Figure 6-14 A Six-Node Ring With Two Vt1.5 Tunnels; Table 6-5 Vt1.5-Mapped Sts Use In Figure - Cisco 15454-TCC - Network Processor Card Operation Manual

Cross-Connect Card Capacities

Figure 6-14 A six-node ring with two VT1.5 tunnels

Node 6
Node 5
Table 6-5 VT1.5-Mapped STS Use in Figure 6-6
Node VT Tunnel (BLSR)
1 4
2 0
3 2
4 2
5 0
6 0
When planning VT1.5 circuits, weigh the benefits of using tunnels with the need to maximize STS
capacity. For example, a VT1.5 tunnel between Node 1 and Node 4 passing (transparently) through
Nodes 2 and Node 3 is advantageous if a full STS is used for Node 1 – Node 4 VT1.5 traffic (that is, the
number of VT1.5 circuits between these nodes is close to 28). A VT tunnel is required if:
•
•
However, if the Node 1 – Node 4 tunnel will carry few VT1.5 circuits, creating a regular VT1.5 circuit
between Nodes 1, 2, 3, and 4 might maximize STS capacity.
When you create a VT1.5 circuit, CTC determines whether a tunnel already exists between source and
drop nodes. If a tunnel exists, CTC checks the tunnel capacity. If the capacity is sufficient, CTC routes
the circuit on the existing tunnel. If a tunnel does not exist, or if an existing tunnel does not have
Cisco ONS 15454 Installation and Operations Guide
6-20
VT1.5 source
Node 1
28 VT1.5
circuits
Node 4
VT1.5
drop
VT Tunnel (UPSR, 1+1) No VT Tunnel (BLSR)
6 4
0 4
3 4
3 2
0 0
0 0
Node 2 or Node 3 have XC cards, or
All VT1.5-mappable STSs at Node 2 and Node 3 are in use.
Node 2
28 VT1.5
circuits
Node 3
VT1.5
drop
BLSR
VT Tunnel
No VT Tunnel (UPSR) No VT Tunnel (1+1)
6
3
3
3
2
2
Chapter 6 Circuits and Tunnels
6
8
6
3
0
0
November 2001