About Registration Cache Additions Modifications and Removals

When it receives a REGISTER message with new contact information for a user, the Oracle® Enterprise Session Border Controller considers it an addition to the cache and augments the number of registration cache entries. Then the Oracle® Enterprise Session Border Controller forwards the message to the registrar, and—when and only when the registrar returns both the original and new contacts in the 200 OK—the registration cache count stays the same. However, if the registrar returns only the new contact (making this a case of modification), then the Oracle® Enterprise Session Border Controller removes the old contact information and subtracts accordingly from the number of registration cache entries.

Thus the Oracle® Enterprise Session Border Controller does not know whether a REGISTER might result in an addition or a modification until it receives a response from the registrar. For this reason, the Oracle® Enterprise Session Border Controller first assumes it is to make an addition, and then updates the registration cache and count when it has the necessary information from the registrar.

The registration cache count does not reflect removals during the rejection check because the Oracle® Enterprise Session Border Controller ignores registration messages or expires headers with their expires values set to zero when it counts new entries. The fact that removals take place after additions and modifications means that messages which remove one contact while adding another might be rejected. That is, the addition might exceed the registration cache limit before any removal can take place to make room for it.