Internet Measurment Multimedia 1

Properties Challenges Tools State of the Art 2

Streaming Multimedia Slow but steadily growing part of internet traffic P2P is a driving force of multimedia file exchange Manner of delivery is different from HTTP or FTP  More than one stream may be involved Audio Video Associated Parameters  Sequencing 3

Streaming Multimedia Protocols HTTP is often used to initiate the delivery Session Initiation Protocol (SIP) initiates session by inviting users – used in IP telephony Microsoft Media Server (MMS) – popular protocol – start/stop and change rate commands Real Time  Real Time Transport Protocol (RTP) – divides streams into labeled packets  RTP Control Protocol (RTCP)  Real Time Streaming Protocol (RTSP) – enable users to send multimedia request via URLs 4

Multimedia Properties Challenges Tools State of the Art 5

Properties Multimedia transfer are impacted by network performance as well as non network issues  User reaction to delay or jitter or Packet loss Components of video quality can be examined  Bit-rate  User’s interaction 6

Multimedia Properties Challenges Tools State of the Art 7

Challenges How user may react to network characteristic such as jitter  skip ahead, rewind Multimedia transfer can take from minutes to hours The bit rate might depend on end client connection Protocols may be blocked at firewalls Streaming content might not be on the origin server 8

Multimedia Properties Challenges Tools State of the Art 9

Tools Survey based tools Mmdump: capable of parsing packets associated with control protocols Rtpmon: A graphical tool that can display variety information about RTP session RealTracer: Test performance of a Real Video server Ethereal: can analyze numerous protocol including p2p, games and multimedia 10

Multimedia Properties Challenges Tools State of the Art 11

Real Video Examination RealTracer was used to test the performance of a video server serving a few hundred Real Video tracks to a small number of users Jitter of over 50ms was deemed as the threshold for non-smooth delivery of video  Large initial buffering done by Real Player is responsible Frame rate of over 15 was acceptable (10 by users) 12

User’s interactions A study examined live streaming media workload of nearly users in one month User’s interactions are different when compared to viewing streaming of stored objects  be more willing to put up with glitches Duration for which a user is connected to a stream follows a lognormal distribution while inactive time follows exponential distribution 13

H.323 Conferencing Examination Extract acceptable bounds for important network characteristics:  Delay  Jitter  Loss ITU proposes acceptable delay to be under 300ms User’s perceptions are driven more by jitter than others 14