WIRELESS NETWORKING OPTIONSA PRESENTATION FOR

WIRELESS NETWORKINGWIRELESS NETWORKINGSETUP AND CONFIGURATIONSSETUP AND CONFIGURATIONS

Northridge Consulting Group

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Wireless NetworkingWireless NetworkingSetup and Setup and ConfigurationsConfigurations

Overview Overview

hree configurations hree configurations

of WLAN’sof WLAN’s

Basic Service Set

Extended Service Set

Independent Service Set

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Wireless Local Area Network

Wireless Local Area Networks

Access Point Configuration

Two types

WLAN is an acronym for Wireless Local Area Network. It is usually called Wireless LAN. So it’s a local network in your home, school, office or company build without wires … thus it is Wireless.

Wireless devices can connect to wire LAN backbone for communication with both wired and wireless nodes.

Replace wired LANs IEEE 802.11 standard

ad-hoc network Infrastructure network

3Overview continued…….

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The Media Access Control Layer Standards or (MAC)

Performs several vital functions in a WLAN. These functions can be broken into four distinct classifications:

Discovering a WLAN signalJoining the WLANTransmitting on a WLANAnd remaining connected to the WLAN

The mechanics of how these functions are performed center around the frames that are sent and received in a WLAN.

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Discovering the WLANPart 1

he first major function of the MAC layer involves defining procedures for a wireless device to discover the WLAN.When a wireless device is powered on or roams into an area of wireless coverage it must find or discover the access point or other wireless devices.

This discovery is a twofold process: the AP or other wireless devices must transmit an appropriate frame, and the wireless device must be looking for those frames.

BeaconingAt regular intervals the AP in an infrastructure network or wireless device in an ad hoc network sends a beacon frame both to announce its presence and to provide the necessary information for other devices to join the network. This process is known as beaconing.

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Discovering the WLANPart 2

And then there is Scanning….

Just as the AP (or wireless device) must transmit a beacon frame, the receiving wireless device must be looking for those frames. This is known as scanning.

There are two types of scanning

The first is called passive scanning & active scanning.

The Basic Service Set

Which is a group of wireless devices that is served by a single Access Point (AP)

The Basic Service Set (BBS) is a term used to describe the collection of Stations which may communicate together within an 802.11 Wireless Local Area Network.

The BSS may or may not include Access Point which provides a connection onto a fixed distribution

system such as an Ethernet network or Hard line.

This chart is an example of the Basic Service Set which includes a weird network via hard line to an access point. This set up gives internet access to both A and B nodes (sections).

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The Basic Service Set

Wireless LAN networking works in either of the two modes: Ad-hoc and Infrastructure.

In infrastructure mode, wireless devices communicate to a wired LAN via access points.

Infrastructure mode wireless networking bridges (joins) a wireless network to a wired Ethernet network.

Infrastructure mode wireless also supports central connection points for WLAN clients.

In ad hoc mode (also known as peer-to-peer mode), wireless devices communicate with each other directly and do not use an access point. This is an Independent BSS (IBSS).

Each access point and its wireless devices are known as a Basic Service Set (BSS).

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Advantages Disadvantages

Infrastructure mode networks offer the advantage of scalability

centralized security management and improved reach.

The disadvantage of infrastructure wireless networks is simply the additional cost to purchase AP hardware.

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The Basic Service Set

Extended Service Set

or (ESS)

An ESS is comprised of two or more Basic Service Set networks that are connected through a common distribution system.

APs are connected by distribution system (DS) typically: an Ethernet switch

For example the chart has a router connected to access points and the internet with support wireless networks.

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Extended Service Set11

In an ESS environment, users are able to move from one access point to another without losing the connection.

In this diagram, when the user moves from BSS (1) to BSS (2) the WLAN client devices automatically switches to the channel used in BSS (2).

The Access Points or (AP) can be positioned so that the cells overlap to facilitate movement between cells known as roaming.

When a mobile wireless user enters into the range of more than one AP, the wireless device will choose an AP based on signal strength.

The mobile device continues to survey the appropriate radio frequencies at regular intervals to determine if a different AP can provide better service.

If it finds one, then the device associates with the new AP ;The process is called a handoff, tuning to the radio frequency of the new AP.

