Topic 7


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  • The only one in use today is Full-Duplex
  • MAC address is cradle to grave, can't be changed. TCP/IP address can be changed.
  • Ring subject to failures – if any segment goes down, the whole ring is down.
  • The categories are IEEE specifications for quality of transmission. Cat 5 meets a certain set of requirements, and so on… Given the same environmental circumstances, you can have a longer run of higher cat cable.
  • A poor connection causes a lot of packet re-transmissions, dropping perceived speed.
  • Topic 7

    1. 1. Network Fundamentals
    2. 2. Network Definition <ul><li>Two or more computers connected together to share information (e.g., files) or resources (e.g., printers) </li></ul>
    3. 3. Network Services <ul><li>File Services – Allows multiple users access to sets of files for distribution or collaboration. </li></ul><ul><li>Print Services – Allows multiple users to connect to, and use, centralized printers. </li></ul><ul><li>Mail Services (including IM) – A server on the network acts as an E-mail server, receiving all E-mail for the domain. </li></ul>
    4. 4. Network Services <ul><li>Directory and Name Services – Enables users to connect to particular files and devices without knowing the physical location of the resource. </li></ul>
    5. 5. The Internet <ul><li>A network of networks </li></ul><ul><li>The Internet itself is nothing more than a set of facilities that connect separate, little networks together into one gigantic network. </li></ul><ul><li>The Internet doesn't provide the information you're looking for, one of the smaller networks does. </li></ul>
    6. 6. Network Administration <ul><li>Setting up user accounts and services </li></ul><ul><li>Monitoring network performance </li></ul><ul><li>Repairing network failures </li></ul><ul><li>Enforcing security </li></ul><ul><li>Providing fault tolerance (backing up) </li></ul>
    7. 7. Network Modes of Transmission <ul><li>Simplex – One direction only </li></ul><ul><ul><li>Over the air television </li></ul></ul><ul><ul><li>Burglar, Fire Alarms </li></ul></ul><ul><li>Half-Duplex – One direction at a time </li></ul><ul><ul><li>Two-way radios </li></ul></ul><ul><li>Full-Duplex – Transmit & Receive at the same time. Network connections allow full-duplex transmission. </li></ul>
    8. 8. Types of Networks <ul><li>Peer-To-Peer </li></ul><ul><ul><li>All computers are equal partners </li></ul></ul><ul><ul><li>Each user responsible for access to resources on his/her computer </li></ul></ul><ul><ul><li>Each workstation acts as either a server or a client in each transaction </li></ul></ul><ul><ul><li>Easy to install and operate </li></ul></ul><ul><ul><li>No extra equipment or software </li></ul></ul><ul><ul><li>Because each person controls access, network security can be a problem. </li></ul></ul>
    9. 9. Types of Networks <ul><li>Client-Server </li></ul><ul><ul><li>Centralized administration of resources </li></ul></ul><ul><ul><li>Users must authenticate themselves to use network resources </li></ul></ul><ul><ul><li>Server is equipped to handle requests from multiple users at the same time </li></ul></ul><ul><ul><li>There is a cost for ease of administration (software, hardware, a trained staff) </li></ul></ul>
    10. 10. Types of Networks <ul><li>Local Area Network (LAN) </li></ul><ul><ul><li>Computers connected over a relatively small geographic area (a home, an office, a building or a campus). </li></ul></ul><ul><li>Wide Area Network (WAN) </li></ul><ul><ul><li>Designed to work over a larger area than a LAN, across a city, state, country or the planet. </li></ul></ul><ul><ul><li>Use either a circuit-switched or packet-switched network. </li></ul></ul>
    11. 11. Connecting a Computer to a Network <ul><li>Network Interface Card (NIC) </li></ul><ul><ul><li>Different cards for different types of network (Ethernet or Token Ring) and for different types of media. </li></ul></ul><ul><ul><li>Each card has a particular Media Access Control (MAC) address to uniquely identify it. </li></ul></ul><ul><ul><li>Each card is programmed with a TCP/IP address so that other computers can connect to it. </li></ul></ul>
    12. 12. TCP/IP Address <ul><li>Four series of numbers from 0 – 255 </li></ul><ul><li>Every network-connected device has to have a unique address. </li></ul><ul><li>There are only 4.3 Billion addresses available. </li></ul>
    13. 13. Dynamic Host Configuration Protocol (DHCP) <ul><li>On large networks, you can run into problems if you let everyone administer their own IP addresses. </li></ul><ul><li>DHCP centralizes the administration of IP addresses on the network. </li></ul><ul><li>A DHCP server doles out unique IP’s to requesting computers. </li></ul><ul><li>The IP is leased to the device for a specified period of time (72 hours). </li></ul>
    14. 14. Domain Name System <ul><li>When a network is connected to the Internet, it’s difficult to remember the IPs of all the computers you want to connect to. </li></ul><ul><li>Hosts are identified by human-friendly names (, </li></ul><ul><li>A DNS server translates the name into the IP address. </li></ul>
