As a retirement/lockdown project, I have written a series of articles exploring when and how you should fix the address values sent in some SIP headers. These articles will be ideal for beginners to use as a tutorial explaining some of the tricky basics of the SIP protocol, but also for more experienced VoIP solution designers who want to understand how OpenSIPS handles tricky problems with NAT and how it conforms to International SIP standards.
They say it’s good to learn something new as an antidote to lockdown blues, so I hope these articles will give your brain a good workout: