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Telecommunications
and Networking
What is Telecommunications
• The transportation of information via
electronic means
– Could include telephone & telegraph
• Data Communications is the part of
telecommunications that relates to
computer systems or the electronic
transmission of data
Importance of
Telecommunications
• Provides the foundation for the Internet
• Dramatic cost reductions in the areas of
applications development deployment
Importance of
Telecommunications
• Transportation of different types of data
– Voice, Video, Data, Fax, etc.
• Collaboration
Components of
Telecommunications Systems
• Hardware and Telecommunications
Software
• Communications Channels
– Links required for data and voice to be
transmitted and received
• Communications Processors
– Support functions for transmission and
reception
• Protocols
Types of Signals
• Analog
– Used in everyday telephone conversations
• Digital
– Electrical impulses representing a high
signal (1) or a low signal (0)
• Digital has several advantages
– Lower error rates
– Higher transmission speeds
– Inherently less noise
• Noise is filtered out
– No conversion required
Purpose of the Modem
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Modulator/Demodulator
Converts analog to digital
Converts digital to analog
Handshaking or “Interfacing”
– Ensures correct protocols are used
• Filters the signal to reduce errors
• Clocking
– Timing the rates to sparse data correctly
Communications Channels
• Twisted Pair
• Coaxial Cable
• Fiber Optic
• Microwave
• Satellite
Characteristics of
Communications Channels
• Buad Rate
– The number of discrete signals over a period of
time
• Bandwidth
– Determines how much data can be pushed
through
– Difference between lowest frequency and
highest frequency as measured in Hertz
– Telephone lines transmit between 300hz and
3300hz
• Bandwidth is 3000 hz
Sources of Error
• White Noise
– Gaussian Noise
– Hissing noise due to movement of electrons
• Impulse Noise
– External spikes, ex. Lightning
• Crosstalk
– Signals from one channel interferring with another
• Echo
– The reflection or reverse of the signal transmitted
• Attenuation
– Decrease in signal strength dues to distance
Error Detection
• Parity Checking
• Cyclical Redundancy Check
• Error Prevention
– Telephone line conditioning
• Service performed by Telephone Company
– Lower transmission speeds for digital
– Shielding
Media Selection Criteria
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Cost
Speed
Availability
Expandability
Error Rates
Security
Distance
Environment
Application
Maintenance
Network Topologies
• Star
– All are connected to a central computer
– If the central node goes down, all are down
• Bus
– Entire network on a single circuit
– Popular in LANS
– Message is sent over the network and each station is
checked to see if the addresses match
• Token Ring
– Each node is sequentially checked to determine if they
have a message to send
– You must wait for the token before you can send your
message
• You can combine networks
LAN and WAN Components
• File Server
– Stores programs and/or data for users to
access via a network
• Bridges
– Connects similar networks together to
facilitate communications
• Gateways
– Connects dissimilar networks together to
facilitate communications
Protocols
• TCP/IP
– Extremely popular
– Used to establish connections on the Internet
• IPX
– Protocol used with Novell Communications
software
• SNA
– Used by many mainframes and other IBM
systems
TCP/IP
• Transmission Control Protocol / Internet
Protocol
• Developed for the sole purpose of
communicating over large geographic
areas
• Well suited to allow connectivity between
dissimilar operating systems
• Standard used on the Internet since 1983
• To understand TCP/IP is to understand
the Internet……. So let’s try
TCP/IP
• TCP/IP Protocol Stacks
– Provides standards for network
communications
• Consists of 4 layers
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Network Interface Layer
Internet Layer
Transport Layer
Application Layer
Network Interface Layer
• Consists of the Network Interface Card
and the Network Interface Card Driver
• Responsible for putting packets on and
off the wire
• Packet Switched Technologies supported:
– X.25
– Frame Relay
– ATM
Internet Layer
• Encapsulates packets into internet
datagrams and runs the routing
algorithms
• Controls the messages as they are sent
and received
• Resolves addresses
Transport Layer
• Provides communications sessions
between computers
• Establishes sessions by polling
destination computer’s port address
• TCP tells host computer how much data
the destination computer can receive
• Establishes a connection
Applications Layer
• Area where applications gain access to
the network
– How applications talk to the network
• Microsoft provides two API’s
(Application Programming Interfaces)
for use with TCP/IP
– Windows Sockets
– NetBios over TCP/IP
IP Addresses
• Looks like 223.107.2.200
• Acts as your mail address on the Internet
• Provided by a local ISP
– Internet Service Provider
• 223.107.2 portion
– Defines the network id
• 200
– Defines the node on the network
• Subnet Addresses are used when a
network has a sub-network
Controlling TCP/IP
• Dynamic Host Configuration Protocol
(DHCP) is a program that centrally
manages the allocation of TCP/IP
information
• DHCP is a server program which runs on
a Windows NT Server
• DHCP must have a static IP address
Network Communications
• Telnet
– Remote terminal emulation protocol
– You must be known to the host and have an
account on the host
• FTP
– File Transfer Protocol
– Must have an account or the server allows
anonymous accounts
– Program that transfers text and binary files
between TCP/IP computers
Network Communications
• Web Browsers
– Netscape, Internet Explorer
• Access documents and multimedia files
using HTTP
– Hypertext Transfer Protocol
• After the data is sent the connection is
closed
Competitive Advantages using
Telecommunications
• Groupware
– Users share common databases
– Able to collaborate on a variety of issues
– Disparate forms of information can be
contained in a central database
• Word Documents, Excel spreadsheets, Email
• RDBMS’ required standardized data
– Easily facilitates mobile computing
– Virtual meetings
Knowledge Sharing Editorial
• Leading-edge firms create and maintain
a culture which promote knowledge
creation by encouraging information
sharing, openness and trust, cooperation
and collaboration, continual search for
knowledge and truth, risk taking,
experimentation, and a respect other’s
knowledge and expertise
Telecommunications and
Teamwork
• Team
– A well-defined group of individuals sharing a
common goal who must interact among themselves
to perform their work
• Today’s teams must often transcend time and
space
• Communication speed and convenience often
make or break a team’s efforts
• Teams need the right information at the right
time
– Pulled rather than pushed
Telecommunications and
Teamwork
• Teams need to rely on repositories of
information from previous experiences
rather than “re-invent the wheel”
• Telecommunications provide the tools to
allow teams to quickly communicate,
store and share results and cross time
and space boundaries to maximize efforts
Competitive Advantages using
Telecommunications
• The Internet
• Cost reductions through teleconferencing
and videoconferencing
• Voice Mail and electronic mail
– Cost reductions
– Information can be pulled when needed
• EDI
– Lower cost
– Lock in customers and/or suppliers