What does this TCPDUMP result mean on a FreePBX server?

Question

freepbx

ran tcpdump on the FreePBX server and there I saw the following:

........SUBSCRIBE sip:[email protected]адрес моего сервера.ru SIP/2.0
Via: SIP/2.0/UDP 11.12.13.19:65219;rport;branch=z9hG4bKPjc44ee5be26c84c42a35dc0e
daf9bade6
Max-Forwards: 70
From: "Registratura-04" <sip:[email protected]адрес моего сервера.ru>;tag=d7205e99f92740e1ade6
402043f55445
To: <sip:[email protected]адрес моего сервера.ru>
Contact: "Registratura-04" <sip:[email protected]:65219;ob>
Call-ID: 00ea6570f17f4a698715732701c793fd
CSeq: 19895 SUBSCRIBE
Event: presence
Expires: 600
Supported: replaces, 100rel, timer, norefersub
Accept: application/pidf+xml, application/xpidf+xml
Allow-Events: presence, message-summary, refer
User-Agent: MicroSIP/3.19.8
Content-Length:  0

bϴ\i6...........%".....)%B...E`[email protected]
...
......m3.SIP/2.0 401 Unauthorized
Via: SIP/2.0/UDP 11.12.13.19:65219;branch=z9hG4bKPjc44ee5be26c84c42a35dc0edaf9ba

Please explain what SUBSCRIBE means sip:[email protected] server.ru address Should I worry about this?
PS on a .19 computer, no one is dialing anyone. Oh, and also, these requests only appear when the browser is open