networking and telecomunications

Introduction to Computer Science2007-2008

Networking & Telecommunications

4626. Introd to Computer Science

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


Contents

1. Basic Network Anatomy

2. Communication Software

3. E-mail and Instant Messaging


Basic Network Anatomy

• Hardware: share resources → reduce costs, powerful equipment

• Software: share data → increases efficiency

• People: enable people to work together and collaborate (CSCW)


Networks Near and FarLocal 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

Some interesting terms

Node:any network peripheral

Backbone:high capacity lines

Hub:connects devices to a network (broadband)

Switch:connects devices to a network (isolates)

Router:interconnect network fragments

Gateway:protocol converter


Specialised NetworksGPS (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


The Network Interface

Direct connection

• connects a device directly to the net

• computer ports (serial, USB, Infrared)

• Network Interface Cards (NIC) e.g. Ethernet


The Network Interface

Remote connection

• modem or broadband connection device

• Telephonic or TV networks to cover long distances

• e-commerce


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)


Broadband Connection

• DSL (digital subscriber line) over phone lines

• cable-modem over cable TV networks

• high-speed wireless connections

• satellite dishes

Bandwidth: quantity of inform. that can be transmitted

Broadband connection: connection that use greater bandwidth


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

fiber-optic BackbonesWANs

2 a 100 km. high

infrared LANs 1 a 300 m. medium

wireless (radio) Mobile devices variable high


Bluetooth

Wireless (WiFi)

Infrared

Wireless Technology

• infrared tech. (as remote controls for TV)

• short distances (about 1m.)

• Radio tech.

• standards: 802.11 a/b/g/n

• 50m. from base station

• Radio tech.

• create personal area networks (PAN)

• device oriented

• distance up to 10.


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


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


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


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”


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)


Computer Telephony

• Integrates telephonic services and computers

• Examples

• voice email

• voice IP (VoIP)

• Current trends: integration in one device


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


Origin of the term ‘spam’

click to see the skeetch

http://www.youtube.com/watch?v=ODshB09FQ8w



networking and telecomunications

Technology

computer science

net computer ports serial

broadband connection

personal area networks

basic network anatomy

phone lines cablemodem

wireless wifi

use of online communication