Working with snooper:
what happens when user initiates Lync call:
1. Invite: From address , To address & Unique Call id:
2. Static code : 180. early media: Before initiating call Lync will negotiate information about specific client through session deceptive protocol(SDP) built on top of SIP
3. SDP: Contains Session Id, Client IP, Destination IP, TCP , UDP, TRP headers.
4. First Lync client will send candidate information
5. Ack from 2nd client to 1st client saying that am available ,busy etc.
6. 2nd client will share SDP information saying that will you be able to communicate ?
7. SIP signaling will go this can be a ring , desktop sharing , IM popup.
8. When user answer the call, Other client doesn’t know the other client location it could be LAN, WAN, Internet.
9. ICE: Internet connectivity establishment. It is the protocol used to travers over firewalls.
10. If we have two firewalls between the client networks then ICE will come into the picture it will use STUN & TURN to find out how can connect these two clients
11. After exchanging the IP address and if they are belongs to same subnet then the call will be Peer-to-Peer. SIP Signaling stick to server.
12. There will be 3-5 negotiation happen between the networks i.e., possible network via Intranet, Internet, WAN, Peer-to-Peer tec. And these negation happens simultaneously.
13. There is option available to switch over to another path.
14. Early media will calculate the Least cost IP to reach or connect with client. After establish the call if early media identifies that another path is Least cost IP then it will switch over to another path.
15. Invite, ACK, SDP, ICE, STUN & TRUN, PUSH(Actual media)
16. Bye: Disconnect the session.