============================================================ Question 3/II - Network operational aspects of international telephone service (New Question 1989-1922 study period) Considering that 1. Study Group I is studying: (a) telephone services and their related human factor issues (i.e. Questions 27/I to 31/I); (b) computerized information service for telephone subscriber numbers in foreign countries (Directory Assistance) reserved for operators, (Questions 16/I and 33/I); (c) International Telecommunication Credit Card service (Question 34/I); decides that Study Group II should study the network operational aspects of international telephone service for the provision of optimum services to the customer. ============================================================ Question 4/II - International interconnection of the different mobile services and the public switched telephone network or ISDN (Continuation and expansion of Question 16/II, 1985-1988) Considering 1. the existence of a world-wide maritime mobile satellite system (INMARSAT); 2. the existence of and plans for automatic maritime mobile VHF/UHF telephone services and land mobile telephone services; 3. the requirements specified in Resolution No. 201 of the WARC-79 and Resolution No. 320 of MOB WARC-83 and Appendix 43 of MOB-83 and the possible existence of plans for aeronautical services; 4. the Recommendations relating to numerical ship station identification and numbering systems and selection procedures for international telephone and ISDN service (E.210, E.211, E.215 and E.216); 5. the Recommendations relating to the identification plan for land mobile stations and telephone numbering plan for land mobile stations in public land mobile networks (E.212, E.213); 6. the Recommendation relating to numbering in the aeronautical satellite system of INMARSAT (E.215); 7. the development of complementary Recommendations by other CCITT Study Groups and the work of the cognizant Study Groups and Interim Working Parties in the CCIR; 8. the basic requirements for common procedures at mobile units having different communications capabilities e.g. telephony/telex, satellite/VHF/UHF; 9. the planned introduction of land mobile satellite systems; 10. the planned implementation of mobile service location and registration centres by some administrations; 11. the need to study the numbering and selection procedures for VHF/UHF maritime mobile radio telex service in view of the deletion of Recommendation F.121; 12. the rapid development of Integrated Services Digital Network Recommendations, What new Recommendations are required and what additions or modifications to existing Recommendations are needed to provide for international interconnection of the different mobile telephone or ISDN services and the public switched telephone network and the ISDN? The following items should, in particular, be included in the studies: i) numbering and selection procedures for VHF/UHF maritime mobile radio telex service; ii) numbering and selection procedures for interconnection between mobile systems, in particular INMARSAT, and terrestrial networks; iii) numbering and selection procedures for group coast station calls; iv) network quality of service. ============================================================ Question 5/II - Evolution of numbering and numbering plan interworking for the ISDN era (Continuation of Question 17/II, amended and expanded from 1985- 1988 study period) It is suggested that the following (preliminary) considerations be included in a new Question for the next study period: Considering that (a) numbering solutions to various ISDN-PSTN and ISDN-PDN interworking issues (e.g., modem pooling, terminal identification, supplementary services, service discrimination etc.) will be required; (b) long-term network identification needs to be urgently studied; (c) development of the NCD concept needs to be studied (NDC: National Destination Codes); (d) further guidance on the transition from the E.163 to E.164 numbering plans may be needed; (e) new application of SS7 SCCP will emerge, which may have an impact on the numbering plans; (f) selection procedures based on sound operational principles are urgently required; (g) special needs for numbering plan studies are emerging in mobile networks, What revisions or enhancements to the existing number and numbering plan interworking Recommendations should be made, and what new Recommendations should be developed? Note 1 - A joint and unified Recommendation on numbering plan interworking based on E.166 and X.122 should be sought in the next study period. Note 2 - Establishment of MMI procedures used with ISDN terminals, in conjunction with Q.31/I of Study Group I is a matter for urgent study. Note 3 - Study of numbering plan and numbering plan interworking requirements for mobile networks is also an area for urgent study in the next study period. ============================================================ Question 6/II - Evolution of routing plan in the ISDN era (Combination and expansion of Questions 18/II and 19/II studied in the 1985-1988 period) Considering (a) the evolution of the world networks towards ISDN; (b) the multiservice aspects of the ISDN (e.g., Packet Mode Bearer Service) with the possibility that each service will require different routing algorithms; (c) that there may be new signalling elements and SPC capabilities that will also require analysis for call routing (e.g., number of links with DCME, number of echo control devices, number