Networking &
Telecommunications
Introduction to Computer Science
2007-2008

Aims
• Describe tech. that make telecomm. possible
• Describe the nature and function of LANs
and WANs
• Discuss the use of online communication
• Explain how wireless tech. is transforming
how people work and comunicate
• Describe trends in telecomm. and networking
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Contents
1. Basic Network Anatomy
2. Communication Software
3. E-mail and Instant Messaging
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Basic Network Anatomy
• Hardware: share resources
→ reduce costs, powerful equipment
• Software: share data
→ increases efficiency
• People: enable people to work
together and collaborate (CSCW)
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Networks Near and Far
Local Area Netwok (LAN)
• nodes: computers and peripherals
• cable or wireless connections
• different operative systems
Metropolitan Area Netwok (MAN)
• provided by telecomm. companies
Wide Area Netwok (WAN)
• nodes are networks
• different media (telephonic lines, microwave, satellites)
• bridges, gateways and routers connect networks
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Node: Backbone:
any network peripheral high capacity lines
Some interesting terms
Hub: Switch:
connects devices to a connects devices to a
network (broadband) network (isolates)
Router: Gateway:
interconnect network protocol converter
fragments

Specialised Networks
GPS (Global Positioning System)
• 24 sat. arounf Earth,
4 always over horizon
• civil and military use
Global Financial Systems
• paper replaced by digital patterns as money
• ATM (automatic teller machine)
• e-commerce
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The Network Interface
Direct connection
• connects a device directly to
the net
• computer ports (serial,
USB, Infrared)
• Network Interface Cards
(NIC) e.g. Ethernet
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The Network Interface
Remote connection
• modem or broadband
connection device
• Telephonic or TV networks
to cover long distances
• e-commerce
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Communication with
Modem
• Modulator/demodulator (analog/digital)
• Internal or external (using serial/USB ports)
• Modem fax to communicate with facsimile (fax)
machines
• Speed:
• bits per second (bps): between 28,000 bps
and 56,600 bps (56Kbits)
• baud rate (symbols per second)
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Broadband Connection
Bandwidth: quantity of inform. that can be transmitted
Broadband connection: connection that use greater
bandwidth
• DSL (digital subscriber line) over phone lines
• cable-modem over cable TV networks
• high-speed wireless connections
• satellite dishes
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Fiber-optic and Other
Media
Type Uses Distance Cost
twisted pair small LANs 100 m. low
coaxial cable big LANs 200 a 500 m. medium
Backbones
fiber-optic 2 a 100 km. high
WANs
infrared LANs 1 a 300 m. medium
wireless (radio) Mobile devices variable high
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Wireless Technology
Infrared
• infrared tech. (as remote
controls for TV)
• short distances
Bluetooth
(about 1m.)
• Radio tech.
Wireless (WiFi)
• create personal area networks
• Radio tech. (PAN)
• •
standards: 802.11 a/b/g/n device oriented
• •
50m. from base station distance up to 10.
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Communication
Software
Protocols
• Rules for exchange data
• Hardware must follow them
• Network Operative Systems
Network models
• client/server
• peer to peer (P2P)
Terminal and emulation software
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The Network
Advantage
Share hw resources
• reduce costs
• more powerful devices
Share data and programs
• file servers to keep data and applications
• P2P models in small networks
• site and network licenses (economical)
Groupware
• support groups working together
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The Many Faces
of E-mail
• sent & receive messages from the network
• stored on a server until user reads them
• web-mail: accessing using
a web browser
• files as attachments
• HTML or plain
ASCII text emails
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Services Based on
E-mail
Mailing lists
• participate on discussion groups
• messages arrive to your mail box
• subscription needed to participate
Newsgroups
• public discussion groups (without registration)
• messages stored on a “notice board”
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Instant Messaging
• text-based in early ages of internet (talk)
• graphic interfaces nowadays
• chat rooms (public)
• bidirectional video conferences
• variety of software and services
• MS Messenger
• Jabber (open source)
• Pidgin (multiprotocol)
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Computer Telephony
• Integrates telephonic services and computers
• Examples
• voice email
• voice IP (VoIP)
• Current trends:
integration in one device
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Advantages of Online
Communication
• e-mail is fast
• e-mail doesn’t depend on location
• e-mail facilitates group communication
• e-mail is digital data that can be combined with other
computer generated documents
• online comm. is less intrusive than telephone
• online comm. allows time shifting
• online comm. enables decisions to evolve over time
• online comm. makes possible long-distance meetings
• e-mail and instant messaging emphasize message over
messenger
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click to see the skeetch
Origin of the term ‘spam’
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