LBSC 690

Session 3Networking

Analog to Digital

• We live in an analog world:• Sound, temperature, light, etc.

– Sensory inputs.

• Are continuous signals.• Can assume all (essentially infinite)

values in a given interval.• Basis for analog computers:

– Uses electrical voltage/current to variables. to represent.

Digital

• Discrete representation: assumes a finite number of values in a given interval.

• Basis for digital computers:– Use 2 discrete values to represent

data, & instructions. (Binary system).• Analog signals converted to digital

by Pulse Code Modulation (PCM).

PCM

• Three step process:• Analog signal is sampled:

– Nyquist’s Theorem.

• Samples are quantized.• Quantized samples are encoded into

binary digits, called “bits” for short.• See handout.

Evolution

• Computers initially stand alone.• Need to communicate.

– Transmit data at a distance.

• Communications:– Data communication.– Telecommunication:

• Provides electrical communications at a distance.

• Service provided by a number of companies internationally.– The “telecommunications industry.”

Telecommunications Industry

• Carriers:– LECs (RBOCs: 7 to 4); CLECs.– IXCs.

• Internet Service Providers (ISPs).• Vendors/Consultants & Manufacturers.• Judicial/Political/Legislative:

– Regulatory agencies.

• Standards Making Organizations.• Customers: business & residential.• Technology and research.

Networking

• Simplest form:• Directly connect two

communicating devices.• Not practical solution.

– Problem of topology:• How to deal with fully connected mesh.

• Need network.– Nodes and segments.

The Universal Seven Part Data Model

DTE DCE DCE DTE

DTE: Data Terminal Equipment

DCE: Data Communication Equipment

DTE/DCE Interface

Transmission Channel

DCE/DTE Interface

Network (Cont’d.)

NETWORK

N

N

N

NS

S

S

S

S: Network Station

N: Network Node

“Local loop”

Network Types

• Switched Communication Network:• Circuit-switched.• Packet–-switched.• Broadcast communication Network:• Packet radio network.• Satellite network.• Local area network.

Generic Switching Network

• Reference handout.

LANs

• What are they?• Need & functions.• Hardware/software components.• Concept of packets.• Ethernet and token ring.• Need to interconnect LANs.

LANs

• Data communication facilities designed to provide high-speed switched connections between processors peripherals and terminals within a local area, e.g., buildings or a campus.

LAN Functions

• File sharing• Printer sharing• CD ROM sharing• On-line databases• Groupware• OPAC access

• Dial in & out• Fax in & out• Voice-video-multi-

media• E-mail• Internet access

LAN Benefits

• Shared access• Increased security• Application and data highway

– Adding new applications is done once (on server)

• Support services more effective and lower cost

LAN Installation

• Network Operating System (NOS).• Network Interface Cards (NIC).• Cabling and connectors.• Concentrators/Hubs/ Switches.• Network Servers:

– File, Print, Communication, etc.

TRAINING

• Network Management:– Network Administrator & Support

Personnel.– Certification.– Continuing education.

• User training.

Ethernet

• Developed in 1973 at Xerox Corporation’s Palo Alto Research Center (PARC).

• Developed by Bob Metcalfe.• Uses the Ethernet Protocol.• Protocol: A code prescribing strict adherence to

correct etiquette and precedence.• Communication protocols: symbols (Character

set), rules for sequence and timing of messages, and procedures for error detection and handling.

• Messages broken into frames (packets).– With source address and destination address.

Network Topology

• Bus• Star• Ring• Mesh• Hybrid

Ethernet

• Broadcast• Carrier Sense Multiple Access/Collision

Detection (CSMA/CD)• Collision retry (random wait)• Need for repeaters• Hubs• Switches• Bridges (internetting)

Ethernet Media

• 4-wire phone 3kbps 200 ft.• UTP 100Mbps 100 ft.• STP 16Mbps 100 ft.• Coax 10Mbps 500

ft.• Fiberoptic 10Gbps2-5 km.

The Internet

• Historical development.• TCP/IP Protocol Suite.• Telnet.• FTP.• E-mail.• Assignment 1:

– Two exercises.

• Packet switching.• Addressing: URLs.

Packet Switching

• General Switching Diagram:– Reference Handout

Modems

• Function:– Modulation – demodulation.

• Types and speeds:– ISDN.– Cable.– ADSL.– Satellite

World Wide Web (WWW)

• Historical development.• HTTP.• HTML.• XML.• Multimedia.

Trends

• Convergence.• Voice over IP (VIP).• Wireless.• Remote access.• Remote device control.