QoS in the ITU-T

1. QoS in the ITU-T Charles Dvorak Vice-Chairman of SG12 Division Manager, AT&T Presented by:V. Androuchko, TSB, Project Administrator

2. General Points on QoS • Real QoS is end-to-end, as the user sees it • QoS and its various performance aspects are core competencies of the ITU-T • There are many QoS activities in the ITU-T • Some SGs work QoS as a generic item; others do system-specific work • SGs 2, 4, 11, 12, 13 and 17 do QoS work thatis not limited to any one technology • SGs 9, 15, 16 and SSG do QoS work that is typically system-dependent (e.g., cable, wireless, H.323-based, DSL, etc.)

3. General Points on QoS(continued) • Consistent with the previous points about the ITU having the lead expertise on QoS, many years ago it started the world’s QoS standards work by creating definitions and taxonomy in Rec. E.800, G.100, P.10, and by publishing QoS and Network Performance handbooks. • In recent years there has been widespread attention to QoS across ITU-T SGs, to assure new network technologies satisfy user needs (examples are E.430, E.860, G.107, G.109, G.1000, G.1010, I.350, I.356, J.163, Y.1541, etc) • Thus it is the ITU-T that reflects end user needs by setting end-to-end requirements that other protocol-oriented forums need to address

4. Study Group 12 • As the only SG in the ITU whose mandate and entire work program is QoS-oriented, SG12 was chosen to be the ITU-T’s Lead SG on QoS, with any needed coordination done in Q.15/12 • The mandate of SG12 is:“ End-to-end transmission performance of networks, terminals and their interactions, in relation to the perceived quality and acceptance by users of text, speech, and image applications; including the transmission implications of all networks (PDH, SDH, ATM and IP) and terminals.”

5. Study Group 12 (cont’d) • All SG12 work is performance- and QoS-related • WP1 deals with terminal-related performance issues • WP2 deals with performance planning/assessment • WP3 deals only with QoS over IP (all 5 projects) • Examples of current activities are • performance of IP terminals and gateways • multimedia performance/QoS over IP • voiceband application QoS over IP • test signals and objective assessment tools • transmission planning for all networks • QoS of VoIP across multiple domains

6. SG 12 Working Questions (1) • 1/12 - Evolution of the work programme • 2/12 -Speech Transmission Characteristics and Measurement methods for Terminals and Gateways interfacing Packet-Switched (IP) Networks • 3/12 - Transmission characteristics of speech terminals both for fixed circuit-switched and mobile networks • 4/12 - Telephonometric methodologies for hands-free terminals and speech enhancement devices (including AEC and Noise Reduction) • 5/12 - Telephonometric methodologies for handset and headset terminals

7. SG 12 Working Questions (2) • 6/12 - Analysis methods using complex measurement signals • 7/12 - Methods, tools and test plans for the subjective assessment of speech and audio quality • 8/12 - Extension of the E-Model • 9/12 - Objective measurement of speech quality under conditions of non-linear and time-variant processing • 10/12 - Transmission planning for voiceband, data and multimedia services

8. SG 12 Working Questions (3) • 11/12 - Speech transmission planning for multiple interconnected networks (e.g. public, private, Internet)  • 12/12 - Transmission performance considerations for voiceband services carried on networks that use Internet Protocol (IP) • 13/12 - Multimedia QoS/performance requirements • 14/12 - Effects of interworking between multiple IP domains on the transmission performance of VoIP and voiceband services

9. SG 12 Working Questions (4) • 15/12 - QoS and performance coordination • 16/12 - In-service non-intrusive assessment of voice transmission performance

10. Study Group 13 • SG13’s area is “Multi-protocol and IP-based networks and their internetworking” • WP4 is where QoS and performance is done; other WPs also do work that is QoS-affecting • The key QoS and performance activities are: • IP performance parameters and QoS classes • Traffic control • MPLS performance • Error performance & availability parameters • Ethernet performance • Call processing performance

11. Study Group 9 • SG 9 covers integrated broadband cable, and television and sound transmission • SG 9 has several QoS/performance activities: • Q.4 QoS of television transmission • Q.13 Voice and Video IP over cable • Q.19 Transport of video and audio over IP • Q.20 MPEG-2 transport quality parameters • Q.21 Eval. of conversational A/V quality • IP Cablecom provides dynamic QoS (J.163) in access part of the PacketCable network to requesting applications on a per-flow basis.

12. Study Group 2 • SG 2 is service- and operations-oriented • Q.5/2 is “Service Quality of Networks,” and has recently revised its Handbook on Quality of Service and Network Performance • The Quality of Service Development Group meets independently but reports to Q.5/2 Study Group 4 • SG4 is maintenance/management-oriented • Q.3/4: performance and fault management; IP network error perf. management in M.2301 • Q.9/4 is producing M.3341 (QoS/SLA over TMN X-interface for IP

13. Study Group 11 • SG11 is “Signaling requirements and protocols” • Q.8/11 deals with requirements for flexible management of dynamic bandwidth and QoS demands in connection control • Draft TRQ.qos.sig.cs1is specifying end-to-end Signaling Requirements for IP-QoS Study Group 15 • WP 2 is “Network Signal Processing” and deals with many items that are QoS-affecting • QoS is also an embedded aspect of other work, such as DSL and access networks

14. Study Group 16 • Q.F/16 is “Quality of Service (QoS) and End-to-End Performance in Multimedia Systems” • Producing 8 new Rec. on QoS policy, classification, call processing, signaling, architecture & mgmt. Study Group 17 • Q.2/17 is “Network performance and quality of service in data communication networks” • Current work is mostly oriented to Frame Relay Study Group SSG • No specific QoS activities, but its importance is recognized and there are frequent mentions of needed QoS capabilities; QoS is considered a key aspect of evolving wireless systems

