Chapter Multimedia Networking 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 Computer Networking: A Top Down Approach Featuring the Internet, 3rd edition Jim Kurose, Keith Ross Addison-Wesley, July 2004 Thanks and enjoy! JFK / KWR All material copyright 1996-2006 J.F Kurose and K.W Ross, All Rights Reserved 7: Multimedia Networking 7-1 Multimedia, Quality of Service: What is it? Multimedia applications: network audio and video (“continuous media”) QoS network provides application with level of performance needed for application to function 7: Multimedia Networking 7-2 Chapter 7: Goals Principles Ì Classify multimedia applications Ì Identify the network services the apps need Ì Making the best of best effort service Ì Mechanisms for providing QoS Protocols and Architectures Ì Specific protocols for best-effort Ì Architectures for QoS 7: Multimedia Networking 7-3 Chapter outline Ì 7.1 Multimedia Networking Applications Ì 7.2 Streaming stored audio and video Ì 7.3 Real-time Multimedia: Internet Phone study Ì 7.4 Protocols for RealTime Interactive Applications r RTP,RTCP,SIP Ì 7.5 Distributing Ì 7.6 Beyond Best Effort Ì 7.7 Scheduling and Policing Mechanisms Ì 7.8 Integrated Services and Differentiated Services Ì 7.9 RSVP Multimedia: content distribution networks 7: Multimedia Networking 7-4 MM Networking Applications Classes of MM applications: 1) Streaming stored audio and video 2) Streaming live audio and video 3) Real-time interactive audio and video Jitter is the variability of packet delays within the same packet stream Fundamental characteristics: Ì Typically delay sensitive r r end-to-end delay delay jitter Ì But loss tolerant: infrequent losses cause minor glitches Ì Antithesis of data, which are loss intolerant but delay tolerant 7: Multimedia Networking 7-5 Streaming Stored Multimedia Streaming: Ì media stored at source Ì transmitted to client Ì streaming: client playout begins before all data has arrived Ì timing constraint for still-to-be transmitted data: in time for playout 7: Multimedia Networking 7-6 Cumulative data Streaming Stored Multimedia: What is it? video recorded video sent network delay video received, played out at client time streaming: at this time, client playing out early part of video, while server still sending later part of video 7: Multimedia Networking 7-7 Streaming Stored Multimedia: Interactivity Ì VCR-like functionality: client can pause, rewind, FF, push slider bar r 10 sec initial delay OK r 1-2 sec until command effect OK r RTSP often used (more later) Ì timing constraint for still-to-be transmitted data: in time for playout 7: Multimedia Networking 7-8 Streaming Live Multimedia Examples: Ì Internet radio talk show Ì Live sporting event Streaming Ì playback buffer Ì playback can lag tens of seconds after transmission Ì still have timing constraint Interactivity Ì fast forward impossible Ì rewind, pause possible! 7: Multimedia Networking 7-9 Interactive, Real-Time Multimedia Ì applications: IP telephony, video conference, distributed interactive worlds Ì end-end delay requirements: r audio: < 150 msec good, < 400 msec OK • includes application-level (packetization) and network delays • higher delays noticeable, impair interactivity Ì session initialization r how does callee advertise its IP address, port number, encoding algorithms? 7: Multimedia Networking 7- RSVP: building up path state Ì next, H5 sends path message, creating more state in routers L6 L1 m1: in out L1 L2 L6 m1: in L7 out L3 L4 L5 L6 m1: in out L5 L6 L7 H3 H2 L3 L2 H1 L1 R1 L6 R2 L5 L7 R3 L4 H4 H5 7: Multimedia Networking 7- RSVP: building up path state Ì H2, H3, H5 send path msgs, completing path state tables L1 L2 L6 m1: in out L1 L2 L6 m1: in L3 L4 L7 out L3 L4 L7 L5 L6 L7 m1: in out L5 L6 L7 H3 H2 L3 L2 H1 L1 R1 L6 R2 L5 L7 R3 L4 H4 H5 7: Multimedia Networking 7- reservation msgs: receiver-to-network signaling Ì reservation message contents: desired bandwidth: r filter type: r • no filter: any packets address to multicast group can use reservation • fixed filter: only packets from specific set of senders can use reservation • dynamic filter: senders who’s p[ackets can be forwarded across link will change (by receiver choce) over time r filter spec Ì reservations flow upstream from receiver-to- senders, reserving resources, creating additional, receiver-related state at routers 7: Multimedia Networking 7- RSVP: receiver reservation example H1 wants to receive audio from all other senders Ì H1 reservation msg flows uptree to sources Ì H1 only reserves enough bandwidth for audio stream Ì reservation is of type “no filter” – any sender can use reserved bandwidth H3 H2 L3 L2 H1 L1 R1 L6 R2 L5 L7 R3 L4 H4 H5 7: Multimedia Networking 7- RSVP: receiver reservation