Understanding Computer Networks: LANs, WANs, and Protocols

1. Chapter 6Data Communications

2. What is a computer network?

3. What is a computer network? • Collection of computers that communicate with each other • Types of Networks

4. Local Area Networks (LANs) • Connects computers at a single physical site • Typically within ½ mile (i.e., LOCAL) • Could be 2 computers/devices or as many as several hundred • Communication lines • Cables that connect devices • Wireless connections also used • Protocol – set of rules used by all devices on the network

5. Wide Area Networks • Connects computers at different geographical locations (i.e., WIDE) • Communication lines • Cables that connect locations are usually dependent upon what is available from others (can’t just lay cable between New York and Texas without any help!) • Protocol – also have set of rules that devices on the network must follow

6. Internet • Network of networks • Connects single computers, LANs, WANs, and other internets • Protocols are in layers • Physical • Data link • Internet • Transport • Application

7. What are the components of a LAN?

8. What are the components of a LAN? • Switch • Special purpose computer that receives/transmits traffic • Connects devices on the LAN • Usually within the “LAN device” • NIC • Network Interface Card • Internal “onboard” or physically in expansion slot on device • Unique identifiers on Media Access Control (MAC) Address • UTP cables • Unshielded Twisted Pair cables connect devices • Twisted to reduce cross wire signal interference

9. Optical Fiber Cables • Optical fiber cables • Also used to connect devices to a LAN • Glass wires transmit signals in the form of light rays • Optical fiber carries more traffic than UTP cables.

10. Protocol for a LAN • IEEE - Institute for Electrical & Electronics Engineers • Committee that creates and publishes protocols and standards used by virtually every network. • The IEEE 802.3 – Ethernet protocol • Used by all LAN devices • Specifies hardware characteristics and describes how messages are packaged and processed • 10/100/1000 Ethernet transmission rates – now standard

11. IEEE 802.11 Wireless Protocol • Wireless connections are popular for LANs • NIC replaced by WNIC • Almost all PCs today have WNIC onboard • What does that mean? • Many networks will need to use both 802.11 and 802.3 • Connected at Access Point that can handle both protocols • Bluetooth – wireless

12. Group Task • In your groups: • Describe pictorially your home network • Wireless • Wired • Internet connection • Printers • Switches • Access Points

13. Summary for LANs

14. What are the alternatives for a WAN?

15. What are the alternatives for a WAN? • Must obtain connection capabilities from another company licensed by the government to provide communications • Dial Up Modem to ISP – regular phone • DSL Modem to ISP – dsl phone • Cable Modem to ISP - cable • Point to Point lines – network of leased lines • PSDN – lease usage of private network • Virtual Private Network – use of internet to provide private network

16. ISPs • Internet Service Providers – Their purpose • Provide you with a legitimate internet address • Serve as gateway to internet • Receives/transmits data • Pay for the internet

17. Modems • Digital data is converted to an analog signal by modem • Modem modulates signal and then sends by phone or cable • Dial Up – max speed is 56kbps • DSL – Digital Subscriber Line – signals don’t interfere with voice traffic – always on – speeds vary • Cable – don’t interfere with TV cable – always on – broadband is >256kbps

18. Gradations of Speed and Performance • ADSL vs. SDSL • Asymmetric – download faster than upload • Symmetrical – same speeds • Which would be more appropriate for a home? • Which would be better for a business?

19. WAN Wireless connections • Available from Verizon, Sprint, others • What types of networks and connections are being used in a Nike Sensor? • http://bcove.me/rk3kyzaa

20. Virtual Private Networks • Uses Internet to create the appearance of a private point-to-point connection • Tunnel – pathway from client to server • Client software encrypts; server decrypts

21. VPNs • Appearance of a private point to point connection • “Tunnel” to the network • Encrypted transmissions

22. Protocols • TCP/IP Protocol • Layers of protocols (set of rules and data structures for organizing communication) • Application, transport, internet, data link, and physical layers • Application Layer Protocols • HTTP/HTTPS – the Web • SMTP - mail • FTP – transfer files over the internet

23. IP Address • Number that identifies a specific device • Public IP addresses governed by ICANN • Private IP addresses controlled within the LAN • Why are there Private IP addresses? www.findmyipaddress.com

24. Public IP Addresses • Domain name – worldwide unique name affiliated with a Public IP address • URL – address on the internet • How do you get a domain name?

25. Firewall • Firewall – computing device that prevents unauthorized network access • Computer • Program • Router • Perimeter firewall – sits outside the network • Internal firewall – inside the network • Packet filtering firewall – examines messages and determines whether or not to let it in • Access control lists – encodes the rules stating what is/isn’t allowed

26. Upcoming Deadlines • SharePoint Survey – due Friday the 12th • Access Project • ERD – posted tomorrow and due Monday the 15th • Access Project due the Monday the 22th