Introducing Wireless LANs

1. Introducing Wireless LANs BCMSN Module 6 Lesson 1 & 2

2. Objectives • Describe the different wireless data technologies that are currently available • Describe wireless LANs • Distinguish WLANs from other wireless data networks • Describe similarities and differences between WLANs and wired LANs • Describe types of WLAN topologies • Describe WLAN access topologies • Explain roaming between wireless cells • Describe WLAN support for VLANs and QoS • Describe wireless mesh networking

3. Wireless Data Technologies

4. Wireless Data Technologies (Cont.) WAN (Wide Area Network) MAN (Metropolitan Area Network) LAN (Local Area Network) PAN (Personal Area Network)

5. Wireless LAN (WLAN) • A WLAN is a shared network. • An access point is a shared device and functions like a shared Ethernet hub. • Data is transmittedover radio waves. • Two-way radio communications (half-duplex) are used. • The same radio frequency is used for sending and receiving (transceiver).

6. Wireless LAN Evolution • Warehousing • Retail • Health care • Education • Businesses • Home

7. They are: Local In building or campus for mobile users Radio or infrared Not required to have RF licenses in most countries Using equipment owned by customers They are not: WAN or MAN networks Cellular phone networks Packet data transmission via celluar phone networks Cellular digital packet data (CDPD) General packet radio service (GPRS) 2.5G to 3G services What Are Wireless LANs?

8. Similarities Between WLAN and LAN • A wireless LAN is an 802 LAN. • Transmits data over the air vs. data over the wire • Looks like a wired network to the user • Defines physical and data link layer • Uses MAC addresses • The same protocols/applications run over both WLANs and LANs. • IP (network layer) • IPSec VPNs (IP-based) • Web, FTP, SNMP (applications)

9. Differences Between WLAN and LAN • WLANs use radio waves as the physical layer. • WLANs use CSMA/CA instead of CSMA/CD to access the network • Radio waves have problems that are not found on wires. • Connectivity issues • Coverage problems • Multipath issues • Interference, noise • Privacy issues • WLANs use mobile clients. • No physical connection • Battery-powered • WLANs must meet country-specific RF regulations.

10. More on CSMA/CA • CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) • The wireless 802.11 standard uses CSMA/CA or "collision avoidance." The method is used because the wireless stations have no way to detect collisions WHILE sending. • Attempts to avoid collisions rather than detect them • How it works: • Transmitting device listens to the network (senses the carrier) and waits for it to be free • Device then waits a random period of time and transmits. • If the receiver gets the frame intact, it sends back an ACK to the sender. • If no ACK is received, the message is re-transmitted. • If the channel is not clear, the node waits for a randomly chosen period of time (backoff factor), and then checks again to see if the channel is clear.

11. Activity • Find a Wi-Fi Zone! • Use the Wi-Fi Zone finder to Search for a Wi-Fi ZONE™ site near your current location, your home airport, or another area you might need connectivity. • Go to http://wi-fi.jiwire.com/ and complete the necessary information to find zones. • Explore the connection options for hotspots in your area. Are any free? What is the average cost?

12. Self Check • Describe 2 differences between wireless LANs and wired LANs. • Describe 2 similarities between wireless LANs and wired LANs. • What is CSMA/CA and how does it function? • Name 4 types of wireless networks based on coverage area.

13. Focus on Teaching • Possible Challenges: The existence of many wireless terms will confuse learners and it takes time to get used to these terms. Memorization will not be solution. Practice and hands on helps learners to retain what these terms mean. • Tip: Highlight the key abbreviated terms of wireless technology. • Key Words in this section are: WLANs, CSMA/CD, 802.11, 3G, GPRS • Method of Teaching: Ask Instructors to share challenges or best practices that they can share with you. • Misconception Questions: • Q1: Is WLAN technology only for laptops? • A1: No. WLAN systems are ideal for networking laptops but they are equally useful for connecting desktop computers, emerging mobile platforms like PDA’s and Tablet PC’s. • Q1: Is a WLAN suitable for home networking? • A: Yes. With no wires to run and little networking knowledge required, installing a WLAN is one of the easiest ways to setup a home network. • Q1: Are Wireless networks costly to set up? • A1: Wireless networks are usually less expensive to set up and operate than traditional wired networks.

14. Wireless LAN Topologies

15. Wireless LAN Topologies • Wireless client access • Mobile user connectivity • Wireless bridging • LAN-to-LAN connectivity • Wireless mesh networking • Combination of bridging and user connectivity

16. WLAN and LAN

17. Service Set Identifier (SSID) • SSID is used to logically separate WLANs. • The SSID must match on client and access point. • Access point can broadcast SSID in beacon. • Client can be configured without SSID.

18. Association Process (Active Scanning) Steps to Association: Client Sends Probe AP Sends Probe Response Client Evaluates AP Response, Selects Best AP Client Sends Authentication Request to Selected AP (A) AP A Confirms Authentication and Registers Client Client Sends Association Request to Selected AP (A) AP A Confirms Association and Registers Client

19. WLAN Access Topology

20. Wireless Repeater Topology

21. Workgroup Bridge Topology

22. Alternative Peer-to-Peer Topology Peer-to-Peer Configuration (Ad Hoc Mode)

23. Service Sets & Modes • Ad hoc mode • Independent Basic Service Set (IBSS) • Mobile clients connect directly without an intermediate AP. • Infrastructure mode • Basic Service Set (BSS) • Mobile clients use a single AP for connecting to each other or to wired network resources. • Extended Services Set (ESS) • Two or more Basic Service Sets are connected by a common distribution system (DS).

