Network access point
Network access points (NAP) provide the physical and logical means for networks to interconnect. The actual equipment present at a NAP can vary widely depending on the philosophy of the network engineers who design the NAP, the availability and cost of the equipment, and the speed and number of access links required. However, they usually share the same basic design and include the components listed below.
- A backbone network that interconnects the access nodes. Typically this network comprises bridged Ethernet or high-speed asynchronous transfer mode (ATM).
- A number of high capacity, high throughput routers that connect via the backbone, each of which aggregates customers’ network traffic onto it.
- A route server, which holds a copy of the Internet routing table makes routing information available to the backbone routers as they need it.
- Associated equipment, such as channel service unit/data service units (CSU/DSU), wiring hubs, power supplies, etc.
Internet Architecture: The NAPs
The Chicago, San Francisco, Washington, D.C., and New York (Pennsauken, NJ) network access points (NAP) established as part of the 1994–1995 National Science Foundation (NSF) network reorganization remain the most important points of network interconnection. In recent years, though, providers have pushed ahead with the creation of their own NAPs. All that is really necessary to establish a NAP, after all, is the willingness of a number of access providers to interconnect their networks at some physical location.
So what distinguishes a NAP from just any connection between providers? The answer is little, if anything. But, typically a NAP is established when at least some of the following conditions are met.
- A large number of providers connect to each other at the same location.
- The connection is made through a high-speed switching system. Often this system is as simple as a number of high-speed routers connected via an asynchronous transfer mode (ATM) or high-speed LAN backbone.
- Corporate and other large customers of the ISPs connect to them via this site.
- Perhaps most importantly, the ISPs themselves announce the creation of the NAP with the intention of promoting it as an interconnection point in the future.
The visual shows the four NSF NAPs (identified by their original owners), as well as another site established by MFS, called MAE-West. Traditionally, “the NAPs” refers to the original four points, but sometimes includes others. Currently there are hundreds of locations that meet at least some of the above criteria, and therefore call themselves NAPs as well.