Basic Concepts of Internet Technology What is a computer network? Isolated computers vs. networked computers internetworking The Internet What’s a protocol?

Basic Concepts of Internet Technology

• What is a computer network?

• Isolated computers vs. networked computers

• internetworking

• The Internet

• What’s a protocol?

What is a computer network?• An interconnected collection of computers

• Examples of networks:

– Telephone networks

– Satellite networks

– Mobile telephone networks

– Cable TV networks

– Intranets and extranets

– Internet

• Computer networks vs. other types networks

(general, different types of data vs particular application)

Basic Concepts: Isolated Machines

IndependentWorkstations

(Local Processing)

How to share data?

Basic Concepts: Networked Machines

ComputerNetwork

Workstations(Local Processing)

FileServers

ApplicationServers

Client-Server Model

Classifications of Computer Networks

• Based on size:– System/Storage area networks (SAN)

• within the same room• connecting processors to storage servers.

– Local area networks (LAN)• in a close proximity

– Metropolitan area networks (MAN)• span a city

– Wide area networks (WAN)• connecting computers situated anywhere• Connects many networks together

internetwork• A collection of networks

The Internet Topology

See http://www.cybergeography.org/atlas/topology.html for more Internet topologies.

What’s the Internet: a service view

• communication infrastructure: enables distributed applications:– WWW, email, games, e-

commerce, database.,

• cyberspace

What’s the Internet: “nuts and bolts” view

• millions of connected computing devices: hosts, end-systems– pc’s workstations, servers– PDA’s

• communication links– fiber, copper, radio, satellite

• routers: forward packets (chunks) of data across networks

local ISP

companynetwork

regional ISP

router workstation

servermobile

What’s the Internet: “nuts and bolts” view• protocols: control sending,

receiving of msgs– e.g., TCP, IP, HTTP, FTP

• Internet: “network of networks”– public Internet versus

private intranet

– collection(s) of SAN, LAN, MAN, WAN

local ISP

companynetwork

regional ISP

router workstation

servermobile

What’s a protocol?a human protocol and a computer network protocol:

Hi

Hi

Got thetime?

2:00

TCP connection req.

TCP connectionreply.Get http://gaia.cs.umass.edu/index.htm

<file>time

What’s a protocol?human protocols:• “what’s the time?”• “I have a question”• introductions

… specific messages sent

… specific actions taken when messages received, or other events

network protocols:

• machines rather than humans

• all communication activity in Internet governed by network protocols

protocols define format, order of messages sent and received among network entities, and

actions taken on message transmission, receipt