HP-UX C SIP Stack Programmer's Guide (Novembery 2007)

276 HP-UX C SIP Stack Programmer’s Guide

REFER-Subscription API

Figure 13-1 REFER Process Call Flow

The following four call-legs are involved in the complete REFER scenario:

 Call-leg A—the call-leg that sends the REFER request. This

call-leg sends the REFER using Refer-subscription A that is

created in the context of Call-leg A.

 Call-leg B—the call-leg that receives the REFER request. The

incoming REFER is handled by Refer-subscription B that is

created in the context of Call-leg B.

 Call-leg—a new call-leg created to contact the REFER target.

 Call-leg C—the referenced party call-leg.

The steps for a complete REFER process on an established call are as follows.

1. Call-legs A and B are connected.

2. To send a REFR from Call-leg A to Call-leg B, the application

creates subscription A by calling the

RvSipSubsMgrCreateSubscription() function. It initializes the

subscription with REFER parameters using the

REFER

202

NOTIFY

Subscription-state:active

SIP/2.0 100 trying

200

INVITE

200

Connected

Subscription A

Subscription B

200

ACK

NOTIFY

Subscription-state:terminated

SIP/2.0 200 Accepted