Because Aspera’s algorithms are proprietary, Crowcroft says it’s impossible to tell whether fasp-AIR “is a huge win compared with other solutions.” However, he notes, if fasp-AIR includes, as its makers claim, an algorithm that can distinguish between whether packets are being dropped because a network is congested or simply because the wireless signal is weak, fasp-AIR represents a workable solution. “I don’t know how they figure out which scenario they’re in,” says Crowcroft, “and that’s the clever bit.”
Crowcroft’s own solution to this problem, first implemented with Vodafone almost a decade ago, involved configuring the proxies that connected the wireless network to the wired data and voice backbones so that they could monitor all TCP traffic. This allowed the proxy to tell individual devices when they were in a “lossy” part of the wireless coverage area. “It’s not a general solution,” says Crowcroft. “If [Aspera] has a general solution, good luck to them.”
Another wireless network company, the San Francisco-based Meraki, takes a similar approach, mapping a network’s usage and lossiness and then using that information to optimize it at the level of individual wireless routers.
“What we have found is that when it’s deployed properly, 802.11n can be pretty darn fast, even with standard TCP traffic,” says Kiren Sekar, product marketing manager at Meraki. Sekar sees Meraki’s approach as complementary to efforts like fasp-AIR.
One issue that fasp-AIR does not resolve is the limited capacity of existing networks, a problem that has affected parts of AT&T’s 3G network, largely due to overwhelming iPhone data traffic. “Networks are already over-provisioned, even without good utilization [such as what’s achievable with fasp-AIR],” says Munson. “Things like fasp-AIR will create pressure on AT&T, and I don’t know where it will lead.”
Munson imagines that in the future, wireless providers could use more sophisticated data-transfer protocols to charge more for faster deliveries of large files. But this prospect raises the specter of violating the principles of Net neutrality, which hold that all data should be treated equally by Internet service providers. BitTorrent already exploits weaknesses in TCP by opening up multiple connections at once, Munson notes.
“If one application is greedy, then there’s no way within TCP to enforce bandwidth limits [on that application],” says Munson. “When using fasp-AIR, however, you could control bandwidth on a flow-by-flow basis so one application can’t get around observing whatever caps there are.”