Cisco access point at fault for Duke's wireless issues (Was Re: [LINK] iPhones & Cisco)

[Kim Holburn]

http://www.macworld.com/news/2007/07/20/dukecisco/index.php

> Cisco access point at fault for Duke's wireless issues
>
> By Jim Dalrymple
>
> After blaming Apple’s iPhone for its wireless networking problems,  
> Duke University said earlier today that it hadn’t been able to  
> pinpoint what the problem was. Now, it has been confirmed that a  
> Cisco wireless access point was at fault for the networking issues.
>
> “Cisco worked closely with Duke and Apple to identify the source of  
> this problem, which was caused by a Cisco-based network issue,”  
> said Cisco in a statement provided to Macworld. “Cisco has provided  
> a fix that has been applied to Duke’s network and the problem has  
> not occurred since.”
>
> In a statement posted to the universities Web site late Friday  
> Tracy Futhey, Duke’s chief information officer, said that “Earlier  
> reports that this was a problem with the iPhone in particular have  
> proved to be inaccurate.”



On 2007/Jul/17, at 8:57 PM, Stephen Loosley wrote:

> iPhones flooding wireless LAN at Duke University
>
> By John Cox, Network World July 17, 2007
> <http://www.infoworld.com/article/07/07/17/iphones-flood-wireless- 
> lans_1.html?source=NLC-TB&cgd=2007-07-17>
>
> The built-in 802.11b/g adapters on several iPhones periodically  
> flood sections of the Durham, N.C., school's pervasive wireless LAN  
> with MAC address requests, temporarily knocking out anywhere from a  
> dozen to 30 wireless access points at a time.
>
> Campus network staff are talking with Cisco, the main WLAN  
> provider, and have opened a help desk ticket with Apple. But so  
> far, the precise cause of the problem remains unknown. <snip>
>
> The misbehaving iPhones flood the access points with up to 18,000  
> address requests per second, nearly 10Mbps of bandwidth, and  
> monopolizing the AP's airtime.
>
> The access points show up as "out of service." For 10 to 15  
> minutes, there's no way to communicate with them, Miller says.
>
> "When the problem occurs, we see dozens of access points in that  
> condition," Miller says. The network team began capturing wireless  
> traffic for analysis, and that's when they discovered that the  
> offending devices were iPhones. Right now, Miller says, there are  
> about 150 of the Apple devices registered on the campus WLAN.
>
> The requests are for what is, at least for Duke's network, an  
> invalid router address. Devices use ARP (Address Resolution  
> Protocol) to request the MAC address of the destination node, for  
> which it already has the IP address. When it doesn't get an answer,  
> the iPhone just keeps asking.
>
> Most of the WLAN comprises Cisco thin access points and  
> controllers. Some older autonomous Cisco Aironet access points tend  
> to uncover the flooding first, since they try to resolve the ARP  
> request themselves.
>
> But Miller's team has seen the CPU utilization on the WLAN  
> controllers spiking as they try to process the request flood passed  
> on to them in control traffic from the thin access points.
>
> "I don't believe it's a Cisco problem in any way, shape, or form,"  
> he says firmly.
>
> So far, the communication with Apple has been "one-way," Miller  
> says, with the Duke team filing the problem ticket. He says Apple  
> has told him the problem is being "escalated," but as of mid- 
> afternoon Monday, nothing substantive had been heard Apple.
> --
>
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--
Kim Holburn
IT Network & Security Consultant
Ph: +39 06 855 4294  M: +39 3494957443
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Democracy imposed from without is the severest form of tyranny.
                           -- Lloyd Biggle, Jr. Analog, Apr 1961