Chapter 6 Multimedia Networking Computer Networking: A Top Down Approach Featuring the Internet, 2 nd edition. Jim Kurose, Keith Ross Addison-Wesley, July 2002. A note on the use of these ppt slides: We’re making these slides freely available to all (faculty, students, readers). They’re in powerpoint form so you can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following: If you use these slides (e.g., in a class) in substantially unaltered form, that you mention their source (after all, we’d like people to use our book!) If you post any slides in substantially unaltered form on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this material. Modified by Amy Chung, Melissa Utzinger, and Brigitte Bolos Thanks and enjoy! JFK / KWR
Transcript
Chapter 6Multimedia Networking
Computer Networking: A Top Down Approach
Featuring the Internet, 2nd edition.
Jim Kurose, Keith RossAddison-Wesley, July 2002.
A note on the use of these ppt slides:We’re making these slides freely available to all (faculty, students, readers). They’re in powerpoint form so you can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following: If you use these slides (e.g., in a class) in substantially unaltered form, that you mention their source (after all, we’d like people to use our book!) If you post any slides in substantially unaltered form on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this material. Modified by Amy Chung, Melissa Utzinger, and Brigitte BolosThanks and enjoy! JFK / KWR
All material copyright 1996-2002J.F Kurose and K.W. Ross, All Rights Reserved
Chapter 6 outline
6.1 Multimedia Networking Applications
6.2 Streaming stored audio and video RTSP
6.3 Real-time, Interactivie Multimedia: Internet Phone Case Study
6.4 Protocols for Real-Time Interactive Applications RTP,RTCP SIP
6.5 Beyond Best Effort 6.6 Scheduling and Policing
Quality of Service: The ability to provide consistent, predictable data service delivery to satisfy customer application requirements. [Sysmaster.com]
“Best-effort” does not guarantee Quality of Service End-to-end packet delay and loss
All packets are treated equally at routers
Beyond “Best Effort”
Future: next generation Internet with QoS guarantees
Differentiated Services
RSVP
Integrated Services
Four principles of QoS Guarantees Packet classification Isolation: scheduling and policing High resource utilization Call Admission
Why do we NEED QoS guarantees?
The Chronicle of Higher Education. Napster Was Nothing Compared With This Year’s Bandwidth Problems, 28 Sept. 2001. http://chronicle.com/free/v48/i05/05a04401.htm
First-In-First-Out (FIFO) Priority Queuing Round Robin Weighted Fair Queuing (WFQ)
What are some possible scheduling mechanisms? (hint: similar policies are used for the dispatcher in OS )
First In First Out
discard policy: if packet arrives to full queue• Tail drop: drop arriving packet• priority: drop/remove on priority basis• random: drop/remove randomly
Non-Preemptive: Transmission of a packet is not interrupted once it has begun.
FIFO scheduling: send in order of arrival to queue
real-world example: Airline check in.
Priority Queuing
class may depend on marking or other header info, e.g. IP source/dest, port numbers, etc..
Starvation Prone. Motivation for our next two scheduling mechanisms
Round Robin
real world example: traffic jam
multiple classes cyclically scan across queues, serving one from each class (if available)
Weighted Fair Queuing (WFQ)
Guaranteed a percentage of the bandwidth
Generalized Round Robin
Each class gets weighted amount of service in each
cycle
Policing Mechanisms
Burst Size: max. number of pkts sent consecutively
(with no intervening idle)
Goal: limit traffic to not exceed declared parameters
Three common-used criteria:
Average Rate: How many pkts can be sent per unit time (in the long run)?
crucial question: what is the interval length: 100 packets
per sec or 6000 packets per min have same average!
Peak Rate: 6000 pkts per min. (ppm) avg. rate
1500 pkts per sec. (pps) peak rate
The Leaky Bucket
Token Bucket: limit input to specified Burst Size and Average Rate.
bucket can hold b tokens tokens generated at rate r token/sec unless bucket full over interval of length t: number of packets admitted
less than or equal to (r t + b).
The Leaky Bucket
token bucket, WFQ combine to provide guaranteed upper bound on delay, i.e., QoS guarantee!
WFQ
token rate, r
bucket size, b
per-flowrate, R
D = b/Rmax
arrivingtraffic
Other Sources
The Chronicle of Higher Education. Napster Was Nothing Compared With This Year’s Bandwidth Problems, 28 Sept. 2001. http://chronicle.com/free/v48/i05/05a04401.htm
