On the Ports page, you specify the communications ports that the Active Directory Lightweight Directory Services (AD LDS) instance will use to communicate with directory-enabled applications. Directory-enabled applications locate an AD LDS instance by using a combination of the name of the computer on which the AD LDS instance is running and a communication port number. An AD LDS instance can communicate using Lightweight Directory Access Protocol (LDAP) or Secure Sockets Layer (SSL). You must provide a port number for each.
If you are not sure what communication port numbers to use, accept the default values.