Software-based iPad Wi-Fi problems detailed by Princeton
A software glitch in Apple's iPad causes the device to continue using a network-assigned IP address after its lease has expired, according to data collected by Princeton University.
The Internet Protocol (IP) address of a device is a unique identifier that allows communication between devices. An IP address is assigned through a method known as Dynamic Host Configuration Protocol (DHCP), and these addresses can dynamically change over time on a private network as devices disconnect and reconnect.
A DHCP client, such as an iPad, will "lease" a unique IP address to a device on a network for a set period of time. Once that time has elapsed, the DHCP client asks the server to renew that lease. Apple's iPad, however, does not go through that renewal, according to information from the Office of Information Technology at Princeton University.
Instead, the office has found that the iPad will incorrectly continue using an IP address without renewing the lease, usually for hours. The issue is resolved when the iPad asks for a new DHCP lease, or the iPad disconnects from the network.
The information suggests it is a software issue within iPhone OS 3.2, and is likely something that Apple could repair through an update to its mobile operating system.
The problem was found to be common on Princeton's campus, with more than half -- 25 of 41 -- of all iPads demonstrating the malfunction as of April 18. If that ratio bears out on a larger scale, there are likely a huge number of iPad owners experiencing similar issues, as Apple sold more than 500,000 devices in its first week.
The report noted that some devices have demonstrated the malfunction several times, and eight devices were outright blocked from the university's network.
"When a DHCP client malfunctions this way repeatedly, Princeton blocks the device from using those campus network services which rely on the device's DHCP client respecting lease times," the IT office said. "These include our wireless services. We do this to protect other customers of those services from the disruptions caused by the malfunctioning devices."
The school has published a temporary workaround for the issue, but is working with Apple and providing them with technical data in hopes of solving the problem. That data was sent to Apple on April 7.
The IT office also noted that it has been incorrectly attributed with diagnosing the cause of Wi-Fi signal issues or connectivity issues that have been widely reported by iPad users. The university noted that information is inaccurate, as its documentation relates only to a DHCP client issue, not Wi-Fi signal or connectivity issues.
Princeton has been able to replicate the problem regularly by allowing the iPad to lock its screen before the DHCP lease renewal time, and allowing it to remain locked, with the screen off, until the DHCP lease has expired.
Princeton's workaround has users reconfigure the iPad's settings so that the screen never locks. This can be done by going to Settings, General, Auto-Lock and choosing "Never." Users must also turn off Wi-Fi before they manually lock the screen, turn the iPad completely off (rather than just locking it), or simply leave the iPad on without locking the screen.
"We recognize that this workaround represents some inconvenience to the iPad customer," the documentation reads. "We view the workaround as a temporary workaround to allow these customers the opportunity to use their devices on the campus network until there is a fix from Apple."
Soon after the iPad was introduced earlier this month, users began to report connectivity issues with the device. One of the most common problems experienced relates to rejoining a Wi-Fi network after the iPad has been restored from sleep. Apple responded by issuing a support document.
Wi-Fi is currently the only method by which users can access the Internet on their iPad. Apple revealed on Tuesday that its 3G capable model, which offers high-speed wireless data over cellular networks, will be released in the U.S. on April 30.
The Internet Protocol (IP) address of a device is a unique identifier that allows communication between devices. An IP address is assigned through a method known as Dynamic Host Configuration Protocol (DHCP), and these addresses can dynamically change over time on a private network as devices disconnect and reconnect.
A DHCP client, such as an iPad, will "lease" a unique IP address to a device on a network for a set period of time. Once that time has elapsed, the DHCP client asks the server to renew that lease. Apple's iPad, however, does not go through that renewal, according to information from the Office of Information Technology at Princeton University.
Instead, the office has found that the iPad will incorrectly continue using an IP address without renewing the lease, usually for hours. The issue is resolved when the iPad asks for a new DHCP lease, or the iPad disconnects from the network.
The information suggests it is a software issue within iPhone OS 3.2, and is likely something that Apple could repair through an update to its mobile operating system.
The problem was found to be common on Princeton's campus, with more than half -- 25 of 41 -- of all iPads demonstrating the malfunction as of April 18. If that ratio bears out on a larger scale, there are likely a huge number of iPad owners experiencing similar issues, as Apple sold more than 500,000 devices in its first week.
The report noted that some devices have demonstrated the malfunction several times, and eight devices were outright blocked from the university's network.
"When a DHCP client malfunctions this way repeatedly, Princeton blocks the device from using those campus network services which rely on the device's DHCP client respecting lease times," the IT office said. "These include our wireless services. We do this to protect other customers of those services from the disruptions caused by the malfunctioning devices."
The school has published a temporary workaround for the issue, but is working with Apple and providing them with technical data in hopes of solving the problem. That data was sent to Apple on April 7.
The IT office also noted that it has been incorrectly attributed with diagnosing the cause of Wi-Fi signal issues or connectivity issues that have been widely reported by iPad users. The university noted that information is inaccurate, as its documentation relates only to a DHCP client issue, not Wi-Fi signal or connectivity issues.
Princeton has been able to replicate the problem regularly by allowing the iPad to lock its screen before the DHCP lease renewal time, and allowing it to remain locked, with the screen off, until the DHCP lease has expired.
Princeton's workaround has users reconfigure the iPad's settings so that the screen never locks. This can be done by going to Settings, General, Auto-Lock and choosing "Never." Users must also turn off Wi-Fi before they manually lock the screen, turn the iPad completely off (rather than just locking it), or simply leave the iPad on without locking the screen.
