Extrait du rapport ETSI TR

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1 AHQ Extrait du rapport SI TR Date : 1/05/2013 Cet extrait du rapport technique SI Partie 1 commence par décrire les fonctions essentielles des différents éléments de service avant de dresser un tableau indiquant la sensibilité de chacun de ces éléments aux critères de QoS retenus par Qostic : Latence, Gigue, Intégrité, Capacité et Disponibilité. Pour chacun des services le tableau indique également les classes de service correspondantes selon les différentes normes actuellement en usage ITU-T Y.1541, UMTS, ITU-T G1010, PHB et INTRADIFF.

2 SI TR V1.1.1 ( ) Technical Report User Group; End-to-end QoS management at the Network Interfaces; Part 1: User's E2E QoS - Analysis of the NGN interfaces (user case)

3 27 SI TR V1.1.1 ( ) Annex A: Mapping of services and QoS requirements Table A.1 provides a list of the main services with the description of their essential functions and their use conditions in order to be able to define the key criteria to ensure a proper management of the end-to-end QoS. The services listed are drawn from ITU-T Recommendation G.1010 [i.1] with some changes to take into account the current market situation. Some of these services contain several components. In fact, since many services are built on a composition of several components that could be provided by differing providers, tables A.1 and A.2 should highlight the specific requirements of each component. Some attempts have been done in table A.2 to bring in such components (e.g. signalling, authentication or DNS) but further study is needed to embrace all the service components. In today's technology the QoS is most of the time managed as a whole and therefore should be handle according to the most straining component of the service. As technology evolves, this should be revisited accordingly. Table A.1: Service functional definitions Services or service components Audiobroadcast Audio-conference Authentication Directory enquiry services DNS e-commerce Electronic mail Fax Files downloading Instant messaging games Internet access Multimedia Message Service (MMS) Basic functions A mechanism whereby audio content can be rendered at the same time that it is being transmitted to the client over the data network. Connection between two or more terminals, exchanging audio information only. (See note 1). Benefit consisting in proving that a user is authorised (by means of an identifier and password or other more robust process) to use a service. This applies to a network service or to an application (web, , etc.) Operator or machine based service intended to provide information on phone number, addresses or addresses of people or organizations on user request. (See note 2). Allowing a user to ask a server to convert a domain name into address IP. This service is pre-requisite to most Internet usages. It is generally provided with the access to Internet. The commercial activities carried out through computer networks such as the Internet, including online promotion and sale of products, services and information, as well as the exchange of electronic correspondence. (See note 3). Exchange of text files with possible attached files between two PCs via networks and through distant servers where the message can be stored until the recipient downloads it. The minimal protocols aiming at issuing the service are POP3 and SMTP. A file containing multimedia data (text, picture or digitized sound) can be linked with electronic mail. Reception and sending may have different requirements: 1) (reception): transfer of the distant server to the local machine. 2) (sending): transfer of the local machine to the distant server. Telecommunications service of transport of facsimile via the PTN such that any user can use equipment connected to a network termination point to exchange facsimiles with another user of equipment connected to another termination point. Service allowing to search and to transfer files from the user computer to a distant server in ftp or http mode or conversely. Internet oriented system, notifying the presence of a user for instantaneous exchange of messages. Differs from primarily in that its primary focus is substantially immediate end-user delivery. Internet-based electronic games involving several individuals interacting with each other or with a machine in ongoing, open-ended play. Making facilities and/or services available for the purpose of providing an access to the public Internet in order to provide a user with access to services or resources of the Internet. (See notes 4, 5, 6 and 7). Transfer of multimedia messages between users without the requirement for the multimedia messages to be transferred in real-time. SI

