1. S305 – Network Infrastructure Chapter 6 Local Area Network

2. Announcements and Outline Announcements Rest of semester is on designing networks (LAN -> WAN) Tests grades will be posted before next class Outline LAN/WLAN Components Traditional Ethernet (IEEE 802.3) Switched Ethernet Wireless LAN Best Practices Improving Performance 2 Copyright 2010 John Wiley & Sons, Inc

3. Why Use a LAN? Information sharing Resource sharing 3

4. Network Types Dedicated server network Permanently assigned a specific task May form a powerful enterprise network replacing mainframes Runs a server network operating system (NOS) (Windows 2008) Common Servers: web, email, print Peer-to-peer network Having hardware devices shared by all users (printers, internet) All computers act as both clients and servers Results in reduced costs 4

5. Basic LAN/WLAN Components 5

6. Component - Network Interface Cards (NICs) Also called network cards and network adapters Mostly built into motherboards today 6

7. Component - Hubs & Switches Act as junction boxes, linking cables from several computers on a network May allow connection of more than one kind of cabling, such as UTP and coax. Repeater (reconstruct and strengthen) incoming signals 7

8. Component - Network Cables Used to connect a computer physically to the network Types of cables  Unsheilded wire pairs (UTP) – leading LAN cable type  Shielded twisted pair (STP)  Optical fiber – high capacity, just beginning in LANs 8

9. 1. Ethernet Media Types 9

10. Planning for LAN Installations Critically important with today’s LAN explosions Cheapest point to install the cable?

11. Wiring Closets 11

12. Wiring Closets 12

13. Wiring Closets 13

14. Component – Software Software that controls the LAN Parts of Network Operating System  Server version of NOS Runs on the network servers  Client version of NOS Runs on the client computers  Network Profiles Indicate the resources available in the network and authorized users  Directory Service Provide information about resources on the LAN 14

15. Traditional Ethernet (IEEE 802.3) - Wired Used by almost all LANs today Originally developed by a consortium of Digital Equipment Corp., Intel and Xerox Standardized as IEEE 802.3 Types of Ethernet: 15

16. Switched Ethernet Uses workgroup switches Logical and physical topology of the network becomes a star topology via switch Switch reads destination address of the frame and only sends it to the corresponding port How does a hub handle frames? 16

17. Forwarding Tables What happens when a frame is received? 17

18. Media Access Control (MAC) Uses a contention-based protocol called CSMA/CD (Carrier Sense Multiple Access / Collision Detect) Frames can be sent by two computers on the same network at the same time 18

19. Best Practice Recommendations - LAN 19

20. Improving LAN Performance 20

21. Identifying Network Bottlenecks 21

22. Improving Network Server Performance 22

23. Improving Network Circuit Capacity 23

24. Network Segmentation 24

25. Reducing Network Demand

26. Wireless LANs (WLANs) Use radio or infrared frequencies to transmit signals through the air (instead of cables) Basic Categories  Use of Radio frequencies  Use of Infrared frequencies (Optical transmission) Wi-Fi grown in popularity  Eliminates cabling  Facilitates network access from a variety of locations  Facilitates for mobile workers (as in a hospital) 26

27. Component - Access Points and NICs

28. Principal WLANs Technologies WI-FI  IEEE 802.11b Standardization started after.11a, but finished before, more commonly used than.11a  IEEE 802.11g  IEEE 802.11n Bluetooth  Also an IEEE standard 802.15 28

29. WLAN Basics - Radio Frequencies WLANs use radio transmissions to send data between the NIC and the AP (either 2.4 GHz or 5 GHz)

30. A WLAN Using Different Channels

31. Types of Wi-Fi Type Published Transmission Speed Actual Transmission Speed Range (ft) Freq (GHz) 802.11a54 Mbps20 Mbps1155 802.11b11Mbps6 Mbps1252.4 802.11g54 Mbps20 Mbps1252.4 802.11n 150 Mbps 300 Mbps 2302.4/5 802.11ac866.7 Mbps230

32. WLAN Media Access Control May use two MAC techniques simultaneously  Distributed Coordination Function (DCF)  Point Coordination Function (PCF)

33. Physical WLAN Design More challenging than designing a traditional LAN Begin design with a site survey, used to determine: 

34. WLAN Design Specs for 802.11g

35. Multi-story WLAN Design Must include  Usual horizontal mapping, and  Vertical mapping to minimize interference from APs on different floors

36. Copyright 2010 John Wiley & Sons, Inc 7 - 36 WLAN Security Especially important for wireless network  Anyone within the range can use the WLAN Finding a WLAN  Move around with WLAN equipped device and try to pick up the signal  Use special purpose software tools to learn about WLAN you discovered Wardriving – this type reconnaissance Warchalking – writing symbols on walls to indicate presence of an unsecure WLAN

37. 7 - 37 Types of WLAN Security

38. Types of WLAN Security, cont’d

39. 7 - 39 Best Practice Recommendations - WLAN Select best one, cost permitting Adopt 802.11g or n  Will replace 802.11b and.11a  Prices of.11g and n NICs and APs coming down Wireless vs. Wired Similar data rates for low traffic environment When mobility important  802.11g or n Using WLAN as an “overlay network,” or in conjunction with a wired LAN  WLANs installed In addition to wired LANs  To provide mobility for laptops  To provide access in hallways, lunch rooms, other sites

40. Copyright 2010 John Wiley & Sons, Inc 7 - 40 Improving WLAN Performance (similar to LANs) Improving device performance  Upgrade devices to 802.11g or n  Buy high-quality cards and APs Improving wireless circuit capacity  Upgrade to 802.11g or n  Reexamine placement of APs  Check sources of interference (other wireless devices operating in the same frequencies))  Use different type of antennas Reducing network demand  Never place a server in a WLAN  Place wired LAN jacks in commonly used locations

41. Improving LAN Performance - Summary Increase Server Performance  Software: Fine-tune the NOS settings  Hardware: Add more servers and spread the network applications across the servers to balance the load Upgrade to a faster computer Increase the server's memory Increase the number and speed of the server's hard disk(s) Upgrade to a faster NIC Increase Circuit Capacity  Upgrade to a faster circuit  Segment the network Reduce Network Demand  Move files from the server to the client computers  Increase the use of disk caching on client computers  Change user behavior 41