User Agent
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... sessions between users. SIP end systems are called
user agents, and intermediate elements are known as proxy servers. A
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... next hop element, called a server (it can be a proxy or a user
agent). Such processing could, in principle, occur at every hop
between elements.
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... client usage. We assume that the client is stateful
(either a User Agent Client (UAC) or a stateful proxy). Stateless ...