DMG 3200/3100/3000 – User Manual
Page 265 (306)
10.3.2 IP Output Redundancy
The DMG’s “always-on” intelligent redundancy software is a seamless integration between
broadcast equipment and IP networks; providing unmatched reliability of service up-time using
the minimum amount of operating resources possible.
The IP output redundancy functionality makes it possible to have multiple units with IP output
modules multicasting the same services and letting the network handle data loss.
By adding one or more redundant units with IP output modules, service outage may be
prevented; given the error is an isolated one.
Figure 10.13 - Output Redundancy
The IP output module sends services out as IP multicasts, relying on OSPF and PIM messages
to configure the network. The routers use this information to route the multicasts. The network
automatically detects the presence of more than one route and redundant packets are thrown
away by the routers before they reach the STBs.
A typical scenario is to broadcast a Digital TV service from two locations using the same
multicast destination address. The network is designed to route only one copy of the multicast
stream to the receiver. In case of a source failure, with IP output redundancy implemented, the
network should automatically switch to the spare source.
By assigning the same (Source, Group) address from the virtual segment for the “main” and
“backup” service the routers regard the multicast from the “main” and the “backup” unit as one
multicast origin from the virtual source network and will automatically chose to forward packets
only from the one with the lowest cost. This is important and must be ensured when the unit is
configured.
The output redundancy configuration is split on two locations. The global settings that applies to
an output card, and the per stream settings applied on a particular output.
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