ZyXEL Communications MSC1000G Series, Руководство пользователя

Страница: 605 / 1168

Chapter 16 VoIP
Management Switch Card User’s Guide
605
Figure 409
H.248 Media Gateway SC and MC
An MC sends line events (like “onhook” and “offhook” to the SC. The SC sends signal events (like
ring, metering pulse, and various tones) to the MCs. To ensure quality of service, you can use IEEE
802.1p and/or DSCP for the messages the SC sends to the MGC. These are generally H.248
protocol messages with a higher priority than other regular packets.
An MC packetizes audio signals from the subscriber line into RTP packets. The SC queries the MGC
and tells the MC the destination media gateway for the RTP packets. The MC terminates RTP
packets from other media gateways and converts them into audio signals for the subscriber line.
You can set the IEEE 802.1p and/or DSCP priority for the RTP packets the MC sends. At the end of
each RTP session the MSC sends a statistics report of the RTP stream to the MGC.
You can use a backup SC card for higher reliability. If the active SC goes down, the standby SC
automatically takes over. Active calls continue, although calls that the active SC was setting up are
discarded and the users must initiate them again.
C
MC
MGC 1
ANALOG
IP NETWORK
SC
Other MG
H.248 signaling
Line events
Signal events
RTP payload
ANALOG
MGC 2