"We recognize that this workaround represents some inconvenience to the iPad customer," the documentation reads. "We view the workaround as a temporary workaround to allow these customers the opportunity to use their devices on the campus network until there is a fix from Apple."
Soon after the iPad was introduced earlier this month, users began to report connectivity issues with the device. One of the most common problems experienced relates to rejoining a Wi-Fi network after the iPad has been restored from sleep. Apple responded by issuing a support document.
Wi-Fi is currently the only method by which users can access the Internet on their iPad. Apple revealed on Tuesday that its 3G capable model, which offers high-speed wireless data over cellular networks, will be released in the U.S. on April 30.
Comments
C
I was at Princeton for an internship last summer, and I have to say that their network is ridiculous. My MacBook Pro got banned for a couple days because of some detail of how VMWare Fusion shared the connection. Had to hack the os to fix it. Bottom line, OIT at princeton is a bunch of (oh shit, here comes godwin's law!) Nazis, and have the network locked down to a ridiculous degree. This nonsense doesn't reflect poorly on Apple, but on Princeton for having a bizarrely non-standard wifi network.
C
You have to wonder why there aren't tons of universities reporting similar problems.
A software glitch in Apple's iPad causes the device to continue using a network-assigned IP address after its lease has expired, according to data collected by Princeton University....
While it's definitely a bug in Apple's software that's at the root of it, if you read the report carefully, you can see that this is a "problem" of Princeton's own making.
20 devices (campus wide over a multi-week period), *sometimes* don't release their IP??? Seriously? And the only effect if they did absolutely *nothing* about it, would be that once in a while a user would get an "IP in use" dialogue box before they were instantly handed a valid IP?
Wow, that's totally a good reason to ban the devices campus wide.
The IT office also noted that it has been incorrectly attributed with diagnosing the cause of Wi-Fi signal issues or connectivity issues that have been widely reported by iPad users. The university noted that information is inaccurate, as its documentation relates only to a DHCP client issue, not Wi-Fi signal or connectivity issues.
And yet the title of your article is "Software-based iPad Wi-Fi problems detailed by Princeton"
I thought the issue was that it holds an IP even while in sleep? It seems more like it is by design then anything. If you haven't left the network, why give up the IP? Maybe they should expand their subnet. This would make sense as to why it isn't a problem at other universities, they thought ahead and have a higher class subnet or supernet.
except when it wakes up and still has the same IP it will cause a conflict with another device that was assigned that IP
The company I work for locks down it's network to this sort of level also. Networks within companies are pretty much mission critical, and anything that misbehaves is treated as a potential threat.
People here need to remember that just because we like Apple products does not mean Apple are infallable.
Sure, it's not Apple's fault
I saw your comment before you changed it !
I'm not saying it's not Apple's fault. But these things go both ways: This is only getting attention because it's Apple. How many other wifi enabled devices cause similar headaches for organizations and we never hear about it?
I used to have a Netgear router that had problems with all my Apple gear: It rarely handed out the reserved address. Without wasting time digging into it I couldn't tell who was to blame. The situation at Princeton involves more layers of equipment and software that could be to blame, but maybe they've done enough research to say without question that it's Apple's fault. But maybe they haven't.
Sure, it's not Apple's fault
I think I have found 5 schools that are anti-ipad. and actually none of them have banned it. just they won't be giving them away to students. And 4 of them admitted that their campus networks can't handle the potential added load which is why they won't give them away or carry them in the campus store at this time.
except when it wakes up and still has the same IP it will cause a conflict with another device that was assigned that IP
wouldn't keeping track of assigned IPs and not duplicating assignments be a part of the network not the device software.
20 devices (campus wide over a multi-week period), *sometimes* don't release their IP??? Seriously? And the only effect if they did absolutely *nothing* about it, would be that once in a while a user would get an "IP in use" dialogue box before they were instantly handed a valid IP?
The problem comes as the devices get more popular. Not giving up a DHCP lease is a big deal, but I understand why it would be done (especially on networks with ridiculously short lease periods) to conserve battery life.
I think we are coming into the dawn of the era where WiFi just stops working effectively. A single access point can't support that many users-- 50-60 on the good equipment, 20-25 on the cheap stuff. It really requires a lot more effort than it did 3-5 years ago to make things work effectively.
If your access point is doing the DHCP (bad design), your network will come to its knees quickly. If you centralize management of the access points and have reasonable address space for the DHCP it shouldn't be a major issue though.
A software glitch in Apple's iPad causes the device to continue using a network-assigned IP address after its lease has expired, according to data collected by Princeton University.
I have heard that an increasing number of universities and hospitals are banning the iPad for various reasons.
I hope that Apple or someone else can fix that.
Without university support, the dream of textbooks widely issued on the iPad becomes more distant.
And medical use? That too was thought to be a promising market.
My MacBook Pro got banned for a couple days because of some detail of how VMWare Fusion shared the connection. Had to hack the os to fix it.
You changed your MAC address, didn't you?
I think I have found 5 schools that are anti-ipad. and actually none of them have banned it..
Princeton.
GWU
Cornell.
None of them lightweights. My guess is that textbook publishers are taking notice of this trend.
wouldn't keeping track of assigned IPs and not duplicating assignments be a part of the network not the device software.
The device has responsibility NOT use an dynamic address without an active and valid lease. Duplicate IP addresses can be a nasty problem.