INFS 361Chapter 1 Notes

UTMBob Bradley

Fall 2005

Network Types

• LANs – Local Area Networks

• WANs – Wide Area Networks

• internets – Connections of networks

• The Internet

Four Elements of a Network• Hardware Devices

– Server Stations (Hosts)• PCs and Appliances

– Clients Stations (Hosts)• PCs, Set-top boxes, PDAs

– Switches (Hubs)– Routers

• Software Application Programs– E-Mail, Web, IM, DB– Clients, Servers, P2P

• Media– Wires, Fiber, Wireless – Transmission Lines

• Access lines and Trunk Lines• Messages

– Frames and packets

Stations and Applications

• The computers that communicate over networks are called stations– On the Internet we call them hosts– Client stations and server stations

• Servers provide service to clients

• Clients and servers run application programs

A Network

• A network is a transmission system that allows an application on any station in the network to communication with an application on any other station in the network.

Server Station / Hardware Client Stations / Hardware

Stations: the computers that communicate over a network are called stations.

Server Station / Hardware Client Stations / Hardware

Server SoftwareWeb ServerApache

Server SoftwareMail ServerSMTPdor MS Exchange

Client ApplicationWeb BrowserIE or Firefox

Client ApplicationE-Mail ClientOutlook or Eudora

Apache

SMTPd

Software: Client and server stations on a network run application programs that communicate with each other

Server Station / Hardware Client Stations / Hardware

Server SoftwareWeb ServerApache

Server SoftwareMail ServerSMTPdor MS Exchange

Client ApplicationWeb BrowserIE or Firefox

Client ApplicationE-Mail ClientOutlook or Eudora

Apache

SMTPd

Messages: The applications communicate by sending messages. In a single network, the messages are called frames.

Message

Message

Message

Message

Switches: Stations (and other devices) on a Local Area Network are connected by switches (hubs).

Switch

SwitchSwitch

Frame

Frames: Switches forward messages between stations called frames. Frames stay within a single network (LAN)

Frame

Frame

Switch

Frame

FrameSwitch

Switch

Router: Routers forward messages outside of a single network, to another network.

In order for a device to communicate with a device on a different network, it sends the message to a router.

Frame

Frame FrameSwitch Router

Internet or

another network

Media

• All of these stations and devices are connected together with media:– Wires

• Copper, Cat 5, UTP, Coax

– Fiber• Single Mode & Multi-Mode

– Wireless• Microwave• Radio – 802.11b• Satellite

– Media Converters

Packets

• When messages are transmitted over a network, they are broken down into shorter messages called packets.– typically a few hundred bytes long

Parts of a Packet

• Each packet contains:– Header

• To, from, sequence, flags, checksum

– Payload / Data

Dest-Addr Source-Addr GET /index.htm HTTP/1.0….

Header Payload / Data

• Packet Switching– The breaking of transmissions into short self-

contained messages

• Multiplexing– Messages of many conversations can be sent

over the same transmission lines• Reduces the number of lines that have to be run• Reduces the costs

• WANs – Wide Area Networks– Networks that link sites together– Trunk Lines

• 56 k, T1, T3, Frame Relay

• LANs – Local Area Networks– Networks within sites– Switches

• Workgroup Switches• Central Core Switches• Ethernet

• Picture in book on page 8

Internets

• A collection of networks connected by routers so that any application on any host computer on any network can send messages called packets to any other application on any host computer on any other network in the internet.

• Use the TCP/IP protocol

Internet Terms

• Hosts– A computer connected to an internet

• IP Address– Each host on an internet has an Internet

Protocol address or IP Address– 32 bit number– Dotted decimal notation

• 10.1.2.3

Switches Versus Routers

• Switches– Provide connection within

networks– Operate at layer 2 (Data

Link Layer)

• Routers– Provide connection between networks

– Operate at layer 3 (Network Layer)

Packets and Frames

• Within single networks, messages are called frames. – Frames only travel in a single network.

• Within internets, messages from the source host to the destination host are called packets.– A packet is carried in a frame

• Packets are encapsulated in frames

– A packet goes all the way from the source to the destination host

The Internet

• The global collection of connected networks.– Hundreds of millions of host computers

• ISPs – Internet Service Providers– Connect organizations to “The Internet”

• NAP – Network Access Points– Connect up ISPs.– Internet Backbone

• TCP/IP– All the ISPs can work together because all ISPs and

all hosts transmit according to the TCP/IP standard.

• internets versus the Internet– internets: any internet that connects multiple

networks– The Internet: the worldwide Internet

• Intranet– Internal internet for use within an organization– Based on the TCP/IP tandards

• Extranet– To connect multiple firms