of A/MV law conversions); (d) the numbering interworking Recommendation and the need to develop a clear Interworking Routing Plan for all services on the ISDN; (e) that E.172 routing rules allow for the selection of signalling systems other than C7 ISUP for ISDN calls; (f) the routing techniques outlined in Recommendation E.170, the telephone routing plan (E.171) and the ISDN routing plan (E.172) together with the experience gained from using these plans; (g) the urgent need for guidance on call routing in support of mobile networks, What new Recommendations should be provided, or what revisions and additions should be made to the existing Routing Recommendations? What further enhancements are required to the "connection history", "performance monitoring/QoS" and "environment of connection" parameters in order to enhance call routing capabilities? ============================================================ Question 7/II - Non-voice aspects of network during the transition period from PSTN to ISDN (Continuation of Question 20/II, expanded, from the 1985-1988 period) Considering that the ISDN will evolve from the telephone network: the standardization by the CCITT and the appearance on the telecommunication market of increasingly numerous non-voice applications, (e.g., facsimile, data, and other telematic services) likely to be handled by the telephone network; the diversity of possible interconnections between these applications and the telephone network, ranging from a straightforward connection or the subscriber line to a network-to-network interconnection (telephone network to non-telephone network): that Recommendation E.301 describes the impact of non-voice applications on the telephone network; the experience already acquired by certain administrations in this respect; the network interworking techniques being studied in the related Study Groups; in view of the constraints peculiar to the telephone network and arising from: (a) telephone network design practices, particularly in terms of: - planning; - traffic engineering; - numbering and routing plans; (b) specifications laid down in the numerous relevant Recommendations and in particular the evolution of telephone switching techniques and their limitations; (c) telephone operation practice in terms of: - Quality of Service; - human factors; - network management; - traffic measurement and recording etc.; finally, taking into account in broad terms the responsibility of administrations for the operations of telephone network and ISDN at the national and international level, 1. What additions and enhancement should be made to Recommendation E.301? 2. What repercussions would the introduction of any known or foreseeable non-voice applications in the telephone network have as far as the Series-E Recommendations are concerned? ============================================================ Question 8/II - Service quality of networks, including operational performance and service measurements (PSTN/ISDN) (Continuation of Question 22/II amended, studied during the 1985-1988 study period) Introduction This Question has two parts: The first part (considerata (a) to (e) and items 1 and 2 of the Question) serves as a continuation of studies on operational performance of networks including service measurements. It recognizes the previous development of Recommendations on operational guidance, connection establishment and connection retention. The main thrust of this Question will focus on connection quality; the use of supplementary information contained is common channel signalling systems to improve service quality of networks, and the migration towards the ISDN. The second part (considerata (l) to (q) and items 1 and 2 of the Question) addresses the general framework of future studies on service quality requirements and operational performance of networks. In this study period studies will focus on PSTN and ISDN. Considering (a) that the main parameters describing the service quality of networks are given in Recommendation E.420; (b) that the CCITT has adopted Recommendations E.426 on connection establishment and E.428 on connection retention; (c) that common channel signalling systems (C6 and C7) are being introduced into the international network and the enhanced capabilities of these systems could provide additional information to enable a detailed analysis of call failures; (d) that delays in call establishment, e.g., post-dialling delay, and in particular variation in the delay, significantly influences service quality; (e) that techniques based on speech envelopes may be applicable for the automatic measurement of connection quality; (f) that billing is adversely affected by the absence of answer signals on answered calls or by the presence of false answer signals; (g) that service quality measurements and improvement programmes are integrally related to network management and network maintenance activities; (h) that significant input is obtained from the Quality of Service Development Group (QSDG); (i) the necessity to identify the contact points within each administration for service quality improvements; (j) that the Telecommunications Management Network (TMN) can be used to transport measurements including text call and observation data; (k) that in view of the increasing complexity of networks and services, the timely publicizing of number plan changes is an important means of maintaining service quality at the time of such changes; (l) a framework is necessary to harmonize future studies on service quality of networks; (m) Recommendation I.350 on general principles of Quality of Service and network performance in ISDN has been prepared; (n) Recommendations X.134 - X.137 and X.140 adopting these principles for data services are already available; (o) relevant studies will continue especially in Study Groups VII, XII and XVIII; (p) the principles, results and future works mentioned should be taken into account in studies relevant to service quality of networks; (q) guidelines are necessary now to handle Quality of Service and network performance problems in Study Groups A and B, 1. What modifications should be made to the E.420-Series of Recommendations and to other relevant Recommendations to reflect the need to ensure the operational performance and service quality of networks? 