1、INTERNATIONAL TELECOMMUNICATION UNIONITU-T Y.1241TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU(03/2001)SERIES Y: GLOBAL INFORMATION INFRASTRUCTUREAND INTERNET PROTOCOL ASPECTSInternet protocol aspects Architecture, access, networkcapabilities and resource managementSupport of IP-based services using
2、 IP transfercapabilitiesITU-T Recommendation Y.1241(Formerly CCITT Recommendation)ITU-T Y-SERIES RECOMMENDATIONSGLOBAL INFORMATION INFRASTRUCTURE AND INTERNET PROTOCOL ASPECTSGLOBAL INFORMATION INFRASTRUCTUREGeneral Y.100Y.199Services, applications and middleware Y.200Y.299Network aspects Y.300Y.399
3、Interfaces and protocols Y.400Y.499Numbering, addressing and naming Y.500Y.599Operation, administration and maintenance Y.600Y.699Security Y.700Y.799Performances Y.800Y.899INTERNET PROTOCOL ASPECTSGeneral Y.1000Y.1099Services and applications Y.1100Y.1199Architecture, access, network capabilities an
4、d resource management Y.1200Y.1299Transport Y.1300Y.1399Interworking Y.1400Y.1499Quality of service and network performance Y.1500Y.1599Signalling Y.1600Y.1699Operation, administration and maintenance Y.1700Y.1799Charging Y.1800Y.1899For further details, please refer to the list of ITU-T Recommendat
5、ions.ITU-T Y.1241 (03/2001) iITU-T Recommendation Y.1241Support of IP-based services using IP transfer capabilitiesSummaryThis Recommendation classifies IP-based services, introduces the concept of the IP service planeand presents resulting IP transfer capability attributes. This Recommendation desc
6、ribes the servicelevel agreement and identifies the range of SLA attributes to be considered.SourceITU-T Recommendation Y.1241 was prepared by ITU-T Study Group 13 (2001-2004) and approvedunder the WTSA Resolution 1 procedure on 1 March 2001.KeywordsATM, B-ISDN, Interworking, IP, Network, PSTN, Serv
7、ice Plane, Service Level Agreement (SLA),Transfer Capability.ii ITU-T Y.1241 (03/2001)FOREWORDThe International Telecommunication Union (ITU) is the United Nations specialized agency in the field oftelecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ ofIT
8、U. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendationson them with a view to standardizing telecommunications on a worldwide basis.The World Telecommunication Standardization Assembly (WTSA), which meets every four years,establishes the topics for
9、study by the ITU-T study groups which, in turn, produce Recommendations on thesetopics.The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.In some areas of information technology which fall within ITU-Ts purview, the necessary standards areprepared on a c
10、ollaborative basis with ISO and IEC.NOTEIn this Recommendation, the expression “Administration“ is used for conciseness to indicate both atelecommunication administration and a recognized operating agency.INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implem
11、entation of this Recommendation mayinvolve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence,validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or othersoutside of the Recommendation development process.As
12、of the date of approval of this Recommendation, ITU had not received notice of intellectual property,protected by patents, which may be required to implement this Recommendation. However, implementors arecautioned that this may not represent the latest information and are therefore strongly urged to
13、 consult theTSB patent database. ITU 2001All 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 ITU.ITU-T Y.1241 (03/2001) iiiCONTENTSPage1 Scope . 1
14、2 References 13 Definitions 24 Abbreviations . 35 IP-based service 35.1 General. 35.2 IP-based service classes and categories. 45.3 Communication configurations. 55.3.1 Point-to-point communication configuration 55.3.2 Unidirectional point-to-multipoint communication configuration. 55.3.3 Unidirecti
15、onal multipoint-to-point communication configuration. 55.3.4 Multipoint-to-multipoint communication configuration . 55.3.5 Bidirectional point-to-multipoint communication configuration. 65.4 IP service plane 65.5 End-system model 86 IP transfer capability attributes . 86.1 General. 86.2 Attributes f
16、or IP transfer capability. 97 Service level agreement 97.1 General. 97.2 SLA components 97.3 SLA attributes 107.3.1 Service level objectives 107.3.2 Service monitoring 107.3.3 Financial issues 107.4 Procedure for service level agreements. 108 Protocol reference model 119 Functional architecture . 12
17、9.1 Applications of functional groups. 129.1.1 IP interface functional group 139.1.2 IP routing and forwarding functional group 139.1.3 IP server functional group 139.1.4 IP client functional group. 139.1.5 IP conversion functional group 13iv ITU-T Y.1241 (03/2001)Page10 Support of IP-based services
18、 by ATM 1410.1 Relationship with ATM transfer capabilities. 14ITU-T Y.1241 (03/2001) 1ITU-T Recommendation Y.1241Support of IP-based services using IP transfer capabilities1ScopeThis Recommendation specifies: service plane concept for IP-based services; support of IP-based services by ATM; attribute
