The most insightful portion of the essay lies in the always-exciting discussion of revenue streams for the service providers. As the applications are separating themselves from the pipe and will continue to do so, service providers are likely to explore different pricing mechanisms for their services. It'll happen with the RBOCs because of voice, and the MSOs won't be too far behind as video becomes IP.Video P2P traffic is inherently more symmetric than the Web and rich media broadcast content that most broadband networks have been optimized for, and its usage patterns differ from the baseline in other significant respects.
Some network traffic flows roughly equally in both directions. The telephone network as a whole, for example, has this characteristic. On average, people make and receive about the same number of calls. In local cases, though, this symmetry does not hold. Ticket agencies, for example, receive many more calls than they make, while outbound telemarketing call centers have the reverse pattern.
When networks designed for one type of traffic encounter a new distribution, they can experience economic and technical problems. Thus, when local phone companies first experienced high levels of dial- up Internet access in the mid-1990s, they complained that the increased number of long, outbound calls to ISPs forced them to make unplanned investments to add ports to their local switches.
Though dial- up Internet connections are exclusively upstream from the perspective of the phone network – people call their ISP, not the reverse – Internet access traffic itself has historically been primarily downstream. Users of the Web request content from Websites. They rarely operate servers which send content out to others. The asymmetry of Internet traffic traditionally tended to increase as file sizes grew. Text based emails are largely symmetric, static graphics are largely send downstream from Websites, and rich media content is almost always received in one-way broadcast mode.
Broadband access providers have architected their networks to take advantage of this asymmetry. Asymmetric access networks allow providers to save on capacity, improving downstream performance at a lower cost. One of the fundamental properties of information theory is Shannon’s Law, which postulates a maximum information carrying capacity for a given communications link.
Introducing asymmetry allows communication in one direction to exceed the apparent Shannon’s Law limit. Moreover, asymmetric networks simply do not require the same investment in upstream capacity.
This distinction is particularly important for cable modem systems. Cable networks were built for television, which is almost exclusively a downstream application. Cable
operators have had to spend money upgrading their networks for upstream capacity, which still comes at a premium.Asymmetric broadband networks offer other benefits to access providers. They may be able to charge premium rates for specialized video, audio, and gaming content that flows down from their servers to their users. Even if they cannot, they have much more control for traffic engineering purposes over traffic that originates in their network or flows in through a limited number of peering points, compared to that originating at a large number of individual users’ edge machines.
With P2P traffic, every user is potentially an originator as well as a recipient of content.
Classifying services at the application level potentially allows broadband providers to offer differentiated value-added services and enhance security. It also could be used to identify and either block or degrade third-party VoIP traffic. Though major broadband providers have so far disclaimed any intention of doing so, they may have economic incentives to tilt the scales in favor of their own voice offerings, absent regulation to the contrary.The next 3-10 years are going to be exciting from many of us, and extremely challenging for a few of us as well. This is going to be big. Viva la IP revolucion!