2. What benefits can be gained by improving the service quality of networks? 3. What general framework of further studies on the operational performance and service quality of networks should be applied? Note 1 - Reference should be made to the study of Q.9/II - Network management and Q.10/II - Traffic measurement requirements on telecommunication networks (including the ISDN) because the outcome of the study will most likely comprise the inclusion of more parameter measurements in Recommendation E.425. Close liaison will be required with other Study Groups. Note 2 - Close liaison is needed with Study Groups VII, XII and XVIII. ============================================================ Question 9/II - International network management (Continuation of Question 23/II, amended, studied in the 1985-1988 study period) Considering 1. that digital exchanges and digital transmission systems have been introduced in the international network, and these facilities will have the ability to dynamically allocate digital transmission capacity; 2. that these digital facilities will provide the means to introduce a variety of new services, and that these new services may generate varying amounts of revenue, and administrations may wish to assign different priorities to the various services, particularly during periods of network congestion; 3. that the introduction of new services may generate new or unusual traffic flows in the network, and the effect of these new traffic flows may not be fully understood when the service is introduced; 4. that interworking between the telephone network and non-telephone networks is developing, and that congestion in one network (or in the interface between the networks) has the potential to cause problems in the connected network; 5. that time-dependent or state-dependent dynamic routing schemes may be considered for use in the international network, and their introduction may create new considerations for network management; 6. that network management controls can be effective in alleviating congestion in common channel signalling networks, and can also help during CCS fault recovery, and these controls could be applied automatically and in any case should be coordinated with the internal CCS flow control and fault recovery mechanisms; (Note - This part of the Question has some urgency, considering reports from administrations of exchange failures apparently caused by inadequate resources for common channel signalling.) 7. that with the increasing size of digital exchanges and transmission systems, failures of such facilities may have a severe impact on service if network management actions are not pre-planned and implemented; 8. that the Telecommunications Management Network (TMN) can support a wide range of network management functions between a network management centre (or operation system) and exchanges, and also between exchanges, What new Recommendations, or changes to existing Recommendations, are necessary to provide guidance on the network management surveillance and control capabilities which may be necessary for the ISDN, and in particular during the transition to ISDN? Note - In progressing this Question, close coordination will be necessary with Study Group XI for common channel signalling and digital exchange aspects, Study Group XVIII for ISDN, Study Group X for the specification of MML functions for network management, Study Groups IV, XI and XV for TMN and with Study Group VII for data network aspects. ============================================================ Question 10/II - Traffic measurement requirements on telecommunications networks (Continuation of Question 33/II, renumbered and amended, from the 1985-1988 study period) Considering (a) that CCITT has adopted Recommendations E.502, E.503 and E.504 concerning the traffic measurement requirements for SPC (especially digital) telecommunications exchange; (b) that the set of basic measurement types specified in Recommendation E.502 has to be refined and extended to cover common channel signalling systems, the ISDN and its services; (c) that traffic measurement requirements for customer access to ISDN need to be considered; (d) that the data analysis functions given in Recommendation E.503 and the list of man-machine functions given in Recommendation E.504 requires definition and extension to cover all traffic measurement functions; (e) that close cooperation is required in providing traffic measurement functions to complement traffic engineering theory, network management and Quality of Service requirements; (f) that TMN protocols and common channel signalling systems, such as CCITT No. 7, will be available for transporting measurement data between