The () phenomenon occurs in a conference when the microphone is used at the same time as the speaker and the sound system emits sound that can be collected by the microphone.

In the default configuration of the firewall, traffic from a high-security network (intranet) to a low-security network (Internet) is generally not restricted, otherwise the firewall blocks.

SIP is an application layer protocol that is independent of the transport layer protocols below and can be hosted on different transport protocols, such as UDP/TCP/TLS/SCTP, currently Most commonly used TCP. ( )

Which signaling does it mainly include?

The function of the redirect server is to map the addresses in the request to zero or more new addresses, which are returned to the client.