LBSC 690

Session 3

Networking

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.

Concepts:

Bandwidth Measure of channel capacity: frequency range

Radio Spectrum (Next Slide) Frequencies available for telecommunications

Modulation Process of embedding intelligence in a carrier wave

Multiplexing Process that combines multiple calls or messages on a

single channel Examples; TDMA (Time Division Multiple Access),

CDMA (Code Division Multiple Access)

Spectrum

A limited resource Government controlled: FCC & ITU, e.g.

Some assigned frequencies: Am radio: 535-1635 KHz Analog cordless phones: 44-49 MHz TV channels 2-6: 54-88 MHz FM radio: 88-108 MHz TV channels 7-13: 174-216 MHz Cellular phones: 806-890 MHz PCS: 900-929 MHz Satellite TV (small dish): 11.7-12.7 GHz

Cell PhonesMore than 115 million users in US 46,000 people subscribing every day

Based on concept of cells 10 sq. mi. in area with a Base Station in it Low power: 0.3 & 6 watts

Mobile Telephone Switching Office (MTSO).Special codes: electronic serial no. (ESN), mobile identif. no.(MIN, system ident, code (SID).Analog vs. digital.American vs. European approaches GSM (Global System For Mobile communication) TDMA vs. CDMA

LANs

What are they?

Need & functions.

Hardware/software components.

Concept of packets.

Ethernet and token ring. ANSI/ IEEE 802.3 (ISO 8802-3)

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.

Hubs/ Switches.

Network Servers: File, Print, Communication, etc.

Clients

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 and destination addresses.

Ethernet

Broadcast networkCarrier Sense Multiple Access/Collision Detection (CSMA/CD)Collision retry (random wait)Need for repeatersHubs Basic, Smart, Intelligent, Switches

BridgesRouters (internetting)

Network Topology

Bus

Star

Ring

Mesh

Hybrid

Transmission Channels (Media)

4-wire phone 3Kbps 200 ft.

UTP 100Mbps 100 ft.

STP 16Mbps 100 ft.

Coax 10Mbps 500 ft.

Fiber optic 10Gbps 2-5 km.

The Internet

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

Packet switching.Addressing: URLs.

Packet Switched Networks

General Switching Diagram: Reference Handout

Modems

Function: Modulation – demodulation.

Types and speeds: Standard ISDN. Cable TV. xDSL. Satellite

World Wide Web (WWW)

Historical development.

HTTP.

HTML.

XML.

Multimedia.

Trends

Convergence.

Voice over IP (VIP).

Wireless. 3G (Third Generation) PCS (Personal Communication Services)

Ubiquitous networking

Remote device control.