    15. 15. Physical Network Characteristics <ul><li>Network Topologies </li></ul><ul><li>Networking Media </li></ul><ul><li>Common Network Devices </li></ul>
    16. 16. Network Topologies <ul><li>Star – Each device is connected to a centralized point, like spokes in a wheel. </li></ul><ul><li>Extended Star – Additional networking devices added to some spokes. Typical in schools, large corporations. </li></ul><ul><li>Bus – Single cable running from server. All workstations connect to cable. </li></ul>
    17. 17. Network Topologies <ul><li>Ring – Devices connected in a circle. A signal (token) is passed from device to device, and only the device with the token may transmit. </li></ul><ul><li>Double Ring – Two complete circles. Provides for fault tolerance. If one circle gets broken, the other takes over. </li></ul>
    18. 18. Networking Media <ul><li>Coaxial Cable </li></ul><ul><ul><li>Similar to video cable </li></ul></ul><ul><ul><li>Maximum speed is 100 MB/s </li></ul></ul><ul><ul><li>Maximum run is 500 meters. </li></ul></ul>
    19. 19. Networking Media <ul><li>Shielded Twisted Pair </li></ul><ul><ul><li>Pairs of wires are twisted together and have a foil shield around them for noise and interference cancellation. </li></ul></ul>
    20. 20. Networking Media <ul><li>Unshielded Twisted Pair (UTP) </li></ul><ul><ul><li>The most common LAN cabling. </li></ul></ul><ul><ul><li>Category 3 used for telephone service. </li></ul></ul><ul><ul><li>Categories 5, 5e, 6 used for networks. </li></ul></ul><ul><ul><li>Rely solely on twisting for interference cancellation. </li></ul></ul>
    21. 21. Networking Media <ul><li>Fiber Optic Cable </li></ul><ul><ul><li>Transmits beams of light instead of electrical impulses. </li></ul></ul><ul><ul><li>Much higher bandwidth, less subject to electrical interference. </li></ul></ul><ul><ul><li>Much more expensive to deal with. </li></ul></ul>
    22. 22. Networking Media <ul><li>When any kind of wiring is going to be too expensive, wireless connections are the answer. </li></ul><ul><ul><li>Wireless connections come with a whole new set of security concerns. </li></ul></ul><ul><ul><li>Home wireless routers and equipment should not be used in a commercial environment. </li></ul></ul>
    23. 23. Network Devices <ul><li>Hubs </li></ul><ul><ul><li>Connect multiple network clients together. </li></ul></ul><ul><ul><li>Not very smart, send everything to everyone. </li></ul></ul>
    24. 24. Network Devices <ul><li>Switches </li></ul><ul><ul><li>Similar to a hub, but intelligent. </li></ul></ul><ul><ul><li>Switches know the IP addresses of the devices attached to it, and send the message only to the correct device. </li></ul></ul><ul><li>Bridges – connect segments of a network together. </li></ul><ul><li>Routers – connect different types of networks together, like LAN to WAN. </li></ul>
    25. 25. Network Utilities <ul><li>ping – Test connectivity to another computer. </li></ul><ul><li>arp – Displays mapping between IP addresses and MACs. </li></ul><ul><li>nslookup – Displays IP address for a given host name. </li></ul><ul><li>netstat – Displays information about active network connections. </li></ul><ul><li>ipconfig – Displays TCP/IP configuration information. </li></ul>
    26. 26. Connecting to the Internet <ul><li>Dialup </li></ul><ul><li>DSL </li></ul><ul><li>Cable </li></ul><ul><li>Satellite </li></ul>
    27. 27. Connecting to the Internet <ul><li>Dialup </li></ul><ul><ul><li>Not always on </li></ul></ul><ul><ul><li>Customer does not get an IP address </li></ul></ul><ul><ul><li>Ties up the phone line. </li></ul></ul><ul><ul><li>Communicates with ISP via low speed modem. </li></ul></ul><ul><ul><li>ISP groups many low speed connections together for transmission to the internet. </li></ul></ul>
    28. 28. Connecting to the Internet <ul><li>Digital Subscriber Line (DSL) </li></ul><ul><ul><li>High speed connection using telephone lines. </li></ul></ul><ul><ul><li>Generally, customer must be within 18,000 feet of a telco central office. </li></ul></ul><ul><ul><li>Customer becomes a remote computer on the ISP's network, and does get an IP address. </li></ul></ul>
    29. 29. Connecting to the Internet <ul><li>Cable </li></ul><ul><ul><li>Generally, anyone who has cable TV service can get cable high speed internet, but not all cable companies provide service. </li></ul></ul><ul><ul><li>Like DSL, always on, customer becomes a remote computer on ISP's network, gets an IP address. </li></ul></ul><ul><ul><li>All customers in your neighborhood share the same bandwidth. </li></ul></ul>
    30. 30. Connecting to the Internet <ul><li>Satellite </li></ul><ul><ul><li>Provided by satellite TV companies. </li></ul></ul><ul><ul><li>Good for people in rural areas who can't get cable or DSL service. </li></ul></ul><ul><ul><li>Because satellite TV is really one way service, extra stuff has to be added to make service 2-way. Upload speeds are one tenth of download speeds. </li></ul></ul><ul><ul><li>Expensive </li></ul></ul>