There are many cases where you want to hide customer information from your upstream peers. There are three main reasons to use topology hiding (TH). The first one is that you do not want to send information that can identify your customer. The second reason is security—the less information a hacker has about your network, the safer you are. The third reason to use TH is when a client is not well-behaved and incapable to work with the Record-Route and Route headers and there are many of them in the field. Using TH tricks the user agent client in seeing the SIP proxy as an endpoint, disregarding these headers.
This is different from the older versions, where topology hiding was a part of the dialog
module, but now it is a separate module. It can run on top of the Transaction Module (TM) or the dialog
module. When using the TM module, OpenSIPS will encode the information in the Contact header. On the other hand, when using the dialog
module, you will have shorter messages.
To...