4 28 SI TR V1.1.1 ( ) Services or service components Newsgroup (Usenet) Short Message Service (SMS) Telecontrol Basic functions A newsgroup is a repository within the Usenet system for messages posted from many users at different locations. Real-time dispatch of messages between local machines and server on which all the messages are available for consultation by the general public or by a restrained group of users. Gives the ability to send character messages to phones. SMS messages can be Mobile Originate (MO) or Mobile Terminate (MT). Real-time interaction between local and remote machines to control and monitor equipment and Inputs/Outputs signals from various facilities in remote locations. Telephone-conference: Three or more terminals exchanging audio information. (See note 8). Telephony Service Provides users with the ability for real time two way speech conversation via the network. (See note 9). Telnet The Internet standard protocol for remote login. Runs on top of TCP/IP. Defined in STD 8, RFC 854 [i.16] and extended with options by many other RFCs. Video broadcast A mechanism whereby video content can be rendered at the same time that it is being transmitted to the client over the data network. (See note 10). Video TeleConferencing service (VTC) Service providing an interactive, bi-directional, real time audio-visual communication, normally intended for multiple users at either end. (See notes 11, 12 and 13). Voice messaging Any system for sending, storing and retrieving audio messages, like a telephone answering machine. A voice mailbox is typically associated with a telephone number or extension. This service is a multicomponents service generally including: a) recording, storage and transmission of a welcome message by the voic owner; b) recording and storage of a message by a caller on no reply or busy line under the guidance of a voice server; c) information of the voic owner that a message is available; d) listening of a recorded message by the voic owner. NOTE 1: This service includes necessarily a signalling component with its specific QoS requirements. NOTE 2: This service includes necessarily a signalling component having specific QoS requirements. NOTE 3: Includes On line shopping. NOTE 4: The Internet access can be separated into two parts, the physical and the logical access. The physical access provides a connection form the user's premises to, but not including, the POP (normally a dialup circuit or broadband link or leased line) whereas the logical access consist of the setting up of an account that later on enables the user by a login process with the ability to access to the services and resources of the Internet (normally by assigning an IP address). NOTE 5: The physical and logical access may be provided by different service providers. NOTE 6: The function of the physical access may be provided by several interconnected networks. NOTE 7: Internet access is an example of multicomponents services: it cannot work without authentication and domain name services but it usually also includes other components such as Web browsing (consultation, data transfer), web page hosting, etc. Specific QoS requirements are needed for such components. NOTE 8: This service includes necessarily a signalling component and sometimes additional facilities with their specific QoS requirements. NOTE 9: This service includes necessarily a signalling component with its specific QoS requirements. NOTE 10: This service usually includes an audio component with its specific QoS requirements. NOTE 11: The terminals are normally exchanging audio/video/graphic information. NOTE 12: This service includes necessarily signalling and audio components with their specific QoS requirements. NOTE 13: Two options are possible: a) Audio and Video using the same channel. b) Audio and Video using differing channels. Details on the requirements for each of these services can be found in ITU-T Recommendation G.1010 [i.1]. Additional information on IP-TV should be soon available from SI and ITU-T. Table A.2 gives example of QoS requirements for the above services. As stated earlier, some services contain several components, each of them having often differing QoS requirements. This should results in detailing the QoS requirements for each component but this would need technologies not available at the moment. This is why the table provides for each service the QoS requirements of the most constraining component. These requirements may also vary depending on how a particular provider intends to deliver such a service. SI

5 29 SI TR V1.1.1 ( ) Table A.2 : Mapping of the various standard QoS classes for some services Service Medium Sensitivity to QoS parameters QoS class CoS QoS class PHB QoS criteria components Fidelity Y.1541 UMTS G1010 depending (Information Capacity Availability classes variation loss) (INTRADIFF) games < 200 ms U Zero DBW UAT Class 2 AF1.1 CoS 6.4 Telecontrol < 250 ms U Zero DBW UAI Class 2 AF1.1 CoS 6.4 Telnet < 200 ms U Zero DBW UAI Class 2 AF2 CoS 6.4 Video TeleConferencing service (VTC) Audio-conference Telephone service Voice messaging record and playback Electronic mail SMTP/POP server access Web Browsing MMS (Multimedia Message Service) Instant messaging (chat) High priority transaction services e.g. e-commerce, ATM Video Audio Audio Audio <150 ms U 400 ms with echo control U < 150 ms < 1 ms 400 ms with echo control < 1 ms < 150 ms < 1 ms 400 ms with echo control < 2 s for record < 1 s for playback < 2 s (< 4 s acceptable) <2 s/page (< 4 s/page acceptable) < 2 s (< 4 s acceptable) < 2 s (< 4 s acceptable) < 2 s (< 4 s acceptable) < 1 ms < 1 ms PLR < 1 % PLR < 1 % PLR < 3 % PLR < 3 % PLR < 3 % PLR < 3 % PLR < 3 % DBW UAT Class 0 DBW 16 kbit/s to 384 kbit/s DBW 4 kbit/s to 64kbit/s DBW 4 kbit/s to 64 kbit/s UAT Class 1 UAT Class 0 Convers. UAT Class 1 Convers. DBW UAT Class 0 Convers. DBW UAT Class 1 Convers. DBW 4 kbit/s to 32 kbit/s UAT Class 1 U Zero VBW UAT Class 4 U Zero VBW UAT Class 3 U Zero VBW UAT Class 3 U Zero VBW UAI Class 3 U Zero VBW UAI Class 4 Responsive Responsive Responsive Responsive Responsive Responsive AF1.2 CoS 6.2 AF2 CoS 6.3 EF CoS 6.0 EF CoS 6.1 EF CoS 6.0 EF CoS 6.1 AF3.2 CoS 5.2 AF3.2 CoS 5.0 AF3.1 CoS 5.2 AF3.1 CoS 5.2 AF3.1 CoS 5.2 AF3.1 CoS 5.1 AF3.1 CoS 5.1 SI

