21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
Streaming
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21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10Agenda
Types of Streaming Unicast and Multicast mechanisms Stream Control Transmission Protocol
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21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10Types of Streaming
Streaming stored audio/video refers to on-
demand requests for compressed
audio/video files.
Streaming live audio/video refers to the broadcasting of
radio and TV programs through the Internet.
Interactive audio/video refers to the use of the Internet for interactive
audio/video applications.
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21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10User Datagram Protocol (UDP)
Simple protocol and limited overhead as compared to IP packet.
No additional services added into the IP packet, apart from start and stop the connection.
Connectionless and unreliable transport protocol. Independent datagram - not numbered Suitable for simple request-response communication
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21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10Transmission Control Protocol (TCP)
Connection-oriented protocol and reliable transport protocol.
Create a virtual connection between two application programs to send data.
Virtual connection – connected as in the transport layer
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21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10Streaming Multimedia: UDP or TCP?UDP server sends at rate appropriate for client (oblivious to network
congestion !)
– often send rate = encoding rate = constant rate
– then, fill rate = constant rate - packet loss short playout delay (2-5 seconds) to remove network jitter error recover: time permitting
TCP send at maximum possible rate under TCP fill rate fluctuates due to TCP congestion control larger playout delay: smooth TCP delivery rate HTTP/TCP passes more easily through firewalls
21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10Unicasting
In unicasting, the router forwards the received packet through only one of its interfaces.
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21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10Multicasting
In multicasting, the router may forward the received packet through several of its interfaces
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21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10Multicasting versus Multiple casting
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21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10Streaming Stored Multimedia
1. videorecorded
2. videosent
3. video received,played out at client
Cum
ulat
ive
data
streaming: at this time, client playing out early part of video, while server still sending laterpart of video
networkdelay
time
21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10Web Server Streaming
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audio or video stored in file files transferred as HTTP object
– received in entirety at client
– then passed to player
21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10Web Server with Metafile Streaming
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browser GETs metafile
browser launches player, passing metafile
player contacts server
server streams audio/video to player
21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10Media Server Streaming
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allows for non-HTTP protocol between server, media player
UDP or TCP for steps (4,5)
21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10Media Server and RTSP Streaming
RTSP - Real Time Streaming Protocol
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21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10Streaming Live Multimedia
Examples: Internet radio talk show live sporting event
Streaming (as with streaming stored multimedia) playback buffer playback can lag tens of seconds after transmission still have timing constraint
Interactivity fast forward impossible rewind, pause possible!
21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10
Real-Time Interactive Multimedia
end-end delay requirements:– audio: < 150 msec good, < 400 msec OK
• includes application-level (packetization) and network delays• higher delays noticeable, impair interactivity
session initialization– how does callee advertise its IP address, port number, encoding algorithms?
applications: IP telephony, video conference, distributed interactive worlds
21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
Real-Time Protocol (RTP)
RTP specifies packet structure for packets carrying audio, video data
RTP packet provides
– payload type identification
– packet sequence numbering
– time stamping
RTP runs in end systems
RTP treated like application program and encapsulated in UDP segments
interoperability: if two Internet phone applications run RTP, then they may be able to work together
21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
Real-Time Control Protocol (RTCP) works in conjunction
with RTP. each participant in RTP
session periodically transmits RTCP control packets to all other participants.
each RTCP packet contains sender and/or receiver reports– report statistics useful to
application: # packets sent, # packets lost, interarrival jitter, etc.
feedback can be used to control performance– sender may modify its
transmissions based on feedback
21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
Synchronization of Streams
RTCP can synchronize different media streams within a RTP session
consider videoconferencing for which each sender generates one RTP stream for video, one for audio.
timestamps in RTP packets tied to the video, audio sampling clocks
each RTCP sender-report packet contains (for most recently generated packet in associated RTP stream):– timestamp of RTP
packet – wall-clock time for
when packet was created.
receivers uses association to synchronize playout of audio, video
21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10
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21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10Stream Control Transmission Protocols
SCTP is a message-oriented, reliable protocol that combines the good features of UDP and TCP.
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21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10Multiple-stream Concept
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21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10Multihoming Concept
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21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10Summary
SCTP is a message oriented, reliable protocol that combines the good features of UDP and TCP
SCTP provides additional services that are not provided by UDP or TCP.
More reading from Wikipedia– http://en.wikipedia.org/wiki/
Stream_Control_Transmission_Protocol
– http://en.wikipedia.org/wiki/Unicast
– http://en.wikipedia.org/wiki/Multicast
– http://en.wikipedia.org/wiki/Streaming_media
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21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing
IADCN - Week 10Reading about Streaming Methods
Streaming from a Web Server (http://www.microsoft.com/windows/windowsmedia/howto/articles/webserver.aspx)
Streaming Methods: Web Server vs. Streaming Media Server (http://www.microsoft.com/windows/windowsmedia/compare/webservvstreamserv.aspx)
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