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iPhones fill Duke University’s Wi-Fi network with requests: Duke discovered that an iPhone is an effective denial of service attack against their Cisco access points. An assistant IT director reports to Network World that iPhones can generate spurious ARP (address resolution protocol) requests—up to 18,000 per second, effectively shutting down 12 to 30 APs at a time! ARP is used to obtain the unique media access control (MAC) layer address for an adapter when a device has the IP address. It’s used on local networks to address Ethernet frames properly. There’s no good reason for ARP to churn. In this case, the ARP request is for a non-existent IP address on the local network; Duke’s Kevin Miller speculates that the iPhone improperly caches the gateway IP address at a home network and then attempts to perform ARP on that address on Duke’s network.
From the lovely idea department, free Wi-Fi in honor of a late parent: Jonathan Plesset must love his father, who died eight years ago, because he’s carried out what I believe is a unique idea in honor of R. Jeffrey Plesset: a free Wi-Fi network in his memory. The younger Plesset and his uncle operate Shadyside Inn Suites in Pittsburgh, and the Wireless Shadyside network spans several blocks in that neighborhood. They’ve seen 1,000 users before they even announced availability. They’re using Meraki mesh equipment backed by two high-speed DSL lines, with nearly 10 Mbps of downstream bandwidth.
Posted by Glennf at July 17, 2007 9:30 AM
Categories: Wee-Fi
TrackBack URL for this entry:
https://db.isbn.nu/mt3/mt-tb.pl/4690
And it probably won't stop with Duke. To me, this is more reasoning not even bother with the iPhone. I already get all I want from my Treo, including my digital music wirelessly through the "M" app from Mercora, along with all the calendaring and visual options I need.
Posted by: Peekay21 at July 19, 2007 10:38 AM
Something is wrong with that Duke story. Look at the 802.11 protocol. There is no way excessive wireless traffic could take down an AP. What that article describes does sound like odd behavior by the iPhone, but not something that would cause an AP to shut down or reboot. This sounds like a problem with the way Cisco's WLAN controllers are handling the traffic.
(in the interest of full disclosure, I did type this on an iPhone)
[Editor's Note: I have a hard time figuring out how an iPhone could transmit 18,000 ARP requests in a second, but these folks at Duke aren't amateurs. I'm guessing two separate conditions, one on the iPhone and one in the Cisco AP code, are triggering each other.-gf]
Posted by: Rusty at July 17, 2007 3:06 PM