The access layer is the point at which
local end users are allowed into the network, as shown in the figure. This layer can
also use access control lists or filters 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
The access layer connects users into
LANs, and LANs into WAN backbones or WAN links. This approach enables designers to distribute services of devices operating at this layer.
The access layer allows logical segmentation of the network and grouping of users based on
their function. Traditionally, this
segmentation is based on organizational boundaries (such as Marketing,
Administration, or Engineering). However, from a network management
and control perspective, the main function of the access layer is to
isolate broadcast traffic to the individual workgroup or LAN. In
non-campus environments, the access layer can give remote sites access
to the corporate network via some wide-area technology, such as Frame
Relay, ISDN, or leased lines, which are covered in the following
chapters.
|