1. 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 All material copyright 1996-2002 J.F Kurose and K.W. Ross, All Rights Reserved

2. 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 Mechanisms  6.7 Integrated Services  6.8 RSVP  6.9 Differentiated Services

3. Quality of Service on IP Networks Review 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

4. 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

5. 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

6. Download File Size Comparison Compressed movies Crouching Tiger Hidden Dragon 800 Mb Video Games Tomb Raider 3 203 Mb TV shows The Simpsons 25 Mb MP3s Metallica song 5.7 Mb Photos 8 x 10 Color image81 Kb Text documents Microsoft Word Document 19 Kb

7. Inbound/Outbound Traffic

8. Simple Network Scenario w/2 applications

9. Principles for QOS Guarantees  Example: 1Mbps IP phone, FTP share 1.5 Mbps link.  bursts of FTP can congest router, cause audio loss packet marking needed for router to distinguish between different classes; and new router policy to treat packets accordingly Principle 1

10. IP datagram format ver length 32 bits data (variable length, typically a TCP or UDP segment) 16-bit identifier Internet checksum time to live 32 bit source IP address head. len type of service flgs fragment offset upper layer 32 bit destination IP address Options (if any)

11. Application Priority?  Should multimedia applications get priority over non-delay sensitive applications?

12. Bandwidth Shaping 1.Monitor a.Traffic types b.Traffic issues c.Problem location 2.Classify a.WAN links or Departments b.Applications and Protocols 3.Enforce (Traffic Control) a.Policy writing and application 4.Report 5.Conclude

13. Bandwidth Shaping: Traffic Types  What Internet applications are we running?  Which applications are important to academics?  Which applications are not important?  Which applications are sensitive to delay? Bandwidth Shaping: Traffic Issues  What do you think are some of the traffic issues on this campus?  Where is the problem?

14. Bandwidth Shaping: Classify  Pipes  WAN links  Departments  Virtual Channels  SMTP  VoIP  FTP  HTTP MP3 downloads (*.mp3)

15. Bandwidth Usage Analysis by Pipes

16. Bandwidth Usage Analysis by Virtual Channel

17. Pipe Bandwidth Usage Analysis by Time of Day

19. Bandwidth Shaping: Enforcing Policy  Policy Writing and Application  Minimum  Maximum  Maximum number of connections  Priority NetEnforcer Training Demo

20. Principles for QOS Guarantees (more)  Scenario 1: 1Mbps Audio app and FTP transfer r Scenario 2: 1Mbps Audio app and High-Priority FTP r Scenario 3: Misbehaving Audio App and FTP transfer

21. Principles for QOS Guarantees (more)  what do you think it means when an audio app misbehaves? m usually audio app needs and uses 1Mbps m sometimes either maliciously or due to application error, it sends out packets at 1.5Mbps or higher m this is usually termed application misbehaving r what do you think happens when an audio app misbehaves? m ftp starvation (FTP packets starve and get no bandwidth) m they will receive no service on the R1 – R2 link

22. Principles for QOS Guarantees (more)  policing mechanisms at the network edge  marks all packets so it can tell  if application misbehaves the policing mechanism will enforce by: drop or delaying packets audio cannot exceed peak rate of 1Mbps provide protection (isolation) for one class from others Principle 2

23. Principles for QOS Guarantees (more) While providing isolation, it is desirable to use resources as efficiently as possible Principle 3 r second enforcement scenario m Can allocate a fixed amount of bandwidth (audio: 1 Mbps, ftp: 0.5Mbps) m Any forseeable problems? when audio is not in use, ftp will be stuck with 0.5 Mbps

24. Principles for QOS Guarantees (more)  Scenario 1: 1Mbps Audio app and FTP transfer r Scenario 2: 1Mbps Audio app and High-Priority FTP r Scenario 3: Misbehaving Audio App and FTP transfer r Scenario 4: Two 1Mbps Audio apps overloaded 1.5Mbps link

25. Principles for QOS Guarantees (more)  Final scenario two 1Mbps audio applications  even with the first three principles, this is a lose-lose situation  If they share, each will get 0.75Mbps, which is no good for audio transfers 25% loss on both lines

26. Principles for QOS Guarantees (more)  So what to do?  when minimum quality of service is needed network will block flow or allow flow  telephone network is an example that performs call blocking Call Admission: flow declares its needs, network may block call (e.g., busy signal) if it cannot meet needs Principle 4

27. Summary of QoS Principles Let’s next look at mechanisms for achieving this ….

28. 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 Mechanisms  6.7 Integrated Services  6.8 RSVP  6.9 Differentiated Services

29. What is Scheduling? Scheduling: the mechanism which chooses the next packet to send out on a link

30. Four Scheduling Mechanisms  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 )

31. 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 m real-world example: Airline check in.

32. Priority Queuing  class may depend on marking or other header info, e.g. IP source/dest, port numbers, etc..  Real world example: Airplanes Priority scheduling: transmit highest priority queued packet first. r multiple classes, with different priorities

33. Potential Problem with Priority Queuing  Starvation Prone.  Motivation for our next two scheduling mechanisms

34. Round Robin  real world example: traffic jam r multiple classes r cyclically scan across queues, serving one from each class (if available)

35. Weighted Fair Queuing (WFQ)  Guaranteed a percentage of the bandwidth r Generalized Round Robin  Each class gets weighted amount of service in each cycle

36. 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: r Average Rate: How many pkts can be sent per unit time (in the long run)? m crucial question: what is the interval length: 100 packets per sec or 6000 packets per min have same average! r Peak Rate: 6000 pkts per min. (ppm) avg. rate 1500 pkts per sec. (pps) peak rate

37. 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).

38. 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-flow rate, R D = b/R max arriving traffic

39. 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 Allot Communications. NetEnforcer Online Tutorial. http://www.bandwidth-qos.co.uk/bandwidth-shaping- product/