example Ì H1 reservation msgs flows uptree to sources Ì routers, hosts reserve bandwidth b needed on downstream links towards H1 m1: in L1 L2 out L1(b) L2 L6 L6 m1: L2 H1 b b L1 R1 b L6 L7 L7(b) L7 L6 L6(b) L7 m1: in L5 out L5 H2 L4 L4 in L3 out L3 b R2 L5 b L7 b R3 L3 b L4 H3 H4 H5 7: Multimedia Networking 7- RSVP: receiver reservation example (more) Ì next, H2 makes no-filter reservation for bandwidth b Ì H2 forwards to R1, R1 forwards to H1 and R2 (?) Ì R2 takes no action, since b already reserved on L6 L6 m1: in L1 L2 out L1(b) L2(b) L6 m1: b L2 H1 b b b L1 R1 b L6 L7 L7(b) L7 L6 L6(b) L7 m1: in L5 out L5 H2 L4 L4 in L3 out L3 b R2 L5 b L7 b R3 L3 b L4 H3 H4 H5 7: Multimedia Networking 7- RSVP: receiver reservation: issues What if multiple senders (e.g., H3, H4, H5) over link (e.g., L6)? Ì arbitrary interleaving of packets Ì L6 flow policed by leaky bucket: if H3+H4+H5 sending rate exceeds b, packet loss will occur L6 m1: in L1 L2 out L1(b) L2(b) L6 m1: b L2 H1 b b b L1 R1 b L6 L7 L7(b) L7 L6 L6(b) L7 m1: in L5 out L5 H2 L4 L4 in L3 out L3 b R2 L5 b L7 b R3 L3 b L4 H3 H4 H5 7: Multimedia Networking 7- RSVP: example Ì H1, H4 are only senders send path messages as before, indicating filtered reservation r Routers store upstream senders for each upstream link r Ì H2 will want to receive from H4 (only) H3 H2 L3 L2 H1 L1 R1 L6 R2 L7 R3 L4 H4 7: Multimedia Networking 7- RSVP: example Ì H1, H4 are only senders r send path messages as before, indicating filtered reservation in L1, L6 L2(H1-via-H1 out L6(H1-via-H1 L1(H4-via-R2 in ; H4-via-R2 ) ) L4, L7 L3(H4-via-H4 out L4(H1-via-R2 L7(H4-via-H4 ) ; H1-via-R3 ) ) ) H3 H2 R2 L2 H1 L1 R1 L7 L6 in L3 R3 L4 H4 L6, L7 L6(H4-via-R3 out L7(H1-via-R1 ) ) 7: Multimedia Networking 7- RSVP: example Ì receiver H2 sends reservation message for source H4 at bandwidth b r propagated upstream towards H4, reserving b in L1, L6 L2(H1-via-H1 out L6(H1-via-H1 L1(H4-via-R2 H2 L2 H1 in L4, L7 L3(H4-via-H4 ; H1-via-R2 out L4(H1-via-62 ) L7(H4-via-H4 (b)) ;H4-via-R2 (b)) ) ) ) H3 b L1 R1 b L6 in R2 b L7 R3 L3 b L4 H4 L6, L7 L6(H4-via-R3 (b)) out L7(H1-via-R1 ) 7: Multimedia Networking 7- RSVP: soft-state Ì senders periodically resend path msgs to refresh (maintain) state Ì receivers periodically resend resv msgs to refresh (maintain) state in L1, L6 Ì path and resv msgs have TTL field, specifying in L4, L7 L2(H1-via-H1 ;H4-via-R2 (b)) refresh interval L3(H4-via-H4 ; H1-via-R3 ) out L6(H1-via-H1 L1(H4-via-R2 H2 L2 H1 out L4(H1-via-62 ) L7(H4-via-H4 (b)) ) ) H3 b L1 R1 b L6 in R2 b L7 R3 L3 b L4 H4 L6, L7 L6(H4-via-R3 (b)) out L7(H1-via-R1 ) 7: Multimedia Networking 7- RSVP: soft-state Ì suppose H4 (sender) leaves without performing teardown Ì eventually state in routers will timeout and disappear! in L1, L6 L2(H1-via-H1 out L6(H1-via-H1 L1(H4-via-R2 H2 L2 H1 in L4, L7 L3(H4-via-H4 ; H1-via-R3 out L4(H1-via-62 ) L7(H4-via-H4 (b)) ;H4-via-R2 (b)) ) ) ) H3 b L1 R1 b L6 in R2 b L7 R3 L3 b L4 gone H4 fishing! L6, L7 L6(H4-via-R3 (b)) out L7(H1-via-R1 ) 7: Multimedia Networking 7- The many uses of reservation/path refresh Ì recover from an earlier lost refresh message r expected time until refresh received must be longer than timeout interval! (short timer interval desired) Ì Handle receiver/sender that goes away without teardown r Sender/receiver state will timeout and disappear Ì Reservation refreshes will cause new reservations to be made to a receiver from a sender who has joined since receivers last reservation refresh E.g., in previous example, H1 is only receiver, H3 only sender Path/reservation messages complete, data flows r H4 joins as sender, nothing happens until H3 refreshes reservation, causing R3 to forward reservation to H4, which allocates bandwidth r 7: Multimedia Networking 7- RSVP: reflections Ì multicast as a “first class” service Ì receiver-oriented reservations Ì use of soft-state 7: Multimedia Networking 7- Multimedia Networking: Summary Ì multimedia applications and requirements Ì making the best of today’s best effort service Ì scheduling and policing mechanisms Ì next generation Internet: Intserv, RSVP, Diffserv 7: Multimedia Networking 7- ... conceal errors: repeat nearby data r 7: Multimedia Networking 7- Chapter outline Ì 7. 1 Multimedia Networking Applications Ì 7. 2 Streaming stored audio and video Ì 7. 3 Real-time Multimedia: Internet. .. available bandwidth 7: Multimedia Networking 7- Chapter outline Ì 7. 1 Multimedia Networking Applications Ì 7. 2 Streaming stored audio and video Ì 7. 3 Real-time Multimedia: Internet Phone study Ì 7. 4... at a PC-2PC Internet phone example in detail 7: Multimedia Networking 7- Interactive Multimedia: Internet Phone Introduce Internet Phone by way of an example Ì speaker’s audio: alternating talk