Download Introducing Wireless LANs

Introducing Wireless
LANs
BCMSN Module 6 Lesson 1 & 2
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
1
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
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
2
Wireless Data Technologies
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
3
Wireless Data Technologies (Cont.)
WAN
(Wide Area Network)
MAN
(Metropolitan Area Network)
LAN
(Local Area Network)
PAN
(Personal Area
Network)
PAN
LAN
MAN
WAN
Standards
Bluetooth
IEEE 802.11a,
802.11b,
802.11g
802.16
MMDS, 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, lastmile access
PDAs, mobile
phones, cellular
access
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
4
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).
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
5
Wireless LAN Evolution
Warehousing
Retail
Health care
Education
Businesses
Home
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
6
What Are Wireless LANs?
 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
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
 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
7
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)
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
8
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.
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
9
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.
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
10
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?
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
11
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.
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
12
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.
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
13
Wireless LAN
Topologies
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
14
Wireless LAN Topologies
 Wireless client access
Mobile user connectivity
 Wireless bridging
LAN-to-LAN connectivity
 Wireless mesh networking
Combination of bridging and
user connectivity
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
15
WLAN and LAN
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
16
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.
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
17
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
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
18
WLAN Access Topology
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
19
Wireless Repeater Topology
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
20
Workgroup Bridge Topology
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
21
Alternative Peer-to-Peer Topology
Peer-to-Peer Configuration
(Ad Hoc Mode)
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
22
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).
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
23
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?
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
24
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?
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
25
WLAN Features
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
26
Roaming Through Wireless Cells
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
27
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.
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
28
Layer 2 vs. Layer 3 Roaming
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
29
Wireless VLAN Support
 Multiple SSIDs
 Multiple security
types
 Support for
multiple VLANs
from switches
 802.1Q trunking
protocol
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
30
Wireless VLAN Support (Cont.)
 VLANs propagate
across APs.
 VLAN numbers are
unique.
 Autonomous access
points handle up to
16 VLANs.
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
31
Enterprise Voice Architecture
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
32
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.
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
33
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?
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
34
Mesh Networks
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
35
Wireless Mesh Networking
 In a mesh network topology, devices are connected with
redundant connections between nodes.
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
36
Wireless Mesh Solution Components
Cisco Wireless
Control Systems
Cisco Wireless
LAN Controller
Root Access
Point “RAP”
Mesh Access
Point “MAP”
• 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 rooftops or towers
• Connects up to
32 “Pole-top”
APs using
802.11a
• 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
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
37
Mesh AP Roles
 Mesh APs automatically
establish connection
to Controller
Root AP (RAP) via wired
connection
Mesh AP (MAP) via selfconfiguring 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
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
38
Dual Radios
 2.4 GHz for client access
 5 GHz for backhaul
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
39
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.
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
40
Why Mesh Technology?
Enterprise Mesh
Municipal Mesh
Service Provider
Moving Indoor
Wi-Fi Outside
State, County
and City
Managed
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, handheld scanner, RFID, etc.
• Wireless bridging
P2P/P2MP links between
buildings
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
• Public safety/homeland
defense
1st
Police, fire and
responders
Wireless infrastructure,
vehicles and clients
• Wireless access for
fixed applications
Video surveillance, sensors
• Public service
Hot Spot access for city
workers, utilities, inspectors
• “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
• Digital divide and
economic development
Wi-Fi broadband access in
under-served communities
41
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.
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
42
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?
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
43
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.
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
44
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.
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
45
Q and A
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
46
BCMSN 6 – 1 & 2
© 2006 Cisco Systems, Inc. All rights reserved.
47