When using ‘pjsip send register’ to renew an outbound registration, it will first send an unregister (i.e. REGISTER with Expires:0) to the SIP server. I can’t see why it would do this in any given scenario.
- If the given registration had already been active, simply refreshing it by sending another REGISTER wont do any harm
- If the given registration had not already been active, then there is nothing to unregister anyway.
- If it really was my intention to first unregister and then register again, I would probably use ‘pjsip send unregister’ followed by a ‘pjsip send register’, but that’s not really an option when ‘pjsip send register’ already does the unregister.
As I see it, sending an unregister first only generates unnecessary traffic and puts more strain on the SIP servers.