The cable and telephone companies’ networks are not static; they continue to be upgraded. The various network providers are in different stages of deploying digital IP technology. They are each employing unique network architectures that build off their legacy networks and/or reflect their perceptions of the most cost- effective networks to deploy. Despite these differences, however, each of the networks has three primary components:
- the broadband “last mile” grid out to end-user customers;
- the company’s proprietary IP network, with servers for the various applications feeding into a service router that controls the flow of traffic all the way to the customer premise; and
- the company’s facilities in what has traditionally been called the internet backbone (and is sometimes referred to as the “public internet”).
The latter connects to independent applications providers, though it is also possible for independent applications providers to connect directly to a broadband network provider’s proprietary IP network.
Many independent applications providers also have substantial internet facilities. For example, in order to minimize the number of times their content must be handed off from one internet backbone provider to another when responding to an end-user query, these applications providers “cache” their content close to their customers by maintaining multiple servers scattered around the country in which they maintain frequently-updated databases. Since it is possible that congestion could cause delay at any of those handoff points, caching data at multiple servers reduces the risk of service degradation.