Avia Tablet Accessory Avaya Custom Edition Uživatelský manuál stáhnout pdf (Strana 25)

Agents and Servers. These components can take the form of

an additional software program (on a laptop computer, for

example), or as an inherent part of a mobile device such as a

PDA or cell phone.

Using user agents

User agents (UAs) are applications in SIP endpoints (such

as a SIP phone, cell phone, PDA, or workstation, as shown

in Figure 2-1) that interface between the user and the SIP

network. A user agent can act as either a client or a server.

When sending SIP messages, the UA acts as a user agent client

(UAC), and when receiving messages, it acts as a user agent

server (UAS). A back-to-back user agent (B2BUA) is an applica-

tion that acts as an intermediary between two parties, but

appears as an endpoint to both parties — like a middleman.

It serves as both UAS and UAC simultaneously to process ses-

sion requests.

Figure 2-1: Some typical SIP user agents.

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Softphone

PDA

SIP Phone

Dual-Mode

Mobile Phone

Instant Messaging

SIP Communications For Dummies, Avaya Custom Edition

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Avia Tablet Accessory Avaya Custom Edition Uživatelský manuál Strana 25