exchanges, network operations centres and other network entities such as transmission terminals; (g) that traffic measurement requirements for network entities for other than telecommunications exchanges need to be considered; (h) that internal automatic observations in the Public Switched Telephone Network are contained in Recommendation E.425; (i) that progress in other Questions may impose other measurement requirements on telecommunications networks, What modifications to existing or new Recommendations are required in order to provide a comprehensive specification on traffic measurement requirements for telecommunications networks? Note 1 - Close coordination will be required between this Question and Questions 8/II (Quality of Service), 9/II (Network Management), 12/II (Common Channel Signalling System), 16/II (Application of Traffic Measurements in Telecommunications Networks), 17/II (ISDN traffic engineering), Study Groups IV and XV on the TMN, Study Group XI on signalling and exchange design and Study Group XVIII on ISDN. Note 2 - It should be noted that the new proposed Question 10/II will require extensive coordination with other CCITT Study Groups and the activities relating to Quality of Service and network management to ensure that sound answers to all aspects of the new Question proposed by administrations are achieved. ============================================================ Question 11/II - Terms and definitions for Quality of Service, dependability and teletraffic engineering (Revised Question 25/II from 1985-1988 period) Considering 1. that Recommendation E.800 gives terms and definitions for Quality of Service, network performance and related performances; 2. that Recommendation E.600 gives terms and definitions for use in the field of teletraffic engineering; 3. that Recommendation E.100 gives terms used in international telephone operation; 4. that Supplement X gives terms and definitions for dependability and related concepts as well as for statistical concepts; 5. that Quality of Service, dependability and traffic engineering work within CCITT is being studied for an expanding range of applications; 6. that the E-Series Recommendations may contain inconsistencies between existing definitions, What new and revised definitions are required in Recommendations E.100, E.600, E.800 and Supplement? ============================================================ Question 12/II - Traffic, operational and network planning objectives of common channel signalling networks (Note 1) (Revised Q.26/II from 1985-1988) Considering (a) that CCITT Recommendations in the Q.700 Series specifying the structure and design criteria for CCITT Signalling System No. 7, are in an advanced stage; (b) that such Recommendations on structures and design criteria need to be complemented by Recommendations on the operational and traffic aspects; (c) that the common channel signalling networks are different from the speech (and non-speech) networks, e.g., structure, traffic performance and network availability; (d) that the common channel signalling networks will carry many different types of information through the user and application parts of Signalling System No. 7, including in particular user-to-user signalling information and signals related to supplementary services (e.g., credit card validation); (e) that the end-to-end performance of the various user networks will depend on how well signalling networks are configured and dimensioned; (f) that proposed and existing signalling networks are packet switched type networks and are an essential part of end-to-end ISDN capability; (g) that CCITT Recommendations in the E.700 Series specifying the traffic aspects of ISDN are available; (h) that these signalling networks require evaluation of signalling routing techniques, interworking with network management techniques and new traffic measurements, 1. What new traffic models and performance measures are needed to dimension common channel signalling networks? 2. What information about the interworking of ISDN networks and the common channel signalling network is needed to perform CCS network dimensioning? Note 1 - This Question is closely related to the Question of Study Group XI and Questions 9, 16 and 10 of Study Group II. In the course of studies under this Question new requirements may emerge in the areas of signalling routing, measurement parameters, and network management which will be identified to the relevant Question. ============================================================ Question 13/II - Design alternatives for telecommunication networks (Continuation of Questions 27/II and 41/II, 1985-1988 study period, amended) Considering (a) that sophisticated routing methods may be applied to networks designed under simpler assumptions; (b) that more cost efficient utilization of networks can be attained, especially for intercontinental networks, by the use of dynamic routings, in which routing patterns are changed (for instance, time or state dependent) according to the traffic profile; (c) that certain network design alternatives might yield a more robust network and thereby reduce the impact of a failure or unexpected traffic overload on the GOS as perceived by the customer; (d) that the network needs to be planned to incorporate restoration and diversity in order to increase the level of network survivability; (e) that Recommendation E.522 incorporates a multi-hour engineering procedure and considers the impact of transit charges on