User guide

Telephony and Multimedia Services
74 1/1551-HSC 901 35/3 Uen C 2005-12-02
Figure 52 Telephony over IP Architecture
Telephony over IP is based on an H.323 to V5.2 voice gateway (VoGW),
connected to a local exchange. H.323 signaling is used between the
subscriber’s Integrated Access Device (IAD) and the voice gateway while
V5.2 signaling is used between the voice gateway and the local exchange.
The use of V5.2 signaling enables utilization of existing class 5 services
available in the local exchange, in the same way as done in circuit switched
networks with Remote Sub Systems (RSS). The voice gateway just
prolongs the services supported by the exchange over the packet-based
network, using H.323 signaling. Consequently, with Telephony over IP it is
possible to support all class 5 services
1
.
The use of V5.2 and H.323 constitutes a very flexible architecture. The
voice gateway may be connected to an exchange physically located at a
site within an EDA Ethernet Access Domain, or to a centralized exchange
system, covering several Ethernet Access Domains with a voice gateway
each.
If the broadband network between the Ethernet Access Domains provides
QoS capabilities to support Telephony over IP, the voice gateways may
also be centralized. The location of the voice gateway and the local
1
With the single exception of Private Metering