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Chapter 6
Circuits and Tunnels
•
6.8.2 VT Tunnels
To maximize VT matrix resources, you can tunnel VT1.5 circuits through ONS 15454 pass-through
nodes (nodes that are not a circuit source or drop). VT1.5 tunnels provide two benefits:
•
•
Figure 6-13
used by the tunnel, which can carry 28 VT1.5s. However, the tunnel does use two STS matrix ports on
each node through which it passes.
Figure 6-13 A VT1.5 tunnel
OC
Trunk
Figure 6-14
from Node 1 to Node 3. The second tunnel carries VT1.5 circuits from Node 1 to Node 4.
shows the VT1.5-mapped STS usage at each node in a ring based on protection scheme and use of VT
tunnels. In the
VT-mapped STS usage at these nodes is greater than at Nodes 5 and 6.
November 2001
In the
Figure 6-10
example, three STSs are used at the source and drop nodes and four STSs are used
at pass-through nodes. In
Figure
STSs at the pass-through nodes.
They allow you to route VT1.5 circuits through ONS 15454s that have XC cards. (VT1.5 circuits
require XCVT or XC10G cards at circuit source and drop nodes.)
When tunneled through nodes with XCVT or XC10G cards, VT1.5 tunnels do not use VT matrix
capacity, thereby freeing the VT matrix resources for other VT1.5 circuits.
shows a VT tunnel through the XCVT and XC10G matrices. No VT1.5-mapped STSs are
shows a six-node ONS 15454 ring with two VT tunnels. One tunnel carries VT1.5 circuits
Figure 6-14
example, the circuit travels west through Nodes 2, 3, and 4. Subsequently,
6-12, six STSs are used at the source and drop nodes and four
STS Matrix
VT1.5 Matrix
Cisco ONS 15454 Installation and Operations Guide
Cross-Connect Card Capacities
OC
Trunk
VT Tunnel
VT1.5
Table 6-5
6-19
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