6 30 SI TR V1.1.1 ( ) Service Medium Sensitivity to QoS parameters QoS class CoS QoS class PHB QoS criteria components Fidelity Y.1541 UMTS G1010 depending (Information Capacity Availability classes variation loss) (INTRADIFF) Authentication < 250 ms U Zero VBW UAI Class 2 AF4 CoS 4.1 DNS < 250 ms U Zero VBW UAI Class 2 AF4 CoS 4.1 Signalling < 250 ms U Zero DBW UAI Class 3 AF4 CoS 4 SMS (Short Message Service) Files downloading (FTP) < 30 s U Zero VBW UAT Class U Background < 15 s (< 60 s acceptable) Audiobroadcast Audio < 10 s < 1 ms Video broadcast Video < 10 s < 1 ms Electronic mail SMTP to POP server transfer Newsgroup (Usenet) Can be several minutes Can be several minutes U Zero VBW UAT Class U Background PLR < 1 % PLR < 1 % VBW 16 kbit/s to 128 kbit/s VBW 16 kbit/s to 384 kbit/s UAT Class 5 Streaming UAT Class U Streaming U Zero VBW UAT Class 5 Background U Zero VBW UAT Class 5 Background DNC Timely Timely Timely DNC DNC AF3.2 CoS 3.1 AF3.1 CoS 3.0 AF CoS 2.1 AF CoS 2.0 BE CoS 1.1 BE CoS 1.1 SI

7 31 SI TR V1.1.1 ( ) Service Medium Sensitivity to QoS parameters QoS class CoS QoS class PHB QoS criteria components Fidelity Y.1541 UMTS G1010 depending (Information Capacity Availability classes variation loss) (INTRADIFF) Non-critical Fax ("real-time") U <10-6 BER VBW UAT Class 5 Background BE CoS 1.0 < 30 s/page DNC Non-critical: Can be Fax (store & forward) several minutes NOTE 1: BER: Bit Error Rate DNC: Non Critical DBW: Dedicated Bandwidth : Error Tolerant : Error Intolerant PHB: Per Hop Behaviour PLR: Packet Loss Rate U: Unspecified UAI: UnAvailability Intolerant UAT: UnAvailability Tolerant VBW: Variable Bandwidth NOTE 2: Per Hop Behaviour parameters: AF: Assured Forwarding BE: Best Effort EF: Expedited Forwarding U <10-6 BER VBW UAT Class 5 Background DNC BE CoS 1.0 SI

