A SERVICE OF

logo

Chapter 9 Voice
P-2812HNU-51c User’s Guide
220
to the IP address that it received back from the redirect server. Redirect servers
do not initiate SIP requests.
In the following example, you want to use client device A to call someone who is
using client device C.
1 Client device A sends a call invitation for C to the SIP redirect server (B).
2 The SIP redirect server sends the invitation back to A with C’s IP address (or
domain name).
3 Client device A then sends the call invitation to client device C.
Figure 98 SIP Redirect Server
SIP Register Server
A SIP register server maintains a database of SIP identity-to-IP address (or
domain name) mapping. The register server checks your user name and password
when you register.
RTP
When you make a VoIP call using SIP, the RTP (Real time Transport Protocol) is
used to handle voice data transfer. See RFC 1889 for details on RTP.