1、ITU-T RECIN*X-327 73 9 4862591 0594925 869 = INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU DATA NETWORKS AND OPEN SYSTEM COM M UN ICATIONS INTERWORKING BETWEEN NETWORKS X.327 (1 1/93) GENERAL ARRANGEMENTS FOR INTERWORKING BETWEEN PACKET SWITCHED PUBLIC D
2、ATA NETWORKS (PSPDNs) AND PRIVATE DATA NETWORKS FOR THE PROVISION OF DATA TRANSMISSION SERVICES ITU-T Recommendation X.327 (Previously “CCITT Recommendation”) FOREWORD The ITU-T (Telecommunication Standardization Sector) is a permanent organ of the International Telecommunication Union (ITU). The IT
3、U-T is responsible for studying technical, operating and tariff questions and issuing Recommen- dations on them with a view to standardizing teleconimunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics f
4、or study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993). ITU-T Recommendation X.327 was revised by ITU-T S
5、tudy Group 7 (i 993- 1996) and was approved under the WTSC Resolution No. 1 procedure on the 16th of November 1993. NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. O ITU 1994 A
6、ll rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical. including photocopying and microfilm, without permission in writing from the ITU. ITU-T RECMN*X.327 93 = 4862593 0594927 b3L CONTENTS Page 1 Scope 2 References 3 Defin
7、itions 4 Abbreviations . 5 General aspects . 5.1 PSPDN 5.2 Private Data Network . 5.3 General interworking arrangements 6 Interworking arrangements 6 .I 6.2 Connection release phase 6.3 Data transfer phase . 6.4 Additional considerations . Connection establishment phase . 1 1 2 2 4 Recommendation X.
8、327 (1 1/93) i ITU-T RECMN*X.327 93 m 48b259L 0594928 578 SUMMARY This Recommendation describes the interworking arrangements between PSPDNs and private data networks for the provision of data transmission services. These interworking arrangements include the capabilities required to support the net
9、work service for Open Systems Interconnection for ITU-T applications as described in Recommendation X.213. The current Recommendation has taken into account the market demand for the PSPDN to provide the gateway function allowing interconnection on a peer-to-peer basis between the public and private
10、 network. 11 Recommendation X.327 (11D3) ITU-T RECMN*X-327 93 = 4862591 0594927 404 INTRODUCTION This Recommendation is one of a set of Recommendations produced to -facilitate considerations of interworking between networks. It is based on Recommendation X.300 which defines the general principles fo
11、r interworking between public networks, and between public networks and other networks for the provision of data transmission services. Recommendation X.300 indicates in particular how collections of physical equipment can be represented as “subnetworks” for consideration in interworking situations.
12、 This Recommendation describes the interworking arrangements between PSPDNs and Private Data Networks for the provision of data transmission services. These interworking arrangements should include all the capabilities required to support the Network Service for open systems interconnection as descr
13、ibed in Recommendation X.213. Recommendation X.327 (11/93) . 111 ITU-T RECMN*X.327 73 M 4862593 0574930 126 m Recommendation X.327 GENERAL ARRANGEMENTS FOR INTERWORKING BETWEEN PACKET SWITCHED PUBLIC DATA NETWORKS (PSPDNs) AND PRIVATE DATA NETWORKS FOR THE PROVISION OF DATA TRANSMISSION SERVICES (Me
14、lbourne, 1988; revised Geneva, 1993) 1 Scope The purpose of this Recommendation is to describe the general arrangements for the interworking between PSPDNs for the provision of data transmission services. These arrangements are applicable only to the interworking involving transmission capabilities
15、and not to interworking involving communication capabilities as described in Recommendation X.300. 2 References - Recommendation X.1 International User Classes of Service in and Categories of Access to Public Data Networks and Integrated Services Digital Networks (ISDNs). - Recommendation X.2 Intern
16、ational Data Transmission Services and Optional User Facilities in Public Data Networks and ISDNs. - Recommendation X.25 Interface Between Data Terminal Equipment (DTE) and Data Circuit- Terminating Equipment (DCE) for Terminals Operating in the Packet Mode and Connected to Public Data Networks by D
17、edicated Circuit. - Recommendation X.35 Inregace Between a PSPDN and a Private PSDN which is based on X.25 Procedures and Enhancements to Define a Gateway Function that is Provided by the PSPDN. - Recommendation X.75 Packet Switched Signalling System Between Public Networks Providing Data Transmissi
18、on Services. - Recommendation X. 12 1 International Numbering Plan for Public Data Networks. - Recommendation X.2 13 Information Technology-Network Service Definitions for Open Systems Interconnection. - Recommendation X.223 Use of X.25 to Provide the OS1 Connection-Mode Network Service for CCITT Ap
