SIP User Agent registration on <a href="https://en.wikipedia.org/wiki/Session_Initiation_Protocol" class="extiw" title="en:Session Initiation Protocol">SIP</a> Registrar with authentification by login
<a href="//commons.wikimedia.org/wiki/User:Korolev_Alexandr" title="User:Korolev Alexandr">Korolev Alexandr</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>