1.3 LAN Switching and the Hierarchical Model of Network Design
1.3.4 The access layer

The access layer is the point at which local end users are allowed into the network. This layer may also use access lists to further optimize the needs of a particular set of users. In the campus environment, access-layer functions can include the following:

  • Shared bandwidth
  • Switched bandwidth
  • MAC-layer filtering
  • Microsegmentation

In the noncampus environment, the access layer can give remote sites access to the corporate network via some wide-area technology, such as Frame Relay, ISDN, digital subscriber line (xDSL), or leased lines.

It is often mistakenly thought that the three layers (core, distribution, and access) must exist in clear and distinct physical entities, but this does not have to be the case. The layers are defined to aid successful network design and to represent functionality that must exist in a network. The way the layers are implemented depends on the needs of the network being designed. However, it is important to remember that for a network to function optimally and maintain scalability as growth occurs, hierarchy must be maintained.