NT1210 Introduction to Networking Unit 6: Chapter 6, Wireless LANs

Class Agenda 4/19/16 Learning Objectives Midterm Exams. Lesson Presentation and Discussions Lab Activities will be performed in class. Assignments will be given in class. Break Times. 10 Minutes break in every 1 Hour. Note: Submit all Assignment and labs due today.

Objectives  Identify devices required in wireless networks.  Differentiate between Layer 1 and Layer 2 concepts in wireless networks.  Analyze wireless standards.  Design a basic small business wireless Ethernet network.  Troubleshoot wireless LANs for connectivity and performance 3

Defining Wireless LANs: Wireless vs. Wired  Both described as LANs  LAN uses wire but WLAN uses do not  WLAN allowed Mobility  Both typically support devices close by  Both provide LAN edge connection in Enterprise LANs  WLAN headers differ from Ethernet LAN headers, but both use same MAC addresses with same format and size  Wired and wireless LANs can be combined into single design 4

Defining Wireless LANs: Wireless vs. Wired Figure 6-1Typical Campus LAN with Wired and Wireless LAN Edge LAN edge: Refers to the part of any network where the user devices sit. The LAN edge includes each user device, each device’s link to the network, along with the network device on the other end of that link (usually a LAN switch or wireless Access Point [AP]). 5

Defining Wireless LANs: Wireless Distances  “Run” distances from user device to switch/AP Figure 6-2UTP 100m Maximum Length Vs. WLAN Range / Coverage Area 6

Defining Wireless LANs: Wireless Distances  Rules for planning distances in wired Ethernet LANs much more objective than those for WLANs  Will a device work well 50 feet from the AP? 150 feet?  Network engineer needs to do test called wireless site survey  Engineer installs AP in wiring closet and then walks around to different locations with wireless testing tool to determine bandwidth capabilities 7

Defining Wireless LANs: Bit Rates Table 6-1WLAN Standards and Speeds IEEE WLAN Standard IEEE Standard Ratified in this Year Maximum Stream Rate (Mbps) Maximum Theoretical Rate, One Device, Maximum Streams b199911N/A a199954N/A g200354N/A n (20 MHz) n (40 MHz)* ac (80 MHz)* ad (80 MHz)* Gbps 60 Gbps 5Gbps * n, ac & ad allow the use of multiple channels bonded together which allows for their faster speeds. 8

Defining Wireless LANs: Bandwidth  Bandwidth means different things in networking, but usually refers to link speed (bit rate)  Each Ethernet link between nodes either shares or dedicates bandwidth  If nodes use half-duplex logic (and CSMA/CD), they take turns sending (shared bandwidth)  If nodes use full duplex, switch can use that speed at any time without waiting (dedicated bandwidth) Figure 6-5 Dedicated Bandwidth and Shared Bandwidth and the Effect on LAN Capacity 9

Defining Wireless LANs: Bandwidth Figure 6-6Increasing Capacity 4X by Adding 4X Access Points The WLAN has 20 end user devices, but it has four APs placed around the floor of the building. As a result, four devices at a time can send or receive data at the same time to a nearby AP without interfering with each other. 10

Defining Wireless LANs: Comparing Table 6-2Comparing Wired LANs with Wireless LANs TopicWiredWireless Uses cablesYesNo UTP cable distance/wireless range is defined by the standard, and not significantly affected by local site conditionsYesNo A single LAN standard specifies a single speed, rather than a set of allowed speedsYesNo Allows Full Duplex on each link, rather than sharing bandwidth among all devices using Half DuplexYesNo 11

Defining Wireless LANs: IEEE Standards  WLAN standards follows story similar to Ethernet  Before standards existed, vendors created products  Eventually, IEEE created working group to define WLAN standards  working group ratified first standard (802.11) in 1997 that used frequencies around 2.4 GHz and maximum speed of 2 Mbps Figure 6-7 Timeline of IEEE WLAN Standards and Max Single Stream Bit Rates 12

Defining Wireless LANs: Standards  The Wi-Fi Alliance (WFA): Vendor Group standards- setting process 1.Vendor develops new wireless LAN product 2.Before selling product, vendor sends product to WFA for testing 3.WFA puts product through pre-defined set of tests 4.WFA also tests if new product works with existing approved wireless products 5.Once product passes tests, WFA certifies product as having passed; vendor can claim it is certified, and use WFA logos on product packaging and advertising 13

Defining Wireless LANs: Standards  Degree of interoperability in wireless networking happens in part because of cooperation between vendors, IEEE, and WFA  WFA helps vendors deal with product testing task by building formal set of interoperability tests  Vendors working with WFA, as well as cooperate with IEEE  IEEE and WFA also cooperate as WFA wants Wi-Fi vendors to be successful Figure 6-8Some Relationships and Results: Vendors, Wi-Fi Alliance, and IEEE 14

Defining Wireless LANs: LAN Edge  Example 1: Business that has a large number of small remote offices, plus a small number of large sites; like a bank or an insurance company.  At both the small offices and the large main sites, these companies could use a wireless-only LAN edge.  All user devices use WLAN technology to connect to the Enterprise network. Figure 6-9Enterprise Branch Office with Wireless LAN Edge 15

