Internet Communications Using SIP : Delivering VoIP and Multimedia Services With Session Initiation Protocol {2Nd Ed.}

Figure 19.5 Call flow for collecting DTMF digits

1 INVITE

CALLER CONTROLLER DTMF Collector CALLED

3 200 OK

5 INVITE

1 - The controller calls

the DTMF collector

first to get the SDP

connection data.

2 - SDP from DTMF

collector in step 3 is

sent to caller in

re-INVITE in step 11.

A second media

stream is established

in step 14 from caller

to DTMF collector.

3 - DTMF digits

collected by the DTMF

collector are sent to

the controller via

HTTP in the GET

request

9 SIP ACK

7 200 OK

2 INVITE

4 ACK

10 RTP audio

11 re-INVITE

12 200 OK

16 HTTP OK

14 RTP DTMF digits

13 ACK

15 HTTP GET

8 ACK

6 200 OK

SIP Component Services 331