5 — VoIP overview
5-6 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
GR-303/TR008 call flow
The following is a high-level description of the flow for the GR-303/TR008 type call
that is initiated by the PSTN side through a Class 5 switch.
1 After the voice gateway receives a GR-303 setup request, it sends an equivalent
H.248/Megaco connect message to the ONT. This establishes the bearer path
between the Class 5 switch and the ONT. After the bearer path is established, the
voice gateway acknowledges the GR-303 setup request to the Class 5 switch.
2 The Class 5 switch sends ABCD codes to ring the phone. The codes alternate
between ring-on and ring-off. The voice gateway forwards the codes to the ONT
transparently. During ringing, the Class 5 switch sends frequency-shift-keying
(FSK) tones along the bearer path between the first and second ring to deliver the
caller identifier information.
3 When the phone goes off-hook, the ONT reports the off-hook status using ABCD
signaling. The voice gateway forwards the signaling to the Class 5 switch. The
Class 5 switch stops sending ringing ABCD codes when it receives the off-hook
signaling, then allows the voice data to flow through the bearer path.
4 When the phone goes on-hook, the ONT reports the on-hook status using the
ABCD signaling to the voice gateway. The voice gateway forwards the signaling
to the Class 5 switch.
5 When the Class 5 switch receives the on-hook signaling, it sends a GR-303
release message to the voice gateway and disconnects the voice path. The voice
gateway in turn sends the H.248/Megaco message to the ONT to disconnect the
bearer path.
V5 mode
The G6 voice gateway supports V5.2 interfaces with the Class 5 switch. In this mode,
the voice gateway translates the V5.2 PSTN signaling messages into H.248 messages
to the ONT. These messages are used for all aspects of call control, including call
setup, call teardown, and analog interface control for ringing or off-hook/on-hook
notifications. The H.248 messages are also used to set up the bearer path and voice
connection with the ONT.
V5 call flow
The following is a high-level description of the flow for a V5 type call that is initiated
from the PSTN side through a Class 5 switch.
1 After the voice gateway receives a V5 channel allocation request, it sends an
equivalent H.248/Megaco connect message to the ONT. This establishes the
bearer path between the Class 5 switch and the ONT. After the bearer path is
established, the voice gateway acknowledges the channel allocation request to
the switch.
2 The Class 5 switch sends Establish and Signal messages to ring the phone. These
messages indicate the ringing cadence number to use. The voice gateway
translates the messages to H.248 signaling and passes the cadence number on.
The ONT then rings the phone according to the profile data in the current
configuration profile for that cadence.
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