OIT Networking & Monitoring Services

Temporary Visitor Wireless Network Access (TVWNA): Persistent TVWNA Campers

OIT Network Systems
April 27 2009
Last revised: May 16 2009

OIT has modified Temporary Visitor Wireless Network Access (TVWNA), a service that provides short-term Internet connectivity to wireless devices brought by visitors to Princeton University. We have made the change to help conserve the supply of IP addresses that serve TVWNA clients.

The change should not affect the customers TVWNA is intended to serve. It will affect devices belonging to customers TVWNA was not intended to serve; we believe most of those customers will not notice the change.

As in the past, a device may use TVWNA on any seven days within a single calendar month. Once a device has used TVWNA on seven days within a calendar month, the device is declared a TVWNA Camper. A TVWNA Camper cannot use TVWNA during the remainder of that calendar month. This has not changed.

The modification is as follows: If a device is declared a TVWNA Camper as a result of seven days of TVWNA usage during the first fifteen days of a month, and this happens for three months in a row, the device is declared a Persistent TVWNA Camper. A Persistent TVWNA Camper cannot use TVWNA for a year, counting from the date it became a Persistent TVWNA Camper.

The Devices Blocked from Temporary Visitor Wireless Network Access document has been expanded to include the wireless hardware addresses of current Persistent TVWNA Campers. The date on which a device was declared a Persistent TVWNA Camper appears, along with the months of TVWNA Camping that led caused the device to earn that designation.

We have also published Old TVWNA Campers. This new document shows the TVWNA usage of devices that were declared TVWNA Campers during several previous months.

We have also published TVWNA Clients This Month. This new document shows the dates of TVWNA usage for all devices during the current month.

Why Have We Made This Change?

We have made the change to help conserve the supply of IP addresses that serve TVWNA clients.

A growing number of devices are being declared TVWNA Campers month after month in a way that indicates those devices reside at the University year-round, or least, throughout the academic year.

Each of these devices obtains TVWNA starting on (or near) the start of each calendar month. The device uses TVWNA for seven days causing it to be declared a TVWNA Camper. As a result it loses the use of TVWNA for the remainder of the calendar month. At the start of the next calendar month the process repeats. This continues through the academic (or calendar) year.

The pattern indicates the device is not affiliated with a short-term visitor to the University. Most likely the device belongs to a member of the Princeton University faculty, staff, or student body, or a longer-term visitor. Or the device may reside in a home or business near the University. TVWNA is not intended to provide service to those devices.

We suspect that in the majority of these cases, the owner of the device does not realize the device has connected to TVWNA each month. The device is simply configured to connect to any wireless network it can find. If the owner were aware that the device is using TVWNA, in most cases we would expect the owner to be inconvenienced by the loss of service every month (when the device is declared a TVWNA Camper), and eventually register the device in the Host Database to obtain ongoing network service.

We suspect that many of these devices are small mobile devices (phones, music players, PDAs) for which the owner already obtains network service via another carrier, or for which the owner doesn't expect to use "online". Others of these devices may instead be desktop computers connected to the campus network via Ethernet, but which also have an wireless interface that the customer has neither registered in the Host Database nor disabled.

As the number of devices in this category grows, they consume an increasing number of the IP addresses available for TVWNA clients. They are placing unecessary stress on that limited resource. Because these devices are not among those TVWNA is intended to serve, identifying these devices and blocking them from further use of TVWNA helps conserve IP addresses for legitimate TVWNA clients.

To reduce the chance that we might declare a short-term visitor's device a Persistent TVWNA Camper, we only declare a device a Persistent TVWNA Camper after it has been declared a TVWNA Camper three months in a row. And to further reduce the chance of misidentification, we only count those months when the device's seven days of TVWNA use were within the first fifteen days of a month. Devices present year-round tend to obtain TVWNA soon after the previous month's list of TVWNA Campers is cleared. They tend to exhaust their seven days of TVWNA eligibility during the start of the month. (We consider the first fifteen days of the month instead of only the first seven because the presence of weekends and holidays causes some devices -- such as those carried by staff or faculty, or those powered on only during business days -- to spread out their TVWNA use throughout the first half of the month.)

We expire a device from Persistent TVWNA Camper status after a year. That's so that if the device is afffiliated with a member of the University who later leaves the University, s/he will eventually be able to use the device with TVWNA when visiting the University in the future.


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The Office of Information Technology,
Princeton University