Wireless LAN in High School

1. Group 8: Brian Sanger Vater Lor Garrett Bahr Wireless LAN in High School

2. Overview • Scenario • WLAN • Basics • Standards and Protocols • Security • OPNET Simulation • Analysis • Budget

3. Scenario • Local High School • 900 Students + 100 Faculty users • Types of mobile devices allowed: • Laptops • iPads, iPhone, iTouch, Smartphones • Previously installed LAN

4. Goals • Integrate into current High School's LAN • Continuous Connectivity • Mobility • Improve H.S. Technology • More aesthetically pleasing • Low-cost

5. Possible Problems • Mobility issues • Data Access issues • Continuous Synchronization for end users

6. Advantages of WLANs • Easy to add/remove workstations/devices • Provide connectivity in places inhibited by cables • Installation/conversion to WLAN is simple if a LAN is already in place • Reduces/eliminates web of cables • Easy to expand network coverage • Connectivity between devices within network • Improved aesthetics

7. Disadvantages of WLANs • Changing standards or cabling can be difficult • Lower wireless bandwidth slows the speed of high demand applications (streaming video/audio) • Security is difficult to configure and control • Obstructions of the Access Points (walls/buildings) • Necessary to have a LAN backbone already in place

8. Standards & Protocols

9. IEEE 802.11b Standard • Max data rate: 11 Mbps • Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) media access methods • Attempts to divide the wireless channels equally among transmitting nodes • Frequency: 2.4 GHz • Range: ~50-100 ft Indoors

10. Distributed Coordination Function (DCF) • A form of CSMA/CA inside the Access Point • Ensures that all stations first sense the medium before transmitting • Avoids stations from transmitting at same time • This prevents collisions and retransmissions • Contention-based & Asynchronous • Simple Explanation: In a meeting, where everyone waits for an opening to speak and everyone else who is hearing the speaker nods their head.

11. Point Coordination Function (PCF) • A form of CSMA/CA inside the Access Point • Priority over DCF • Steps through all the stations operating in PCF mode and polls each of them • Then assigns priority to each client • Contention-free and Synchronous

12. IEEE 802.11b: Infrastructure Mode • Basic Service Set (BSS) • A single wireless AP supports one or more wireless clients • ALL communicate with the access point

13. IEEE 802.11b: Infrastructure Mode (Cont...) • Extended Service Set (ESS) • A set of BBS's where access points communicate between each other (backbone) • Forwards traffic from one BSS to another

14. Virtual Carrier Sense • 4-way “handshake” protocol • When a sending station wants to transmit data: • First sends a Request to Send (RTS) and waits for the Access Point to reply with a Clear to Send (CTS) • Since all stations in the network can hear the Access Point, the CTS causes them to delay any intended transmissions, allowing the sending station to transmit and receive a packet acknowledgment (ACK) • Poses “Hidden Node Problem”

15. Hidden Node Problem • A+B & B+C can see each other • A+C cannot see each other • These two can possibly interrupt each others' transmissions

16. Solution to Hidden Node Problem • Between Virtual Carrier Sense and MAC Control Frames, the “Hidden Node Problem” can be avoided

17. Media Access Controls • Permits the registering of one MAC address per device • Students must register their devices to use the WLAN using their previous LAN credentials • Only allowed to access Student Server • Administrators use their LAN credentials to gain access to the Administration Server

18. Security • Firewall • WEP at MAC layer • Wired Equivalency Privacy • By encrypting packets at the MAC layer, only users with a registered MAC address can associate with an access point. Anyone without a key may be able to see network traffic, but every packet is encrypted. • Websense – Web security gateway software • Controls web access

19. OPNET Simulation • Condensed the scenario to a smaller scale for presentation purposes • 100 users (1/10th of actual size) • Did not include preexisting LAN in testing • We assumed that the previously set up LAN was running at its optimal efficiency • Subnets are organized by department • Some high demand departments have multiple access points per subnet

20. Base Model • Servers (2): Student & Administration Data • Firewall: ethernet2_slip8_firewall • Routers (2): Internal & External • ethenet_4_slip8_gtwy • ISP: ip32_cloud • Subnets (8): • Access Points (10): wlan_ethernet_router (11 Mbps) • PCF Enabled • “Workstations”: wlan_wkstn (~1 Mbps each) • ~10-15 devices per access point

21. Profile & Application Configurations • Administration Profile: • Email (Heavy) • File Transfer (Heavy) • File Print (Heavy) • Video Conferencing (Light) • Web Browsing (Heavy) • Database Access (Light) • Students Profile: • Email (Light) • File Transfer (Light) • File Print (Light) • Web Browsing (Light)

23. Office Library Science Room

24. Analysis • 0%, 25%, 75% Background Network Utilization • Ethernet Delay • HTTP Page Response Time • Email Traffic Sent/Received

25. Ethernet Delay0%

26. Ethernet Delay25%

27. Ethernet Delay75% As Utilization Increases, Delay Increases

28. 75% 25% 0%

29. Email Traffic Sent/Received *This graph was the same for all three utilizations

30. HTTP Page Response Time 25% 0% *0% & 25% utilization are similar because the network has sufficient resources, so there is little variation in page load time 75%

31. Budget

32. Personnel • Previously installed LAN is managed by 2 network administrators • Provide training classes • Websense & ISP will provide some technical support with previous contract agreement

33. Conclusion • Do benefits outweigh costs? • Improved mobility • Wider coverage range • Easy to modify, move, & add devices • Future expansion simplified

34. Questions?