Multimedia Systems WS 2010/2011 22.11.2010 M. Rahamatullah Khondoker (Room # 36/410 ) University of Kaiserslautern Department of Computer Science Integrated Communication Systems ICSY http://www.icsy.de
Outline Flow Characteristics Techniques to improve QoS Scheduling • FIFO Queuing • Priority Queuing • Weighted Fair Queuing Traffic Shaping • Leaky Bucket • Token Bucket Resource Reservation Admission Control 2 M. Rahamatullah Khondoker, University of Kaiserslautern
Flow characteristics
Flow Characteristics A data flow can be characterized by Reliability Delay Jitter And Bandwidth 4 M. Rahamatullah Khondoker, University of Kaiserslautern
Flow Characteristics: Reliability Reliability means to deliver packets without loss, duplication and error Lack of reliability means losing a packet or acknowledgement Different applications have different reliability needs Electronic mail, file transfer and internet access requires more reliability Telephony and audio conferencing requires less reliability 5 M. Rahamatullah Khondoker, University of Kaiserslautern
Flow Characteristics: Delay End-to-end delay: the time requires for a packet to travel from source to destination Different applications have different delay needs Telephony, audio conferencing, video conferencing and remote login requires minimum delay The delay of file transfer or email is not so important 6 M. Rahamatullah Khondoker, University of Kaiserslautern
Delay 7 M. Rahamatullah Khondoker, University of Kaiserslautern
Flow Characteristics: Jitter Jitter: The variations in delay for packets belonging to the same flow Packets Departing Arrival time Delay (s) time Packet 1 10:00 10:05 5 Packet 2 10:01 10:08 7 Packet 3 10:02 10:08 6 Packet 4 10:03 10:11 8 Different applications have different jitter needs For audio and video the above scenario is not acceptable For emails and file transfer the above scenario is acceptable 8 M. Rahamatullah Khondoker, University of Kaiserslautern
Flow Characteristics: Bandwidth Bandwidth is the band (range) of data transfer rate Example: 32Mbps bandwidth modem Different application needs different bandwidths Video conferencing requires more bandwidth Email requires less bandwidth 9 M. Rahamatullah Khondoker, University of Kaiserslautern
Techniques to improve QoS
Techniques to improve QoS Scheduling Traffic Shaping Admission Control Resource Reservation 11 M. Rahamatullah Khondoker, University of Kaiserslautern
Techniques to improve QoS: Scheduling Treating different flows in a fair and appropriate manner Scheduling techniques are FIFO queuing Priority queuing Weighted fair queuing FIFO Queuing In First-in, first out (FIFO) queue, packets wait in the buffer until the node (router or switch) is ready to process them Packets discarded when the arrival rate is higher than the processing rate 12 M. Rahamatullah Khondoker, University of Kaiserslautern
Techniques to improve QoS: Scheduling Priority queuing Packets are assigned to a priority class Each priority class has its own queue Packets in the highest priority class is processed first Packets in the lowest priority class is processed last 13 M. Rahamatullah Khondoker, University of Kaiserslautern
Techniques to improve QoS: Scheduling Weighted Fair Queuing Packets are assigned to a priority class Each priority class has its own queue Queues are weighted based on the priority of the queues Higher priority means higher weight System processes the queue in a round robin fashion Number of packets selected from each queue based on corresponding weight 14 M. Rahamatullah Khondoker, University of Kaiserslautern
Techniques to improve QoS: Traffic Shaping
Techniques to improve QoS: Traffic Shaping Leaky Bucket (Shaping): Token Bucket (Policing): Drop the packet if the bucket is full Allows bursty traffic at a regulated maximum rate 16 M. Rahamatullah Khondoker, University of Kaiserslautern
Techniques to improve QoS: Others Resource Reservation A flow of data needs resources (buffer, bandwidth, CPU time, etc) These resources are reserved in beforehand Admission Control Accepts or rejects packets of a flow based on flow specifications Used by routers or switches Flow specification specifies the necessary bandwidth, buffer size, CPU speed etc. 17 M. Rahamatullah Khondoker, University of Kaiserslautern
Thanks for your attention Any questions, comments or concerns?
M. Rahamatullah Khondoker, M.Sc. Integrated Communication Systems ICSY University of Kaiserslautern Department of Computer Science P.O. Box 3049 D-67653 Kaiserslautern Phone: +49 (0)631 205-26 43 Fax: +49 (0)631 205-30 56 Email: khondoker@informatik.uni-kl.de Internet: http://www.icsy.de
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