24. Activity Do you have multiple SSIDs configured on your laptop? • Open your wireless configuration utility. • If you have multiple SSIDs configured, what order are they in? • Does your management utility provide information about WLANs in the area that are not currently configured on your laptop?

25. Self Check • What is an SSID? • How much overlap is suggested between wireless cells? • How much overlap is suggested between an access point and an access point serving as a repeater? • Which service set is associated to the ad hoc mode? • What are the steps in client association to an access point?

26. WLAN Features

27. Roaming Through Wireless Cells

28. Client Roaming • Maximum data retry count exceeded • Too many beacons missed • Data rate shifted • Periodic intervals • Roaming without interruption requires the same SSID on all access points.

29. Layer 2 vs. Layer 3 Roaming

30. Wireless VLAN Support • Multiple SSIDs • Multiple security types • Support for multiple VLANs from switches • 802.1Q trunking protocol

31. Wireless VLAN Support (Cont.) • VLANs propagate across APs. • VLAN numbers are unique. • Autonomous access points handle up to 16 VLANs.

32. Enterprise Voice Architecture

33. Autonomous or Lightweight? • Most Cisco wireless access points/bridges are available as autonomous or lightweight devices. • Lightweight APs use Lightweight Access Point Protocol (LWAPP) and must have a LAN controller to function within the network. • Autonomous APs can be configured via Cisco IOS or may operate with the CiscoWorks Wireless LAN Solution Engine (WLSE). • Most Cisco autonomous APs can be software upgraded to function as lightweight APs. • The Cisco Networking Academy FWL course focused on autonomous APs.

34. Self Check • What is client roaming? • What factors cause a client to roam? • How are Layer 2 and Layer 3 roaming different? • What standard specifies QoS for WLAN networks? • Which type of access point uses LWAPP and require LAN controllers?

35. Mesh Networks

36. Wireless Mesh Networking • In a mesh network topology, devices are connected with redundant connections between nodes.

37. Wireless Mesh Solution Components Mesh Access Point “MAP” Cisco Wireless Control Systems Cisco Wireless LAN Controller Root Access Point “RAP” • Serves as “Root” or “Gateway” AP to the wired network • Typically located on roof-tops or towers • Connects up to 32 “Pole-top” APs using 802.11a • Links the wireless Mesh APs to the wired network • Handles RF algorithms and optimization • Seamless L3 mobility • Provides security and mobility mgt • Provides 802.11b/g client access • Connects to Root AP via 802.11a • Takes AC or DC power; PoE capable • Ethernet port for connecting peripheral devices • Wireless Mesh management system • Enables network-wide policy configuration and device management • Supports SNMP and Syslog

38. Mesh AP Roles • Mesh APs automatically establish connection to Controller • Root AP (RAP) via wired connection • Mesh AP (MAP) via self-configuring backhaul connection • Mesh AP uses Cisco’s Adaptive Wireless Path Protocol “AWPP” to establish best path to the Root AP • AP authenticates to Controller and downloads configuration and radio parameters

39. Dual Radios • 2.4 GHz for client access • 5 GHz for backhaul

40. Adaptive Wireless Path Protocol (AWP) • Adaptive Wireless Path (AWP) protocol establishes an optimal path to root. • Each access point carries feasible successor or successors if topology or link health changes. • AWP uses a “parent sticky” value to mitigate route flaps.

41. Why Mesh Technology? Enterprise Mesh Moving Indoor Wi-Fi Outside Municipal Mesh State, County and City Service ProviderManaged Wi-Fi Services • Universities and healthcare • Extending Wi-Fi coverage throughout the entire campus • Hospitality • Outdoor mesh can open up new hospitality markets (EMEA) • Manufacturing—shipping and receiving • Inventory applications, hand-held scanner, RFID, etc. • Wireless bridging • P2P/P2MP links between buildings • Public safety/homeland defense • Police, fire and 1st responders • Wireless infrastructure, vehicles and clients • Wireless access for fixed applications • Video surveillance, sensors • Public service • Hot Spot access for city workers, utilities, inspectors • Digital divide and economic development • Wi-Fi broadband access in under-served communities • “Hot Zones” • Extend the existing “Hot Spots” into “Hot Zones” covering high traffic outdoor areas • Wireless ISPs • Competitive last-mile access providers using Wi-Fi for broadband service • Cable operators • Extend the network offering beyond the cable plant

42. Activity • Mesh networking has opened up opportunities for both profit and non-profit ventures. • Explore the NetEquality website at http://www.netequality.org/index.html to read about an interesting mesh networking project. • Explore the site to determine the average operating cost per user under this project.

43. Self Check • What protocol is used by Mesh APs? • What is a Root AP? • What is the “parent sticky” concept in Mesh networks? • What is the purpose of dual radios in a mesh WLAN?

44. Summary • Different wireless data technologies with different characteristics are available. • WLANs were introduced to provide local connectivity with higher data rates. • WLANs use half-duplex transmission. • WLANs have similarities and differences compared to wired LANS. • Types of WLAN topologies are client access, bridging, and mesh networking. • Wireless networks are built with multiple wireless cells • WLAN roaming occurs seamlessly between wireless cells. • WLANs support VLANs and QoS. • WLAN mesh networks extend the wireless network beyond the boundaries of wired LANs. • Mesh networking employs a new protocol, Adaptive Wireless Path Protocol (AWP) to form and maintain the mesh.

45. Resources • Web Links • http://www.fcc.gov • http://www.etsi.org • http://standards.ieee.org/getieee802 • http://www.wi-fi.org • Books • “Cisco 802.11 Wireless Networking Quick Reference”, Cisco Press, 2005. • “802.11 Wireless LAN Fundamentals”, Cisco Press, 2004.

46. Q and A