February 28. 1989 . CEPT T/TE*O8=04*E 89 M 232b4hY 005lI7blI 637 M TITE 08-04 E Page 2 Table of Contents FUNCTIONAL STANDARD T/41 IN THE T.70 CASE FOR TELEMATIC END SYSTEMS DIGITAL DATA CIRCUIT (CSDN): PROVISION OF THE OS1 CONNECTION-MODE TRANSPORT O . INTRODUCTION . 3 1 . SCOPE AND FIELD OF
5、APPLICATION 3 2 . REFERENCES 3 2.1. General reference documents . 3 2.2. National network attachment specifications . 4 2.3. Additional references 4 3 . 3.1. 3.2. 3.3. 3.4. 4 . 5 . 5.1. 5.2. 6 . 6.1. 6.2. 6.3. 6.4. 6.5. 7 . 7.1. 7.2. 7.3. 7.4. 7.5. 7.6. 7.7. 7.8. 7.9. 7.10. DEFINITIONS 4 Digital Dat
6、a Circuit . 4 End System 4 Functional Standard Option . 5 DTE . 4 ABBREVIATIONS . 5 SCENARIO DESCRIPTION AND MODEL DESCRIPTION . 5 Scenario description . 5 Model description 6 CONFORMITY 6 Conformity principles 6 Conformity at layer 4 6 Conformity at layer 3 6 Conformity at layer 2 7 Conformityatlay
7、erl 7 LAYER4 . 7 Strategyforimplemcntation . 7 Options to be used . 7 Recommended parameter values 7 Addressing . 7 Class negotiation 8 Quality of service 8 Management of network connections 8 Transport protocol identification . 8 Use of the Network Service . 8 Protocol errors . 8 8 . LAYER3 . 8 8.1
8、. Strategy for implementation . 8 8.2. Connection establishment phase 8 8.3. Data transfer phase . 8 8.4. Connectionreleasephase . 9 9.1. Strategy for implementation . 9 9.2. GeneralRules . 10 9.3. SpecificRules . 10 10.1. Strategy for implementation . 11 10.2. Physical interface 11 10.3. Data signa
9、lling rates 11 10.4. Connectors . 11 ANNEXES Annex A . Contact points for additional information on circuit switched data networks 12 9 . LAYER2 . 9 10 . LAYER1 . 11 Annex B . Recommendations for implementation of X.21 14 Edition o February ?S. 1989 CEPT T/TE*O-O4*E 4 m 2326414 0011762 573 m T/TE 08
10、-04 E Page 3 FOREWORD This Functional Standard is a single Part document which defines: - the provision of the network independent basic Transport Service. as specified in CCITT Recommendation T.70 (1984), between an End System (“The Reference End System”) which uses a Digital Data Circuit and anoth
11、er End System (“The Compatible End System”) which is accessible, by permanent or switched methods, either directly from the same Digital Data Circuit. or indirectly through the provided Network Service: - the provision of a connection-mode network service that satisfies the requirements of T. 701. I
12、t is applicable to environments which support the CCITT defined Telematic Services. BRIEF HISTORY This European Prestandard (ENV) was drawn up by Working Group TE of CEPT as requested by the CEN CENELEC/CEPT Information Technology Steering Committee (ITSTC) on 1985-07- 17. This ENV was adopted by CE
13、N CENELEC on the strength of its acceptance by the following member countries: Austria, Belgium, Finland, Germany, Greece. Italy. Norway. Spain, Sweden. and United Kingdom through a voting procedure by correspondance which ended on 1987- 10-1 5. Further editorial improvements were made during a Join
14、t meeting with CEPT on 1988-01-14. O. INTRODGCTION The 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 stan
15、dards should be used. This Functional Standard specifies telecommunication function T 41 as defined in the CEN CENELEC CEPT Memorandum M-IT-O?. 1. SCOPE AND FIELD OF APPLICATION This Functional Standard defines: - the provision of the OS1 Connection-mode Transport Service for Telematic Services betw
16、een a Telematic End System (“The Reference Telematic End System”) attached to a Permanent or Switched Data Circuit, and another Telematic End System (“The Compatible Telematic End System”) which is attached to the same Data Circuit, or indirectly accessible through a Network Interworking function or
17、 interwork- ing arrangement providing support for the 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 T.70; - the provision of a connection-mode network service that s
18、atisfies the requirement of T.70. Note. See Combined 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 capab
19、ilities are limited outside the Telematic Services (e.g. it does not support the ILSAP 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 pl
