CIS105 Networking: Computer Connections
Topics • Describe the basic components of a network. • Explain the methods of data transmission, including types of signals. • List communication equipment and channels options. • Describe various network topologies. • Define firewall and communication protocols.
Network • A Computer Network istwo or more computers connected together with data communications equipment over a communications channel/media. • Benefits of Networks? • Reduce costs by sharing hardware, software, and data (information). • Communication!
Simple Network Model Signal path Converts data Converts data Initiates instruction Receives Instruction
Communication Equipment/Devices • Modem – modulator -demodulator • Converts digital signal to analog and vice versa • Telephone Dialup Modem (56 Kbps) • DSL (Digital Subscriber Line) Modem • Cable Modem (cable companies) • Cellular Modem (uses cellular system) • Network Integrated w/ Motherboard • Network Interface Card (NIC) • Installed in expansion slot • Wired or wireless cards
Communication Channel / Media Physical Media • Twisted Pair (TP) Cable • Shielded (STP) • Unshielded (UTP) • Ethernet uses RJ45 • Telephone uses RJ11 • RJ – Registered Jack • Coaxial Cable (coax) • Copper + 3 layers of insulation • Fiber Optic Cable • Glass/plastic – uses light to transmit • Speed of light • Tubes are insulated • Wireless (next slide)
Communication Channel / Media Wireless Media • Wireless • Generally slower • Susceptible to interference • Wi-Fi – Wireless Fidelity –standard 802.11 MIMO (Multiple-in, Multiple-Out) • Infrared • Bluetooth (see page 205) • Cellular Radio • Microwave (line of site) • Satellite – placed about22,300 miles above
Transmission Characteristics • Bandwidth – is the measurement of how much information can be transmitted over a medium over a prescribed period of time. • Signal Type • Analog (continuous signal for older media). • Digital (individual electrical pulses - binary). • Broadband transmission– multiple signals simultaneously in both directions - shared line - (Internet connections). • Baseband transmission – one signal at a time. • Simplex – data is transmitted one direction only (TV). • Half-duplex – data is transmitted in both directions, but not at the same time (CB Radio, ATM, FAX). • Full-duplex – data is transmitted in both directions at the same time for same device (telephone, modem dial-up service).
Transmission Modes • Asynchronous – start/stop signals for each message. • Message is usually one or two bytes long. • Low-speed communication • Synchronous – larger block of characters are transmitted together. • Includes error-check bits at the end of the message. • More complex and more expensive.
Local Area Network (LAN) • A LAN is a collection of computers connected together to share hardware, software, and data. • LAN Hardware • Communications equipment / devices • Communications channel / media • Hub – connects computers to create a LAN • Bridges and Routers – connects LANS that use the same protocol • Gateways – connects LANS that use different protocols, and also serve as routers.
Star Network Ring Network • Node - each computer, printer, or server on network • Network Topology is the physical layout of a network. • Three common topologies • Star • Ring • Bus • See next slide Bus Network
Star – Ring - Bus • Star • Server is in center with attached clients • If server goes down, network goes down • Easy to expand • Server controls collisions • Ring • All computers connected by a single line • If any computer goes down, the network goes down • Difficult to expand • No collisions, because token travels around one way • Bus • All nodes share a single line • If a computer goes down, the network is still up • Easy to expand • Many collisions – causes resend – Terminator’s located at ends.
Wide Area Network (WAN) • Connecting two or more LAN’s of the same company. • Can link computers across town or span the world. • Common carriers are companies licensed by FCC to provide these services as leased lines. • Dedicated lines provides permanent connection between two or more locations • Companies can build their own (microwave, fiber, etc.) • T1 and T3 high-capacity digital lines can be leased • Digital Subscriber Line (DSL) use telephone lines • Connect with Router or Gateway • Will need a firewall to keep intruders out, which can be hardware and/or software (see after next slide).
GateWay Internet WAN Model
Firewalls block unauthorized users from entering the network and unauthorized software from making outbound connections (spyware). Windows includes personal Firewall protection. Separate products can also be purchased. Firewall
Communication Software • All of this networking hardware requires software. • After connecting all of the hardware, software needs to be installed on the administrator’s computer. • Connect to the networking devices from the administrator’s computer and use the software to configure the hardware. • Then everything will work .
Client/Server Uses • Client computer requests services from server. • Server returns requested information / data. • Common uses include Web Server, Print Server, File Server, and Email Server.
Peer-to-Peer Networks • Connect directly to another computer to create a LAN. • Need to activate Operating System features. • Server is not required. • All computers have equal status. • Users share each other’s files, printers, etc. • Common in small offices.
Communication Protocol • How is all of this communication possible? • Protocol - a set of rules for the exchange of data. • Agreement on how data is to be sent and receipt acknowledged. • Needed to allow computers from different vendors to communicate. • Common protocols include Ethernet, Wi-Fi, TCP/IP • Transmission Control Protocol/Internet Protocol (TCP/IP) • Permits any computer to communicate over the Internet. • Uses packet switching – original message is broken up; each piece has address of destination; each piece may take a different route; receiving computer puts all the pieces together.
Summary • Want to learn more… • CIS190 Introduction to LAN • CNT140 Cisco Networking Basics • MST150 Microsoft Windows Professional • HowStuffWorks-Firewalls • Review MCC’s Wireless Network: http://www.mc.maricopa.edu/its/net_services.html