Regardless of their basic purpose, virtually all e-commerce sites rest on the same network structures, communication protocols, and Web standards. This infrastructure has been under development for over 30 years. This appendix briefly reviews the structures, protocols and standards underlying the millions of sites used to sell to, service, and chat with both customers and business partners. It also looks at the infrastructure of some newer network applications, including streaming media and peer-to-peer (P2P) | While P2P applications like IM enjoy widespread use, there are still some major impediments to continued growth. The first problem is performance. In a client/server application the bottleneck is the processing speed of the server. In P2P the performance of the application depends on the speed of the various network connections and the individual computers on the network. If any these connections or machines are slow, then the performance of the application can degrade. It is one thing to deal with a single server whose performance is slow. It is a harder task to deal with network links and peer computers over which you have little control. The second problem is security. For example, most IM send unencrypted text from one computer to another. This text can be easily captured and read by unauthorized parties. In the same vein, P2P file sharing and distributed processing applications usually bypass the firewall and let one machine control another. These applications are easy targets for hackers who can insert viruses or other rogue programs. Third, in an enterprise environment system administration can become a major hassle. It is very difficult to determine who has what version or who is authorized to use a particular application since many of the applications come from the outside. Finally, there are few standards in the P2P world. All of these applications rely on proprietary protocols. While there are various standards bodies at work (. the Internet Engineering Task Force has proposed the Instant Messaging Presence Protocol), none of these protocols are likely to impact P2P in the near future.
