Cisco Systems IP phone 7960 manual Components of SIP

Chapter 1 Product Overview

What is Session Initiation Protocol?

Components of SIP

SIP is a peer-to-peer protocol. The peers in a session are called User Agents (UAs). A user agent can function in one of the following roles:

•User agent client (UAC)—A client application that initiates the SIP request.

•User agent server (UAS)—A server application that contacts the user when a SIP request is received and that returns a response on behalf of the user.

Typically, a SIP end point is capable of functioning as both a UAC and a UAS, but functions only as one or the other per transaction. Whether the endpoint functions as a UAC or a UAS depends on the UA that initiated the request.

From an architecture standpoint, the physical components of a SIP network can also be grouped into two categories: clients and servers. Figure 1-1 illustrates the architecture of a SIP network.

Note In addition, the SIP servers can interact with other application services, such as Lightweght Directory Access Protocol (LDAP) servers, a database application, or an extensible markup language (XML) application. These application services provide back-end services such as directory, authentication, and billing services.

	Cisco SIP IP Phone 7960 Administrator Guide
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