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 ( , 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
( )
Bit rate

21. Deterministic versus Statistical Multiplexing
22 Mbps
( )
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 the desired service (QoS parameters)
• Network performs admission control to determine if sufficient 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 its specification

33. THANK YOU!