dimensionings; (f) that Recommendation E.175 outlines a possible international network planning process and this process involves steps requiring the review of network design alternatives; (g) that selective trunk reservation may be applied to bi-directional circuit groups; (h) that in ISDN, due to a higher level of concentration, services may require new GOS and dependability constraints, and that these may differ from different services; (i) that dependability covers the aspects of availability performance, reliability performance, maintainability performance and maintenance support performance; (j) that network design should simultaneously take both trafficability and dependability into account; (k) that Recommendation E.862 provides procedures for the planning of the dependability of telecommunication networks; (l) that Recommendation E.880 provides guidelines for the collection and evaluation of data on dependability; (m) that the E.500 Series of Recommendations contains guidelines for the collection of trafficability data, 1. What traffic dimensioning methods and network design alternatives are available for single and multiservice networks, especially with priority and multi-bandwidth capabilities? 2. What computations are required and what pertinent parameters should be measured for various network design alternatives, in particular for reference networks and service protection methods? 3. What is the most appropriate basis for comparison of different network alternatives? 4. What methods should be recommended for the estimation of the economic impact of traffic disturbances in telecommunication networks? 5. How should traffic disturbance be evaluated for a network and balanced against network investments? 6. What guidelines should be provided to assist the planning and economic evaluation of telecommunication networks with sufficient dependability? Note - Liaison must be maintained with Study Groups IV and XV taking account of the partition of work described by Study Group IV (see COM IV-R 14, 1985-1988 study period) ============================================================ Question 14/II - Methods for forecasting international traffic (continuation of Question 28/II, 19851988 study period, amended) Considering (a) that a number of new services have been defined which have not been taken into account before for international traffic forecasting purposes; (b) that the continuing evolution of the traditional network to the ISDN is introducing new services and enhanced services; (c) that various services on ISDN will have different characteristics (international time, holding time, profile, etc.) and that the forecasting models must take the characteristics into account; (d) that a new data base and also new explanatory variables are necessary for forecasting traffic on ISDN; (e) that the integration of forecasts for traditional telephone traffic and other existing and totally new services requires further exploration on a continuing basis; (f) that the new Recommendation E.508 is an introduction to new service forecasting and has left several areas open for further study; (g) that the introduction of new design methods induced by advanced routing techniques, e.g., dynamic routing (Recommendation E.170) implies a need for short-term traffic forecasts on an hourly and daily basis, 1. What services will have a significant impact on the traffic on existing networks and ISDN? 2. How should these services be classified recognizing that a different type of service may require different forecasting approaches? 3. How should a forecasting model for the mixed traffic on ISDN be developed? 4. What traffic data and type of explanatory variables are required for forecasting these services? 5. How does the quality of the data base affect the choice of forecasting technique? 6. How can the results of market research surveys be incorporated in the forecasting methodology? 7. What qualitative forecasting techniques are appropriate to new service forecasting and how can these be incorporated into existing methods? 8. What type of forecasting methods can be used for hourly and daily traffic forecasts as a basis for advanced routing techniques? ============================================================ Question 15/II - Traffic models and measurements required for traffic offered to the network and grade of service (amended Question 29/II of 1985-1988 study period) Considering (a) that traffic offered to circuit groups, to exchanges and on a pointto- point basis, is used in forecasting and network design, using both traditional and advanced engineering concepts (for example, service protection and advanced routing methods); (b) that traffic offered cannot be observed directly and must be estimated from measurements; (c) that in an ISDN new models for traffic offered and grade of service may be required, and different estimation models may be required for different services; (d) that automatic repeat attempt facilities in digital telephone networks and/or the ISDN are unavoidable and attractive to hurried users who are only interested in the total call demand set up time; (e) that the intervals between successive attempts of a given call demand can be very short due to the rapidity of Signalling System No. 7, digital switching and computerized call processing in the terminal equipment; (f) that in circuit switching networks, this rapidity leads to strong statistical correlations between the results of the successive attempts of a given call demand; (g) that these correlations can affect the choice of grade of service parameters, dimensioning rules, traffic and Quality of Service observation methods, 1. How can procedures for the estimation of traffic offered, in particular pointto-point traffic matrices, and the calculation of grade of service in stationary traffic conditions be more clearly defined? 