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Weigh the pros and cons of VoIP over wireless

15 января 2007
Now, with VoIP over wireless — also called VoW, VoWiFi, wVoIP, and a number of other acronyms — organisations can cut all the cords. Numerous vendors are offering Wi-Fi IP phones that operate on the same 802.11 technologies used for wireless networks.

According to a study from Infonetics Research, sales of Wi-Fi IP phones will likely reach $3.7bn (Ј2bn) by 2009. The market already totalled more than $125m in 2005, and it's growing steadily, particularly in business fields that have many mobile workers. That includes people who work in hospitals and factories, on sales floors, etc.

Major consumer-level networking equipment makers such as D-Link, NETGEAR, and Linksys are also getting into the act, selling IP phones that work with their Wi-Fi routers. Enterprise-class vendors make IP phones that work with business WLANs and IP PBX equipment. FierceMarkets hosted the Wireless VoIP Executive Summit in November 2006, which addressed present and future wireless VoIP technologies and issues.

Many technology analysts think the wave of the future will be dual-mode mobile phones, which can function as IP phones on a Wi-Fi network where one is available (be it home, office, or public hot spot) or use cellular technology in areas where there's no Wi-Fi network. Either way, the phone would have the same phone number. Because costs would be low when using Wi-Fi, such a device could replace the landline entirely for many users.

Is your organisation ready for VoIP over wireless? Here's an overview of some of the technology's pros and cons. Advantages of wireless VoIPA big advantage of wireless VoIP is lower cost as compared to traditional cellular phone technology. Wi-Fi networks are already in place in many areas, and companies can deploy them quickly and inexpensively where they're not. People can use IP phones wherever an Internet connection is available, and VoIP call quality is rapidly improving — to the point where in many cases it's equal to or better than cellular.

If properly implemented and marketed, wireless VoIP could become as big a challenger to traditional cellular phones as wired VoIP is becoming to landlines. Major VoIP providers are already going wireless. For example, Skype recently added the ability to run its service on Windows Mobile devices. Two big challengesThe concept sounds great: Combine the low cost of VoIP with the convenience of wireless networking. It's the logical next step in the move toward more cost-effective and mobile telephony. But there are a couple of major obstacles to implementation — reliability and security. The reliability questionMost users are willing to tolerate some downtime and delays associated with computers and data networks. We don't expect to receive our email messages instantly, and if network glitches result in a few minutes' or even a few hours' delay in delivery, we don't think too much about it.

When it comes to voice communications, however, the public switched telephone network (PSTN) system has spoiled us. We expect the phones to work — every time. We expect high-quality transmissions. And we expect the connection to stay connected until we choose to disconnect.

The reliability question is the biggest reason that organisations haven't adopted VoIP more quickly. Because it's a real-time application, VoIP is more sensitive to packet loss and other networking problems than most data-oriented applications.

And wireless technologies add another layer of things that can go wrong. RF interference, range limitations, weak signals, and the like can cause a VoIP call to break up or disconnect. Performance and quality problems with a VoIP-over-wireless connection can originate with the network/bandwidth, QoS configuration, or the endpoints (handset or call server).

But tools are available to help troubleshoot VoIP performance problems. For example, enterprises can use AirMagnet's VoFi Analyzer to validate and watch QoS and monitor VoIP calls end to end. Security issuesWireless security concerns have kept many companies from implementing 802.11 networks on their sites, and it's as much of an issue for VoIP as for other applications that transmit over wireless. Because the VoIP packets travel across the airwaves, it's easier for an intruder or attacker to intercept them as they move across the network.

The same security threats exist for wireless VoIP as for wired VoIP — and then some. The same security mechanisms used for wired VoIP — such as IPSec encryption to protect the confidentiality of packets at the network layer, TLS encryption to protect session initiation and secure call traffic at the session layer, and Secure RTP (SRTP) to encrypt the media at the application layer — are all applicable to wireless VoIP as well. But companies need to take additional steps to secure the wireless link itself.

To secure wireless VoIP, organisations need to establish the right policies, use the right security protocols, and select the right equipment. Here are some tips:
  • Policies should prohibit "rogue" access points and ensure the authentication and encryption of all VoIP calls using wireless channels.
  • Wireless encryption should not be Wired Equivalent Privacy (WEP), which has many known weaknesses, but a stronger wireless encryption method such as Wi-Fi Protected Access (WPA).
  • When selecting IP phones, use "hard phones" that are less prone to viruses and attacks than "soft phone" software installed on a regular PC operating system, and choose phones that support strong encryption.

The next natural step in network convergence is the combination of VoIP and wireless networking technologies, which have the potential to dramatically lower the cost of anywhere/anytime telephone service. While there are some obstacles to implementing wireless VoIP — primarily issues of reliability/performance and security — there are steps companies can take to improve performance, increase security, and make VoIP over wireless a viable option for your organisation.

Deb Shinder, TechRepublic

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