August 01, 2008
| by Jeff Winston
In the beginning, DSL was a path out of slow dial-up speeds, then the cable companies developed HFC systems using DOCSIS for Internet. Now, Verizon claims FiOS is the fastest Internet you’ll ever need. You gotta admit, these guys are great with the acronyms, but what do they mean? And how much speed do you really need?
Though modern cable systems send their signals on fiber as far as each neighborhood, they use the older coax for the “last-mile” to each home. This is called a “hybrid-fiber-coax” or “HFC” system. On these systems, cable companies use “DOCSIS” standards to convert one (or more) of their 100+ TV channels to a 30-40Mb/s shared Internet connection, which is then shared by as many as 250 homes.
With FiOS, Verizon took a simpler but more expensive approach. Rather than stopping at the neighborhood loop, Verizon ran a fiber strand to every grouping of 2-3 homes. This provides them with much higher bandwidth and, at first glance, removes the need for shared Internet.
However, FiOS shares one limitation with its older cousin DSL. DSL was the phone company’s first attempt to provide high-speed Internet. It provided a (relatively) high-speed dedicated connection to the phone company’s central office, and at the time, phone companies ran memorable ads about cable users complaining to their neighbors about tying up the net. However, what they didn’t tell you is that the phone companies did some Internet connection-sharing of their own. Their central office contained a switch which connected all the DSL users to a single “back-haul” connection to the Internet. The capacity of the back-haul was significantly less than the sum of the capacity of all the user connections. In fact, the technical name of the switch was a “statistical multiplexer” because it dolled out limited back-haul capacity to satisfy user requests as best it could, just as the cable solution tries to provide balanced access to the limited local loop.
FiOS employs the same “statistical multiplexer” technology, doling out limited back-haul bandwidth to hundreds of users. Thus, it’s hard to say whether FiOS seems better because it has more bandwidth, or because Verizon’s penetration in a typical town is less than 30-percent, leaving much of their capacity underutilized for now.
How does this translate to surfing speed? Well, simple web-surfing rarely requires more than 2Mb/s of bandwidth (the speed of a good DSL connection or a first generation cable modem or wireless network). Games don’t often require much more (though games also require low-latency, which is another story).
Any speed above the first few Mb/s may be unnoticeable to you unless you are downloading or streaming. Both cable and FiOS provide ample speed for downloading software or streaming audio and MP3 files. In fact, it’s likely that your download speeds for these sort of files are limited by the source rather than your connection. For example, if iTunes or Adobe won’t permit an individual download to use more than 1Mb/s of their capacity, the rest of your 5Mb/s (or 15Mb/s) connection will go unused.
When does really high speed matter? In a word: Video. We all want larger, higher-resolution pictures when we stream, and really fast downloads of our favorite TV shows and movies. Unfortunately, making these wishes a reality requires more than the fastest FiOS you can buy. It requires massive servers that can simultaneously provide thousands of streams of high-speed content, and an Internet infrastructure that can provide sufficient bandwidth for all those simultaneous streams. Video support will be lacking until the entire Internet infrastructure can easily support hundreds of thousands of users downloading at speeds in excess of 1Gb/s. 1Gb/s would allow you to download an hour of regular video in a minute, or an hour of HD video in 5-10 minutes (remember when it took that long to download a song?).
Jeff Winston has been writing about home electronics since 1998. An electrical engineer, Jeff has contributed to the development of products in the computer, consumer electronics, and wireless industries. He spends his spare time with his wife, kids, and many PCs, sometimes in that order.