A system and method for uniquely identifying an SIP device extends the SIP
communications protocol with an end point identifier, carried for example
in the header of an SIP transmission. The end point identifier is useful
for routing, registration, subscription, and authentication. The end
point (device) of a given user epid can be uniquely identified by
creating a key from an epid and a user's address-of-record (URI). This in
turn enables improved connection management and security association
management when the connections/IP addresses are transient, such as when
HTTPS tunneling is used.