INFS 361 Chapter 1 Notes UTM Bob 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 – , 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 / HardwareClient Stations / Hardware Stations: the computers that communicate over a network are called stations.

Server Station / HardwareClient Stations / Hardware Server Software Web Server Apache Server Software Mail Server SMTPd or MS Exchange Client Application Web Browser IE or Firefox Client Application Client Outlook or Eudora Apache SMTPd Software: Client and server stations on a network run application programs that communicate with each other

Server Station / HardwareClient Stations / Hardware Server Software Web Server Apache Server Software Mail Server SMTPd or MS Exchange Client Application Web Browser IE or Firefox Client Application Client Outlook or Eudora Apache SMTPd Messages: The applications communicate by sending messages. In a single network, the messages are called frames. Message

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

Frame Frames: Switches forward messages between stations called frames. Frames stay within a single network (LAN) Frame Switch Frame 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 Switch 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 – b 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-AddrGET /index.htm HTTP/1.0…. HeaderPayload / 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

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