OIT Network Systems

Temporary Unregistered Dormnet IP Address Service

OIT's Temporary Unregistered Dormnet (TUD) IP Address service allows devices attached to the Dormnet network but not currently subscribed to Dormnet to have some limited access to campus network. This service is provided for the sole purpose of allowing students to submit Dormnet Subscription forms from their own computers before those computers are receiving normal Dormnet service (because they are not yet subscribed to Dormnet).

(As a side-effect, TUD service also provides limited network access for office machines attached to the Dormnet network which are not yet registered in the Host Database. Owners of office machines attached to the Dormnet network should not rely on this side-effect.)

Contents

  1. TUD Service Makes it Easier to Subscribe to Dormnet
  2. TUD Service Makes it Easier to Correct Your Hardware Address
  3. TUD Service Relies on DHCP
  4. How Can I Tell if I'm Using TUD Service?
  5. TUD Service is Limited
  6. How Does it Work?
  7. Changing a Hardware Address
  8. TUD Campers
  9. Related Resources
  10. If You Need Additional Assistance

TUD Service Makes it Easier to Subscribe to Dormnet

We provide TUD service to make it more convenient for students to subscribe a new device to Dormnet, or to update their subscription's Host Database entry after replacing a computer with a new (or repaired) computer that has a different Ethernet address.

Subscribing to Dormnet involves using World Wide Web to complete a subscription form on an OIT Web site at Princeton University. The computer used to access the Web must already have working IP networking services (obviously), and for security and accountability reasons, must also be already registered in Princeton University's Host Database in the "Princeton.EDU" domain. In the absence of TUD Service, a computer that is not currently subscribed to Dormnet (or registered as an office machine in the Host Database), wouldn't meet those requirements. (The computer wouldn't have an active registration in the Host Database, and wouldn't even have working IP networking services.) As a result, the owner would need to visit another computer (e.g. a working computer in a friend's room which had already subscribed, or a computer in one of the University's public Computing Facilities) to complete the Dormnet subscription form.

TUD Service is intended to allow a student to complete the Dormnet subscription form from his or her own computer, so the student need not visit another already-subscribed computer. It does this by providing the student's currently-unsubscribed computer with limited IP networking service -- enough so that if the computer already has properly-configured appropriate software, it can access the OIT Web site to submit a Dormnet subscription form. After the subscription form is processed and the student's computer is restarted, it will stop using TUD Service, and begin using normal Dormnet service.


TUD Service Makes it Easier to Correct Your Hardware Address

If after subscribing to Dormnet, a student replaces his or her computer's network (e.g. Ethernet) interface (or replaces the entire computer), the computer's hardware (e.g. Ethernet) address will normally change. Until the student changes the computer's entry in the Host Database to reflect its new hardware address, its Dormnet subscription will not work properly.

Just as with subscribing to Dormnet, completing the change form requires that one use a computer that has working IP networking services, and is registered in the Host Database in the "Princeton.EDU" domain. In the absence of TUD Service, the computer would not meet those requirements, since the new Ethernet hardware address does not appear in the computer's Host Database entry. As a result, the owner would need to visit another computer to complete the form.

TUD Service will allow a student to complete the form from his or her own computer, so the student need not visit another already-subscribed computer to do so. It provides the currently-misregistered computer with limited IP networking service -- enough so that if it already has properly-configured appropriate software, it can access the OIT Web site to submit a change form. After the change form is processed and the student's computer is restarted, it will stop using TUD Service, and resume using normal Dormnet service.


TUD Service Relies on DHCP

Temporary Unregistered Dormnet IP Address service uses DHCP to lease an IP addresses to computers that are attached to Dormnet wiring, but whose hardware addresses do not appear in the Host Database for current Dormnet subscriptions, nor for any office machines' active Host Database entries.

As a result, the only clients that receive TUD Service are those which are not registered at all in the Host Database, or appear in entries which are not currently-subscribed to Dormnet, or appear in entries which have a "*-INACTIVE" ENTRY-TYPE. TUD IP addresses are not assigned to devices with Ethernet addresses that are currently subscribed to Dormnet, or registered as office machines in an active Host Database entry


How Can I Tell if I'm Using TUD Service?

Currently our convention for the Internet hostnames associated with TUD IP addresses is: temp-oit-unregistered-dormnet-NETWORK-LETTER-NUMBER.Princeton.EDU, where NETWORK is the name of a campus network ("subnet") and LETTER denotes which OIT DHCP server owns the TUD IP address. This convention may change in the future.

The Identify My Computer tool (available only to on-campus customers) will identify the IP address and hostname your computer is currently using, and also tell you if it is a Temporary Unregistered Dormnet IP Address. (If your computers is simultaneously attached to the campus network via two interfaces (e.g. Ethernet and Wireless), which interface the tool identifies will depend on your computer; the tool cannot tell.)