2. What measurements are required to collect the data necessary for these procedures? 3. What end-to-end grade of service parameter (or parameters) associated with the call demand should be defined to represent the digital telephone and/or the ISDN user's point of view and what would be the consequences for ISDN grade of service standards, dimensioning methods and Quality of Service observation practices? 4. What new Recommendations may be needed taking repeated attempts into account? ============================================================ Question 16/II - Application of traffic measurements in telecommunication networks (continuation of Question 30/II, amended, of the 1985 1988 study period) Considering (a) that traffic measurements have different purposes, for forecasting, dimensioning and monitoring; (b) that measurements may be taken on a continuous or non- continuous basis; (c) that new routing techniques and service protection methods have been recommended; (d) that existing telephone network has to respond to new traffic demands with other traffic characteristics than those of traditional telephone traffic; (e) that for voice and non-voice services in existing networks further work in determining traffic measurement analysis procedures is required; (f) that for the service mixture in the ISDN appropriate traffic measurements have to be defined; (g) that traffic measurements on a destination basis are gaining more interest; (h) that for planning of the ISDN knowledge of traffic profiles according to the service mix is needed, the following is to be studied: 1. What new traffic measurement analysis procedures are required? 2. What evaluation procedures should be recommended to obtain relevant traffic parameter values (carrier traffic intensity, grade of service, etc.) from the measured data? 3. What improvements to Recommendation E.500 can be made? 4. What are typical traffic profiles and the characteristics of other traffic parameters of the services of the ISDN separately or heterogeneously mixed with telephone traffic? Note - Studies under this Question require close coordination with Question 10/II (Traffic measurement requirements on telecommunications networks). ============================================================ Question 17/II - Traffic reference models for ISDN traffic engineering (continuation of Question 31/II, amended, of the 19851988 study period) Considering (a) that ISDN will evolve from digital telephone network and will include various non-voice and value-added services; (b) that ISDN will make use of standard access interfaces, layered network architecture and different connection types; (c) that users can generate, through a top down process, traffic for the resources associated with each layer in the layered network architecture; (d) that user packets and user-to-user signals as well as call control messages are offered to D-channel; (e) that the evolution towards additional packet mode and broadband ISDN services will require new traffic modelling studies; (f) that new GOS objectives should be pursued for ISDNs taking into account the close interrelation of various network performance and Quality of Service factor in ISDN; (g) that in the E.700-Series a basic structure of ISDN traffic Recommendation has been established together with some basic reference models, 1. What new and revised Recommendations are needed for basic traffic models (E.700 and E.710-Series) and GOS requirements (E.720-Series)? 2. What new Recommendations are needed for traffic dimensioning methods (E.730-Series) especially D-channel traffic capacity. Note - Studies under this Question will include the possible use of SDL as a working tool. Liaison will be maintained with Study Group X (Working Party X/3). ============================================================ Question 18/II - Grade of service during and after a total failure of network components or traffic peak conditions (new Question) Considering (a) that due to accumulated demands during a period of a failure (see Recommendation 550, section 3.1, points a) and b)), the network components will experience a heavy traffic load during and after a failure condition; (b) that depending on daily traffic profile such heavy traffic load may also occur after having removed severe overload condition; (c) that Recommendation E.550 concerning the Grade of Service and new performance criteria only under failure conditions does not cover the period of time immediately after a failure condition or heavy traffic peak have been removed; (d) that in case of lack of facilities for re-routing in the network the whole traffic offered has to be processed, 1. What parameters should be proposed for evaluation of Grade of Service of network components during and after a failure condition or severe overload traffic condition? 2. What is the way of calculating and measuring these parameters? 