Internet Measurment Multimedia 1
Jan 04, 2016
Internet Measurment
Multimedia
1
Multimedia
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
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
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
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
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 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
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