20、aced on an End System in this Functional Standard are solely those necessary for operation of the protocol set specified. 2. REFERENCES 2.1. General reference documents IS0 80721 IS0 80731 IS0 8073-DAD1 IS0 83481 IS0 8348-AD21 T.70 Information Processing Systems. Open Systems Interconnection Transpo
21、rt Service Definition. Version 1986. Information Processing Systems. Open Systems Interconnection Transport Protocol Specification. Version 1986. Information Processing Systems. Open Systems Interconnection. Connection-mode Transport Protocol Specification. Addendum covering the hetwork Connection M
22、anagement Subprotocol. Version 1986-02-22. Information Processing Systems. Data Communications -Network Service defini- tion, Version 1987. Information Processing Systems. Data Communication- Addendum to the Yet- work Service Definition covering Network Layer Addressing, Version 1986. Setwork indepe
23、ndent basic Transport Service for the Telematic Services. Version 1984. Edition of February 28, 1989 CEPT T/TE*OB-OY*E 89 232bYLLi 00L17b3 LiOT M Tin 08-04 E Page 4 iX.21 X.21 X.llhis X.25 X.75 X.121 X.213 X.2 141 X.224 Intcrnationai data transmission services and optional user facilities in Public
24、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 in the packet mode and connected
25、to PDNs by dedicated circuits, Version 1984. Terminal and transit citll 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. Network Service Definition for Open S
26、ystem Interconnection for CCIT 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 CCIT Applications. Version 1984. 2.2. National network attachment s
27、pecifications/requircments If additional information regarding specific national PDNs or services is required to find out what local options can be used on u specific network. a non-exhaustive list of contact points from which such information can be obtained is given in Annex A to this document. 2.
28、3. Additional references ENV 41 104 (T/31) Packet Switched Dard Network Permanent Access- OS1 COTS over either the OS1 CONS or the T.70 case (1987) Recommendation CEPT T/CD 08-01 Packet Switched Data Network Permanent Access OS1 COTS over either the OS1 CONS or the T.70 (1987) ENV 41 105 (T/32) Pack
29、et Switched Data Network -Switched Access OS1 COTS over either the OS1 CONS or the T.7Q case (1988) Recommendation CEPT T/CD 08-06 Packet Switched Data Network Switched Accrsq OS1 COTS over either the OS1 CONS or the T.70 case (1988) CEN/CENELEC/CEPT Memorandum on the Concept and Structure of Functi
30、onal Standards for Information Technology (March 1986) CEN/CENELEC/GEPT Memorandum on the Directory of Functional Standards (March 1987) M-IT-O 1 M-IT-02 3. DEFINITIONS 3.1. Digital Data Circuit In this Functional Standard, a Digital Data Circuit is provided through a CSDN or through a concatenation
31、 of CSDNs, and may be switched or permanent. 3.2. End System The term End System is tukcn from the OS1 Reference Model terminology and is used to refer to the functionality of the communicating system in an abstract form. independent of the physical realisation. An End System in real world terminolo
32、gy may. therefore. 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 function. Note. This Functional Standard only upplies to Tclematic End Syhtcms. 3.3. DTE The term Data Term
33、inal Equipment (DTE) is used by CCITT to define the users equipment that is con- nected to a Public Data Nctwsrk (PDN). or a modem in the Public Switched Telephone Network (PSTN) case. Nule. In the general case u DTE does not nwscrsarily contain u Trunqwrt Luycr entity function. Since this Functiona
34、l Standard is only concerned with equipment that does contain Transport Layer entities, both terms will be used synonymously. Edikion of February 28. 1989 CEPT T/TE*O-O4*E 89 9 2326434 0033764 346 9 Reference End System (CSDN) TITE 08-04 E Page 5 System i End System 3.4. Functional Standard Option S
35、tandards and Recommendations support many options. In a Functional Standard based on these Stan- dards and Recommendations such an option may be: - precluded, because it may limit the interworking Capabilities: - out of the scope, but it does not limit the interworking capabilities: - kept as an opt
