A T M ( QoS )

1. A T M (QoS)

2. QoS (Quality of Service) ATM - Service Classes CBR - Constant Bit Rate Circuit emulation, e.g. T1 (1.5 Mbit/s) or E1 (2 Mbit/s) Real-time audio / video coded at a constant bit rate rt-VBR - real time Variable Bit Rate Compressed video (MPEG-2) coded at a variable bit rate with stringent real- time requirements (video conference) nrt-VBR - non real time Variable Bit Rate Frame Relay, data transfers for transaction-processing applications (airline reservations, banking transactions, etc.) UBR - Unspecified Bit Rate „Best effort“ without any guarantees (e-mail, file transfer, etc.) ABR - Available Bit Rate Adaptive „best effort“ service with guaranteed minimum cell rate (LAN emulation)

3. ATM - Traffic Parameters PCR - Peak Cell Rate Maximum rate at which cells will be sent SCR - Sustainable Cell Rate Long-term average cell rate MCR - Minimum Cell Rate Minimum acceptable cell rate MBS - Maximum Burst Size Maximum number of consecutive cells in a burst CDVT - Cell Delay Variation Tolerance Maximum acceptable cell jitter The traffic parameters make up a traffic descriptor, describing the characteristics of the source.

4. QoS Parameters CTD - Cell Transfer Delay Elapsed time between cell exit event at the source and corresponding cell entry event at the destination. maxCTD - maximum Cell Transfer Delay CDV - Cell Delay Variation Time difference between minimum and maximum cell transfer delay, i.e peak-to-peak cell delay variation. CLR - Cell Loss Ratio Ratio of lost cells to total transmitted cells The QoS parameters describe the desired performance at the destination of the virtual channel.

7. Traffic Characterization Most Understood Least Understood

8. Traffic Characterization Most Understood Voice Least Understood

9. Traffic Characterization Most Understood Voice CBR video Least Understood

10. Traffic Characterization Most Understood Voice CBR video Packet data Least Understood

11. Traffic Characterization Most Understood Voice CBR video Packet data Image Least Understood

12. Traffic Characterization Most Understood Voice CBR video Packet data Image VBR video Least Understood

13. Multiplexing • Two basic approaches • Deterministic multiplexing • Statistical multiplexing

14. Deterministic Multiplexing • The traditional means of bandwidth allocation in telecommunications networks • Each traffic type has an inherent bit rate (e.g., voice traffic = 64 kilobits per second) • Allocate precisely that bandwidth for each call, for the duration of the call

15. Deterministic Multiplexing (Cont’d) • Advantages: • Simple • Works great for CBR traffic (PCR = SCR) • Disadvantages: • Inefficient for VBR traffic (PCR !=SCR) • Allocating PCR can waste lots of capacity

16. A Statistical multiplexer (or stat-mux) is a device which allows broadcaster to change the bitrate of channels according to those channels' needs. If, for example, a broadcaster is showing news on Channel 1 and football on Channel 2, with fixed multiplexing each channel has, say, 2 Mbps. The news channel is fine — no movement requires very little bandwidth. The football channel however begins to suffer as fast movement and crowd shots require large bandwidth to produce a clear picture. A statistical multiplexer allows the broadcaster to allocate bandwidth to wherever it is needed. Thus 0.5 Mbps are allocated to the news and 3.5 Mbps to the football. This results in good a quality picture for both channels.

17. Deterministic versus Statistical Multiplexing Bit rate Source 1: peak 12 Mbps, mean 8 Mbps

18. Deterministic versus Statistical Multiplexing Bit rate 12 Mbps

19. Deterministic versus Statistical Multiplexing Source 2: peak 10 Mbps, mean 6 Mbps Bit rate

20. Deterministic versus Statistical Multiplexing 22 Mbps (12 + 10) Bit rate

21. Deterministic versus Statistical Multiplexing 22 Mbps (12 + 10) Bit rate Average utilization will be 14/22 = 64%

22. Deterministic versus Statistical Multiplexing Bit rate Bit rate

23. Deterministic versus Statistical Multiplexing Bit rate Bit rate

24. Deterministic versus Statistical Multiplexing Bit rate Bit rate

25. Deterministic versus Statistical Multiplexing Bit rate Bit rate

26. Deterministic versus Statistical Multiplexing Bit rate Bit rate

27. Deterministic versus Statistical Multiplexing Bit rate Bit rate

28. Deterministic versus Statistical Multiplexing Bit rate Bit rate

29. Deterministic versus Statistical Multiplexing Bit rate Bit rate

30. Deterministic versus Statistical Multiplexing Bit rate Bit rate

31. Deterministic versus Statistical Multiplexing Bandwidth saving with Statistical Multiplexing Bit rate Bit rate

32. Traffic Contract • User submits to network a request for a connection with a description of its traffic (traffic parameters) and thedesired service (QoS parameters) • Network performs admission control to determine ifsufficient resources are available to (a) satisfy the desired QoS of new connection (b) without violating QoS of existing connections If sufficient resources are available, it accepts the flow. Otherwise, it rejects the flow • Network performs policing and shaping at the network entrance to ensure that user’s adheres to itsspecification

33. THANK YOU!