Voice Quality John Horrocks (DTI) Direct line: Date: 20 November

2 Inter-relationship of factors Codec Performance Network Delay Network Packet Loss Network Jitter Overall Delay Application Factors Overall Packet Loss Jitter Buffers Perceived Speech Quality QoS Service Level

3 Approach to Characterizing Speech QoS  QoS is defined subjectively as perceived by the user,  It is end to end (e.g. mouth to ear for speech),  A number of QoS Service Classes are defined,  Classes include guaranteed quality (statistically) and unguaranteed (best effort).

4 Specifying the TIPHON Speech QoS Classes Undefined Better than G.711 Listener Speech Quality (One-way Non- conversational) Equivalent or better than GSM-FR Equivalent or better than G.726 at 32 kbit/s Class Wideband Narrowband Acceptable Unguaranteed (Best Effort) < 400ms* < 150ms < 100ms End-to-end Delay (G.114) > 50* > 80 N.A. Overall Transmission Quality Rating (R) > 70 MediumHigh < 400ms > 50 Undefined * Target (MOS>2.5) (MOS>3.6) (MOS>4.0) (MOS: 5=Excellent, 4=Good, 3= Fair, 2= Poor, 1=Bad)

5 TIPHON QoS Classes High Medium Acceptable Best effort

6 Call Signalling Packet Flow Application Plane Transport Plane Today’s Internet QoS Model Transport Domain 1 Transport Domain 2 Transport Domain 3

7 QoS Signalling if same technology eg RSVP Packet Flow Tomorrow’s Internet QoS Model Call Signalling Application Plane Transport Plane Transport Domain 1 Transport Domain 2 Transport Domain 3

8 Problems with Today’s Approach BUT Transport domains may support different QoS mechanisms and policies. Need a business model for supplying and charging for QoS QoS messages are not signalled to the service provider - how can he control the QoS levels offered? No mechanism to select transport domain on basis of QoS levels supported. c.f choice of alternative long distance carriers. Who owns the end to end picture?

9 Call Signalling Packet Flow QoS Signalling The TIPHON Application Controlled Approach to QoS Application Plane Transport Plane Service Domain 1 Transport Domain 1 Transport Domain 2 Transport Domain 3

10 Advantages of the TIPHON Approach to End-to-end QoS CLEAR BUSINESS MODEL  The Application Service Provider is in the driving seat. End-to-end (inter-domain) QoS control takes place within the Application Plane. (Between Service Providers)  Required end-to-end QoS levels are established within the Application Plane (Between the End User and Service Provider)  Transport Domains (Operators) provide a QoS service to the associated Service Domains (Service Providers). QoS control within a Transport Domain is the responsibility of the Operator of that domain

11 Advantages of the TIPHON Appoach to End-to-end QoS (Cont) OTHER ADVANTAGES  A common interface can be defined between a Transport Domain and its associated Service Domain even though different QoS mechanisms may be present within the Transport Plane  No QoS information need be exchanged between the End User and Network Operator or between Network Operators  Application Controlled Firewalls and NATS can be accommodated

12 Call Signalling Media Flow QoS Signalling Mixed Transport QoS Mechanisms Application Plane Transport Plane Service Domain 1 Service Domain 2 Transport Domain 1 (RSVP) Transport Domain 2 (Diff Serv) Transport Domain 3 (MPLS/ATM) Transport Domain 4 (RSVP)

13 RSVP Example TRM TPE ICF Transport Domain Media Path QoS Signalling RSVP Signalling Call Control Signalling QoS Signalling & Addressing - from Application Plane Media stream TRM=Transport Resource Manager TPE= Transport Policy

14 Diff Serv Example TRM TPE ICF Transport Domain Media Path QoS Signalling Call Control Signalling QoS Signalling & Addressing - from Application Plane Add Diff Serv Marker Media stream Policy Enforceme nt Element

15 Summary TIPHON uses a layered architecture which separates Application and Transport Planes. Administrative Domains define roles of End User, Service Provider (SP) and Transport Operator. Basis for security protection and SLAs. The initiating SP negotiates transport QoS budgets, domain by domain, with transport network operators and other SPs End-to-end QoS is responsibiliy of initiating SP. TRM and ICF model enables any transport QoS mechanisms to be deployed in transport plane ICF models QoS boundaries, firewalls and NATs.

16 Documents

17 NICC VoIP Quality Group Working about a year to revise UK transmission plan for public networks Inputs from TIPHON Aims to complete by Easter 2002 Assume normal NTP at customer premises

18 Progress so far Delay is the most critical impairment Everyone should use G.711 “standard PSTN” coding to use less delay Minimise speech frame size and frames/packet Use RTP header compression and data packet fragmentation Keep packet loss below 1% overall Need to minimise the number of IP-Circuit switched transitions, but IP based interconnection will develop only slowly so this will be difficult Avoid transcoding

19 Comments Some routings involving number portability and non- geographic services are very tortuous Use on onward routing solution Lack of direct interconnection routes Will need a statistical approach Not tackled the design / apportionment issue yet Still quite a long way to go…with some tough decisions to come…