5 — VoIP overview
5-8 November 2013 Alcatel-Lucent 7302 ISAM | 7330 ISAM FTTN | 7360 ISAM FX ONT R04.06.02
Edition 01 3FE 55873 AAAA TCZZA
ONT Product Information Guide
Figure 5-2 Softswitch network topology
The ONT supports redundant softswitch servers. When operating in a redundant
configuration, the ONT contacts the secondary server if the primary server is lost.
Softswitch call flow
The call flow associated with a conventional softswitch for traffic originating from
the ONT is generally the same as specified in the IETF/ITU-T H.248/Megaco call
flow.
One fundamental difference between the gateway mode and the softswitch mode is
that, in the softswitch mode, the Megaco signaling protocol instructs the ONT in
terms of playing tones, and on-hook and off-hook event through out-of-band
signaling messages.
PSTN
gateway
Softswitch
Signaling
channel
BRAS
IP cloud
PSTN
cloud
L2
Ethernet
cloud
OLT
POTS
phone
IP phone
POTS
phone
IP
phone
RJ11
RJ45
Class 5 PSTN
switch
18189
ONT
Server (s) DHCP,
application, FTP etc.,
Management channel
Note — To implement redundant softswitch servers, you must use the
DHCP option 120 for a second softswitch IP address.
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