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Data and Computer Communications
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Data Communications, Data Networks, and the Internet
“The fundamental problem of communication is that of reproducing at one point either exactly or approximately a message selected at another point”
- The Mathematical Theory of Communication,
Claude Shannon Message
Message
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Technological AdvancementDriving Forces
•Development of new services
•Advances in technology
Traffic growth at a
high & steady rate
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Changes in Networking Technology
* Emergence of high-speed LANs
* Digital electronics
* Corporate WAN needs
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Communications Model
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Communications Tasks
Transmission system utilization Addressing
Interfacing Routing
Signal generation Recovery
Synchronization Message formatting
Exchange management Security
Error detection and correction Network management
Flow control
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Data Communications Model
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The basic building block of any communications facility is the transmission line.
The business manager is concerned with a facility providing the required capacity, with acceptable reliability, at minimum cost.
Capacity
Reliability
Cost
Transmission
Line
Transmission Lines
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Transmission Mediums
Two mediums currently driving
the evolution of data communications transmission are:
Fiber optic transmissions
and
Wireless transmissions
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Networking
Voice Data
Image Video
Advances in technology have led to greatly increased capacity and the concept of integration, allowing equipment and networks to work simultaneously.
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LANs and WANs
Local Area Networks (LAN)
Wide Area Networks (WAN)
There are two broad categories of networks:
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Wide Area Networks (WANs)
Span a large geographical area
Require the crossing of public right-of-ways
Rely in part on common carrier circuits
Typically consist of a number of interconnected switching nodes
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Wide Area Networks
Alternative technologies used include: Circuit switching Packet switching Frame relay Asynchronous Transfer Mode (ATM)
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Circuit Switching
Uses a dedicated communications path Connected sequence of physical links
between nodes Logical channel dedicated on each link Rapid transmission The most common example of circuit
switching is the telephone network
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Packet Switching
Data are sent out in a sequence of small chunks called packets
Packets are passed from node to node along a path leading from source to destination
Packet-switching networks are commonly used for terminal-to-terminal computer and computer-to-computer communications
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Frame Relay
Developed to take advantage of high data rates and low error rates
Operates at data rates of up to 2 Mbps Rate of errors dramatically lowered thus
reducing overhead of packet-switching
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Asynchronous Transfer Mode (ATM)
Referred to as cell relay Culmination of circuit switching and packet
switching Uses fixed-length packets called cells Works in range of 10’s and 100’s of Mbps
and in the Gbps range Data rate on each channel dynamically set
on demand
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Local Area Networks (LAN)
Smaller scope,
typically a single
building
LANs are usually owned by the same
organization that owns attached devices
Internal data rates greater than WANs
Most common configurations are switched LANs and wireless
LANsLAN
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Metropolitan Area Networks (MAN)
Covers a geographic area such as a town, city or suburb
Middle ground between LAN and
WAN
Supports both data and voice Private
or public network
MAN
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The Internet
Internet evolved from ARPANET Developed to solve the dilemma of
communicating across arbitrary, multiple, packet-switched network
TCP/IP provides the foundation
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Internet Key Elements
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Internet Architecture
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Internet Terminology
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A Networking Configuration
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Summary Trends challenging data communications:
• traffic growth• development of new services• advances in technology
Transmission mediums• fiber optic• wireless
Network categories:• WAN• LAN
Internet• evolved from the ARPANET• TCP/IP foundation