Internet Measurment Multimedia 1. Properties Challenges Tools State of the Art 2

Internet Measurment

Multimedia

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Multimedia

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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

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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

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Multimedia

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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

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Multimedia

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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

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Multimedia

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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

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Multimedia

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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)

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User’s interactions

A study examined live streaming media workload of

nearly 700000 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

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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

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