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Telecom and IT administrators charged with supporting telecommuters have as many product and technology options as users have reasons (or excuses) to work from home.

Voice is the lifeblood technology of telecommuters — more so than e-mail, IM or any other means of electronic communications. An array of VoIP and hybrid IP/digital technology options exist for tying home-office workers to a corporate voice. But IT executives should consider how much in-office features available in the office should be extended to those at home, and at what cost.

VPN + VoIP

This is becoming a standard way for corporate IT administrators to support telephony for work-from-home employees. The approach requires two well-established technologies: remote-access VPN support, and a VoIP-enabled or pure-IP PBX in the central site. The common approach is for users to set up a VPN tunnel session between their home-office PC and the corporate network via standard access technologies, such as IPSec tunnelling or SSL encryption.

From this point, connecting the users with telephony is pretty much the same as linking an on-premises cubicle or office, since VPN links emulate LAN connections for remote users.

The easiest and fastest way to set up a teleworker phone connection is to deploy an IP softphone on the user's laptop or PC. All major PBX and IP PBX vendors have softphone software that ties into a corporate phone system extension and supports the same feature set as a desktop phone in an office.

At American National Bank of Texas, 25 to 30 percent of the workforce could be equipped with work-at-home capabilities in the next few years, says Kurt Paige, network administrator for the bank. "Not necessarily for working from home full-time," says Paige. "Employees would have softphones installed on notebooks, so they have the choice to work either in the office or from home."

The bank uses softphones from Nortel that tie into a CS 1000 IP-PBX. A Cisco VPN concentrator is used to provide remote-access VPN links for voice and data.

The softphone approach is preferred for supporting teleworkers because voice and data are combined on one platform — the notebook or home PC, Paige says.

For VPN links with decent bandwidth and QoS controls, teleworkers can even have IP hardware-based phones deployed in a home office. These devices — the same headsets deployed on desktops in the office — register with a central PBX or IP PBX over the VPN link and act as regular extensions on the system.

This is the case at Ball Homes, a custom home building company based in Kentucky that supports several executives and managers with VoIP for teleworking. Several managers, including the company president, have Cisco IP phones in their home offices, which ring at both the office desk and the home-office desk when an employee's phone extension is dialled, according to Brandon Buffin, systems administrator for Ball Homes. The IP phones used by teleworkers plug into a cable/DSL router and LAN switch in the home offices, and connect to a Cisco VPN Concentrator 3000 in the company's headquarters, where a CallManager IP PBX is also located.

Hybrid approach

Most makers of traditional PBXs based on legacy time division multiplexing (TDM) technology have several options for extending connectivity to a home office. Avaya, Nortel, Siemens, NEC and others offer simple and elaborate product packages that can either tie a home phone into a corporate PBX (with the help of PC-based software and a VPN link) and full telecommuter packages, complete with desktop hard phones.

Avaya and Nortel, as two examples, have a "telecommuter" option in their IP softphone clients that allows users to run call and access features from the softphone application but use a landline telephone for the voice traffic. In such a scenario, calls would be placed via the softphone interface on a PC — connected to the corporate PBX by a VPN link, according to the companies. When an external call is placed, the PBX rings the landline phone of the user (usually the home phone number), then calls the external number and bridges the two lines together.

This approach could help teleworkers without broadband connections, VPNs that do not support QoS for VoIP traffic, or users who run data-intense applications over their VPN links. (Signalling and call set-up traffic can run over a dial-up link; signalling and VoIP traffic on the same IP link usually require at least a 1Mbps link). Downloading large files or frequent server transactions could cause interference when packets of a VoIP conversation share the same pipe as data.

A teleworker could also enter a mobile telephone number as the forwarding line, allowing them to take incoming calls from co-workers via three, four or five digit extensions, or from external parties. This method also allows employees to use their office telephone numbers and extensions while keeping their home phone numbers private.

JetBlue Airlines uses this approach, with technology from Avaya, for its well-known work-at-home call agent workforce. The company extends IP applications and telephony/call control software to agents over VPN links to the home office, while a dedicated public switched telephone network line to the house runs the voice calls. This allows voice conversations with customers to continue even if a PC dies or a VPN line goes down, the company says.

The drawback to this IP/analogue approach is that every external call a user makes could incur up to two external long distance calls — one call from the PBX to the users phone to initiate the call, then the second long distance call to the external number being contacted.

This method of placing a call on a PC, then having the home phone ring, followed by a click to bridge the external party may seem cumbersome. Vendors also offer hybrid IP/digital offerings that allow teleworkers to make calls from a real office phone.

Siemens, for instance, has its MobileOffice Teleworking Suite, which is a package of home-office-side hardware and software, and a back-end server component. Specifically for users of Siemens PBXs, the home-office component consists of a PC-based software client, a Siemens digital or analogue desk phone, and an adapter for hooking the digital/analogue handset into the remote-office handset. The server on the headquarters side converts the Siemens CoreNet PBX protocol to IP, brokering connections among the switch and remote teleworker clients.

VoIP appliance maker MCK also offers an extension product for corporate PBXs from multiple vendors. The MCK EXTender is a gateway appliance that routes digital/TDM voice signals over an IP network back to a corporate telephone switch. Like the Siemens approach, the set-up requires hardware at both ends — the EXTender box in the home office, and ExTender PBXgateway in the main office where the phone switch is located.

For more information, our sister site Techworld has a comprehensive VoIP resource page.