џWPCL ћџ2BJ|xа АH аа АА X агга ХА6p&А6p&Х аеЮ† а Hр аааУ Уб cмˆ4 PŽТ б Fascicle II.3 Р-Р Rec. E.720 Ф ФPAGE1У Уб cмˆ4 PŽТ б ЮееЃ† а HH аааб cмˆ4 PŽТ бPAGE2У Уб cмˆ4 PŽТ б Fascicle II.3 Р-Р Rec. E.720 Ѓеа H№ ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаа X  аб cмˆ4 PŽТ бAll drawings appearing in this Recommendation have been done in Autocad. ‚У УRecommendation E.720 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр(IСб cмˆ4 PŽТ бISDN GRADE OF SERVICE CONCEPT аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ б1ТX ТIntroductionФ ФЦЦ а H аС СThis Recommendation outlines the general considerations for the ISDN Grade of Service (GOS) concept and provides guidelines for selecting GOS parameters. In this Series of Recommendations, the term GOS always refers to traffic Grade of Service parameters as defined in Recommendation E.600. а H аС СISDN GOS parameters are given in subsequent Recommendations in the E.720 Series. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС‚У У2С  Сб cмˆ4 PŽТ бGOS conceptЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФ ФС СGOS uses a number of traffic engineering parameters to provide a measure of adequacy of plant under specified conditions; these GOS parameters may а H аbe expressed as probability of blocking, probability of delay, etc. Blocking and delay are caused by the fact that the traffic handling capacity of a network/network component is finite and that the demand traffic is stochastic by nature. а H аС СThe users of telecommunication services can experience the effects of GOS parameters depending on their perception of events such as: а H аТа ТТ№ ТС€ С1)СpСfailure of a call demand or excessive delay to satisfy a call demand;ЦЦ а H аТа ТТ№ ТС€ С2)СpСfailure of call attempts or excessive delay to satisfy call attempts;ЦЦ а H аТа ТТ№ ТС€ С3)СpСfailure of automatic reР-Рattempts or excessive delay to satisfy automatic reР-Рattempts.ЦЦ а H аС СEvents of the first class are always perceived by the user. Events of the other two classes may be perceived by the user depending on the capability of the terminal equipment to transmit signalling information to the calling user. С СIn all three classes the ability to distinguish GOS depends on having distinct indications of called user conditions and network conditions. а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаС  СGOS may be distinguished as the user GOSй€ user GOSйб cмˆ4 PŽТ б, network GOSб cмˆ4 PŽТ бй network GOSйб cмˆ4 PŽТ б and network component GOSб cмˆ4 PŽТ бй network component GOSйб cмˆ4 PŽТ б as shown in Figure 1/E.720. User GOS relates to user call demands. Network GOS relates to any call attempts including both user generated call attempts and terminal generated automatic reattempts. Network component GOS relates to bids for the utilization of a specific network component including both bids generated by call attempts and bids generated by call attempts and bids generated by internal retrials in the network. Parameters related to user GOS and network component GOS are for further study. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаС СRecommendation E.721 defines network GOS parameters based on any call attempt. Subsequent Recommendations in the E.720 Series will define other GOS parameters. Recommendations in the E.740 series will define traffic measurement and performance monitoring requirements. С СUser GOS performance effects and other trafficР-Рindependent, userР-Рperceived effects such as availability and service integrity contribute to Quality of Service (QOS). Network GOS parameters and their values provide information on the traffic aspects of the QOS. ‚У Уб cмˆ4 PŽТ б3ТX ТPrinciples to select ISDN GOS parametersФ ФЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС3.1С   СУУб cмˆ4 PŽТ бISDN traffic characteristicsЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СISDN has many characteristics different from the existing dedicated networks such as Public Switched Telephone Network (PSTN), Circuit Switched Public Data Network (CSPDN), Packet Switched Public Data Network (PSPDN), а H аetc. The following characteristics are taken into account when defining GOS parameters for ISDN: а H аТа ТР-РТ№ ТISDN provides integrated access to a wide variety of telecommunication services through a small set of standardized userР-Рnetwork interfaces.ЦЦ а H№ аТа ТР-РТ№ ТServices have heterogeneous traffic demand profiles and diverse performance requirements.ЦЦ а H аТа ТР-РТ№ ТThe traffic streams generated by user demands for bearer services and teleservices utilize layer 1, 2 and 3 resources.ЦЦ а H аТа ТР-РТ№ ТThe configuration and implementation of a user's terminal and its manР-Рmachine interface may vary from one service to another service and one user to another user.ЦЦ а H аТа ТР-РТ№ ТOutР-РofР-Рband signalling and call control capability, based on DР-Рchannel and Signalling System No. 7 (S.S. No. 7) are provided.ЦЦ а HH а‚Ср8DСб cмˆ4 PŽТ бFigure 1/E.720 Љ T0201181Љ88 б cмˆ4 PŽТ б 3.2Тh  ТУУParameter selection principlesЦЦ а H аФФС СThe GOS parameters defined in the E.720 series of Recommendations applies to the first phase of ISDN. The definitions of these parameters may be expanded or additional GOS parameters defined to accomodate future evolution of ISDN architecture and services. Considering the above characteristics in ISDN, the following principles are recommended for selecting GOS parameters in ISDN: а H аТа ТТ№ ТС€ Сi)СpСA minimum common set of GOS parameters is defined for attempts on layers 1, 2 and 3 Р-Р such attempts belonging to different services may or may not share the same outР-РofР-Рband call setР-Рup and release procedures. (See Note.)ЦЦ а H аТа ТТ№ ТС€ Сii)СpСThe GOS parameters are defined and specified in such a way that the GOS can be derived at wellР-Рdefined reference points (traffic significant points).ЦЦ а H аТа ТТ№ ТС€ Сiii)Си СThe GOS parameters should be specified with reference to traffic load conditions in the sense of Recommendation E.500.ЦЦ а H аТа ТТ№ ТС€ Сiv)СpСBlocking GOS parameters may in the future need to take account of repetitions due to network status, but are presently based on lostР-РcallР-Рcleared assumptions.ЦЦ а H аТа ТТ№ ТС€ Сv)СpСGOS parameters related to the user plane information transfer phase are for further study.ЦЦ а H аС СУУNoteФФ Р-Р To assess the performance directly perceived by a user, other additional parameters which are specific to the user's terminal equipment may also be necessary. 3.3Тh  ТУУGOS standard setting principlesЦЦ ФФС СGOS standard setting principles will take into account the current standards for voice and data services so that when the user migrates from a dedicated network to the ISDN, the user does not encounter a marked undesirable contrast.