ITU Workshop on “Quality of Service and Quality of Experience of Multimedia Services in Emerging Networks” (Istanbul, Turkey, 9-11 February 2015) Overview and application of ITU-T Rec. G.1010 Paul Coverdale Consultant 1

Important caveat... The title of Rec. G.1010 “End-user multimedia QoS categories” should really be “End-user multimedia QoE categories” – At the time of publication (2001) there was no ITU-T definition of QoE, although the Rec. E.800 definition of QoS talks about “the degree of satisfaction of a user of the service” – This could be the subject of another workshop! 2

Basic premise of Rec. G.1010 The main rationale for G.1010 was to provide guidance on network performance requirements for different applications from an end-user point of view, and try to group them into a small number of categories – At the time, there was a school of thought which wanted to set different network performance values for every application 3

Key parameters impacting the end- user It was soon realised that in a digital (or packet) network, the important network impairments impacting the end-user are delay* and information loss (error tolerance) * Delay variation is not normally apparent to the end-user, since it is normally buffered out (although at the expense of additional fixed delay) 4

Derivation of model By examining the error tolerance and delay requirements for a range of different applications, it became possible to group these into a simple model having 8 different categories 5

Model for user-centric QoE categories 6

Similarity to well-known human perception limits From “Response Times: The 3 Important Limits”by Jakob Nielsen, 1993 The basic advice regarding response times has been about the same for thirty years [Miller 1968; Card et al. 1991]: – 0.1 second is about the limit for having the user feel that the system is reacting instantaneously – 1.0 second is about the limit for the user's flow of thought to stay uninterrupted, even though the user will notice the delay – 10 seconds is about the limit for keeping the user's attention focused on the dialogue. For longer delays, users will want to perform other tasks while waiting for the computer to finish, so they should be given feedback indicating when the computer expects to be done. Feedback during the delay is especially important if the response time is likely to be highly variable, since users will then not know what to expect. 7

Alternative view of model 8

Application of model The model provides an indication of the upper and lower boundaries for applications to be perceived as essentially acceptable to the user. Exceed an upper boundary (in loss or delay) and the service will be considered unsatisfactory; exceed a lower boundary, and the service will still be considered acceptable but may be wasteful from a network resource point of view because the service is using unnecessary resources. The model provides a simple means of determining whether a bearer channel qualifies to carry a given application's data. For example, a channel with one-way delay of 1 second cannot support effective, natural real-time communication such as voice and Telnet. Furthermore, even if the one-way delay were reduced to 100 ms, Telnet would still be compromised if there were any information loss: loss of a single character would be conspicuous. 9

Application of model The model shows how the underlying impairments of information loss and delay can be grouped appropriately, without implying that one class is "better" than another (as in categorisations that use Gold, Silver, etc.). This can be used as the basis for deriving realistic and meaningful network QoS classes for differentiating service performance. Note that the particular applications cited are exemplars rather than exhaustive. Other applications can be located in the schema by their similarity to these exemplars. 10

On-going enhancements to G.1010 Currently a work item in Q13/12 Title changed to reflect emphasis on QoE Updates solicited to performance targets for specific applications in Appendix I Consideration of whether these performance targets should remain as an Appendix, or move into main body of Rec. 11 Please contribute!

THANK YOU FOR YOUR ATTENTION! 12