Unicast, multicast and SCTP
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Transcript Unicast, multicast and SCTP
Streaming
Michael Chai; Behrouz Forouzan
06/04/2016
Staffordshire University
School of Computing
1
IADCN - Week 10
Agenda
Types of Streaming
Unicast and Multicast mechanisms
Stream Control Transmission Protocol
Michael Chai; Behrouz Forouzan
06/04/2016
2
Staffordshire University
School of Computing
IADCN - Week 10
Types of Streaming
Streaming stored
audio/video refers to ondemand requests for
compressed
audio/video files.
Michael Chai; Behrouz Forouzan
Streaming live audio/video
Interactive audio/video
refers to the broadcasting of
refers to the use of the
radio and TV programs
Internet for interactive
through the Internet.
audio/video applications.
06/04/2016
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Staffordshire University
School of Computing
IADCN - Week 10
User 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
Michael Chai; Behrouz Forouzan
06/04/2016
4
Staffordshire University
School of Computing
IADCN - Week 10
Transmission 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
Michael Chai; Behrouz Forouzan
06/04/2016
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Staffordshire University
School of Computing
IADCN - Week 10
Streaming 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
Michael Chai; Behrouz Forouzan
06/04/2016
Staffordshire University
School of Computing
IADCN - Week 10
Unicasting
In unicasting, the router forwards the received packet
through only one of its interfaces.
Michael Chai; Behrouz Forouzan
06/04/2016
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Staffordshire University
School of Computing
IADCN - Week 10
Multicasting
In multicasting, the router may
forward the received packet through
several of its interfaces
Michael Chai; Behrouz Forouzan
06/04/2016
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Staffordshire University
School of Computing
IADCN - Week 10
Multicasting versus Multiple casting
Michael Chai; Behrouz Forouzan
06/04/2016
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Staffordshire University
School of Computing
IADCN - Week 10
Streaming Stored Multimedia
1. video
recorded
2. video
sent
network
delay
3. 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
Michael Chai; Behrouz Forouzan
06/04/2016
Staffordshire University
School of Computing
IADCN - Week 10
Web Server Streaming
Michael Chai; Behrouz Forouzan
audio or video stored in file
files transferred as HTTP object
– received in entirety at client
– then passed to player
06/04/2016
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Staffordshire University
School of Computing
IADCN - Week 10
Web Server with Metafile Streaming
browser GETs
metafile
browser
launches player,
passing metafile
player contacts
server
server streams
audio/video to
player
Michael Chai; Behrouz Forouzan
06/04/2016
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Staffordshire University
School of Computing
IADCN - Week 10
Media Server Streaming
Michael Chai; Behrouz Forouzan
06/04/2016
allows for nonHTTP protocol
between server,
media player
UDP or TCP for
steps (4,5)
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School of Computing
IADCN - Week 10
Media Server and RTSP Streaming
RTSP - Real Time
Streaming Protocol
Michael Chai; Behrouz Forouzan
06/04/2016
14
Staffordshire University
School of Computing
IADCN - Week 10
Streaming 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!
Michael Chai; Behrouz Forouzan
06/04/2016
Staffordshire University
School of Computing
IADCN - Week 10
Real-Time Interactive Multimedia
applications: IP telephony, video conference,
distributed interactive worlds
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?
Michael Chai; Behrouz Forouzan
06/04/2016
Staffordshire University
School 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
Michael Chai; Behrouz Forouzan
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
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Staffordshire University
School 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
feedback can be used to
control performance
– sender may modify its
transmissions based on
feedback
– report statistics useful to
application: # packets sent,
# packets lost, interarrival
jitter, etc.
Michael Chai; Behrouz Forouzan
06/04/2016
Staffordshire University
School 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
Michael Chai; Behrouz Forouzan
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
06/04/2016
Staffordshire University
School of Computing
IADCN - Week 10
Michael Chai; Behrouz Forouzan
06/04/2016
20
Staffordshire University
School of Computing
IADCN - Week 10
Stream Control Transmission Protocols
SCTP is a message-oriented, reliable protocol that
combines the good features of UDP and TCP.
Michael Chai; Behrouz Forouzan
06/04/2016
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Staffordshire University
School of Computing
IADCN - Week 10
Multiple-stream Concept
Michael Chai; Behrouz Forouzan
06/04/2016
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Staffordshire University
School of Computing
IADCN - Week 10
Multihoming Concept
Michael Chai; Behrouz Forouzan
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Staffordshire University
School of Computing
IADCN - Week 10
Summary
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
Michael Chai; Behrouz Forouzan
06/04/2016
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Staffordshire University
School of Computing
IADCN - Week 10
Reading about Streaming Methods
Streaming from a Web Server
(http://www.microsoft.com/windows/windowsmedia/h
owto/articles/webserver.aspx)
Streaming Methods: Web Server vs. Streaming Media
Server
(http://www.microsoft.com/windows/windowsmedia/c
ompare/webservvstreamserv.aspx)
Michael Chai; Behrouz Forouzan
06/04/2016
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Staffordshire University
School of Computing