19、plications. - Recommendation X.300 General Principles for Intenuorking Between Public Networks, and Between Public Networks and Other Networks for the Provision of Data Transmission Services. - Recommendation X.301 Description of the General Arrangements for Call Control Within a Subnetwork and Betw
20、een Subnetworks for the Provision of Data Transmission Services. - Recommendation X.302 Description of the General Arrangements for Internal Network Utilities within a Subnetwork and Intermediate Utilities Between Subnetworks for the Provision of Data Transmission Services. - Recommendation X.305 Fu
21、nctionalities of Subnetworks Relating to the Support of OS1 Connection- Mode Network Services. Recommendation X.327 (11/93) 1 ITU-T RECMN*X.327 93 4b2593 0594933 Ob2 m - Recommendation X.324 General Arrangements for Interworking Between Packet Switched Public Data Networks (PSPDNs) and Public Mobile
22、 Systems for the Provision of Data Transmission Services. - Recommendation X.325 General Arrangements for Interworking Between Packet Switched Public Data Networks (PSPDNs) and Integrated Services Digital Networks (ISDNs) for the Provision of Data Transmission Services. 3 Definitions This Recommenda
23、tion makes use of the following terms defined in Recommendation X.300: a) transmission capability; b) subnetwork; c) data transmission service. 4 Ab brevia tions CONS Connection-mode Network Service CSPDN Circuit Switched Public Data Network DTE Data Terminai Equipment ISDN Integrated Services Digit
24、al Network IWF Interworking Function PSPDN Packet Switched Public Data Network PSTN Public Switched Telephone Network PvtDN Private Data Network 5 General aspects This Recommendation, in describing interworking arrangements between two subnetworks (a PSPDN and a PvtDN) for the provision of data tran
25、smission services, adheres to the general principles of Recommendation X.300. The environments of these two subnetworks are described in the following subclauses. Interworking should provide the connection-mode network layer service, as defined in Recommendation X.213. 5.1 PSPDN The PSPDN provides p
26、acket switched data transmission services as defined in Recommendations X.l and X.2 for the provision of data transmission services. The PSPDN may be accessed by DTEs by the categories of access C and D as defined in Recommendation X.l. In addition, the PSPDN may also be accessed via other networks,
27、 .e. PSTN (X.10 category L, P), CSPDN (X. 1 category K, O), PSPDN (Recommendation X.75), Mobile systems (Recommendation X.324) or ISDN (Recommendation X.325), or Private data networks (this Recommendation). The PSPDN could be considered globally as an abstract OS1 relay system (or “Type I subnetwork
28、“ as described in Recommendation X.300). Figure 1 depicts the general interworking arrangement when the interworking function resides within the public network as defined in Recornmendation X.35. 2 Recommendation X.327 (11/93) ITU-T RECflN*Xm327 93 4862573 0574932 TT7 Type I subnehiuwk Tpe I subnetw
29、ork c II End System 4 i . . -a._ -. . *. .* . e. :*. IWF .*- . 0. *.*” i I %* * . .* . *.* q. 0.: I * X25 *.*O A i ITF I DTE A 3 P2 - 3 . II End system I I l I I I T071447093/601 FIGURE 1B.327 Interworking at the netwoik layer between a PSPDN and a PvtDN 5.2 Private Data Network The Private Data Net
30、work provides data transmission services. In the context of this Recommendation, the Private Data Network may be one of the following: a) a subnetwork providing packet switched data transmission services as defined in Recommendations X. 1 and X.2 for the provision of data transmission services. The
31、Private Data Network may be accessed by DTEs by the categories of access D as defined in Recommendation X.l; b) a subnetwork providing circuit switched data transmission services as defined in Recommendations X. 1 and X.2 for the provision of data transmission services. The Private Data Network may
32、be accessed by DTEs by the category of access B as defined in Recommendation X. 1; c) a point-to-point subnetwork providing leased circuit data transmission services as defined in Recommendation X. 1 ; d) a subnetwork conforming to IS0 8802. Furthermore, in the context of this Recommendation, DTEs a
33、ccessing the Private Data Network make use at the Network Layer of the protocol defined in IS0 8208. In the context of OSI, the PvtDN and associated IWF could be considered as an abstract OS1 relay system (or “Type I subnetwork as described in Recommendation X.300). Figure 2 depicts the general inte
34、rworking arrangement when the interworking function resides within the private network. Recommendation X.327 (11/93) 3 DTE A II End I I : I ITU-T RECMN*X.327 73 = 4862591 0594933 935 = Type I subnetwork Type I subnetwork r.: -0 a* . *. *. .*. i I *e*.+ f -2 .* 5 a * i *a* p : I %* . % . ! X25 i PvtD
