Lecture 5 - WLAN Infrastruc

Bài giảng Lecture 5 - WLAN Infrastruc

February 2005 Copyright 2005 All Rights Reserved 1

Wireless LAN Infrastructure Devices

(1 September, 2006)

 Configure, install, and manage wireless infrastructure devices

 Configure, install, and manage wireless client devices

 Configure, install, and manage the

different types of wireless gateways

Objectives

Upon completion of this chapter you will be able to:

February 2005 Copyright 2005 All Rights Reserved 3

Access Point Operating Mode

Access Point

 The Access Point (AP) provides mobile station access to

the wired network

 The Access Point (s) and its configuration can determine

the WLAN topology

 Independent Basic Service Set (IBSS) also called

 Ad-Hoc networks

 Infrastructure Basic Service Set (BSS)

 Extended Service Set (ESS)

 An Access Point can be configured in three modes.

 Root Mode

 Repeater Mode

 Bridge Mode

February 2005 Copyright 2005 All Rights Reserved 5

Access Point Contd

This Access Point is operating in the Root Mode within a Basic Service Set (BSS) Topology (single AP connected to the LAN).

Root Mode

 The Root Mode is the default configuration for an AP

 The Access Point (AP) is in Root Mode when it is:

 Connected to the Wired Lan (BSS and EBSS) or

 Operating in AD-Hoc mode

 Two or more APs connected to the same Wired Lan can communicate with one another thus facilitating MS roaming.

February 2005 Copyright 2005 All Rights Reserved 7

Bridge Mode

 An AP configured for the bridge mode connects two wired

Local Area Networks

 It creates a point-to-point connection between Access

Points

 It is normally used with semi or highly directional

antennas

 An AP bridge only associates with another AP Bridge.

 The remote location may require two APs One for the bridge and one for wireless access, however,

 Some APs can be configured to operate as both a Bridge and AP

Repeater Mode

 An AP operating in Repeater mode connects remote mobile

stations to a "root" access point

 The repeater AP acts as a normal AP to the remote mobile stations while simultaneously acting as client to the "root" Access point.

 Both the "root" and the "repeater" can have mobile station clients.

 The BSS area around both AP will overlap a minimum of 50%

thereby reducing the throughput of the mobile units.

 The "repeater" AP must have an omnidirectional antenna.

February 2005 Copyright 2005 All Rights Reserved 9

Access Point

Options

Access Point Options

 Fixed or Detachable Antennas

 Detachable antennas provide greater flexibility

 Highly directional antennas may be required

 The AP and antenna must be certified as a system (FCC Part 15 Rules)

 Diversity antennas may be required, that is, two antennas

to compensate for multipath reception

 Filtering – Employed to screen out intruders

 MAC filter – Filters out intruders based upon the NIC card address

Protocol Filter - Filters out intruders based upon a TCP/IP protocol, eg., UDP, TCP, ICMP, etc

February 2005 Copyright 2005 All Rights Reserved 11

Access Point Options contd

 Removable Radio Cards.

 Some APs have two PCMCIA slots

 One radio card could act as an AP while the other acts as

a bridge or

 Each radio could be an independent AP

 Each on Non-overlapping bands or

 Each on a different band (ISM and UNII)

 Variable Output Power allows the network administrator to

vary the transmit output power This in turn:

 Controls the location of the mobile units

 Adjusts the size of the RF envelope for security

purposes

Access Point Options contd

 Wired Connectivity.

 The default connectivity for most APs is 10/100 Ethernet Lan interface

 The specific type connectivity will depend upon such

factors as throughput, distance from the wiring closet , etc

 The connectivity desired may need to be purchased

separately

 Power over Ethernet (PoE)

 This may be necessary when no standard power outlet

is available near the Access Point

 This connectivity is supported by Enterprise APs but

generally not by SOHO or residential APs

February 2005 Copyright 2005 All Rights Reserved 13

Access Point Options contd

comes as standard on most APs, however, it should

be the encryption security of last resort

in two modes:

 Pre-Shared Key (PSK)

 Remote Authentication Dial-in User Service (RADIUS).

encryption.

