Ch 7. Multimedia Networking

1. Myungchul Kim mckim@icu.ac.kr Ch 7. Multimedia Networking

2. QoS network provides application with level of performance needed for application to function. Multimedia and Quality of Service: What is it? multimedia applications: network audio and video (“continuous media”)

3. Sensitive to end-to-end delay and delay variation • Streaming stored audio/video • Streaming live audio/video • Real-time interactive audio/video

4. Multimedia networking applications • Examples of multimedia applications • Streaming stored audio and video • Stored media • Streaming: RealPlayer, QuickTime, Media • Continous playout • Streaming live audio and video • Internet radio and IPTV • IP multicasting • Application-layer multicast • Real-time interactive audio and video • Internet telephony (150 msec)

5. Hurdles for multimedia in Today’s Internet • Best-effor service • How should the Internet evolve to support multimedia better? • Hard guarantee vs soft guarnatee • Reservation approach • Protocol • Modification of scheduling policies in the router queues • Description of the application traffic • Available bandwidth in the network • Laissez-faire approach • Overprovision bandwidth and switching capacity • Content distribution networks (CDN) • Multicast overlay networks • Differentiated service (Diffserv)

7. Audio compression in the Internet • 8,000 samples per second • 256 quantization with 8 bits • 64Kbps • Pulse code modulation (PCM) • GSM, G.729, G.723.3, MPEG 1 player 3 (MP3) • Video compression in the Internet • MPEG1, 2, 4 • H.261

8. Streaming Stored Audio and Video • Medio player • Decompression • Jitter removal

10. Real-time Streaming Protocol (RTSP)

11. Making the best of the best-effort service • Packet loss • End-to-end delay • Packet jitter • Removing jitter at the receiver for audio • Sequence number • Timestamp • Delaying playout at the receiver

13. Recovering from packet loss

15. Content Distribution Networks

17. Dimensioning best-effort networks to provide Quality of Service • Bandwidth provisioning • Network dimensioning • Models of traffic demand between network end points • Well-defined performance requirements • Workload model

18. Protocols for Real-time Interactive Applications • RTP • UDP • RTP header: the type of audio encoding, a sequence number, and a timestamp

21. RTP control protocol (RTCP) • Using IP multicast • Reports about statistics • Reception report • SSRC of the RTP streams • The fraction of packets lost • The last sequence number received • The interarrival jitter • Sender report • The SSRC of the RTP streams • The timestamp and wall clock time of the most recently generated RTP packet • The number of packets sent • The number of bytes sent

23. Session Initiation Protocol (SIP) • Protocol does • Establishing calls between a caller and a callee over an IP network • For the caller to determine the current IP address of the callee • Call management • Key characteristics • Out-of-band protocol • ASCII-readable • All messages to be acknowledged

25. Setting up a call to known IP address • Alice’s SIP invite message indicates her port number, IP address, encoding she prefers to receive (PCM ulaw) • Bob’s 200 OK message indicates his port number, IP address, preferred encoding (GSM) • SIP messages can be sent over TCP or UDP; here sent over RTP/UDP. • default SIP port number is 5060.

27. Example Caller jim@umass.edu with places a call to keith@upenn.edu (1) Jim sends INVITEmessage to umass SIPproxy. (2) Proxy forwardsrequest to upenn registrar server. (3) upenn server returnsredirect response,indicating that it should try keith@eurecom.fr (4) umass proxy sends INVITE to eurecom registrar. (5) eurecom registrar forwards INVITE to 197.87.54.21, which is running keith’s SIP client. (6-8) SIP response sent back (9) media sent directly between clients. Note: also a SIP ack message, which is not shown.

28. H.323

29. Providing multiple classes of service • Divide traffic into classes and provide different levels of service to the different classes of traffic. • Differentiated service is provided among aggregates of traffic. • Type-of-service (ToS) in the IPv4

30. Scenario 1: a 1 Mbps audio application and an FTP transfer • FIFO • Give strict priority to audio packets at R1 • Each packet must be marked as belonging to one of these two classes of traffic, e.g., ToS in IPv4

31. Scenario 2: a 1 Mbps audio application and a high-priority FTP transfer • Packet classification allows a router to distinguish among packets belonging to different classes of traffic. • A policy decision

32. Scenario 3: A misbehaving audio application and an FTP transfer

33. Scheduling and policing mechanisms • Link-scheduling mechanisms • First-In-First-Out (FIFO)

34. Priority Queueing

35. Round robin and weighted fair queueing (WFQ)

36. Policing: The Leaky Bucket: regulate the injecting rate of packets into the networks • Average rate • Peak rate • Burst size

37. Diffserv • Edge function: packet classification and traffic conditioning: the diffentiated service field of the packet header • Core function: forwarding, per-hop behavior, aggregation

38. Diffserv traffic classfication and conditioning

39. Per-hop behaviors • Differences in performance among classes • Differences in performance observable and measureable • Expedited forwarding, assured forwarding

40. Providing quality of service guarantees • Resouce reservation, call admission, call setup • Traffic characterization and specification of the desired QoS • Signaling for call setup • Pre-element call admission

41. Guaranteed QoS: Intserv and RSVP • Individualized QoS guarantees • Reservations for bandwidth in multicast trees • Receiver-oriented • Provisioning? Using the policing and scheduling