In this chapter, you learned how to configure OpenSIPS to forward calls to a gateway. It is important to take care of the security. Using the permissions
module, you can allow the gateways to bypass the digest authentication and get access by validating its IP address only. The group
module is important to control the access from the UACs, and in order to route your calls to the PSTN gateways, the dynamic routing module is a very powerful and flexible tool. You should also prevent subscribers from sending a REFER method to the PSTN gateways to avoid fraud.
From the point you connect to PSTN, take a lot of care about toll fraud. I recommend that you have a security specialist verifying your environment periodically. Often, analyze your call detail records to detect abnormal activity.
In the next chapter, we will cover the dialog
module. Here, you will learn how to control the dialogs, count calls per user, disconnect calls exceeding a timeout, and more.