There are two types of SIP proxy servers:
1) Stateless proxy server: A simple forwarding function that selects the destination and route of forwarding by requesting information. Messages are discarded as soon as they are forwarded.
2) Stateful proxy server: records incoming requests and sent request information (especially transaction status) and uses this to control future message processing. It also has a fork function for messages.
Now, VoIP phones are increasingly popular with homes, industries, offices, and businesses. VoIP phone, the call quality is stable and completely free, the media is rich in functions and easy to manage. How to set up a voip phone? I will tell you one by one.