The MCPs are the intelligence of the switch. Therefore, a customer can connect inexpensive terminals for each operator, local or remote, and have a standby as well. The DRN, under the direction of the MCP, performs the actual switching of data within the system. Data from the access units pass through the DRN, which connects each port to its destination port. The DRN is based on custom VLSI circuitry.
Specialized chips minimize the number of components, which reduces the opportunities for failure.
The DRN augments this inherent high reliability with redundant system timing cards, redundant access unit controller cards, and even redundant buses. This creates the most reliable switching engine possible. The MCP together with the standby components in the DRN performs diagnostic checks on the off-line links to the access units. In this way the ENS both decides whether to switch to the off-line link and ensures that the secondary link will be available. This figure shows the internal components of the Enterprise Network Switch.