Data and Computer

Communications

Ninth Edition

by William Stallings

Chapter 1 – Data Communications,

Data Networks, and the Internet

1Dr. Mohammed Arafah

What’s the Internet

• millions of connected computing devices: hosts = end systems

– running network appsHome network

Institutional network

Mobile network

Global ISP

Regional ISP

router

PC

server

wirelesslaptop

cellular handheld

wiredlinks

access points

communication links

Wired: fiber, copper

Wireless: radio, satellite routers: forward packets

(chunks of data)

protocols control sending, receiving of messages e.g., TCP, IP, HTTP, Ethernet

Internet: “network of networks”2Dr. Mohammed Arafah

Network edge

end systems (hosts):

run application programs e.g. Web, email

access networks:

physical media:

wired, wireless communication links

3Dr. Mohammed Arafah

Uses existing telephony infrastructure

Home is connected to central office

up to 56Kbps direct access to router (often less)

Can’t surf and phone at same time.

telephonenetwork

Internet

homedial-upmodem

ISPmodem(e.g., AOL)

HomePC

central office

1. Dial-up Modem

Access Networks

4Dr. Mohammed Arafah

Access Networks

Also uses existing telephone infrastructure

Telephone Network

DSL Modem Router

Home Phone Internet

DS

LA

M

Splitter

Central Office

Home PC

Phone Line

Router

Mobilehosts

2. Digital Subscriber Line (DSL)

5Dr. Mohammed Arafah

Digital Subscriber Line (DSL)

6Dr. Mohammed Arafah

Optical links from central office to the home

Much higher Internet rates; fiber also carries television and phone services

Optical Splitter

OpticalFibers

ONT

ONT

ONT

Home

Home

Home

Optical FiberOLT

Internet

Router

Central Office

3. Fiber To The Home (FTTH):

Access Networks

7Dr. Mohammed Arafah

Access Networks

Dr. Mohammed Arafah8

4. WiMAX:

A packet passes through many networks!

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

Tier-2 ISPTier-2 ISP

Tier-2 ISP Tier-2 ISP

Tier-2 ISP

localISP

localISP

localISP

localISP

localISP Tier 3

ISP

localISP

localISP

localISP

Internet Structure: Network of Networks

9Dr. Mohammed Arafah

A Communications Model

10Dr. Mohammed Arafah

Data Communications Model

11Dr. Mohammed Arafah

Communications Tasks

Transmission system utilization

Interfacing

Signal generation

Synchronization

Error detection and correction

Flow control

Addressing

Routing

Recovery

Message formatting

Security

Network management

12Dr. Mohammed Arafah

Data exchange can involve

complex procedures.

Next lecture:

ISO/OSI Reference Model

Transmission Medium

selection is a basic choice

internal use entirely up to business

long-distance links made by carrier

rapid technology advances change mix

Wired: copper, fiber optic

Wireless

13Dr. Mohammed Arafah

Networking

growth of number & power of computers is driving need for interconnection

also seeing rapid integration of voice, data, image & video technologies

two broad categories of communications networks:

Local Area Network (LAN)

Wide Area Network (WAN)

14Dr. Mohammed Arafah

Local Area Networks

smaller scope

Building or small campus

usually owned by same organization as

attached devices

data rates much higher

switched LANs, eg Ethernet

wireless LANs, eg Wi-Fi

15Dr. Mohammed Arafah

Local Area Networks - Example

Dr. Mohammed Arafah16

Access Switch

Access Switch

Access Switch

Faceplate

Main

Switch

Router Access

Network

Internet

Wide Area Networks

span a large geographical area

17Dr. Mohammed Arafah

Packet

Router

The Internet

Internet evolved from ARPANET

first operational packet network

applied to tactical radio & satellite nets also

had a need for interoperability

led to standardized TCP/IP protocols

18Dr. Mohammed Arafah

Internet Elements

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Access

Network

Access

Network

Access

Network

Summary

introduced data communications needs

communications model

defined data communications

overview of networks

introduce Internet

20Dr. Mohammed Arafah