To the user it is seamless because the wireless device never has an interruption of service.

Advantages Disadvantages

When an ESS is installed it is

desirable to configure the areas of coverage much like cells in a cellular telephone system.

By using multiple access points a Extended Service Set can accommodate additional users over a wider area.

Because of the “Hand Off” to the user the service is seamless because the wireless device never has an interruption of service.

One of the weaknesses of the IEEE 802.11 standard is that it does not specify how a handoff should take place.

Because roaming between APs of different vendors can sometimes be a problem, some industry experts recommend that all APs in an ESS be from the same vendor.

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Extended Service Set

Independent Service Set

or (IBSS)

An IBSS is a wireless network that does not use an access point.

It is also known as Peer-to-Peer or Ad Hoc Mode Where wireless devices communicate directly between

themselves.

An IBSS network is the simplest of all IEEE 802.11 networks in that no network infrastructure is required.

As such, an IBSS is simply comprised of one or more Stations which communicate directly with each other.

Service Set Identifier (SSID), also known as the wireless network name,

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eer-to-Peer Configuration (Ad Hoc Wireless LAN) Wireless devices create a LAN by communicating directly with other as pictured in the chart below.

Advantages Disadvantages

Ad-hoc networking is easy for temporary setup

But as long as the stations are within range, you can, for example, share and exchange files.

owner getting-started costs no need to install base stations Well suited to free unlicensed

spectrum with power control & cooperative

relaying, each user contributes to network capacity

Communication is limited to stations that are within range.

Capacity is the limiting factor: a large mobility causes a high volume of routing queries and updates which brings along high congestion, which leads to packet losses.

The capacity of wireless ad-hoc networks can be very low, due to the requirement that nodes forward each others' packets.

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Independent Service Set

Security Within the WLAN16

Today wireless networks are at least secure as wired. You only have to use the right tools and configurations.

The most important thing for WLAN security is to simultaneously use WEP, WPA, MAC filtering, 802.1x and other security options the network may be secure.

There are two types of authentication supported by the 802.11 standard.

Open system authentication & shared key authentication

Wireless Authenticatio

n

Part 1

Wireless authentication requires the wireless device to be authenticated prior to being connected to the network. IEEE 802.11 authentication is a process in which the AP accepts or rejects a wireless device.

Open system authentication is the most basic (and the default) method.

After discovering the network through passive scanning or active scanning and receiving the necessary information, the wireless device sends an association request frame to the AP.

The frame carries information about the data rates that the device can support along with the SSID of the network it wants to join.

After receiving the association request, the access point “considers” the request by comparing the SSID received with the SSID of the network.

If the two match then the wireless device is authenticated. The AP responds with an association response frame, which

contains either an acceptance or rejection notice.

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Wireless Authenticatio

n

Part 2

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The shared key authentication is when both the access point and the wireless device are given the same key value (it is “shared”) in advance.

A wireless device sends an authentication frame to the Access Point (AP).

The AP sends back an authentication frame that contains a block of text known as the challenge text.

The wireless device must encrypt the text and return it to the AP in an authentication frame.

The AP then decrypts what was returned to see if it matches the original challenge text.

If it does, the access point sends an authentication frame signifying the result of the authentication. Shared key authentication is based upon the fact that only pre-approved wireless devices are given the shared key.

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The Solution20

It may be recommended that D-Link switches and wireless access points as an alternative to other expensive solutions.

The D-Link solution offers lower initial buy-in Better overall performance Ease of management that lowers total cost of ownership over the long run. By using D-Link DWL-3200 model and Access Points in numerous strategic locations

throughout the high school campus. The APs connect to the main wired network Which features D-Link DES-1526 24-port POE switches. In total, you can deploy 10 access points and four switches, effectively blanketing an

approximate area of 200,000 square foot of heavy concrete building ( for which most schools are constructed of) with seamless and centrally managed wireless coverage.

The school manages everything centrally via Active Directory with RADIUS authentication.

The system would feature Wi-Fi Protected Access security with Temporal Key Integrity Protocol which makes it easier to deploy RADIUS authentication.

All users are managed through Active Directory, and the switches are all managed through a simple, easy-to use Web utility.