Despite Cisco Systems Inc.’s rollout last June of so-called fast roaming capabilities for wireless LANs, some IT managers said they have switched to WLAN equipment from other vendors because of concerns about quality of service on wireless phone calls.
Cisco’s WLAN architecture is built around smart access points, which contain much of the intelligence that controls handoffs as users roam from one location to another. That requires wireless devices to reauthenticate and obtain new IP addresses from back-end servers as they’re moved — a process that can disrupt voice communications, according to users and analysts.
For example, Pacific Sunwear of California Inc. had problems supporting wireless voice-over-IP calls on a Cisco 802.11b WLAN that was installed to support voice and data traffic at its new headquarters in Anaheim, Calif., said Ron Ehlers, the clothing retailer’s vice-president of information services.
Pacific Sunwear equipped 30 employees with wireless VoIP phones from SpectraLink Corp. after it opened the building last year. But Ehlers said that he soon began receiving complaints about dropped calls when users roamed from room to room, especially in areas where there was heavy data traffic.
Roaming Improves
Late last year, Ehlers called in Meru Networks Inc., a Sunnyvale, Calif.-based start-up that sells a central WLAN controller. He said the voice roaming problems went away immediately after Meru installed its equipment. Ehlers replaced all 16 of his Cisco access points with Meru’s controller and access point technology early this year.
Sirf Technology Inc., a San Jose-based maker of chip sets for Global Positioning System devices, experienced similar problems with SpectraLink and Cisco 7920 VoIP phones operating over Cisco’s WLAN access points, said Ian Chronister, Sirf’s MIS manager.
Chronister also replaced the Cisco infrastructure with a Meru WLAN — a switch announced in December. It was an unusual move for Sirf “because we could be a poster child for Cisco,” he said, noting that his networks are otherwise all-Cisco.
Ron Seide, WLAN product-line manager at Cisco, said the company recognizes that VoIP places more demands on its WLAN technology than data sessions, which can tolerate gaps of one or two seconds as a user moves from one access point to another in a network.
Last June, Cisco introduced what it calls fast, secure roaming features to its IOS internetworking software. Fast roaming is supported within a single access point that acts as a master device for wireless domain services, allowing quick authentication as users roam, Seide said.
Cisco also detailed a longer-term WLAN upgrade strategy called Structured Wireless-Aware Network, which will eventually support central management of wireless devices from its line of wired switches and routers. Seide said he wasn’t familiar with the installations at Pacific Sunwear or Sirf. But he added that he thinks they could have resolved their VoIP problems by doing thorough site surveys to guide the placement of access points and by using Cisco’s fast roaming software.
Brad Noblet, director of technical services at Dartmouth College in Hanover, N.H., said he rectified voice call handoff problems on a campus WLAN by using the fast roaming functionality. But Noblet said he doesn’t think Cisco’s WLAN architecture can scale enough to support a planned expansion that will provide wireless IP phone service to all 4,000 Dartmouth students, plus most faculty and administrative staffers.
Dartmouth has tapped Aruba Wireless Networks Inc. to provide the college with its switch-based WLAN technology and about 1,000 access points, Noblet said.