TUD Service is Limited

Since a TUD IP address is only intended to be used temporarily (to allow you to subscribe to Dormnet without leaving your room), we limit the TUD IP Addresses Service so it cannot be misused as a substitute for subscribing to Dormnet. We limit it in several ways:

OIT may disable TUD Service at any time for a device that appears to be misusing it; for example, when a customer appears to be using TUD Service as a way to avoid subscribing to Dormnet. We also may disable TUD Service for any device which has a DHCP client that malfunctions in such a way as to interfere with TUD Service for other customers. We may also disable TUD Service to devices for which the service is not intended; for example, unregistered offices machines attached to Dormnet, or dedicated NATs or BRIDGES. Devices declared ineligible for receiving TUD service are listed in Devices Blocked from Temporary Unregistered Dormnet IP Address Service.

TUD Service is also unavailable to Devices Blocked from Visitor IP Service, Devices Blocked from Temporary Visitor Wireless Network Access (TVWNA), and Devices Blocked from OIT Mobile IP Service.


How Does it Work?

TUD service relies on DHCP, the Dynamic Host Configuration Protocol. To obtain TUD IP Address Service, your host must meet most of the requirements described in the document DHCP and BootP Services. The exception is that your host's hardware (e.g. Ethernet) address must not appear in the Princeton University Host Database for any active entry. (If your hardware address appears in a Host Database entry that is for a currently-unsubscribed Dormnet entry, your host will receive TUD service. If your hardware address appears in a Host Database entry that is for a current Dormnet subscription, your host will not receive TUD service, as it is already receiving Dormnet service. If your hardware address appears in a Host Database entry that is for an office machine, and that entry is INACTIVE, your host will receive TUD service; if the entry is active, your host will not receive TUD service.)

TUD Service is only available on Dormnet wiring; it is not available on any other campus network.

When your unregistered computer is attached to Dormnet, OIT's DHCP servers assign ("lease") to your computer a Temporary Unregistered Dormnet (TUD) IP Address and Internet hostname. ("Unregistered" refers to your computer's Ethernet address, not the IP address leased to you. The IP address leased to you is in fact registered in the Princeton University Host Database; it is part of a pool of TUD IP addresses.)

This lease has a short duration, typically 30 minutes-3 hours. While your computer remains attached to Dormnet and continues to use IP, it periodically contacts OIT's DHCP servers to renew this lease. If your computer is restarted (or allows the lease to expire for some other reason), the DHCP servers may assign it a different TUD IP address and Internet hostname.

A list of the clients currently assigned TUD IP addresses appears in Current Temporary Unregistered Dormnet IP Address Assignments.

For the most part, a TUD IP address functions like any other IP address on-campus. You can use it to communicate with on-campus hosts. You cannot use it to communicate with Internet hosts (off-campus); traffic from or TUD IP addresses is not permitted to travel off-campus. Attempts to communicate with off-campus hosts will fail in any number of (often-mysterious) ways. Similarly, TUD IP addresses cannot be used to with OIT VPN Service.

You are expected to make use of the TUD Service to promptly Subscribe to Dormnet. The Web servers used to complete the Dormnet subscription form are all located on-campus, so your TUD IP address can communicate with them.

Under normal circumstances, a correctly-completed Dormnet subscription form is processed automatically within a day, and email notifying you of the completed processing is sent to you.

You will need to reboot your computer after processing of your Dormnet subscription form is completed. When you reboot your computer, it will no longer receive TUD Service, because it is now subscribed to Dormnet (your computer's hardware address appears in in the Host Database as part of a current Dormnet subscription). When you reboot, the hardware address registered as your computer's Ethernet address will be assigned the normal (static) Dormnet IP Address which is part of its Dormnet subscription. You can verify this with the Identify My Computer tool, assuming you are connected to Dormnet via that Ethernet interface. (If, when you reboot your computer, it still receives a TUD IP Address, you may not have waited long enough for your Dormnet subscription to be processed, or there may have been an error in your subscription form. Check the email sent to you (within a day of submitting the form) to see if there was an error. You should be able to reboot about an hour after you receive email indicating your subscription was successfully processed, and then be assigned your normal (static) Dormnet IP Address instead of a TUD IP Address.)

If you don't reboot your computer after subscribing to Dormnet, eventually OIT's DHCP servers will stop leasing a TUD IP Address to your computer. (This will happen within a day of succesful processing of your Dormnet subscription form.) Your computer will lose IP service, and any IP-based software running on it may fail. You should reboot your computer, which will cause it to be assigned its normal (static) Dormnet IP Address.

