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Chapter 13 Encryption and Scrambling
Whenever the RFGW-1 sets up a new ECM stream, it selects a connected ECMG. It
then selects the ECMG connection with the highest priority that has available ECM
capacity. If the generators have an equal priority, the one with available ECM
capacity and the least open streams will be selected. When the load on an ECMG
decreases, ECM streams will not automatically spread over equal priority ECMGs.
As soon as the channel connection with an ECMG is broken, or the ECMG runs out
of ECMG capacity, a new ECMG is selected according to the criteria above.
The ECMG working modes can be combined. For example, two generators with the
same priority (load sharing mode) can be combined with a generator that has a
lower priority (backup mode).
Note: If capacity is unavailable, the ECM stream will not be set up and the service(s)
can not be scrambled.
Examples
Load Sharing
Suppose an application has two ECMGs (IP A and B) with the same priority (prio
1), and has a capacity of 10 streams. During stream setup, the streams are spread
over the ECMGs as follows:
- IP A: streams 1, 3, 5, 7, 9
- IP B: streams 2, 4, 6, 8, 10
When the RFGW-1 stops scrambling a number of services (corresponding
streams 5, 7, and 9), no stream balancing is done.
- IP A: streams 1, 3
- IP B: streams 2, 4, 6, 8, 10
ECMG backup
In our application, ECMG IP A has priority 1 and IP B priority 2. The streams are
shared as follows:
- IP A: streams 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
- IP B: streams
If IP A fails, IP B takes over the load.
- IP A: streams
- IP B: streams 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
If IP A restores:
- IP A: streams 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
- IP B: streams
When an additional stream is required, capacity will be taken from IP B.
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