|Access Point Antennas|
|Perhaps the most ignored feature when choosing an access point, antennas should be given considerable thought. Most access points come with omni-directional antennas, which means that the access point sends out a signal in the form of a sphere all around itself. This is especially useful when placing an access point in the centre of a smaller office, as it can cover the entire office area easily. However, it is when we reach larger offices-where numerous access points are needed-that directional access point antennas may offer you some relief.
Directional antennas also offer some relief for those obsessed with security, as you can ensure that all your access points offer a known and fixed coverage area. Directional antenna-based access points could be set to ensure that no one ever gets a signal outside the office walls, and thus cannot hack into the network. Directional antennas also help you plan and position your access points better, so as to offer maximum coverage. Their biggest advantage, however, is the fact that they offer greater bandwidth and range, as a result of being focussed in a single direction.
When deploying a WLAN in a large multi-storeyed office, uni-directional antennas will be needed to ensure that there is no overlap of signals of access points running on the same channel, thus breaking the seamless network.
|The Interference Dilemma|
|The biggest thing that afflicts a WLAN is interference. A WLAN signal is fragile and can easily be disrupted by something as simple as a wall, so the last thing you need are pesky devices sending your WLAN crashing. The 802.11 protocol runs at about 2.4 GHz, and this frequency is prone to interference from numerous sources. The problem with interference is the additional load that is put on your networks. If one wireless device is sending data packets to another, and interference occurs, the receiver gets a packet with errors.
Most often, receivers are programmed to not respond to the sender when this happens, and this results in the sender transmitting the packet once again. The problem here is that all these packets being re-sent can use as much as half your bandwidth, which will hurt the overall WLAN performance. Some devices that can cause interference with WLANs are:
Cordless phones running at 2.4 GHZ
These are the latest cordless phones that offer a longer range from their base station. However, the problem lies in the fact that these cordless phones use the same frequency as WLANs, and thus turn out to be the biggest source for interference. If you have any of these phones installed in your office, you will need to get rid of them whenever you install your WLAN or be ready to face pathetic speeds.
Many mobile phones and PDAs today are Bluetooth-enabled, and this can cause interference if a user uses such a device where the signal strength of an access point is already low-far away from the access point and close to a device connected to the WLAN. Thankfully, current research, driven by the increase in popularity of both Bluetooth-enabled devices and Wi-Fi, will soon put an end to this menace.
Every time employees heat their food, you might find users in the immediate surroundings yanking out clumps of hair. Placing an access point next to a microwave oven is a definite no-no, as these ovens emit signals that clash with Wi-Fi.
Improperly shielded power cables can interfere with wireless signals, and it is best to keep access points positioned away from power cables or power junction boxes.
Most companies in India share buildings, floors or even offices with other companies. In such a scenario, a neighbouring office's WLAN could cause interference with your own deployment. This is something you should inspect and test thoroughly when doing your RF site survey.
|Possibly the best way to check your security is to use the very tools someone would use to gain unauthorised access to your WLAN. Here's a short list of tools that are built either to attack or defend:
AirSnort: A WLAN sniffer tool that recovers encryption keys by passively monitoring transmissions. It calculates the encryption key after it has received enough packets. It can be downloaded from http://snipurl.com/dgif
WEPCrack: This uses the latest RC4 key scheduling to crack a WLAN's WEP code. Get it from http://snipurl.com/dgih
NetStumbler: This tool lets you 'discover' any WLANs or access points in your vicinity. This tool can also be used for your site survey, as it will inform you of any existing WLANs that may cause interference or help you know your signal strength at different points. It can be downloaded from http://snipurl.com/dgij
Internet Scanner: The Internet Scanner provides an automated network vulnerability assessment. It performs distributed or event-driven probes of network services, operating systems, routers/switches, servers, firewalls, and application routers to identify potential risks. Try an evaluation version at http://snipurl.com/dgil
Wireless Scanner: This detects and analyses your WLAN access points and clients. It identifies and reports unauthorised and misconfigured devices. Try it by going to http://snipurl.com/dgim.
BlackIce PC Protection: This is a personal firewall for laptops and Wi-Fi-enabled desktops with the ability to protect you from intrusions and client-to-client attacks. Download a trial from http://snipurl.com/dgio
You should also visit www.iss.net, the homepage of Internet Security Systems, a leading security consultant to companies and governments world-wide. Here, you will find some of the tools mentioned above, and also many security solutions for enterprises, educational institutions and even governments.