If you do not subscribe to Dormnet (or in the case of an office machine, register the office machine in the Host Database) within seven days (fourteen days during the first eight weeks of the academic year), your machine's hardware address is identified as a TUD Camper, and is blocked from receiving any further TUD Service. (More information about TUD Campers appears below.)


Changing a Hardware Address

If after subscribing to Dormnet, you later replace your computer's network (e.g. Ethernet) interface (or the whole computer), so your computer's hardware (e.g. Ethernet) address changes, OIT's DHCP servers will not find your new hardware address in the Host Database, so will assign the normal (static) IP address associated with your Dormnet subscription. Since the new hardware address does not appear in the Host database for any currently-subscribed Dormnet entry (nor for any active office machine's Host Database registration), OIT's DHCP servers will provide your computer with a TUD IP Address.

You are expected to make use of the TUD Service to promptly change your computer's entry in the Host Database to reflect its new hardware address. The Web server used to complete the change form is located on-campus, so your TUD IP address can communicate with it.

Under normal circumstances, a correctly-completed change form is processed automatically within a day, and email notifying you of the completed processing is sent to you.

Just as for a new Dormnet subscription, you will need to reboot your computer after processing of the change form is complete. When you reboot your computer, it will no longer receive TUD Service (it's new hardware address appears in the Host Database as part of a current Dormnet subscription). When you reboot, your computer is assigned its normal (static) Dormnet IP address. You can verify this with the Identify My Computer tool. (If, when you reboot your computer, it still receives a TUD IP Address, you may not have waited long enough for your change form to be processed, or there may have been an error in your change form. Check the email sent to you (within a day of submitting the form) to see if there was an error. You should be able to reboot about an hour after you receive email indicating your change was successfully processed, and then be assigned your normal (static) Dormnet IP Address instead of a TUD IP Address.)

If you don't reboot your computer after submitting the change form, eventually OIT's DHCP servers will stop leasing a TUD IP Address to your computer. (This will happen within a day of succesful processing of your change form.) Your computer will lose IP service, and any IP-based software running on it may fail. You should reboot your computer, which will cause it to be assigned its normal (static) Dormnet IP Address.

If you do not submit the change form to correct your Host Database entry within seven days (fourteen days during the first eight weeks of the academic year), your machine's hardware address is identified as a TUD Camper, and is blocked from receiving any further TUD Service. (See below.)


TUD Campers

A device may only receive TUD Service for a limited number of days. After that time, the device is declared a TUD Camper, and no longer receives TUD Service.

We provide TUD service to your unregistered hardware address for seven days. This is increased to fourteen days during the first eight weeks of the academic year.

After that time, if your hardware address has not been subscribed to Dormnet (or otherwise registered as an office machine in the Host Database), it is declared a TUD Camper.

The primary reason for this time limit is that Temporary Unregistered Dormnet IP Address service is not intended to provide a substitute for subscribing to Dormnet (or registering a network-attached office machine in the Host Database). Another is that unregistered devices attached to the campus data network should be registered (or subscribed to Dormnet) promptly; unregistered devices should not be left attached to the network indefinitely. Lastly, the supply of TUD IP addresses is finite; we must ensure that this finite resource remains available to other students.

The timer begins on the day that your unregistered hardware address first requests DHCP service on Dormnet and is assigned a TUD IP Address by OIT's DHCP servers. (We clear this timer if six days (thirteen days during the first eight weeks of the academic year) go by without your device's hardware address leasing a TUD IP Address. That way, if you attach your unregistered computer to Dormnet wiring briefly on December 10 and receive TUD Service, then shut it down and/or disconnect it from the network, and then reconnect to Dormnet on January 5, you will still receive TUD Service for a seven-day period beginning January 5.) These timers may be tuned in the future.

To see if TUD IP Address Service has been discontinued for your device because it has been declared a TUD Camper, see Devices Blocked from Temporary Unregistered Dormnet IP Address Service.

Once your device is declared a TUD Camper, you no longer will have the convenience of being able to use your own unregistered computer to subscribe to Dormnet (or to register your office device in the Host Database). To subscribe to Dormnet (or register your office computer in the Host Database), you will need to visit a friend's room (or public University Computing Facility) and use a working computer there to complete the Web form (just as if TUD Service were not available). After your subscription (or office machine registration ) is successfully processed, your own computer will receive normal service, and will be removed automatically from the list of TUD Campers.


Related Resources


If You Need Additional Assistance

If you have questions or need assistance with any of the procedures in this document, please contact the OIT Support and Operations Center.


A service of OIT Network Systems
The Office of Information Technology,
Princeton University
Last Updated: December 29 2009