How Dartmouth College Implemented a Campus-wide Wireless Network

Dartmouth replaced more than 600 802.11b intelligent access points with centrally managed 802.11a/b/g APs, and nearly tripled the number of APs covering its 200-acre campus to about 1,400. As if that's not enough, 1 gigabit-per-second (Gbps) wireless technology now connects the offsite Dartmouth-Hitchcock Medical Center to the main campus's network, forming the first link in a planned wireless backbone. This surge of airborne access solidifies Dartmouth's leadership as the most unwired of the Ivy League schools.

“The big thing that pushed us was [the need] to build a converged network for two reasons,” says Brad Noblet, director of technical services and interim chief information officer at Dartmouth. “First, the applications we offer include voice, video and data. We have to integrate those for students, faculty and staff to use in their work.

“Second, it costs a lot of money to build and maintain disparate infrastructures. I was looking at a $4 million PBX [private branch exchange] upgrade and another $1 million cable TV network upgrade, plus redundancy, backup power and all the reliability support.”

The Cisco WLAN cost $1.2 million at its peak of 640 APs. Two members of the Technical Services department maintain the WLAN. “A converged IP [Internet Protocol] environment is simpler and cheaper,” Noblet says.

Students and staff needed no coaxing to use the WLAN, according to studies by David Kotz, professor of computer science; postdoctoral fellow Tristan Henderson; and undergraduates Ilya Abyzov and Kobby Essien. In fall 2003, more than 7,000 WLAN users were logged.

Overall traffic reached peaks of 400 gigabytes per day. Average daily traffic per active user reached 71.2 megabytes. Peer-to-peer file-sharing soared to 37.6 percent of all traffic, while network file systems mounted by notebook users contributed 14.4 percent. Web traffic accounted for 18.8 percent, down from 54.1 percent in 2001. Streaming multimedia traffic hit 3 percent, while VoIP traffic represented only 0.1 percent.

“The main influence [of the WLAN] is that it allows students to work anytime, anywhere; to form impromptu study groups in places where it's comfortable and convenient for them–not just in their dorm room or a computer cluster like in the old days,” says Kotz.

Ted Cooley, assistant professor of engineering, says they have developed location-sensitive wireless applications based on technology from a local vendor. Two such applications display greetings and directions to visitors and beam classroom-specific course materials to students.

In addition, Cooley says the school is using a middleware application that takes help-desk ticket information and delivers it to the technician who is nearest the problem. The system can also display task-specific information on screens near a technician, permitting richer content than a personal digital assistant can handle.

VoIP Joins the WLAN

VoIP came to Dartmouth's wired network in the spring of 2003 at a cost of $2 million, which was split equally between the call manager/media gateway infrastructure and handset costs. There are now 8,000 wired lines that support VoIP, including lines in student residences.

Dartmouth quickly saved $300,000 per year by eliminating its call-accounting system and bundling a flat $12-per-month charge into students' dorm fees for unlimited VoIP local and domestic long-distance calls. “To the students, it looks like they're getting free phone service,” says Noblet.

VoIP joined the WLAN in September 2003, when incoming students were allowed to download softphone software free of charge. The software, along with a USB handset or headset, lets users place or receive calls via their notebook PCs and the WLAN.

However, softphones have not been the hit that Dartmouth expected when it bought 1,100 softphone licenses. Today, 300-plus folks regularly use softphones, says Noblet. “I think the issue is that using your notebook PC as a phone isn't as practical as it is cool,” he says. “People want a ‘real' phone.”

Hardware wireless phones are available. Faculty, staff and students use 150 Star Trek communicator-style devices, which rent for $15 per month. These voice-activated, two-ounce communication badges recognize the spoken name of a person you want to call and can even tell you where he or she is, based on the AP to which his or her device is connected. The wearable speakerphones can recognize complex commands, such as “Conference Jane Doe and John Smith,” to establish a three-way call.

About 150 cordless IP phones are in use as well. “They're still pretty expensive, and the battery life is low,” says Noblet. “Until the cost comes down, the adoption rate [of wireless VoIP] won't be great.”

