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 is two 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!

Initiates instruction Simple Network Model Signal path Converts data Converts data Initiates instruction Receives Instruction

Communication Equipment/Devices Modem – modulate /demodulate Converts digital signal to analog and vice versa Telephone Dialup Modem (56 Kbps) DSL (Digital Subscriber Line) modem Cable Modems (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 478) Cellular Radio Microwave (line of site) Satellite – placed about 22,300 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 Network Interface Cards (NIC) for 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.

Communications Closet

Star Ring Bus See next slide Star 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 Ring Network Bus Network

Star – Ring - Bus Star Ring Bus 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 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 next slide).

Firewall 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.

WAN Model GateWay Internet

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 HowStuffWorks-Firewalls 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