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Collaboration, Voice & AV · Intermediate

SIP Proxy Server

A SIP intermediary that receives requests and forwards them toward the destination, applying routing and policy.

Definition

A proxy server routes SIP requests on behalf of user agents, often after consulting a location service populated by registrations. Stateless proxies forward each message independently, while stateful proxies track transactions, and record-routing keeps the proxy in the path for later requests in the dialog. Unlike a B2BUA, a proxy does not terminate the dialog or originate new requests.

Example

Cisco Unified SIP Proxy routes calls between several CUCM clusters and CUBE based on dialed prefixes.

Exam tip

A proxy forwards requests; a B2BUA terminates and regenerates them, which is why CUCM and CUBE are B2BUAs.

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