3. What standards should be proposed for these parameters? Note - Liaison needs to be established with Study Group XI (Working Party XI/4, Digital Switching) with the objective to define techniques for recognizing the condition and regulating the operation of an exchange during excessive traffic peaks. ============================================================ Question 19/II - Call oriented models for the serveability performance in networks (revised Question 35/II of the 19851988 period) The CCITT, considering (a) that Recommendation E.800 contains definitions of QOS concepts and terms; (b) that Recommendation E.810 presents a call oriented model and serveability performance for the telephone service; (c) that measures for service accessibility, retainability and integrity have already been defined in Recommendations E.845, E.850 and E.855; (d) that Recommendations I.350, X.134, X.135 and X.136 describe a matrix to identify network performance measures, 1. What models should be added to the model in Recommendation E.810 for the various telecommunication services; 2. What mathematical models can be recommended taking into account already defined measures for service accessibility, service retainability and service integrity; 3. In which way can the phases of a call in various telecommunication services and the most important characterizations of these services be uniformly expressed e.g., in the form of a matrix? Note - Dedicated data networks are not included. Annex: Call oriented models for serveability performance of networks. Annex (to Question 19/II) Call oriented models for the serveability performance of networks Introduction This annex is one of a set of closely related documents concerned with the accessibility and retainability and integrity of telecommunication services, as listed below. The material in this annex is provisional and is for study by those involved in telex, telephony, data and ISDN services. The CCITT, considering (a) that there is a need for a comprehensive and uniform evaluation of telecommunication services; (b) that there is a desire to establish overall objectives for the serveability performance of networks; (c) that such objectives can then be used as a basis for the design, planning, operation and maintenance of telecommunication networks and their component parts; (d) that Recommendation E.800 contains terms and definitions for the serveability performance and related characteristics of services and networks; (e) that Recommendation E.810 shows the model of a basic telephone call and its serveability performance. recommends that the call oriented models given in this annex shall be used by administrations to evaluate design, plan, operate and maintain their networks which for the international telephone service the objectives have to be taken into account which are given in Recommendations: E.845 Connection accessibility objective for the international telephone service; E.850 Connection retainability objective for the international telephone service; E.855 Connection integrity objective for the international telephone service; E.830 Models for the allocation of international telephone connection retainability objectives. Objectives for other telecommunication services are under study; in principle these may be derived from appropriate Recommendations of the I, X and F-Series. 1. Models of a basic call in various telecommunication services and the components of serveability performance. The following models are presented: -Simplified model of a virtual call (Packet Terminal) -Simplified model of a virtual call (Non-packet Asynchronous Terminal) -Simplified model of a basic circuit-switched call in ISDN based on "overlap sending" -Simplified model of a basic circuit-switched call in ISDN based on "en bloc sending" -Simplified model of a basic telex message. The simplified models illustrate the principal phases of a basic call in various services. It also interrelates these phases to the service related performance concepts and their principal measures as well as to the main causes of failure in the establishment and retention of such a call and its subsequent billing. The models also indicate where, in this series of phases, user actions or mistakes may influence the call. 1) Network accessibility and connection accessibility combined into service accessibility. 2) The shaded extension shows that a premature release can occur during the time to await Call Connected packet. 3) This packet has two meanings, local and end-to-end. 4) The release of a call is not a separate phase in this model. A release failure may result in network inaccessibility for a new call. 5) The billing integrity has been shown for completeness, but is not a part of serveability performance. FIGURE 2-a Model for serveability performance on a virtual call (Packet Terminal) 1) Network accessibility and connection accessibility combined into service accessibility. 2) The shaded extension shows that a premature release can occur during the time to await Call Connected packet. 3) This packet has two meanings, local and end-to-end. 4) The release of a call is not a separate phase in this model. A release failure may result in network inaccessibility for a new call. 5) The billing integrity has been shown for completeness, but is not a part of serveability performance. FIGURE 2-b Model for serveability performance on a virtual call (non-packet asynchronous terminal) 1) Network accessibility and connection accessibility combined into service accessibility. 2) The routing of the call may start before all digits have been received (overlap). 3) The shaded area shows that a premature release can occur during the time to answer. 