Information Technology Reference
In-Depth Information
Virtual Circuit Switching
Figure 5-18
App. 1
4
5
6
7
App. 1
App. 2
App. 2
0
1
2
3
ATM Layer
ATM Switch Matrix
Port
VPI
VCI
42
3
13
In
App. 1
7
Out
4
39
101
In
3
46
App. 2
Out
7
30
6
When a cell arrives on a particular interface, the switch examines the VPI and interface number.
The switch then changes the VPI in the header of the cell and switches the cell out the appropriate
interface according to the entries in its switching table. The switch does not examine or modify
the cell's VCI.
Figure 5-19 shows two cells being switched across two VP connections in an ATM network.
Conceptually, you can think of the VP as a logical construction that aggregates VCs. Figure 5-20
shows the concept of a VP that contains multiple VCs.
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