35、N IWF : : 3 : 5 P2 _( 0. .* *.* b e . e* *o, 3 . 7- DTE B II End System I I 1 l T0714480-93/402 FIGURE 2K.327 interworking at the network layer between PvtDN and PSPDN 5.3 General interworking arrangements The arrangements at the interface between both “Type I subnetworks” should be based on Recomme
36、ndation X.25. At that interface, a mapping needs to be done between X.25 packets used on each side of the IWF. Clause 6 deals such a mapping for each phase of the connection: connection establishment, connection release, data transfer. This mapping is related to the corresponding primitives of the O
37、S1 Network Layer Service. In general, each type of primitive of the OS1 Network Layer Service, corresponds to a type of packet on the PSPDN or the PvtDN side. Each type is recognized by the “packet type” parameter. Each connection is identified by - a Logical Channel number, on the PvtDN; - NOTE - A
38、 Logical Channel number is usually local to an X.25 interface. On the same connections, its value usually a Logical Channel number, on PSPDN side. changes between two interfaces. 6 Interworking arrangements 6.1 Connection establishment phase 6.1.1 Table 1 shows the relationships between the primitiv
39、es used during the establishment of an OS1 Network Connection through interconnected PvtDN and PSPDN, and the X.25 packets associated with that connection establishment (see also Recommendation X.223). 4 Recommendation X.327 (1 1/93) ITU-T RECMN*X.327 93 m 4862591 0594934 871 m 6.1.2 described in 6K
40、.305. The actions and events at the interfaces to PvtDN or PSPDN which correspond to those primitives are also 6.1.3 In the context of interworking between PvtDN and PSPDN, Table 1 describes a mapping to be performed between X.25 packets on each interface in relation with the OS1 Network Layer servi
41、ce. In particular, the following mapping takes place: a) a received INCOMING CALL packet results in a transmitted CALL REQUEST packet; and b) a received CALL ACCEPTED packet results in a transmitted CALL CONNECTED packet. 6.1.4 identify the called and calling parties involved in the connection. Any
42、call Set-up packet sent or received by the IWF should convey OS1 Network Layer addresses, as needed to 6.1.5 Since several simultaneous connections may be required, it is necessary to identify each of those connections at the interworking between PvtDN and PSPDN (see also 5.3). In order to map the l
43、ogical channel numbering schemes on both sides, the interworking function (IWF) should connect a logical channel on one side to a logical channel on the other side, as illustrated in Figure 3. X25 a) X.Za) PSPDN X.25 I I X25 kqicai channel number I X.25 logical channel number a) 4 k 4 Netwwk layr co
44、nnection T0714490-93/a)3 a) Depending on the type of PvtDN, the two X.25 interfaces shown to the PvtDN may actually be one X.25 interface. FIGURE 3K.327 6.1.6 the connection. During the establishment of a connection, quality of service (QOS) parameters are used to adjust the quality of 6.2 Connectio
45、n release phase 6.2.1 Table 2 shows the relationships between the primitives used during the release of an OS1 Network Connection through interconnected PvtDN and PSPDN, and the X.25 packets associated with that connection release (see also Recommendation X.223). 6.2.2 described in 7K.305. The actio
46、ns and events at the interfaces to PvtDN or PSPDN which correspond to those primitives are also Recommendation X.327 (11/93) 5 6.2.3 In the context of interworking between PvtDN and PSPDN, Table 2 describes a mapping to be performed between X.25 packet on each interface in relation with the OS1 Netw
47、ork Layer service. In particular, the following mapping takes place. A received CLEAR INDICATION packet results in a transmitted CLEAR REQUEST packet (see also 6.4.1) and confirmation of the CLEAR INDICATION packet. 6.3 Data transfer phase 6.3.1 The following Tables 3 to 5 show the relationships bet
48、ween the primitives used for the transfer of data on an OS1 Network Connection through interconnected PvtDN and PSPDN, and the packets associated with that data transfer (see also Recommendation X.223). 6.3.2 described in 8m.305. The actions and events at the interfaces to PvtDN and PSPDN which corr
49、espond to those primitives are also 6.3.3 between X.25 packets in relation with the OS1 Network Layer service. In particular, the following mappings take place: In the context of interworking between PvtDN and PSPDN, Tables 3 to 5 describe a mapping to be performed a) a received DATA packet results in a transmitted DATA packet (see 6.4.2); b) a received INTERRUPT packet results in a transmitted packet; c) a received INTERRUPT CONFIRMATION packet results in a transmitted INTERRUPT CONFIRMATION packet; d) a received RESET INDICATION packet results in a transmitted RESET REQ