4) The release of a call is not a separate phase in this model. A release failure may result in network inaccessibility for a new call. 5) The billing integrity has been shown for completeness, but is not a part of serveability performance. FIGURE 3-a Model for serveability performance on a basic circuit-switched call in ISDN based on "overlap sending" 1) Network accessibility and connection accessibility combine into service accessibility. 2) The shaded area shows that a premature release can occur during the time to answer. 3) The release of a call is not a separate phase in this model. A release failure may result in network inaccessibility for a new call. 4) The billing integrity has been shown for completeness, but is not a part of serveability performance. FIGURE 3-b Model for serveability performance on a basic circuit-switched call in ISDN based on "en bloc sending" 1) Network accessibility and connection accessibility combined into service accessibility. 2) The shaded area shows that a premature release can occur during the time to answer. 3) The release of a call is not a separate phase in this model. A release failure may result in network inaccessibility for a new call. 4) The billing integrity has been shown for completeness, but is not a part of serveability performance. FIGURE 4 Model for serveability performance on a basic telex-message (Telex-subscribers connected to a type aaa exchange) ============================================================ Question 20/II - Serveability performance and service integrity of telecommunication services (amalgamation of Q.37/II, Q.38/II, Q.39/II and Q.40/II from the 19851988 study period) The CCITT, considering (a) that serveability performance and service integrity are defined in Recommendation E.800; (b) that Recommendation E.810 presents a model for telephone service and the relationship between sub-concepts of serveability; (c) that a uniform way of collection, analysis and evaluation of operational data is contained in Recommendation E.800; (d) that Recommendation E.845 contains a measure of connection accessibility; (e) that Recommendation E.850 contains a measure of service retainability performance for telecommunication services; (f) that Recommendation E.855 contains the objective for the time duration occurrence of interruption which disrupts the telecommunication services (annexes from Q.39/II (19851988 study period) to be made available), 1. How can practical parameters for the defined objectives be obtained and what collective actions can be organized to start coordinated measurements amongst different countries? Close coordination with Study Group IV should be aimed for. 2. What further objectives should be recommended for the serveability and its sub-concepts and service integrity for telecommunication service and what should be the measures of these performance concepts? 3. What amendments should be made to the related Recommendation taking into account experiences and observations in the field and the advancement of technologies? 4. What are the appropriate allocations of the serveability and service integrity objectives to the various parts of the various telecommunications services, taking into account the models for the allocation as recommended in Recommendation E.830? 5. How can the observed field data be collected, evaluated and presented in a uniform way based on Recommendation E.880? ============================================================ Question 21/II - CCITT Handbook(s) on application and implementation of Recommendations on Quality of Service (new Question) Considering (a) that administrations need rules and tools to evaluate the performance of services, networks, components, etc. (for example, such evaluation is helpful in discussions with manufacturers); (b) that the majority of existing performance Recommendations and textbooks do not cover the practical need of operating, maintenance and planning staff; (c) the information assembled during the studies for drafting the new Recommendation E.880 (field data collection and evaluation on the performance of equipment, networks and services) (reference COM II- R 29 and Temporary Document 603 from 15-23 February 1988 meeting of Study Group II) is of a generally useful nature; (d) some other proposed new and revised Recommendations developed by Study Group II and related Study Groups can form the basis for handbook material such as E.600, E.550, E.420, E.424, E.428 and X.137; (e) the existence of the CCITT Handbook on Quality of Service, Network Management and Network Maintenance; (f) Recommendation E.800 (Quality of Service vocabulary) (previously G.106) has become a general reference; (g) the need for harmonization of Quality of Service work within the CCITT coordinated by Study Group II and the stated aims of the VIIIth Plenary Assembly and Study Group II to rationalize availability and reliability studies, a CCITT Handbook(s) should be created: Aim: Aid in the understanding and application of related Recommendations. Target Group: Operating, maintenance and planning staff and those involved in establishing and meeting performance criteria. -All Recommendations and proposed Recommendations developed by Study Group II and related Study Groups on Quality of Service, including dependability such as concepts, models, field data collection and evaluation, operation, maintenance and planning should be reviewed and the Handbook prepared based on this material. -The Handbook should contain descriptive explanations, practical instructions, examples and references inside and outside the CCITT.