The increased use of mobile devices is generating more demand for Wi-Fi in branch office networks. Highly distributed enterprises have the complex task of deploying a wireless branch office network in dozens, if not hundreds, of locations. The major networking vendors recognize these challenges and offer wireless branch office network solutions that address these needs.
“The problem with remote offices is that typically there is no IT support there,” said Paul DeBeasi, research vice president for wireless and mobility at Gartner. Because enterprises rarely have local administrators to deploy and manage a wireless branch office network, a branch solution must meet certain requirements. A wireless branch network must be easy to install, offer centralized diagnostic and remote capabilities and be relatively inexpensive, said DeBeasi.
“Virtually every vendor has some solution for branch offices,” he said. “What ends up happening in most enterprises is whatever [vendor] they have at corporate, they buy the same thing for the branch. If I have Cisco at corporate, then I’ll buy Cisco for the branch.”
Wireless branch office network products differ in a few key areas, and enterprises should examine these before selecting an incumbent vendor for the branch.
Troubleshooting connectivity problems is a challenge for branch office deployments -- if you have no way of seeing the wireless energy in the air. That’s where spectrum analysis technology comes in. In a corporate environment with local IT staff, you would use a handheld spectrum analyzer to identify sources of interference. In a wireless branch office network, you need that same technology built into the access point. DeBeasi advises organizations to only deploy access points with embedded spectrum analysis technology. This will allow you to identify interference remotely.
“If you don’t do that, you’re blind … to problems,” DeBeasi said.
Most vendors include spectrum analysis technology in their access points. However, Cisco Systems charges a premium for its hardware-based CleanAir feature, while others like Aruba Networks and Motorola use commercial silicon with this feature built in.
“The Wi-Fi chip does the spectrum analysis, so they don’t charge a premium, and all applications have it,” he said. “Cisco says theirs works better. Aruba says, ‘what we have solves the problem, there’s no need to charge more for it.’ When customers get down to the buying decision, they need to determine whether it’s worth spending more money for it.”
Network management systems
In addition to visibility into the Wi-Fi spectrum, the networking team also needs access to historical data to troubleshoot a wireless branch office network.
“Wi-Fi [troubleshooting is] different [from wired] because wireless problems tend to be both location-dependent and temporal. Wireless problems can vary by where the person connecting is located, and the problems can vary over time.”
For example, a user at a branch office may call the help desk and say that he wasn’t able to connect to the wireless network for over an hour, but by the time a technician responds to his call the connection may be working again with no trace of what the problem was.
In order to troubleshoot a wireless branch office network, IT needs a wireless network management system that includes a database that collects data on network conditions over time and associates that data location information.
“The network management system needs to collect information for each access point -- error rate, interference, number of devices -- and then when a problem occurs and help desk gets a call from the branch, the help desk needs to be able to look back over time to figure out what the problem was,” DeBeasi said. “Not every wireless management system collects stats over time and by location. This is an important aspect of the system.”
Wireless branch office network architecture
Wireless branch office network products also vary widely in their architecture -- specifically, where the controller functionality resides. The control plane of a wireless branch office network can reside in access points themselves, in the cloud or within a central location -- often in the corporate data center. In a centralized, controller-based architecture, the wireless LAN controller makes policy decisions about how wireless traffic is handled. This approach can introduce latency as access points send packets to the controller.
Cisco has a controller-based architecture with centralized data forwarding. Traffic is sent to a central controller by a Cisco Hybrid Remote Edge Access Point (H-REAP), DeBeasi said. Aruba’s architecture is similar, but it has modified its access points to be able to make forwarding decisions at the branch. With its MOVE architecture, Aruba enables branch offices to have up to 16 access points that can operate independently of a central controller. Instead, one of the access points acts as the controller of the wireless branch office network.
Aerohive is controller-less and Meraki has a cloud-based controller, said DeBeasi. Finally, Motorola’s architecture has a central controller appliance, but it has also pushed controller functionality down to the access point with its WiNG 5 architecture so that access points in branch offices can make forwarding decisions.
“It’s a controller-based architecture with distributed forwarding,” DeBeasi said.
Traffic may slow down when sent to a controller, and vendors that do not require a centralized controller say that it can create a bottleneck. “But they can all be configured so that local traffic stays local,” DeBeasi said.
About the author
Crystal Bedell is a freelance technology writer. She writes articles, case studies and white papers that help IT professionals evaluate technology, secure and modernize their IT infrastructure, solve business problems and prepare for IT certifications. She can be reached at firstname.lastname@example.org
This was first published in December 2011