1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 8 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU).4%27/2+).G0G0“%47%.G0G0.%47/2+3%.%2!,(b) that Recommendation X.213 is the network service definition for open systems interconnection forCCITT applications;(c) that Recommendation X.300 defines the general
2、principles for interworking between public networks,and between public networks and other networks for the provision of data transmission services; and thatRecommendation X.300 indicates in particular how real pieces of network equipment can be represented assubnetworks;(d) that different types of s
3、ubnetworks need to be considered, which all support the OSI connection-modenetwork service in different degrees: and that the different ways in which the different types of subnetworks supportthe OSI connection-mode network service need to be described,unanimously declares(1) that the description of
4、 those functionalities of a subnetwork which relate to the connection establishmentphase of the OSI connection-mode network services is given in 6;(2) that the description of those functionalities of a subnetwork which relate to the connection release phaseof the OSI connection-mode network service
5、is given in 7;(3) that the description of those functionalities of a subnetwork which relate to the data transfer phase of theOSI connection-mode network service is given in 8.CONTENTS0 Introduction1 Scope and field of application2 References3 Definitions4 Abbreviations5 Overview and general charact
6、eristics6 Connection establishment phase7 Connection release phase8 Data transfer phaseAnnex A - Functionality related to data transfer phase of the OSI connection-mode network service within the differenttypes of subnetworks.2 Fascicle VIII.6 - Rec. X.305Annex B - Sets of protocols for the provisio
7、n of the OSI connection-mode network service over different examples ofsubnetworks.0 IntroductionThis Recommendation is one of a set of Recommendations produced to facilitate consideration ofinterworking between networks. It is related to Recommendation X.300, which defines the general principles fo
8、rinterworking between public networks, and between public networks and other networks for the provision of datatransmission services. Recommendation X.300 indicates in particular how collections of physical equipment can berepresented as “subnetworks“ for consideration of interworking situations.Thi
9、s Recommendation describes those functionalities of subnetworks which relate to the support of the OSIconnection-mode network service.This Recommendation does not describe those functionalities of subnetworks which do not relate to thesupport of the OSI connection-mode network service (e.g., those a
10、rrangements in Recommendation X.301 which donot relate to the support of the OSI connection-mode network service).1 Scope and field of applicationThis Recommendation defines those functionalities of subnetworks which relate to the OSI connection-modenetwork service in terms of:a) the actions and eve
11、nts which occur at the interfaces to a subnetwork;b) the parameters associated with each action and event, and the form which they take;c) the interrelationship between, and the valid sequences of, these actions and events, for a givenconnection;d) the interrelationship between different connections
12、 established through the same subnetwork.This Recommendation also defines the ways different types of subnetworks support the OSI connectionmodenetwork service, by including within the subnetwork part or all of the functionalities of subnetworks which relate to theOSI connection-mode network service
13、.The principal objective of this Recommendation is to provide guidance for consideration of interworkingbetween subnetworks, in relation with the support of the OSI connection-mode network service.This Recommendation does not specify products, or implementations of those functionalities in real netw
14、orkequipment, nor does it constrain the distribution of those functionalities among the pieces of network equipmentconsidered within a given subnetwork (e.g. PDNs, IWFs, ISDNs,2 ReferencesRecommendation I.430 - Basic user-network - Layer 1 specificationRecommendation I.431 - Primary rate user-networ
15、k interface - Layer 1 specificationRecommendation T.70 - Network-independent basic transport service for the telematic servicesRecommendation Q.701 - Functional description of the signalling system (Message Transfer Part)Recommendation Q.702 - Signalling data linkRecommendation Q.703 - Signalling li
16、nkRecommendation Q.704 - Signalling network functions and messagesRecommendation Q.705 - Signalling network structureRecommendation Q.706 - Message Transfer Part signalling performanceRecommendation Q.707 - Testing and maintenanceFascicle VIII.6 - Rec. X.305 3Recommendation Q.711- Functional descrip
17、tion of the Signalling Connection Control Part (SCCP) of SignallingSystem No. 7Recommendation Q.712 - Definition and functions of Signalling Connection Control Part messagesRecommendation Q.713 - Signalling Connection Control Part (SCCP) formats and codesRecommendation Q.714 - Signalling Connection
