Verified
ISP Organization and Access:
In general, as described in the book, ISPs tend to organize themselves as hierarchical networks with a backbone serving regional subnets and metropolitan subnets. This kind of organization is not only natural but facilitates managing the network. Each level can be managed to have certain policies based on its traffic characteristics. The organization is also easily extended to accommodate growth. However, these hierarchies are far from rigid. ISPs will have no compunction in installing lines that cut across the hierarchy to accommodate anomal ies in traffic between parts of the network or to satisfy a large customer's reliability concerns.
Access to the Internet has made a major transition in the last 10 years from dial-up to broadband. Throughout the 1980s and 1990s, using ordinary telephone lines to connect to the network was about the only means possible when one was not in the office. Starting out at 300 bps in the 1970s, the capacity of these lines quickly topped out at 56k bps by 1990. But this was clearly not going to be sufficient. As described in the book, the cable TV companies moved to offer Internet service using a cable modem operating at several Mbps incoming but less than 500K bps outgoing. The telephone companies, who had enjoyed the increase in lines during the period that everyone needed a second phone line for their computer, now complained bitterly that these calls were lasting much longer than ordinary phone calls and overloading their switches. Rather than trying to get ahead of the coming explosion of network demand, the telephone companies chose to milk as much from their installed plant as they could by going with Digital Subscriber Line (DSL), rather than moving aggressively to achieve a much higher bandwidth technology. This is very adequately described in. DSL connects the customer's phone line and an Internet link of just over 1 Mbps over the existing phone lines. However, DSL has severe distance limitations. Basic DSL requires that the wire from the switching office to the customer be less than 2.5 miles. For very high-speed DSL, the distances are under one mile. The telephone companies have also had considerable problems with "cross-talk" caused by DSL on lines that were never designed to carry such high-speed traffic.
Early forays by the cable companies into the ISP business encountered similar trouble as they learned that the minimal installation used to carry television could not support the higher reliability requirements of data. Cable companies responded by completely replacing their cable plant once, if not twice. Initially, the major complaint about the cable TV offering was that it was a shared media, rather than a dedicated one like DSL. If all of your neighbors were using the 'Net at the same time, you might experience considerably less than the advertised bandwidth. The phone companies tried to use this as an advantage-hoping the customers wouldn't notice that while their wire carried one 4K bps voice channel and a 1.5 Mbps data channel, the cable, despite being shared, was carrying 5 Mbps channel and 300+ television channels at 45Mbps each. The cable companies could throw a lot of the bandwidth at whatever demand they had with essentially a reconfiguration, while the telephone companies would have had to replace all of their wires.
If current advertising is any indicator, this competition has been resolved. The phone companies now advertise DSL as competition for dial-up and the cable companies advertise DSL as being for those people who find cable too fast.
But this is not the whole Internet access story. There are odd gaps that are still being filled. For DSL, as one can easily imagine, a significant part of the population, even in the suburbs of major metropolitan areas, lives further than 2.5 miles from a switching office. Even though the cable industry can claim that the "number of homes passed" (i.e., homes for which cable is available), is above 90%, the entertainment focus of cable has meant that cable access to the Internet was not available to businesses. The cable companies simply hadn't run cable in business districts or office parks because there were no customers there! This is now beginning to change. In major metropolitan areas, wireless is creating a revolution in access. Wi-Fi is common in homes and businesses, and is often free. It is common to walk into a local coffee shop, fast food place, or even your local car dealer and find free Internet access.
But the place where Internet access is most difficult and expensive is rural America. Here high-speed Internet access remains rare and expensive. In towns of roughly 10,000 or greater, cable may be available. Often cable companies are still very much focused on entertainment only. The local cable headend gets its outside feed by satellite with no connection to a land-based high-bandwidth line. Fixed wireless is used in some areas, but it requires line-of-sight access and is subject to interference by weather as well as terrain. Sometimes even a reasonable quality line for dial-up is hard to find in rural areas. The efforts are spotty. The federal government, through the NRECA (National Rural Electric Cooperative Association, which dates back to the New Deal), is moving to facilitate broadband in rural areas. In some cases, the broadband that they have achieved for rural communities is better than what you can get in suburban Boston. In Salem, IL, a town of 8000 about 80 miles east of St Louis in a rural farm area, the local provider, working with the NRECA, is offering voice, 8M bps symmetrical broadband and 88 channels of TV over fiber to the home for roughly $90/month. They are running a fiber ring through several towns ranging in size from a hundred people to three or four thousand. In some cases, the biggest impediment to installation is often local government inefficiency. But if you are a farmer not in line of sight of the local grain elevator (fixed wireless), it is a slow phone line at well under 56k.