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Voice over IP for the Cisco AS5800 3
Figure 1 Two-Stage Dial Toll Bypass
PSTN Voice-Traffic and Fax-Traffic Off load
Carriers can leverage their WAN infrastructure to off load voice and fax traffic from their congested
PSTN networks by using the Cisco AS5800 as a carrier class voice gateway. In this application,
PSTN traffic designated to be off-loaded is forwarded to a tandem switch connected to the Cisco
AS5800 gateway. The AS5800 gateway then encapsulates the off-loaded PSTN traffic into RTP
streams and routes it across the WAN.
The signaling interface between the PSTN and the Cisco AS5800 can be either Common Channel
Signaling (CCS), with SS7 terminated by the VCO-4K service point or Channel Associated
Signaling (CAS), configured in Direct Inward Dial (DID) mode. Figure 2 illustrates this application.
Cisco
gateway
Cisco
gateway
PRI
PRI
Fax
server
H.225/H.245 RTP
RAS
QoS WAN
RAS RAS
Gatekeeper
Zone A
Cisco
IP/PSTN
gateway
Cisco
IP/PSTN
gateway
PRI PRI
Digital sound
voice mail
Gatekeeper
Zone B
Cisco
gatekeeper
Cisco
gatekeeper
PSTN
13342