15. 4 viewpoints on QoSRecommendation G.1000 (Communications Quality of Service : a framework and definitions)

16. Outline • Definitions and framework for QoS • Review of ITU-T activities in Qos, NP and User-perceived Quality • Classes of service for QoS and NP • Modelling and monitoring QoS • Generic parameters and terminals quality • Conclusion and annexes

17. QoS Classes • SG12 considers that the concept of QoS classes should be preferred to individual parameters, in general and for signalling end-to-end QoS. • It is important that the parameters that make up a given QoS class are independent of one another. • In this section will be considered G.1010, Y.1541, and G.109. • Some expected progress in QoS classes signalling will be considered in the last section of this presentation

18. Recommendation G.1010 • End-User Multimedia QoS Requirements • Performance expressed by parameters • Focused on user perceivable effects • Independent of the networks internal design • Parameters • Delay • Delay variation • Packet loss Ratio

19. Model for user-centric performance requirements • Mapping can be formalised into model for QoS categories

20. Benefit of end-user QoS category model • Model is based on end to end user perception of impairments, therefore not dependent on any specific technology for its validity • Provides an indication of the upper and lower boundaries for applications to be perceived as essentially acceptable to the user • Shows how the underlying impairments of information loss and delay can be grouped appropriately, without implying that one class is “better” than another • Provides basis for realistic network QoS classes (eg new draft ITU-T Rec. Y.1541) • Particular applications cited are examples rather than an exhaustive list

21. Recommendation Y.1541 QoS Classes:A Basis for IP Network QoS Control -- Neal Seitz, Chair SG 13/WP 4 • IP QoS control: key to IP/PSTN network convergence • Y.1541: “Step 1” in achieving QoS enabled IP networks • Quantify user/application needs via standard IP QoS classes • Signal the standardized QoS classes to and among networks • Realize the QoS classes using network QoS mechanisms • Encompass the major IP user application categories • Are relatable to practical IP network QoS mechanisms • Can be achieved in realistic network implementations • Are verifiable at jurisdictional network boundaries (TE/IWF can measure QoS to ensure values are met) • Can support QoS negotiation among networks

22. Table 1/Y.1541 –”Provisionnal IP QoS Classes U means « unspecified » or « unbounded » Note for IPVD : The value of 50ms is dependent on the capacity of inter-networks links. Smaller variations are possible where all the capacities are higher than primary rate, or when competing packet information fields are smaller than 1500 bytes

23. Table 2/Y.1541Guidance for IP QoS Classes New parameters intended to be included in Y.1540 : IPSLBR : IP Paket Severely Loss Block Ratio SES ip : Severely Errored Second

24. How to measure voice quality ? Two types of tools : Non-intrusive (I.N.M.D.): on real communication without reference signal, better for the supervision of network quality of service (P.561) End-to-end intrusive: on test calls with reference signal, better fitted for the measurement of quality as perceived by end users. (P.562) End to end measurement unit H.323 Terminal Gatekeeper I.N.M.D. Telephone IP PSTN End to end measurement unit NAS/VoIP gateway End to end measurement unit End to end measurement unit From V. Barriac, Q.16/12 Rapporteur

25. E-Model (G.107) • applicable to network planning of traditional, narrow-band and handset terminated networks • estimates voice transmission quality mouth-to-ear as perceived at receive side • renders a transmission factor R Rapporteurs of Q.8/12 : U. Jekosch, S. Möller

26. E-Model (Rec. G.107) • The Rating factor R is composed of • R = R0 - Is - Id – Ie,eff + A • R0 represents in principle the basic signal-to-noise ratio, including noise sources such as circuit noise and room noise. • Isis a combination of all impairments which occur more or less simultaneously with the voice signal. • Idrepresents the impairments caused by delay and the equipment impairment factor • Ie,eff represents impairments caused by low bit rate codecs; it also include impairments due to packet loss of random distribution; • A, the advantage factor, allows for compensation of impairment factors when there are other advantages of access to the user.

27. E-Model (Rec. G.107)

28. P.862 : Perceptual evaluation of speech quality, an objective method for end-to-end speech quality assessment of narrow‑band telephone networks and speech codecs • Overview of the basic philosophy used: A computer model of the subject, consisting of a perceptual and a cognitive model, is used to compare the output of the device under test with the input, using alignment information as derived from the time signals in the time alignment module

29. Terminals and Telephonometry Mapping Test Conditions And Equipments Handsfree (HFT) Handset Headset Generic Rec. Subjective assessment Methods P.342 Digital handsfree P.310 Digital handset P.380 P.313 Rev Mobile handsets, handsfree and headsets P.58 HATS P.832 Subjective Evaluation of HFT P.341 7 kHz HFT P.311 7 kHz Handset P.57 Artificial ears P.300 Audio group Terminal P.51 Artificial Mouth P.340 Handsfree transmission P.581 Use of Hats P.VoIP IPTerminals P.SPDA Speech processing devices for acoustic enhancement P.501 et P.502 Complex signals and Analysis methods P.GTWY IPgateways P.50 Artificial voice

30. Concluding Remarks • QoS is a big core competency of the ITU-T, the primary global body setting QoS requirements • Application requirements are well understood • Major e2e QoS obstacles/gaps have been identified • agreed-upon delay allocations (network vs. terminal) • lack of scalable, reliable e2e signaling solutions • QoS routing usually a single path w/o fault tolerance • restoration of multi-layer functionality (MPLS, IP, QoS) • Recent developments related to these issues: • e2e QoS signaling requirements being developed • MPLS “fast restore” for guaranteed, restorable QoS paths? • But many industry-wide QoS challenges remain (on-demand dynamic QoS, interdomain QoS, etc.)

31. Thank you very much for your attention!