Expert Advice

Your enterprise wireless LAN questions answered

Wireless LANs were once seen as the easy alternative to the wired LAN. After all, they weren't used for primary network access and they didn't have to be eternally stable or particularly far-reaching. That's no longer the case— and that leaves users with plenty of wireless LAN questions.

SearchNetworking.com readers have sent in a host of wireless LAN questions related to 802.11n migration,

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wireless LAN performance management and design of wireless mesh networks, among other topics.

SearchNetworking.com wireless expert Lisa Phifer has been answering readers’ questions for years. Here is a selection of Phifer's most commonly read questions related to wireless network migration and management.

 

When old technology meets new, wireless LAN questions arise

It's very rare that an IT shop is able to do a complete rip-and-replace on a wireless network. Instead, it often finds itself combining newer 802.11n technology with older 802.11 equipment. Integrating this equipment raises questions of how to use varying APs together and whether neighboring equipment can get along.

Question: What is the impact of having both the 802.11g and 802.11n access points in the same environment? Will this cause conflicts for the clients in this environment? Can you catalog users by the frequency?

Answer: 802.11g access points (APs) operate in the 2.4 GHz ISM band, using 20 MHz wide channels. 802.11n APs can operate in either the ISM or UNII band— that's the set of channels above 5 GHz— with the option of using 40 MHz wide channels.

Read the rest of this answer to the question of combining 802.11g and 802.11n APs.

 

Question: When a company completes migration to 802.11n, what can it do to avoid coexistence problems with neighboring businesses that still use 802.11g?

Answer: The 802.11n high throughput (HT) standard defines three modes of operation: a legacy (non-HT) mode, a greenfield (HT-only) mode and a mixed mode where HT protection mechanisms ensure that transmissions can be detected by both old 802.11a/g/b devices and new 802.11n devices.

Read the rest of Lisa's answer on how to avoid coexistence problems when migrating to 802.11n.

 

Improving wireless LAN performance

Implementing wireless LANs is one thing, keeping them running smoothly is another. That process takes ongoing wireless LAN monitoring and troubleshooting, as well as architecture strategies that optimize networks in the long run.

Question: What is your take on 7/24 Wireless Quality Assurance as a cost-effective alternative to ad hoc troubleshooting?

Answer: Automated performance monitoring and proactive management to maintain quality-of-service targets and service-level agreements (SLAs) is a necessary ingredient of any mission-critical wireless LAN (WLAN).

Read more of Lisa's advice on automated performance monitoring in the wireless LAN.

 

Question: What are the best methods for handling rogue APs? Can you suggest a small-scale business network solution for dealing with rogue access points?

Answer: Any unknown access point (AP) operating in or close to your facility is a potential rogue— but few turn out to be real threats. The trick is to reliably tell the difference— and fast.

Read Lisa's advice on monitoring for rogue APs.

 

Mesh wireless LANs

Using a mesh topology— in which wireless nodes talk to each other to form a network— is not the most common wireless LAN architecture, but it is increasingly being used to extend the reach of Wi-Fi networks over greater outdoor geographic areas. It is also often used to create ad hoc wireless LANs within the enterprise.

Question: We have installed a wireless mesh network that connects two access points (APs) to mesh nodes that are mounted at 25 meters high on 23 light poles. Poles are distributed around a container yard that measures 650 meters by 1,000 meters. There are six rows of containers, varying in height depending upon container movement, stacked to a maximum of 6 containers high. Walkways and vehicle lanes are located in between container stacks. We had expected to achieve 10 Mbps throughput on the ground but do not. Please recommend a solution.

Read Lisa's recommendation for increasing throughput on this wireless mesh network.

 

Question: We have a small business office that is too large to cover with a single 802.11n AP, and we would also like to extend the 802.11n WLAN to a second small building 125 feet away from our main building. How can we extend an 802.11n WLAN to meet these needs?

Answer: To build a network that delivers solid coverage to both offices, you must solve two problems: First, you must extend 802.11n WLAN coverage provided by your indoor WLAN, and then you must join two indoor WLANs together with a short outdoor wireless link.

Lisa says one way to extend this network is through wireless mesh. Read more.

 

Question: I'm setting up a WLAN in a hotel using a Colubris MSC 3200 access point (AP)/controller. For some reason the Internet keeps dropping from the controller. The signal needs to span about 1,000 feet, there is no RADIUS (Remote Authentication Dial In User Service) server, and I do not have any detailed info on the 3200's settings. In the hotel there are 16 APs on the same floor, each addressed by static IP's, with one transmit radio and one receive radio. Is the transmit radio (which uses a different SSID that I cannot connect to) supposed to be a bridge?

Answer: It sounds like your hotel's WLAN might be designed to use a wireless backhaul mesh to connect all APs to the Internet via the Colubris MSC 3200 AP/controller. …

Read the rest of Lisa's advice on what to do about APs dropping from a wireless mesh network.

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This was first published in May 2011

 

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