1. Chapter 6 Local Area Network & Wireless LAN

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

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

4. Network Types Dedicated server network Peer-to-peer 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, , 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 Components5

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
Remember: We talk about network speed in bits (e.g. Gbps is Gigabits per second) 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 - LAN19

20. Improving LAN Performance20

21. Identifying Network Bottlenecks21

22. Improving Network Server Performance22

23. Improving Network Circuit Capacity23

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 b
Standardization started after .11a, but finished before, more commonly used than .11a
IEEE g
IEEE n
IEEE ac
IEEE ad
1st router came out Jan. 2016
7 Gbps (7,000,000,000 bits a second)
Bluetooth
Also an IEEE standard 28

29. Actual Transmission Speed
Types of Wi-Fi
Type
Published Transmission
Speed
Actual Transmission Speed
Range (ft)
Freq
(GHz)
802.11a
54 Mbps
20 Mbps
115 5
802.11b
11Mbps
6 Mbps
125
2.4
802.11g
802.11n
150 Mbps
300 Mbps
40-50 Mbps
230
2.4/5
802.11ac
866.7 Mbps
Mbps

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

31. A WLAN Using Different Channels

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 g

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

36. WLAN Security Especially important for wireless network Finding a WLAN
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
Copyright 2010 John Wiley & Sons, Inc

37. Types of WLAN Security

38. Types of WLAN Security, cont’d

39. Best Practice Recommendations - WLAN
Select best one, cost permitting
Adopt n or ac
Will replace g and .11b
Prices of .11ac and n NICs and APs coming down
Wireless vs. Wired
Similar data rates for low traffic environment
When mobility important  n or ac
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. Improving WLAN Performance (similar to LANs)
Improving device performance
Upgrade devices to ac
Buy high-quality cards and APs
Improving wireless circuit capacity
Upgrade to ac
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