James Tam Computer Networks Concepts covered What is a computer network Benefits and issues of networks Types of networks

James Tam What Is A Network? 2+ computers A communication system that connects them

James Tam Benefits Of Networks (Business View) 1 1)Resource sharing Programs, hardware, data etc. 2)Reliability Multiple copies of files, multiple processors 3)Reducing costs Initial cost of network and future upgrades 4)Communication The network provides yet another means of communicating 1 From “Computer Networks” by Tanebaum

James Tam 4) Communication (Instant Messaging) Instant Messenger (Microsoft)

James Tam 4) Communication (Instant Messaging Continued) AIM (American online/Netscape) ICQ (I seek you)

James Tam Benefits Of Networks (Business View - Continued) 4) Communication - groupware e.g. The TeamWave Workplace (Sonexis Inc.)

James Tam Benefits of networks (person-based view) 1 1)Access to remote information E.g., access to information 2)Person-person communication E.g., Instant messenger services, ICQ, etc 3)Entertainment Fun and games 1 From “Computer Networks” by Tanebaum Diablo (Blizzard) Black Knight (Microsoft) Ghost Recon (Red Storm)

James Tam Social Issues Of Networks 1 1)Determining what is acceptable 2)Privacy Employers. Employees The need for the storage of access to information vs. individual rights 3)Anonymity Costs and benefits 1 From “Computer Networks” by Tanebaum

James Tam What You Need For A Two Computer Network Two computers (obvious) A network interface card (NIC) for each computer Ethernet connection

James Tam A Picture Of A Two Computer Network Computer name = “Fred” Computer name = “Freda” Network name = “Fland”

James Tam What You Need For A Multi (3+) Computer Network The computers A network interface card for each computer Ethernet connection Network hub

James Tam A Picture Of A Multi-Computer Network

James Tam Connecting A Network To Other Networks Router Avoids clogging computers with irrelevant data Ensures that information reaches the proper destination

James Tam Protecting Your Network From The Outside Firewall Filters information -Offensive web sites Protects network -Hackers

James Tam Types Of Networks Local Area Network (LAN) May be located within a single building or campus Metropolitan Area Network (MAN) A larger version of a LAN May span several corporate offices or an entire city Wide Area Network (WAN) May span a country or even a continent LAN MAN LAN WAN

James Tam Bandwidth Determines the amount of information that can be transmitted by a network connection Finite amount Measured in bits per second (bps) Transmission rate analogous to a road Number of “lanes” Speed Categories Narrow band: 40 – 100 bits/second (telegraph line) Voice band: 110 – 9600 bits/second (phone line) Broad band: several Megabits/second (next slides)

James Tam Types Of Network Connections Physical Twisted pair Coaxial cable Fiber optic Wireless Microwave Infrared Light Radio

James Tam Twisted Pair Networks (Physical) Twisting eliminates electrical interference from nearby pairs Increased twisting increases the transmission rate Category 1Less than 1 Megabit/second (phone lines) Category 2Up to 4 Megabits/second Category 310 Megabits/second (U of C) Category 420 Megabits/second (Token Ring) Category 5100 Megabits/second (Fast Ethernet)

James Tam Twisted Pair Networks (Physical - Continued) Twisted pair can be: Unshielded – cheaper and takes up less space Shielded – protects against interference

James Tam Coaxial Cable Networks (Physical) Speed range 10 – 100 Megabits per second Copper core Insulation Braided outer conductor Protective plastic covering Metal connector

James Tam Twisted pair vs. Coaxial cables Both Transmit signals through a metal cable Coaxial cables can be longer 100 meters (twisted pair) vs. 500 meters (coaxial cable) Coaxial cables are linear (one break takes down an entire part of the network) Hub Twisted pair Coaxial cable

James Tam Fiber Optic Networks (Physical) Light is transmitted through a clear plastic tube Fast with few errors 100 Megabits per second

James Tam Pros And Cons of Fiber (Physical Continued) Advantages over copper wires (twisted pair and coax) Long range Not affected by electrical problems Not effected by air borne corrosives Thin and light Secure Disadvantages of fiber over copper New and unfamiliar technology Unidirectional – light travels in one direction

James Tam Microwave-based Networks (Wireless) No physical link required May increase flexibility in location Lower costs Low error rate

James Tam Microwave-based Networks (Wireless continued) Slow transmission rate 8 Megabits per second Linear Microwaves travel in a straight line May be effected by atmospheric conditions Transmissions called on account of rain…

James Tam Infrared Networks (Wireless) No physical link required Cheap and easy to build Need a clear line of sight IR beams don’t pass well through solid objects Slow transmission rate 4 Megabits per second Doesn’t work outside

James Tam Light-based Networks (Wireless) No physical link required Unidirectional and limited range ~ Several hundred meters Highly dependent on the weather

James Tam Radio-wave Networks (Wireless) No physical link required Works outdoors and indoors Omni directional Slow transmission 1 Megabit per second Subject to interference Direct Indirect

James Tam Radio-wave Networks: Bluetooth (Wireless) No physical link required Short range radio 10 m (100 with antenna) Works with any electronic device Keyboard, computer, mouse, cell phone, head phone etc. Slow 1 Megabit per second

James Tam Summary What is a network and what a network consists of Benefits and issues associating with computer networks What are different types of networks LAN, MAN, WAN What are different types of network connections Physical vs. wireless and examples of each.