Detection sensor

Access Point Options contd

 Management

manufacturer but will normally include one or more

of the following: (1) console, (2) telnet, (3) SSH, (4)

SNMP, (5) HTTP or a (6) custom application

 Most residential and SOHO units employ HTTP

 An enterprise AP should include the ability to

manage multiple APs from a central location.

 APs will normally acquire an IP address either

 Statically (10.x.x.x, 172.x.x.x or 192.x.x.x) or through

 Dynamic Host Configuration Protocol (DHCP)

February 2005 Copyright 2005 All Rights Reserved 15

Access Point Options contd

 802.11i – Stronger authentication centered around

Advance Encryption Standard (AES), Temporal Key Integrity Protocol (TKIP) and Counter Mode – CBC MAC Protocol (CCMP)

 802.11e – QoS standards for multimedia transmission

Access Point Options contd

 Mounting options

 The site survey will determine the location of the AP

 Assure power and wire connectivity are available at the

mounting site

 Use vendor mounting kits if possible

 The AP mounting location should be inconspicuous

 The APs status lights should be visible

 The mounting locations should provide convenient access

to the AP

 Employ NEMA compliant enclosures when mounting the

AP outside (NEMA Standards publication 250 NEMA Type 4)

February 2005 Copyright 2005 All Rights Reserved 17

Access Point Mounts

Wireless Bridge

February 2005 Copyright 2005 All Rights Reserved 19

Wireless Bridge

 A wireless bridge provides a point-to-point link

between LANS.

 Most APs can be configured as a bridge while most

bridges can be configured as an AP

 The difference between the two is generally one of intent

Wireless Bridge Contd

 One bridge must be a root while the other bridge must

be non-root.

 Bridge Alignment can be accomplished by:

 A Software Utility that reads signal strength

 Through LEDs on Bridge or

 Through a Voltmeter

Root = On Root = Off

February 2005 Copyright 2005 All Rights Reserved 21

Wireless Bridge Contd

 Bridge Options

 Alignment

 Enterprise grade bridges generally include some

method for aligning bridges whereas a consumer grade does not

 Optimize the alignment then rotate the antenna around it polarization axis to maximize the signal strength

 Long range alignment tools should include such

Wireless Workgroup Bridges

 A Wireless Workgroup Bridge (WGB) connects multiple

wired clients to an Access Point (AP).

 The WGB acts as a client to the AP.

 The WGB forwards and filters the packets from the wired clients.

 Consumer grade WGB can handle between 8-16 clients.

 An Enterprise grade WGB can handle up to 255 clients.

February 2005 Copyright 2005 All Rights Reserved 23

Wireless Router

Wireless Router

 A wireless router is an Access Pont that routes packets

between the wireless and the wired LAN whereas a regular AP

bridges the frames

 The wireless interface has its own IP and subnet and

 The wired interface has its on IP and subnet

 Mobile stations roaming between subnets may break an application

 One advantage of a Wireless Router is that it may be easier

to implement a VPN point in the router than an AP.

 A normal AP may forward the encrypted VPN packet to an endpoint on the Wired network for decryption and

forwarding

February 2005 Copyright 2005 All Rights Reserved 25

Outdoor Wireless Router

Enterprise Wireless Router

MIMO Wireless Router SOHO Wireless Router

Wireless Client Devices

February 2005 Copyright 2005 All Rights Reserved 27

Wireless Client Devices

Wireless Adapter

MU

AP

PCMCIA Card

PC

 Wireless LAN clients are radio Network interface cards

that are recognized by the Access Point

 The clients include but are not limited to:

 PCMCIA cards, Compact Flash and Secure Digital Cards.

 PCI, mini-PCI cards and USB devices.

 PCMCIA-to-PCI adapters and Serial/Ethernet converters.

PCMCIA Cards and Converters

PCMCIA Card

PCI Adapter Wireless Compact Flash

February 2005 Copyright 2005 All Rights Reserved 29

End of Presentation