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SIP: Session Initiation Protocol is an application layer signal control protocol,
creating, modifying and releasing one or multi participants.
Picture 4-3-9 STP server
DDNS: The user
’
s dynamic IP address is mapped to a fixed domain name resolution
service. When connecting network each time, the client
’
s procedure would pass
the host
’
s IP address to the server
’
s procedure which provides DNS service and