A server map has fewer elements than a session table to allow Internet users to initiate connections in NAT and ASPF implementations.
A server map records the connection status of special services with a few key elements.
If you use strict security policies, connections can be initiated only from intranets. However, if NAT or ASPF is implemented, users on the Internet cannot initiate connections to an intranet server due to strict restrictions on the session table 7-tuple. A server map can be utilized to resolve this issue.