18、Control Part proceduresRecommendation Q.921 - ISDN user-network interface data link layer specificationRecommendation Q.931 - ISDN user-network interface layer 3 specificationRecommendation X.21 - Interface between data terminal equipment (DTE) and data circuit-terminating equipment(DCE) for synchro
19、nous operation on public data networksRecommendation 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 networksby dedicated circuitRecommendation X.75 - Packet switched signalling
20、 system between public networks providing data transmissionservicesRecommendation X.200 - Reference model of open systems interconnections for CCITT applicationsRecommendation X.213 - Network service definition for open systems interconnection for CCITT applicationsRecommendation X.223 - User of X.2
21、5 to provide the OSI connection-mode network serviceRecommendation X.300 - General principles for interworking between public networks, and between publicnetworks and other networks for the provision of data transmission servicesRecommendation X.301- General arrangements for call control within a su
22、bnetwork and between subnetworks forthe provision of data transmission services3 Definitions3.1 This Recommendation makes use of the following terms defined in Recommendation X.200:a) network-connection;b) network layer;c) network service;d) subnetwork.3.2 This Recommendation makes use of the follow
23、ing terms defined in Recommendation X.213:a) calling network service user;b) called network service user.3.3 This Recommendation makes use of the following terms defined in Recommendation X.300:a) type I subnetwork;b) type II subnetwork;c) type III subnetwork;d) type IV subnetwork.4 Fascicle VIII.6
24、- Rec. X.3053.4 ConventionsThe arrows used in the figures of 6 to 8 indicate in a generic way the exchange of information that occurs atthe interface of the subnetwork. Their purpose is not to represent the NS primitives conveyed through the horizontalabstract interface between the network layer and
25、 the transport layer.4 AbbreviationsCCSN Common channel signalling networkCONS Connection-mode network serviceCS Circuit switchedCSPDN Circuit switched public data networkDTE Data terminal equipmentISDN Integrated services digital networkIWF Interworking functionLAPB Link access procedure balancedMT
26、P Message transfer partMSS Mobile satellite systemsNC Network connectionNL Network layerNS Network serviceNSP Network service partOSI Open systems interconnectionPLMN Public land mobile networkPLP Packet level protocolPS Packet switchedPSDN Packet switched data networkPSPDN Packet switched public da
27、ta networkPSTN Public switched telephone networkQOS Quality of serviceSCCP Signalling connection control part5 Overview and general characteristics5.1 The functionalities of a subnetwork include provision for the transparent transfer of data between twointerfaces to the subnetwork, on a connection (
28、NC). More than one NC may exist between the same pair of interfaces.Fascicle VIII.6 - Rec. X.305 5Note 1 - The extent to which a subnetwork can support more than one connection (NC) between the same pairof interfaces, may be dependent on the types of subnetworks; also the extent to which a subnetwor
29、k can supportsimultaneous connections (NCs) between a given interface to the subnetwork and other distinct interfaces, may bedependent on the types of subnetworks (see also Figure 5-1/X.305).Note 2 - Also the interfaces to the subnetwork may be using either the same protocol, or different protocolsd
30、epending on the nature of the system attached to that interface (e.g., X.25 if DTE, X.75 if another subnetwork).5.2 Within a subnetwork, support of the OSI connection-mode network service may involve functionalities ofthat subnetwork performed:- either at all the Layers 1 to 3,- or at Layer 1 and 2,
31、- or only at Layer 1.This may depend on the type of subnetwork which is considered.This may also depend on the phase in the network connection (i.e., connection establishment, connectionrelease, data transfer), and also on the element of the connection-mode network service considered within that pha
32、se.6 Fascicle VIII.6 - Rec. X.3056 Connection establishment phase6.1 The functionalities of a subnetwork which relate to the connection establishment phase of the OSI networklayer service correspond to the following actions and events at the interfaces to the subnetwork:a) Connect request, with the
33、following parameters:- called address,- calling address,- receipt confirmation selection (see Note 1),- expedited data selection (see Note 1),- QOS-parameter set (see Note 2),- NS-user-data (see Note 3).b) Connect indication, with the following parameters:- called address,- calling address,- receipt
