Time-based services are sold by access time. These services have no limits placed on the data transmitted. For example, voice long distance service accounts are measured in connection time.
When it authorizes a time-based prepaid account, the account server sets the session timeout based on the current balance of the account. The account server locks the account when the session start is signaled. When the session stop is signaled, the account server updates the account based on the session time and unlocks it.
When the service stops (because the subscriber stops service on the portal, the subscriber logs out, or the session timeout expires), the account is unlocked, and its time balance is decreased by the session time.