Video on Demand, on the Go

For video distribution, Dartmouth employs streaming multimedia servers. A small viewer application is streamed to the client device with each video file requested. It removes itself when the video session is closed, eliminating the need to support client-resident viewer applications and giving IT control of usage. The server converts any analog video/audio source to MPEG (Motion Picture Experts Group) format, encrypts the file, and routes multicast streams to clients on wired or wireless networks.

Dartmouth's video system cost half a million dollars–a bargain compared with the estimated $1.2 to $1.5 million cost of upgrading the school's coaxial cable TV system. Channel capacity is increased to nearly 1,000 from 62, providing practically unlimited capacity for course-specific and student-created content, plus entertainment channels that are delivered by a cable TV provider. Today, 48 entertainment channels and 14 learning/teaching channels are available.

“Students say they love the ability to kick back and watch CNN wherever they happen to be,” says Noblet. “They've expressed some frustration over digital rights management, of course.” The digital content cannot be saved to disk directly, but it can be converted to analog format and stored on a DVD or VHS recorder.

Central Intelligence Wins

The WLAN's capacity had to be expanded dramatically to meet the demands of video and a rapidly growing user population. Noblet wanted to increase AP density and boost channel bandwidth from 11 to 54Mbps to support more users in a given area. He decided the existing architecture, which distributed intelligence down to the access point level, would not scale to meet those needs.

“We faced management issues of load balancing, and for that to happen, you would need APs talking peer to peer, wasting a lot of bandwidth,” he explains. “We had proven with such products that we couldn't scale up as high as we needed. Plus, the cost per AP keeps going up the more intelligence you build into each AP. The economic model for a distributed-intelligence AP doesn't scale.”

Dartmouth decided to replace its WLAN with a system that relies on intelligent switches controlling dumb APs. The makeover began in early 2004 and was completed by fall 2005. About 640 intelligent 802.11b APs have been replaced by 1,400 dumb 802.11a/b/g APs and six switches. Surprisingly, the new WLAN cost just $600,000, half of the three-year-old predecessor's price.

The dumb APs cost under $200 each, less than one-third of an intelligent AP's price, Noblet says. The switches can be clustered for redundancy and management from a single console. The switches enforce policy-based user authentication and access control across the wired and wireless networks, and provide internal network security functions, such as antivirus and content filtering.

Noblet's two WLAN technicians would be very footsore without the switches' centralized management capabilities. A controlling switch can fine-tune each AP's characteristics, such as the frequency band and channel it uses, or the radio frequency (RF) output power level. Indeed, most routine adjustment and remediation functions are carried out automatically.

“One cool thing is that an AP can be placed anywhere near the wired network,” says Noblet. “You can plug an AP into an edge switch, and the wired network funnels AP traffic to the WLAN switch. You don't have to worry about allocating ports. Using this tunneling feature, you can maximize switch utilization.”

The 802.11a/b/g APs can deliver bandwidth on different frequency bands in the same area, avoiding traffic congestion and signal interference. “I can push video on 802.11a and still do other things with 802.11b/g,” Noblet adds. “Each 802.11a AP can support seven channels of video. High-traffic areas have three [overlapping] APs available, so, in theory, we can stream 21 channels.”

Wireless Links Save Time

Dartmouth is installing 1Gbps wireless links between its main campus network and two offsite facilities. The first link, to the Mary Hitchcock Memorial Hospital 1.5 miles from campus, is already in place. A link to the Institute for Security Technology Studies is also planned. “We could have run fiber to the sites, but it would have taken 18 months to negotiate rights of way,” says Noblet.

The school chose a point-to-point licensed-spectrum wireless system that uses RF bands of 71-76 gigahertz and 81-86GHz. A one-time spectrum license cost the university only $475, and the next-generation technology will support up to 10Gbps, according to the vendor.

Wireless networking is saving Dartmouth significant money and staff time, and students are learning to live and work in the unwired world of the future. As Noblet says, “The classroom (or workplace) is everywhere.”