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MIT Pilots VoIP, Internet-Based Phone Service With 500 Users

By Benjamin P. Gleitzman

Information Services and Technology is currently in the midst of a pilot program to route telephone conversations over the Internet without the use of traditional phone lines. The pilot, now available to select departments and groups at MIT, employs Voice over Internet Protocol to send and receive voice conversations over any IP-based network.

More than 500 users are participating in the VoIP pilot at MIT, according to Theresa M. Regan, vice president of IS&T. The MIT network currently has on the order of 20,000 traditional phone lines, including desk phones, fax phones, dorm phones, circuits, and elevator emergency phones.

The transition from traditional telephone line to Internet-based routing offers the advantage of mobility, reduced infrastructure costs, and integration with next generation unified communications applications, according to Mark Silis, manager of Network and Infrastructure Services at IS&T.

The MIT VoIP system uses Asterisk, an open source television switch, to connect VoIP phones with other VoIP phones on the MIT network, as well as with telephones on the worldwide telephone system, also called the public switched telephone network.

Calls made between VoIP phones can be routed completely over the network, but calls placed to land lines will still travel over the PSTN and be subject to long distance charges.

The VoIP phone itself can be a softphone, software for PCs or handheld devices capable of sending and receiving calls, or a physical telephone device that connects to the network via an Ethernet jack or wireless access point.

Advantages, disadvantages of VoIP

Wireless VoIP phones can be used as long as the user maintains a connection to the wireless network, allowing telephone access to locations that cell towers may not be able to provide. Since all calls are routed via the Internet to MIT’s telephone system, a VoIP call placed from anywhere in the world to the Boston area is not subject to long distance charges.

“Disadvantages [of the VoIP service] are mainly focused around the fact that it’s a young technology and traditional voice services have had over a century “to ‘work the kinks out,’” Silis said.

Due to current network configuration, users cannot walk across campus using a wireless VoIP phone without losing their call, but IS&T plans to migrate MIT’s wireless network onto a virtual local area network which will solve the problem.

“This network topology will be gradual, building-by-building,” said Regan.

Call quality is also a concern, as phone conversations are very sensitive to lag and latency.

“Voice in and of itself is not high bandwidth,” said IS&T Director of Telephony Allison F. Dolan, but VoIP phones are subject to jitter, packet loss, and delay, which can cause phone conversations to sound distorted, speed up, or drop completely.

Additionally, with increased mobility comes uncertainty as to the caller’s current location. E911, the emergency 911 calling system, allows the police and fire department to pinpoint a caller’s location in the event of an emergency, but may not be reliable with a call placed from a wireless VoIP phone.

“Currently our VoIP system allows subscribers to enter the primary location where their VoIP service will be used and we then automatically pass this information to the MIT Police,” Silis said. “While there is not currently a solution for roaming VoIP users outside of the MIT network, there are methods available today for locating wireless users on the MIT campus.”

Reduced cost in long run

Officially announced in March, VoIP services at MIT have been an ongoing project since at least nine months prior, according to Dolan. “For two years, we’ve been staying aware of the trends,” Dolan said.

According to Dolan, there was “no compelling cost reason for going in [the VoIP] direction in the short run,” but the VoIP system offers clear long-term cost advantages, especially in new buildings on the MIT campus.

Buildings will not require both network and telephone wire to be run throughout the building, and some telephone boxes and expensive circuits will also not be needed.

“In three to five years, you won’t be able to buy a telephone switch as we know it today,” Dolan said.

Students will eventually be able to use VoIP phones in their dormitories, and IS&T along with Housing have partnered and are currently sponsoring a pilot in the Warehouse residence (NW30), according to Regan. Before the service will be offered to the entire student population, long distance billing issues will have to be addressed.

Other colleges piloting VoIP

Dartmouth College became the “poster child for 100 percent transition” to VoIP when the college made the switch to Ethernet-routed phone conversations in 2003, following a full upgrade of their network infrastructure. At that time, Dartmouth offered free softphones to incoming freshmen. According to Dolan, many of the best colleges and big universities are in a pilot mode of VoIP, including University of Pennsylvania and University of Colorado.

IS&T plans to have more detailed plans for the VoIP system by spring of 2007, Dolan said.

More information about VoIP service at MIT can be found at