introducing wireless lans

© 2006 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialBCMSN 6 – 1 & 2 1

BCMSN Module 6 Lesson 1 & 2

Introducing Wireless LANs

© 2006 Cisco Systems, Inc. All rights reserved.BCMSN 6 – 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


Wireless Data Technologies


Wireless Data Technologies (Cont.)

PAN(Personal Area

Network)

LAN(Local Area Network)

WAN(Wide Area Network)

MAN(Metropolitan Area Network)

PAN LAN MAN WAN

Standards BluetoothIEEE 802.11a,

802.11b, 802.11g

802.16MMDS, LMDS

GSM, GPRS,CDMA, 2.5–3G

Speed <1 Mbps 1–54+ Mbps 22+ Mbps 10–384 kbps

Range Short Medium Medium–long Long

Applications Peer to peer,device to device

Enterprise networks

Fixed, last-mile access

PDAs, mobilephones, cellular

access


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 transmitted over radio waves.

Two-way radio communications (half-duplex) are used.

The same radio frequency is used for sending and receiving (transceiver).


Wireless LAN Evolution

WarehousingRetailHealth careEducationBusinessesHome


What Are Wireless LANs?

They are:LocalIn building or campus for mobile usersRadio or infraredNot required to have RF licenses in most countriesUsing equipment owned by customers

They are not:WAN or MAN networksCellular phone networksPacket data transmission via celluar phone networks

Cellular digital packet data (CDPD)General packet

radio service (GPRS)2.5G to 3G services


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 layerUses MAC addresses

The same protocols/applications run over both WLANs and LANs.

IP (network layer)IPSec VPNs (IP-based)Web, FTP, SNMP (applications)


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.


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 freeDevice 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.


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?

http://wi-fi.jiwire.com/


Self Check

1. Describe 2 differences between wireless LANs and wired LANs.

2. Describe 2 similarities between wireless LANs and wired LANs.

3. What is CSMA/CA and how does it function?

4. Name 4 types of wireless networks based on coverage area.


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.


Wireless LAN Topologies


Wireless LAN Topologies Wireless client access

Mobile user connectivity

Wireless bridgingLAN-to-LAN connectivity

Wireless mesh networking

Combination of bridging and user connectivity


WLAN and LAN


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.


Steps to Association:

AP A Confirms Association and Registers Client

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)

Association Process (Active Scanning)


WLAN Access Topology


Wireless Repeater Topology


Workgroup Bridge Topology


Alternative Peer-to-Peer TopologyPeer-to-Peer Configuration

(Ad Hoc Mode)


Service Sets & Modes Ad hoc mode

Independent Basic Service Set (IBSS)Mobile clients connect

directly without an intermediate AP.

Infrastructure modeBasic 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).


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?


Self Check

1. What is an SSID?

2. How much overlap is suggested between wireless cells?

3. How much overlap is suggested between an access point and an access point serving as a repeater?

4. Which service set is associated to the ad hoc mode?

5. What are the steps in client association to an access point?


WLAN Features


Roaming Through Wireless Cells


Client Roaming

Roaming without interruption requires the same SSID on all access points.

Maximum data retry count exceeded

Too many beacons missed

Data rate shifted Periodic intervals


Layer 2 vs. Layer 3 Roaming


Wireless VLAN Support Multiple SSIDs

Multiple security types

Support for multiple VLANs from switches

802.1Q trunking protocol


Wireless VLAN Support (Cont.) VLANs propagate

across APs.

VLAN numbers are unique.

Autonomous access points handle up to 16 VLANs.


Enterprise Voice Architecture


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.


Self Check

1. What is client roaming?

2. What factors cause a client to roam?

3. How are Layer 2 and Layer 3 roaming different?

4. What standard specifies QoS for WLAN networks?

5. Which type of access point uses LWAPP and require LAN controllers?


Mesh Networks


Wireless Mesh Networking In a mesh network topology, devices are connected with

redundant connections between nodes.


Cisco Wireless LAN Controller

Root Access Point “RAP”

Cisco Wireless Control Systems

• Wireless Mesh management system

• Enables network-wide policy configuration and device management

• Supports SNMP and Syslog

• Links the wireless Mesh APs to the wired network

• Handles RF algorithms and optimization

• Seamless L3 mobility

• Provides security and mobility mgt

• 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

Wireless Mesh Solution Components

Mesh Access Point “MAP”

• 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


Mesh AP Roles Mesh APs automatically

establish connection to Controller

Root AP (RAP) via wired connectionMesh 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


Dual Radios

2.4 GHz for client access

5 GHz for backhaul


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.


• Universities and healthcare

Extending Wi-Fi coverage throughout the entire campus

• HospitalityOutdoor mesh can open up new hospitality markets (EMEA)

• Manufacturing—shipping and receiving

Inventory applications, hand-held scanner, RFID, etc.

• Wireless bridgingP2P/P2MP links between buildings

• Public safety/homeland defense

Police, fire and 1st respondersWireless infrastructure, vehicles and clients

• Wireless access for fixed applications

Video surveillance, sensors

• Public serviceHot 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 ISPsCompetitive last-mile access providers using Wi-Fi for broadband service

• Cable operatorsExtend the network offering beyond the cable plant

Why Mesh Technology?Municipal Mesh

State, County and City

Service ProviderManaged

Wi-Fi Services

Enterprise MeshMoving Indoor Wi-Fi Outside


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.

http://www.netequality.org/index.html


Self Check

1. What protocol is used by Mesh APs?

2. What is a Root AP?

3. What is the “parent sticky” concept in Mesh networks?

4. What is the purpose of dual radios in a mesh WLAN?


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.


Resources

Web Linkshttp://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.

http://www.fcc.gov/

http://www.etsi.org/

http://standards.ieee.org/getieee802

http://www.wi-fi.org/


Q and A

introducing wireless lans

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