Media Links MD8000 Series, Руководство по эксплуатации

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MD8000 Rev. H MD8000 Series Transport System Summary 2.13
Class B
The Class B mode runs under the “ Dual SWCNT/Dual Trunk ” configuration. Figure 2-7
illustrates the flow of packets.
Figure 2-7: Class B Mode Of Operation
In the originating System (#1), the Channel Service board duplicates the encapsulated video
signal with the different MAC addresses “M1-1” and “M1-2” and delivers the same to both the
“ACT” and “STB” SWCNT boards.(See
Dual SWCNT Operation, page 2.33 for Dual SWCNT
operation.) Both SWCNT boards switch the “M1-1” packets to the “Line 1” Trunk board and
the “M1-2” packets to the “Line 2” Trunk board. Both Trunk boards transmit out to the network
packets arrived through the “ACT” SWCNT board and discard all the packets from the “STB”
SWCNT board. The Trunk board continuously monitors the “ACT” input-packet flow and if it
drops off for a certain period of time, the board automatically switches to use the packets from
the “STB” stream.
In the receiving System (#2), both Trunk boards duplicate the received packets and deliver
the same to both #1 (ACT) and #2 (STB) SWCNT boards. The #1 SWCNT board passes all
the received packets to the “Line 1” input of the destination Channel Service board and the
#2 SWCNT board passes all the received packets to the “Line 2” input of the same destination
Channel Service board. The “Line Sel” function of the Channel Service board rejects the input
from the “STB” SWCNT and duplicates the stream using the input from the “ACT” SWCNT for
the following “Filtering” process to pass the “M1-1” packets for Line 1 and “M1-2” packets for
Line 2. The output video signal is reproduced from either the Line 1 or 2 stream selected by
the Hitless switching module.