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Oct 26, 2013 (3 years and 7 months ago)

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CS335 Principles of Multimedia Systems

Multimedia Over IP Networks
--

I

Hao Jiang

Computer Science Department

Boston College

Nov. 6, 2007

CS335 Principles of Multimedia Systems

Introduction


Traffic on Internet was mainly from textual content.



In recent years, multimedia data transmission is
occupying most of the network bandwidth.



IP network, especially Internet, is becoming a very
attractive channel for multimedia communications.


Dedicated networks and ATM are not widely available.


There are many applications for Internet multimedia:


Internet telephone, Internet TV, video conferencing, network
games, remote corroboration, ….

CS335 Principles of Multimedia Systems

Review Of TCP/IP

Basic TCP/IP network model

Data Encapsulation:


Application Layer (
telnet, ftp, etc.
)




Host
-
to
-
Host Transport Layer


(
TCP, UDP
)



Internet Layer (
IP and routing
)





Network Access Layer (
Ethernet,


ATM, or whatever
)


CS335 Principles of Multimedia Systems

Review Of TCP/IP

A TCP/IP node on 2 Ethernets

CS335 Principles of Multimedia Systems

Review Of TCP/IP


Address Resolution Protocol (ARP)

Each machine on a network has an ARP Table in its memory

If “223.1.2.1” wants to send a packet to “223.1.2.2”, an ARP

request will be broadcasted to the Ethernet.

CS335 Principles of Multimedia Systems

Review Of TCP/IP

“223.1.2.2” found the target IP matches its IP, it fills the Ethernet

address and returns an ARP response to “223.1.2.1”

“223.1.2.1” updates its ARP table and starts sending packets to “.2”

CS335 Principles of Multimedia Systems

Review Of TCP/IP


Routing

A sends E an IP packet.

On “development”,

the IP/Ethernet addresses are:

While on “account”:

1

2

3

CS335 Principles of Multimedia Systems

Review Of TCP/IP


Routing Table

1

2

3

Routing table for A

---------------------------------------------------------------------


network direct/indirect router interface number


---------------------------------------------------------------------


development direct <blank> 1


accounting indirect D 1


factory indirect D 1

---------------------------------------------------------------------


Routing table for D

---------------------------------------------------------------------


network direct/indirect router interface number


---------------------------------------------------------------------


development direct <blank> 1


accounting direct <blank> 2


factory direct <blank> 3

---------------------------------------------------------------------



CS335 Principles of Multimedia Systems

Review Of TCP/IP


Transport Protocols


UDP (User Datagram Protocol): A simple protocol for short
delay and unreliable communication.



TCP (Transmission Control Protocol): A much more complex
protocol that guarantees correct data transmission.


By acknowledgement from the receiver.


Retransmission if time is out or data is corrupted.



TCP is a stream protocol. The packet size is determined by
the systems.


TCP also needs to build up a virtual circuit before the real
communication happens.

CS335 Principles of Multimedia Systems

Multimedia over Network


Properties of multimedia traffic


High bit rate.


Many coding schemes have variable bit rate streams.


Partial data missing or corrupted is Ok.


Tight timing constraint.



IP networks have no guarantee for


bandwidth allocation.


Limited delay.



Multimedia applications usually build on top of UDP


which may loses packets, receives packets in wrong
order,…

CS335 Principles of Multimedia Systems

Some Ad Hoc Schemes


For some simple applications, we can in fact use
TCP to transmit videos.

Multiple
-
view Video

Streaming Server

User 1

User 2

User n

A Multiple
-
view Server Demo

CS335 Principles of Multimedia Systems

Some Ad Hoc Schemes

Some commercial products in fact use

TCP for video streaming.

Axis 206 network

camera

http://192.168.1.10/axis
-
cgi/mjpg/video.cgi

For example, to get a motion jpeg video stream:

CS335 Principles of Multimedia Systems

More about Ad Hoc Schemes

UDP

Header

Some

Additional

Information

Multimedia Data

What should we put here?

CS335 Principles of Multimedia Systems

Standard Solutions


The Integrated Services working group in the IETF
(Internet Engineering Task Force) developed an enhanced
Internet service model called Integrated Services that
includes best
-
effort service and real
-
time service, see RFC
1633.



The real
-
time service will enable IP networks to provide
quality of service to multimedia applications.




Resource ReServation Protocol (RSVP), together with
Real
-
time Transport Protocol (RTP), Real
-
Time Control
Protocol (RTCP), Real
-
Time Streaming Protocol (RTSP),
provides a working foundation for real
-
time services.