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Multimedia Communications
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Network Topologies Evolution
LAN: Local Area Network
WAN: Wide Area Network
WLAN: Wireless Local Area Network
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Network Topologies Evolution LAN
A LAN is a high-speed data network that covers arelatively small geographic area. eg. home, office etc
LANs offer computer users many advantages,including shared access to devices and applications,
file exchange between connected users, andcommunication between users via electronic mail andother applications.
LAN data transmissions fall into three classifications:
unicast, multicast, and broadcast. LAN Topologies: bus, ring, star, and tree.
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BUS TOPOLOGY
Bus networks: A bus network topology is a network
architecture in which a set of clients are connected via a shared
communications line, called a bus.
Bus networks are the simplest way to connect multiple clients,but often have problems when two clients want to transmit at
the same time on the same bus.
Thus systems which use bus network architectures normally
have some scheme of collision handling or collision avoidance
for communication on the bus, quite often using Carrier Sense
Multiple Access
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BUS NETWORK
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Ring networks,
A ring network is a network topology inwhich each node connects to exactly twoother nodes, forming a circular pathway forsignals: a ring. Data travels from node to
node, with each node handling every packet. Because a ring topology provides only one
pathway between any two nodes, ringnetworks may be disrupted by the failure of asingle link. A node failure or cable breakmight isolate every node attached to the ring.
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Ring network
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Tree topology
Tree Topology is a combination of the bus and the Star Topology. The
tree like structure allows you to have many servers on the network andyou can branch out the network in many ways.
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Circuit Switching
Switched circuits allow data connections that can be
initiated when needed and terminated when
communication is complete. This works much like a
normal telephone line works for voice communication
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Packet SwitchingPacket switching is a WAN technology in which users
share common carrier resources.
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Wireless LANA wireless LAN or WLAN is a wireless local area
network, which is the linking of two or more computerswithout using wires.WLAN utilizes radio waves to enable communication
between devices in a limited area, also known as the
basic service set.This gives users the mobility to move around within a
broad coverage area and still be connected to the
network.
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Interactive Learning System for Conceptualization
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Interlace is a technique of improving the picture quality
of a video signal by removing flicker without consumingany extra bandwidth.
This animation demonstrates the interline twitter
effect. The two interlaced images use half the bandwidth
of the progressive one.
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Interleaving in disk storage
The primary purpose of interleaving was to adjust the timing
differences between when the computer was ready to transfer data,
and when that data was actually arriving at the drive head to be read.
Interleaving was used to arrange the sectors in the most efficient
manner possible, so that after reading a sector, time would be
permitted for processing, and then the next sector in sequence is ready
to be read just as the computer is ready to do so.
Interleaving is used in digital data transmission technology to protect
the transmission against burst errors. These errors overwrite a lot of
bits in a row, so a typical error correction scheme that expects errors
to be more uniformly distributed can be overwhelmed. Interleaving is
used to help stop this from happening.
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Linear Multimedia
Multimedia may be broadly divided into linear and non-linear categories. Linear active content progresses
without any navigation control for the viewer such as a
cinema presentation. Non-linear content offers user
interactivity to control progress as used with a computergame or used in self-paced computer based training.
Non-linear content is also known as hypermedia content.
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If the sequence and timing of the multimedia elements
can be controlled by the user, then one can name it asNon-Interactive Multimedia.Streaming AudioRealPlayerStreaming Videoquick time
Non-Interactive Multimedia.
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Multimedia Networks Technical Issues
Admission control:Admission control is a network Quality ofService (QoS) procedure.
Admission control determines how bandwidth and latency are
allocated to streams with various requirements.
An application that wishes to use the network to transport traffic
with QoS must first request a connection, which involves
informing the network about the characteristics of the traffic and
the QoS required by the application.
This information is stored in a traffic contract. The network
judges whether it has enough resources available to accept the
connection, and then either accepts or rejects the connection
request. This is known as Admission Control.
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Multimedia Networks Scheduling: Scheduling is a key concept in computer
multitasking and multiprocessing operating system design,
and in real-time operating system design. It refers to the way
processes are assigned priorities in a priority queue. This
assignment is carried out by software known as a scheduler.
Different computer operating systems implement differentscheduling schemes. Unix implementations use a scheduler
with multilevel feedback queues.
Windows 3.1 and Macintosh OS 9 use a simple non-
preemptive scheduler which requires programmers to
instruct their processes to "yield" in order for other processes
to gain some CPU time. Windows NT 4.0-based operating
systems use a multilevel feedback queue.
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Multimedia Networks Congestion Control: A congestion control system
typically monitors various factors like CPUoccupancy, link occupancy and messaging delay.
Based on these factors it takes a decision if the
system is overloaded. If the system is overloaded, it
initiates actions to reduce the load by asking front
end processors to reject traffic.