34、 confirmation selection (see Note 1),- expedited data selection (see Note 1),- QOS-parameter set (see Note 2),- NS-user-data (see Note 3).c) Connect response, with the following parameters:- responding address,- receipt confirmation selection (see Note 1),- expedited data selection (see Note 1),- QO
35、S-parameter set (see Note 2),- NS-user-data (see Note 3).d) Connect confirm, with the following parameters:responding address,- receipt confirmation selection (see Note 1),- expedited data selection (see Note 1),- QOS-parameter set (see Note 2),- NS-user-data (see Note 3).Note 1 - NS provider-option
36、.Note 2 - The implementation of the transit delay negotiation requires urgent further study in order to have aharmonized realization in different types of subnetworks. Special attention is required as regards routing and chargingconsequences.Note 3 - The objective is to make this parameter a mandato
37、ry parameter to be supported by all subnetworks inthe future. However, a number of existing subnetworks cannot support it now. During the interim period, while thesesubnetworks exist and are not modified to provide this parameter, it is considered as a provider-option. No negotiationmechanism is nee
38、ded in the OSI connection-mode network service. Limiting, in some subnetworks, length of NS-user-data to be provided to a value lower than 128 octets (e.g., 16 to 32 octets) for an interim period would imply fewerchanges to existing interfaces and signalling systems and would simplify the introducti
39、on of such a service in existingsubnetworks.6.2 In relation with the support of the OSI connection-mode network service, the various actions and events atthe interfaces to the subnetworks which are described in 6.1 above, are expected to be sequenced according to 11 ofRecommendation X.213. In partic
40、ular a successful connection establishment is expected to be as in the followingfigure:Fascicle VIII.6 - Rec. X.305 76.3 In relation with the support of the OSI connection-mode network service, the parameters listed in 6.1 aboveare expected to be handled as described in 12 of Recommendation X.213.6.
41、4 The ways the different types of subnetworks support the elements of a connection establishment phase of theOSI connection-mode network service, are as follows:a) Type I and Type II subnetworksFunctionalities of Type I and Type II subnetworks include all elements described in 6.1 to 6.3 above.b) Ty
42、pe III subnetworksFunctionalities of Type III subnetworks do not include all elements described in 6.1 to 6.3 above.Note - In some instances (i.e., Type III), the inclusion of some elements described in 6.1 to 6.3 withinthe functionalities of the subnetwork requires further study.c) Type IV subnetwo
43、rksFunctionalities within Type IV subnetworks either include all elements described in 6.1 to 6.3 above,or this type of subnetwork may only include a subset of these elements.7 Connection release phase7.1 The functionalities of a subnetwork which relate to the connection release phase of the OSI con
44、nection-modenetwork service correspond to the following actions and events at the interfaces to the subnetwork:a) Disconnect request, with the following parameters:- reason,- NS-user-data (see Note),- responding address.b) Disconnect indication, with the following parameters:- originator,- reason,8
45、Fascicle VIII.6 - Rec. X.305- NS-user-data (see Note),- responding address.Note - The objective is to make this parameter a mandatory parameter to be supported by all subnetworks inthe future. However, a number of existing subnetworks cannot support it now. During the interim period, while thesesubn
46、etworks exist and are not modified to provide this parameter, it is considered as a provider-option. No negotiationmechanism is needed in the connection-mode network service.7.2 In relation with the support of the OSI connection-mode network service, the various actions and events atthe interfaces t
47、o the subnetwork which are described in 7.1 above, are expected to be sequenced according to 11 ofRecommendation X.213. In particular an NS user initiated connection release is expected to be as in theFigure 7-1/X.305.7.3 In relation with the support of the OSI connection-mode network service, the p
48、arameters listed in 7.1 aboveare expected to be operated as described in 13 of Recommendation X.213.7.4 The ways the different types of subnetworks support the elements of a connection release phase of the OSIconnection-mode network service, are as follows:a) Type I and Type II subnetworksFunctional
49、ities within Type I and Type II subnetworks include all elements described in 7.1 to 7.3above.b) Type III subnetworksFunctionalities within Type III subnetworks do not include all elements described in 7.1 to 7.3 above.Note - In some instances (i.e., Type III), the inclusion of some elements described in 7.1 to 7.3 withinthe functionalities of the subnetwork requires further study.c) Type IV subnetworksFunctionalities within Type IV subnetworks either include all elements described in 7.1 to 7.3 above,or this type of subnetwork may only inclu
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