Chapter 6 Local Area Network & Wireless LAN

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

Why Use a LAN? Information sharing Resource sharing 3

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, 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

Basic LAN/WLAN Components 5

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

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

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

1.        Ethernet Media Types Remember: We talk about network speed in bits (e.g. Gbps is Gigabits per second) 9

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

Wiring Closets 11

Wiring Closets 12

Wiring Closets 13

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

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

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

Forwarding Tables What happens when a frame is received? 17

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

Best Practice Recommendations - LAN 19

Improving LAN Performance 20

Identifying Network Bottlenecks 21

Improving Network Server Performance 22

Improving Network Circuit Capacity 23

Network Segmentation 24

Reducing Network Demand

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

Component - Access Points and NICs

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 IEEE 802.11ac IEEE 802.11ad 1st router came out Jan. 2016 7 Gbps (7,000,000,000 bits a second) Bluetooth Also an IEEE standard 802.15 28

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 70-100 Mbps

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

A WLAN Using Different Channels

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

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

WLAN Design Specs for 802.11g

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

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

Types of WLAN Security

Types of WLAN Security, cont’d

Best Practice Recommendations - WLAN Select best one, cost permitting Adopt 802.11n or ac Will replace 802.11g 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  802.11n 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

Improving WLAN Performance (similar to LANs) Improving device performance Upgrade devices to 802.11ac Buy high-quality cards and APs Improving wireless circuit capacity Upgrade to 802.11ac 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

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