ZXMSG 5200 (V2.0) Technical Manual
52 Confidential and Proprietary Information of ZTE CORPORATION
Bearer System
The bearer software is resident in the unit control boards of functional
units. The software consists of several unit processor modules, whose
functions are described as follows.
CNIC Bearer Subsystem
The CNIC subcard is an interface subcard between the system and IP
networks, providing an IP network side interface. The card separates the
internal network from external IP networks, and provides the system and
network traffic filter measures. The card implements firewall functions
through NAT enhancing the system security.
The CNIC also distributes RTP packets that have entered the system. The
MPR board sends the RTP packets. The RTP packets’ IP destination address
can be directly set as the destination address in the network; and the RTP
packets’ IP source address can be switched to as the uniform external IP
address of the ZXMSG 5200 system.
When the ZXMSG 5200 sends out a RTP packet, the CNIC needs to
process the RTP packet. When the system receives a RTP packet, the CNIC
will distribute the RTP packet to the corresponding MPR board according to
the packet’s RTP number. This procedure is implemented through
changing the destination IP address of the RTP packet to the internal
destination IP address of the system, and changing the MAC address of
the RTP packet to the internal MAC address of the system.
MPR Bearer Subsystem
The MPR software is resident in the bearer layer. The subsystem
implements hardware drives especially VOIP under management and
control of corresponding ICS software and the ZXMSG 5200 database,
achieving service interconnection between PSTN and IP networks.
The subsystem provides service interconnections with coding/decoding
conversion between PSTN G.711 voices and IP network
G.711/G.723.1/G.729A voices, facsimile receiving/transmitting and media
flow packing/unpacking on the IP network interface. The board also helps
process PSTN calls and associated signaling and can provide DTMF number
receiving/sending, displaying and testing Call Progress Tone, FSK
generation and conference function.
Call Connection System
Call Connection Module System Overview
Figure 16 shows an interface model of the call connection system (call
module).
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