A-1
Cisco ONS 15454 Installation and Operations Guide
November 2001
APPENDIX
A

Circuit Routing

This appendix provides an in-depth explanation of ONS 15454 circuit routing and VT tunneling in mixed
protection or meshed environments, such as the one shown in Figure A-1. For circuit creation and
provisioning procedures, see Chapter 6, “Circuits and Tunnels.”
FigureA-1 Multiple protection domains

Automatic Circuit Routing

If you select automatic routing during circuit creation, Cisco Transport Controller (CTC) routes t he
circuit by dividing the entire circuit route into segments based on protection doma ins. For unp rotec ted
segments of protected circuits, CTC finds an alternate r oute to prot ect th e seg ment in a vir tual U PSR
fashion. Each path segment is a separate protection domain, and each protection domain is protected in
a specific fashion (virtual UPSR, BLSR, or 1+1).
55401
BLSR ring
1+1 1+1
1+1
Twoway Twoway
Twoway Twoway
Node 8Node 7
Node 5 Node 6
UPSR UPSR
TwowayTwoway
Node 4Node 3
Node 1 Node 2
Twoway
Node 12Node 11
Node 9 Node 10
Source
Primary path
Path Segment 1
UPSR/MESH
protected
Alternate path
Drop
Path Segment 3
BLSR protected
Path Segment 2
1+1 protected Path Segment 4
1+1 protected