8 32 SI TR V1.1.1 ( ) A.1 ITU-T Recommendation Y.1541 QoS class The characteristics of each Y.1541 QoS class are summarized here: Class 0: Real-time, highly interactive applications, sensitive to jitter. Mean delay upper bound is 100 ms, delay variation is less than 50 ms, and loss ratio is less than Application examples include VoIP, Video Teleconference. Class 1: Real-time, interactive applications, sensitive to jitter. Mean delay upper bound is 400 ms, delay variation is less than 50 ms, and loss ratio is less than Application examples include VoIP, Video Teleconference. Class 2: Highly interactive transaction data. Mean delay upper bound is 100 ms, delay variation is unspecified, and loss ratio is less than Application examples include signalling. Class 3: transaction data. Mean delay upper bound is 400 ms, delay variation is unspecified, and loss ratio is less than Application examples include signalling. Class 4: Low Loss Only applications. Mean delay upper bound is 1s, delay variation is unspecified, and loss ratio is less than Application examples include short transactions, bulk data, video streaming. Class 5: Unspecified applications with unspecified mean delay, delay variation, and loss ratio. Application examples include traditional applications of Default IP Networks. Class 6: Mean delay 100 ms, delay variation 50 ms, loss ratio Applications that are highly sensitive to loss, such as television transport, high-capacity TCP transfers, and TDM circuit emulation. Class 7: Mean delay 400 ms, delay variation 50 ms, loss ratio Applications that are highly sensitive to loss, such as television transport, high-capacity TCP transfers, and TDM circuit emulation. Table A.3 gives some examples of services for each of these classes. Table A.3: Y.1541 IP QoS Class Definitions and Network Performance Objectives QoS class IPTD IPDV IPLR IPER IPRR Applications (examples) ms 50 ms Real-time, jitter sensitive, high interaction (VoIP, VTC) ms 50 ms Real-time, jitter sensitive, ms U Transaction data, highly interactive (Signalling) ms U Transaction data, interactive 4 1 s U Low loss only (short transaction, bulk data, video streaming) 5 U U U U - Traditional applications of default IP network ms 50 ms High bit rate, strictly low loss/error (TV broadcast on IP) ms 50 ms High bit rate, strictly low loss/error A.2 UMTS Classes of Service (CoS) UMTS QoS Classes of Service are defined in [i.6]. When defining the UMTS QoS classes, also referred to as traffic classes, the restrictions and limitations of the air interface have to be taken into account. It is not reasonable to define complex mechanisms as have been in fixed networks due to different error characteristics of the air interface. The QoS mechanisms provided in the cellular network have to be robust and capable of providing reasonable QoS resolution. Table A.4 illustrates the QoS classes for UMTS. SI

9 33 SI TR V1.1.1 ( ) There are four different QoS classes: conversational class; streaming class; interactive class; and background class. The main distinguishing factor between these QoS classes is how delay sensitive the traffic is: Conversational class is meant for traffic which is very delay sensitive while Background class is the most delay insensitive traffic class. A.2.1 Conversational class The most well known use of this scheme is telephony speech (e.g. GSM). But with Internet and multimedia a number of new applications will require this scheme, for example voice over IP and video conferencing tools. Real time conversation - fundamental characteristics for QoS: preserve time relation (variation) between information entities of the stream; conversational pattern (stringent and low delay). A.2.2 Streaming class When the user is looking at (listening to) real time video (audio) the scheme of real time streams applies. The real time data flow is always aiming at a live (human) destination. It is a one-way transport. The delay variation of the end-to-end flow should be limited, to preserve the time relation (variation) between information entities of the stream. But as the stream normally is time aligned at the receiving end (in the user equipment), the highest acceptable delay variation over the transmission media is given by the capability of the time alignment function of the application. Acceptable delay variation is thus much greater than the delay variation given by the limits of human perception. Real time streams - fundamental characteristics for QoS: preserve time relation (variation) between information entities of the stream. A.2.3 class When the end-user, that is either a machine or a human, is on line requesting data from remote equipment (e.g. a server), this scheme applies. Examples of human interaction with the remote equipment are: web browsing, data base retrieval, server access. Examples of machines interaction with remote equipment are: polling for measurement records and automatic data base enquiries (tele-machines). traffic is the other classical data communication scheme that on an overall level is characterised by the request response pattern of the end-user. At the message destination there is an entity expecting the message (response) within a certain time. Round trip delay time is therefore one of the key attributes. Another characteristic is that the content of the packets should be transparently transferred (with low bit error rate). traffic - fundamental characteristics for QoS: request response pattern; preserve payload content. SI