19、s for IP transfer capabilities to support IP-based services; service level agreement for IP-based services.By introducing the concept of the service plane, the possible sets of attributes for IP transfercapabilities to support the IP-based services are given.Figure 1 shows the relationship of this R
20、ecommendation with related IP Recommendations.IP-based services may be supported on IP above any layer 1 and layer 2 transport capable ofsupporting IP. While Figure 1 shows ATM as the transport mechanism, other underlying transfermechanisms can be used to provide the same IP-based services. The use
21、of IP over these othertransfer mechanisms is described in other Recommendations.T1317840-01IP transfer capabilitiesIP-based service planeIP LayerATM transfer capabilitiesATM LayerTelecoms service planeScope of Y.1401ScopeofY.1241ScopeofY.1310Non-IPtransfercapabilitiesPSTN, N-ISDN or ATMProtocol stac
22、kFigure 1/Y.1241 Relationship of IP-based services transport and interworkingRecommendations2 ReferencesThe following ITU-T Recommendations and other references contain provisions which, throughreference in this text, constitute provisions of this Recommendation. At the time of publication, theediti
23、ons indicated were valid. All Recommendations and other references are subject to revision;users of this Recommendation are therefore encouraged to investigate the possibility of applying themost recent edition of the Recommendations and other references listed below. A list of the currentlyvalid IT
24、U-T Recommendations is regularly published.2 ITU-T Y.1241 (03/2001)1 ITU-T I.211 (1993), B-ISDN service aspects.2 ITU-T I.313 (1997), B-ISDN network requirements.3 ITU-T I.321 (1991), B-ISDN protocol reference model and its application.4 ITU-T I.327 (1993), B-ISDN functional architecture.5 ITU-T I.3
25、71 (2000), Traffic control and congestion control in B-ISDN.6 ITU-T I.414 (1997), Overview of Recommendations on layer 1 for ISDN and B-ISDNcustomer access.7 ITU-T Y.1310 (2000), Transport of IP over ATM in Public Networks.8 ITU-T Y.1001 (2000), IP Framework A framework for convergence oftelecommuni
26、cations network and IP network technologies.9 ITU-T Y.1401 (2000), General requirements for interworking with Internet protocol (IP)based networks.10 ITU-T Y.1231 (2000), IP access network architecture.11 ITU-T G.707/Y.1322 (2000), Network node interface for the synchronous digital hierarchy(SDH).12
27、 ITU-T I.371.1 (2000), Guaranteed frame rate ATM transfer capability.3 DefinitionsThis Recommendation defines the following terms:3.1 service plane: The service plane comprises:a) service presentation functionality being presented to the end user;b) service implementation aspects with which the end
28、user interacts. For example, serviceinvocation, control service level agreement function, etc.Note that a) and b) use the totality of the transfer capabilities including control and managementfunctionalities.3.2 IP-based service: An IP-based service is defined as a service provided by the service pl
29、aneto an end user (e.g. a host (end system) or a network element) and which utilizes the IP transfercapabilities and associated control and management functions, for delivery of the user informationspecified by the service level agreements.3.3 IP network service: An IP Network Service is defined as
30、a data transmission service inwhich the data passed across the interface between the user and provider is transferred in the form ofIP (Internet Protocol) packets (sometimes called datagrams). IP Network Service includes the serviceprovided by using the IP Transfer Capabilities.3.4 IP transfer capab
31、ility: IP Transfer Capability is defined as the set of network capabilitiesprovided by the IP layer. It may be characterized by the traffic contract as well as performanceattributes supported by control and management functions of the underlying protocol layers.3.5 service level agreement: Service L
32、evel Agreement (SLA) is a negotiated agreementbetween a customer and the service provider on levels of service characteristics and the associatedset of metrics. The content of SLA varies depending on the service offering and includes theattributes required for the negotiated agreement.ITU-T Y.1241 (
33、03/2001) 34 AbbreviationsThis Recommendation uses the following abbreviations:ABR Available Bit RateABT ATM Block TransferATM Asynchronous Transfer ModeB-ISDN Broadband Integrated Services Digital NetworkCoS Class of ServiceCPN Customer Premises NetworkDBR Deterministic Bit RateFTP File Transfer Pro
34、tocolGFR Guaranteed Frame RateIP Internet ProtocolIP-NE IP Network ElementIP-TE IP Terminal EquipmentIPTC IP Transfer CapabilityLAN Local Area NetworkMPLS Multi-Protocol Label SwitchOAM Operation, Administration and MaintenanceQoS Quality of ServiceSAP Service Access PointSBR Statistical Bit RateSDH
35、 Synchronous Digital HierarchySLA Service Level AgreementSLO Service Level ObjectiveSVC Switched Virtual CircuitTCP Transmission Control ProtocolUDP User Data ProtocolUNI User Network InterfaceVoD Video-on-DemandWWW World Wide Web5IP-basedservice5.1 GeneralAn IP-based service is defined in clause 3.