36、ion, 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 Functional Standard Option which cannot operate with a mandatory mechanism of the Functional Standard, or two or more Functional Standard Optio
37、ns Lvhich 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 indicate the mechanism in use. -_-Fi 4. ABBREVIATION5 CR TPDU CSDX DCE DTE FSO NC NCMS NL NS NSAP os1 QOS SNPA TCA TCR TPDU TSAP TSAP-ID Con
38、nect Request Transport Protocol Data Cnit CIRCUIT SWITCHED DATA NETWORK DATA TERMINAL EQCIPMENT Functional Standard Option h-ETWORK CONNECTION Network Connection - by a connection rcfusal. Quality of service The exchange of QOS parameters is not presently allowed in T.70. Received QOS parameters mus
39、t therefore be ignored if not supported. Management of network connections Noie. T.70 presently only allows the Telemutic End Systems that established the Network Connection to establish the Transport Connection. Transport Protocol Identification No Protocol Identifier is required for Telematic End
40、Systems connected to a CSDN. or Use of the Network Service Only the subset of the Connection-mode Network Service IS0 83481 needed to operate p.701 Transport Protocol shall be used. Protocol errors The treatment of protocol errors ia as described in section 5.4 of T.70. Note. The list of invalid TPD
41、Us (blacks) is given in Table B.4 of T.78. LAYER 3 Strategy for implementation This layer provides the subset of the OS1 Network Service that is required by m.701. Connection establishment phase Optional User Fucilities The Digital Data Circuit is established as described in X.21. No further procedu
42、re is required. Table 2 (T/TE 08-04) shows the Circuit Switched Optional User Facilities that are to be implemented. Services with “spc” status are to be implemented by the End System. If facilities with ”IC” status are implemented this must be specified in the claim of conformity. Addressing The pr
43、esent X.21 procedure does not support addressing beyond the X.i21 numbering plan with the additional subaddressing capability within the X. i211 addressing space (10 national digits). Note. The IS0 addressing scheme defined in IS0 8348/AD2 can therefore not be supported within the scape of this Func
44、tional Standard. Quality of Service No Quality of Service negotiation between the DTE and the network is presently supported in this Functional Standard. Note. Digital networks de normally display low crror ratcs and short transit delays. Longer delays may be cncountered when satellites trunks arc u
45、sed or in intcrworking with PSBN. Data transfer phase The data transfer phase is carried out as described in section 3.3.3 of T.70. Data Network Protocol Dutu Unit A minimal network layer header is present during the data transfer phase and is accommodated through the use of a two-octet network bloc
46、k header. The header comprises a one-octet length indicator followed by a Network Protocol Data Unit (NPDU) identifier network block type code. The only NPDU network block defined in F.701 is the Data Network Protocol Data Unit network data block. Bits 1 to 4 of the second octet of the DATA NPDU wit
47、h the code 0080 are used as a NPDU identifier. Edition of February 28. 1989 CEPT T/TE*08-04*E 89 m 2326414 0011768 T1 m C.2. 1 C.2.7 C.2.3 C.2.4 C.2.5 C.2.6 C.2.7 8.3.2. O I IC Direct call Multi-address calling ns Reverse charging ns RPOA selection ns Abbrebiated address calling I IC Charging inform
48、ation , IC Called line identification ! IC 8.3.3. 8.4. 9. 9.1. T/TE 08-04 E Page 9 Handling of the M-bit The calling DTE shall negotiate the TPDU size with the called DTE at the Transport layer. based on either the maximum TPDU size supported or the optimum TPDU size for the specific call. unless th
49、e default value of 128 octets is used. The agreed value will allow the sending DTE to transfer TPDUs mithout the need for segmenting at the Setwork layer and consequently the M-bit is set to zero. However. receiving DTEs must always be capable of reassembling segmented TPDUs by using the M-bit, since segmenting may take place in the network in some intenvorking situations. e.g. when the composite network connection comprises a PSDN. Error Procedures A DATA PUTDU with a length indicator value different from hexadecimal “01“ an