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Multimedia Networks Resource management
resource management is the efficient and effectivedeployment of an organization's resources when
they are needed.
Resource Management and Scheduling Strategiescollectively addresses multiple issues including
QoS, throughput, responsiveness and efficiency.
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INTERNET
The Internet is a global network of interconnectedcomputers, enabling users to share information alongmultiple channels.
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Internetworking
Despite the incompatibilities among networktechnologies, researchers devised a schemefor providing universal service amongheterogeneous technologies calledinternetworking.
Hardware is used to interconnect a set ofphysical networks and common software on
all the attached computers provides universalservice. The resultant system is known as aninternetwork or internet.
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Connection to Internet
There are many ways to connect to the Internet from a personal
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There are many ways to connect to the Internet from a personal
workstation:
1. Dial-Up:With a dial-up connection, the Internet user can
connect to the Internet via his or telephone line and an Internetservice provider.
Broadband connections offer another way to connect to the
Internet. In this category are cable and DSL connections.
cable connection, the user must subscribe to a cable-television/Internet service.
DSL (Digital Subscriber Line): DSL offers much faster speeds
than those available with dial-up modems.
Satellite Internet service is another form of high-speed
Internet connection .It employs telecommunications satellites to
allow users to connect to the Internet
4.
M lti di I t t P t l
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Multimedia Internet Protocols Multimedia over TCP: TCP in connection-oriented protocol that is
reliable including flow control and supports byte-stream in full
duplex mode.
The multicast method to send data to more than one client is
not supported by the TCP protocol.
Delays is exactly what we do not want in real-time data
transmissions.
For example in a video transmission, we just drop the lost
packet and display the previous packet a second time. For the
human eye this little trick does not affect the quality. So
reliable transmission on transport layer is not exactly what we
need for multimedia transmissions.
TCP is not a good basis to transport multimedia real-time data
over a network, to summarize the usability of TCP.
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Multimedia over UDP
UDP is a connectionless protocol that triesbest effort delivery with no flow-control andincluded message support.UDP is not reliable and that is one of thekey advantages for real-timetransmissions.UDP also supports multicast methods.
This protocol does not support flow-control and that is actually veryimportant for real-time applications.
RTP
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RTP Real-time Transport Protocol (RTP) provides support for
the transport of real-time data such as video and audio
streams.
RTP needs support from lower layers that actually have
control over resources in switches and routers
RTP/RTCP provides functionality and control mechanismsnecessary for carrying real-time content.
RTP/RTCP itself is not responsible for the higher-level
tasks like assembly and synchronization. These have to be
done at application level.
RTCP
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RTCP Real-Time Control Protocol extends RTP
In an RTP session, participants periodically send RTCP packets to convey
feedback on quality of data delivery and information of membership.
Packets defined for carrying control information:
SR: Sender report, for transmission and reception statistics from
session participants that are active senders.
RR: Receiver report, for reception statistics from session participants,
that are not active
senders.
SDES: Source description items, including CNAME
BYE: Indicates end of participation
APP: Application specific functions
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Multimedia Internet Protocols SAP: Session Announcement Protocol:used to assist the advertisement of
multicast multimedia conferences and other multicast sessions, and to
communicate the relevant session setup information to prospective
participants.
SDP: Session Description Protocol protocol for multimedia sessions. A
common mode of usage is for a client to announce a conference session by
periodically multicasting an announcement packet to a well known
multicast address and port using the Session Announcement Protocol
MBONE Tools:MBONE stands for "Multicast Backbone", a virtual
network. The network originated from an effort to multicast audio and
video from the "Internet Engineering Task Force" (IETF) meetings.
MBONE today is used by several hundred researchers for developing
protocols and applications for group communication
SDR(Sesion directory tool), VIC(Video Tool), VAT (Audio tool)and
RAT(Robust audio tool).
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Multimedia Internet Protocols RSVP:The Resource ReSerVation Protocol designed to reserve resources
across a network for an integrated services Internet.
Network control protocol
Allows data receiver to request a special end-to-end quality of service
for its data flows.
RTSP:Real Time Streaming Protocol which allows a client to remotely
control a streaming media server, issuing VCR-like commands such as
"play" and "pause", and allowing time-based access to files on a server.
A client-server multimedia presentation protocol to enable controlled
delivery of streamed multimedia data over IP network.
Aims to provide the same services on streamed audio and video just as
HTTP does for text and graphics.
Multimedia Communications
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Multimedia Communications High-Density File Transfers .
Graphics File Transfers: using ftp Audio File Transfers
Video File Transfers
Audio Communication
Computer-Based Telephony
Computer-Based Audio Conferencing
Streaming Audio
Video Communication
Video Conferencing
Streaming Video
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