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.
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