36、An IP-based service is specified according to the Service Level Agreement (SLA) attributes assigned(see clause 7). While an IP-based service usually has an end-to-end context it may be provided insituations in which part of the connection is IP-based network while another part of the connection is4
37、ITU-T Y.1241 (03/2001)not IP-based. One typical example is a voice service, with voice over IP in an IP-based networkinterworking with the existing circuit switched voice network. Other examples of non IP-basednetwork interworking with IP-based network to support an IP-based service end to end exist
38、. Furtherinformation on IP interworking is given in ITU-T Y.1401 9. In the case of interworking, the SLAattributes will be specified only for the IP-based network portion of the connection.Figure 2 presents a reference framework illustrating applications of IP transfer capability and IP-based servic
39、es. This figure is based on the figures introduced in ITU-T I.414 6, ITU-T Y.1001 8and Y.1231 10. The following subclauses provide information regarding, IP-based services, serviceplane concept, IP-based service classes and categories and IP transfer capability attributes.T1317850-01RPIP-Based Servi
40、ceEnd SystemIP Core NetworkAFIP-Based ServiceAFRP RP RPIP Transfer CapabilityEnd SystemIP-NT IP-EF IP-EF IP-NTAccessNetworkAccessNetworkCustomerPremisesNetworkCustomerPremisesNetworkAFIP-EFIP-NTRPAccess FunctionIP Edge FunctionIP Network TerminationReference PointNOTE The box between RPs is covered
41、in ITU-T Y.1231 and I.414. This arrangement is also alignedwith ITU-T Y.1001.Figure 2/Y.1241 IP-based network reference framework5.2 IP-based service classes and categoriesIP-based service classes are closely related to QoS classes which provide assurances to users on theservice performance to be ac
42、hieved in any given service contract. The IP-based services are specifiedand characterized by the SLA attributes assigned in the service contract.However, using similar concepts as in ITU-T I.211 1, IP-based services can be categorized as“Interactive“ and “Distributive“.The interactive category is s
43、ubdivided into three classes:conversational services: such as internet telephony, remote login, electronic data exchange,videoconferencing, video telephony, home banking, tele-education and interactive games;messaging services: such as electronic mail (e-mail), voice e-mail, video e-mail, and intern
44、etfax;ITU-T Y.1241 (03/2001) 5retrieval services: such as web browsing (www, gopher), file downloading (ftp),internet VoD (Video-on-demand) and news retrieval.The distributive category is subdivided into two classes:distribution services without user individual presentation control: such as broadcas
45、ting,multicasting and electronic newspaper;distribution services with user individual presentation control: such as video-on-demand andnews-on-demand.5.3 Communication configurationsCommunication in IP-based networks can be divided in several configurations similar to B-ISDN asdefined in ITU-T I.313
46、 2. In this Recommendation configurations are classified as point-to-point,unidirectional point-to-multipoint, unidirectional multipoint-to-point, multipoint-to-multipoint andbidirectional point-to-multipoint.5.3.1 Point-to-point communication configurationA point-to-point connection configuration m
47、ay provide unidirectional or bidirectional symmetric orasymmetric communication between two parties. Examples of services applicable to point-to-pointcommunication configuration are: conversational services; messaging services; retrieval services; distribution services with user individual presentat
48、ion control.5.3.2 Unidirectional point-to-multipoint communication configurationA unidirectional point-to-multipoint connection configuration may provide unidirectionalcommunication between one-to-many parties. Examples of services applicable to unidirectionalpoint-to-multipoint communication config
49、uration are: messaging services; distribution services without user individual presentation control.5.3.3 Unidirectional multipoint-to-point communication configurationA unidirectional multipoint-to-point connection configuration may provide unidirectionalcommunication between many-to-one parties. Examples of services applicable to unidirectionalmultipoint-to-point communication configuration are: messaging services; distribution services without user individual presentation control.5.3.4 Multipoint-to-multipoint com
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