Defining Wireless LANs: LAN Edge  Example 2: Those same companies could use a combined wired and wireless LAN edge.  Essentially, the company creates a wired Ethernet LAN for every location where a device might need to connect to the network.  This design also creates WLAN coverage for the exact same space, and possibly some spaces the Ethernet cables cannot reach. Figure 6-10Wired and Wireless LAN Edge 16

Defining Wireless LANs: LAN Edge  Small Office / Home Office WLANs: The networking industry uses the term small office / home office (SOHO) to refer to smaller sites that use the types of technology and devices that you might find at someone’s home office.  Examples of different SOHO sites (left): Each is at the home of a different employee of the same company.  SOHO networks often use integrated networking devices (e.g., router, switch, AP, modem). Figure 6-11Wired-only Versus WLAN Only Small Office, with Combined Devices 17

Defining Wireless LANs: WLAN Roles Figure 6-12Single-Site WLANs (Protected and Unprotected) and Public Hot Spot  For retailers who want their customers to spend more time in the store, the wireless hotspot concept has become pretty popular as well.  The hotspot allows strangers to use the company’s network. 18

Exploring WLAN Physical Layer Features  Ad-hoc wireless LAN: Provides very basic WLAN service by letting two (or more) WLAN devices send data directly without AP  Two wireless devices connect directly via their WLAN NICs to send data to one another  Known formally as Independent Basic Service Set (IBSS)  Gives users flexibility as no AP is needed for connectivity Figure 6-13Ad-hoc Wireless LAN: Independent Basic Service Set (IBSS) 19

Exploring WLAN Physical Layer Features  Basic Service Set (BSS): Offers basic wireless service with one—and only one—AP to create wireless LAN  Each wireless client connects to network through AP  AP controls BSS, with all wireless frames flowing either to AP from user devices or from AP back to user devices Figure 6-14Single AP Wireless LAN: Basic Service Set (BSS) 20

Exploring WLAN Physical Layer Features  Extended Service Set (ESS): Extends wireless functions of BSS  Each BSS and ESS defines WLAN name as Service Set Identifier— SSID  In BSS, AP defines SSID  In ESS, all APs use same SSID and cooperate to create WLAN Figure 6-15Multiple AP Wireless LAN: Extended Service Set (ESS) 21

Exploring WLAN Physical Layer Features Table 6-3Comparisons of Wireless LAN Topologies Feature IBSS (ad-hoc) BSSESS Number of APs Used01>1 Data Frame FlowDevice to deviceDevice to AP Connects Clients to Some Other Network? NoYes Allows Roaming?No Yes 22

Exploring WLAN Physical Layer Features: Antennas  Omnidirectional Antenna  Coverage area of AP creates layered coverage  Closer parts of coverage area can run at faster speeds and still work because greater signal strength  Further parts of coverage area run at slower speeds  Coverage area looks like set of concentric circles Figure 6-16Coverage Area for an Omnidirectional Wireless LAN AP 23

Exploring WLAN Physical Layer Features: Antennas Figure 6-17Coverage by Design 24

Exploring WLAN Physical Layer Features  Antenna gain (power) and direction example  4 APs sit in corners of floor, each using directional antenna sending out signal for 90 degrees (quarter circle)  Quarter circle patterns extend further from AP than omnidirectional antennas’ signals would  In middle of floor, along walls, two APs each use antennae with 180-degree pattern Figure 6-19 Four 90 Degree and Two 180 Degree Direction Antennae Cover the Floor 25

Exploring WLAN Common Features: Associating  Series of management and control frames associates new wireless client with AP to allow it access to WLAN  To associate, wireless clients follow process: 1.Client discovers all nearby APs 2.Decides which one to use 3.Passes any security processes 4.Gets AP to agree to allow it to be used 26

Exploring WLAN Common Features: Associating  WLAN frames and addresses  standard defines frame format used by all physical layer standards  Several frame fields work same way as in  Both have 6-byte destination MAC address in header  Both have 6-byte source MAC address field in header  Both have 4-byte FCS in trailer Figure 6-26IEEE Frame Format 27

Exploring WLAN Common Features: Associating  Discovering existing wireless LANs uses beacon frames sent by APs send that announce its existence  Includes name of Wireless LAN (Service Set ID [SSID])  Client listens for beacon frames to learn of new APs and WLANs  Example: Coverage areas of two WLANs overlap, so all WLAN clients in both locations discover SSID of both wireless LANs Figure 6-27Learning about Multiple WLANs through Beacon Frames 28

Unit 6 Assignment Unit 6 Assignment 1: Wireless Ethernet Local Area Networks Review Unit 6 Assignment will also be found on the my website. Reading Assignment. Read Chapter 7

Unit 6 Lab Unit 6 Lab 6.1: Wireless Broadcast Domains Unit 6 Lab 6.2: Identifying WLANs Unit 6 Lab 6.4: WLAN Placement Lab should be completed in class.

Unit 6 Project Unit 6 Research Project 1: Chapter 7 Mind Maps