10 34 SI TR V1.1.1 ( ) A.2.4 Background class When the end-user, that typically is a computer, sends and receives data-files in the background, this scheme applies. Examples are background delivery of s, SMS, download of databases and reception of measurement records. Background traffic is one of the classical data communication schemes that on an overall level is characterised by that the destination is not expecting the data within a certain time. The scheme is thus more or less delivery time insensitive. Another characteristic is that the content of the packets should be transparently transferred (with low bit error rate). Background traffic - fundamental characteristics for QoS: the destination is not expecting the data within a certain time; preserve payload content. A.2.5 Summary and QoS Information processing Table A.4: Main features of traffic classes Traffic class Fundamental characteristics Example of the application Conversational class conversational RT - Preserve time relation (variation) between information entities of the stream Conversational pattern (stringent and low delay ) Streaming class streaming RT - Preserve time relation (variation) between information entities of the stream class best effort - Request response pattern - Preserve payload content Background Background best effort - Destination is not expecting the data within a certain time - Preserve payload content - voice - streaming video - Web browsing - background download of s Explanation on possible way for the QoS Information processing is given in [i.7]. Table A.5: UMTS QoS Information processing QoS class UMTS Traffic Class Traffic Handling Priority A Conversational N/A B Streaming N/A C 1 D 2 E 3 F Background N/A NOTE: QoS class represents the highest class that can be used for the bearer. A.3 ITU-T Recommendation G.1010 QoS categories ITU-T Recommendation G.1010 [i.1] defines a model for multimedia Quality of Service (QoS) categories from an enduser viewpoint. By considering user expectations for a range of multimedia applications, eight distinct categories are identified, based on tolerance to information loss and delay. It is intended that these categories form the basis for defining realistic QoS classes for underlying transport networks, and associated QoS control mechanisms. The impact on QoS of the key parameters impacting the user is detailed hereafter. SI

11 35 SI TR V1.1.1 ( ) A.3.1 Key parameters impacting the user A manifests itself in a number of ways, including the time taken to establish a particular service from the initial user request and the time to receive specific information once the service is established. has a very direct impact on user satisfaction depending on the application, and includes delays in the terminal, network, and any servers. Note that from a user point of view, delay also takes into account the effect of other network parameters such as throughput. A variation variation is generally included as a performance parameter since it is very important at the transport layer in packetized data systems due to the inherent variability in arrival times of individual packets. However, services that are highly intolerant of delay variation will usually take steps to remove (or at least significantly reduce) the delay variation by means of buffering, effectively eliminating delay variation as perceived at the user level (although at the expense of adding additional fixed delay). A Information loss Information loss has a very direct effect on the quality of the information finally presented to the user, whether it is voice, image, video or data. In this context, information loss is not limited to the effects of bit errors or packet loss during transmission, but also includes the effects of any degradation introduced by media coding for more efficient transmission (e.g. the use of low bit-rate speech codecs for voice). A.3.2 Application Figure A.1 shows the main features and applications for these eight categories with an indication of the QoS requirement ranges for some services. Packet Loss 5% 0% Zero loss Conversational voice and video Voice/video messaging Streaming audio/video 100 ms 1 s 10 s Fax 100 s Command /control (e.g. Telnet, games) Transactions (e.g. E-commerce, Web-browsing, access) Messaging, Downloads (e.g. FTP, still image) Background (e.g. Usenet) T Figure A.1: G Mapping of user-centric QoS requirements Figure A.2 provides a recommended model for end-user QoS categories, where the four areas of delay are given names chosen to illustrate the type of user interaction involved. Of course, it is possible that each category could be subdivided into further categories to provide a range of quality levels for a specific service, as has been done for conversational voice in [i.8]. SI

12 36 SI TR V1.1.1 ( ) Figure A.2: G Model for user-centric QoS categories A.4 Per Hop Behaviour parameters (DIFFSERV) The Per Hop Behaviour parameters comprise three classes: AF: Assured Forwarding. BE: Best Effort. EF: Expedited Forwarding. A.4.1 Assured Forwarding IF defines four independently forwarded AF classes, within each class one of three different levels of drop precedence can be specified. AFij, with 1 i 4 and 1 j 3, represents the DSCP for AF class i with drop precedence j. It is recommended to support at least one AF class with two drop precedence levels. A.4.2 Best Effort The IP flows which are mapped to this PHB have no expectations on the level of service received by the SD layers. So for BE traffic packets are directed to a BE FIFO queue, but without any conditioning. They remain in the queue until layer 2 resources are made available, as a result of layer 2 on capacity control and scheduling. A.4.3 Expedited Forwarding The EF PHB is designed to provide low-loss, low-latency, low-jitter, assured bandwidth services, where packets normally encounter short or empty queues. Intuitively the service rate for EF traffic on the output satellite interface should be at least the configured rate R, independent of the offered load of non-ef traffic. SI