Chapter 45 VoIP
IES-1248-51V User’s Guide
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45.1.5 RTP
When you make a VoIP call using H.248, the RTP (Real time Transport Protocol) is
used to handle voice data transfer. See RFC 1889 for details on RTP.
45.1.6 Voice Coding
A codec (coder/decoder) codes analog voice signals into digital signals and
decodes the digital signals back into voice signals. The IES-1248-51V supports the
following codecs.
MGC --> MG1 MGC modifies RTP Termination, providing
information on how to send RTP stream to MG2.
Modify
MGC --> MG1 MGC modifies Analog Termination on MG1 to
send ringing tone to phone A.
Modify
MG1 --> Phone A MG1 send ringing tone to phone A. N/A
MG2 --> Phone B MG2 rings phone B. N/A
Phone B --> MG2 User of phone B picks up. MG2 detects off-hook. N/A
MG2 --> MGC MG2 reports to MGC that phone B is off-hook. Notify
MGC --> MG1 MGC modifies analog Termination on MG1 to
stop playing ringing tone to phone A.
Modify
MGC --> MG2 MGC modifies analog Termination on MG2 to
stop ringing phone B.
Modify
MGC --> MG1 MGC modifies RTP Termination on MG1 to
transfer media with RTP Termination on MG2.
Modify
MGC --> MG2 MGC modifies RTP Termination on MG2 to
transfer media with RTP Termination on MG1.
Modify
Phone A --> MG1 User of phone A finishes call and replaces
receiver on hook.
N/A
MG1 --> MGC MG1 reports on-hook to MGC. Notify
MGC --> MG1 MGC removes MG1’s RTP Termination from its
Context. The RTP Termination is ephemeral and
is destroyed.
Subtract
MGC --> MG1 MGC removes phone A’s analog Termination
from its Context. The Context is destroyed. The
analog Termination is physical and returns to
the Null Context.
Subtract
MGC --> MG2 MGC removes MG2’s RTP Termination from its
Context. The RTP Termination is ephemeral and
is destroyed.
Subtract
MGC --> MG2 MGC removes phone B’s analog Termination
from its Context. The Context is destroyed. The
analog Termination is physical and returns to
the Null Context.
Subtract
Table 111 H.248/MEGACO Call Procedure Example
DIRECTION ACTION COMMAND
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