Cabletron Systems MMAC-Plus SFCS-1000, Configuration Manual

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1-5
Configuring PVCs
The VCI value remains unchanged when cells are switched via a through
path. For example, the through path A4|10 -> B4|20 will map cells received
on port A4 with VPI: 10 and any VCI to port B4 with VPI: 20 and the same
VCI.
Figure 1.5 - An Example of a Through Path
By definition, through paths will only switch cells in one direction; they are
unidirectional. For example, switch fabric X is configured with the through
path B1|20 -> C1|20. If a cell is received on port C1 with VPI: 20, it will not be
transmitted on port B1 with a new VPI: 20. In order for this to happen, the
through path C1|20 -> B1|20 must exist as well. Since through paths are uni-
directional, two through paths are necessary for bidirectional communication.
Figure 1.6 - Through Paths are Unidirectional
switch fabric
cell
cell
VPI: 20
VPI: 10
B4
A4
VCI: X
VCI: X
Through Path
A4|10 -> B4|20
B1|20 -> C1|20
C1|20 -> B1|20
B1 C1