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Cisco ONS 15454 SDH Troubleshooting Guide, R5.0
July 2005
Chapter 1 General Troubleshooting
1.6 Troubleshooting DWDM Circuit Paths With ITU-T G.709 Monitoring
The entire circuit path has now passed its comprehensive series of loopback tests. This circuit qualifies
to carry live traffic.
1.6 Troubleshooting DWDM Circuit Paths With ITU-T G.709
Monitoring
This section provides an overview of the optical transport network (OTN) specified in ITU-T G.709
Network Node Interface for the Optical Transport Network, and provides troubleshooting procedures for
DWDM circuit paths in the ITU-T G.709 OTN using performance monitoring and threshold crossing
alerts (TCAs).
1.6.1 ITU-T G.709 Monitoring in Optical Transport Networks
ITU-T Recommendation G.709 is part of a suite of recommendations covering the full functionality of
an OTN. ITU-T G.709 takes single-wavelength SDH technology a step further by enabling transparent
optical wavelength-based networks. It adds extra overhead to existing SDH, Ethernet, or asynchronous
transfer mode (ATM) bit streams for performance management and improvement.
ITU-T G.709 adds the operations, administration, maintenance, and provisioning (OAM&P)
functionality of SONET/SDH to DWDM optical networks.
Like traditional SDH networks, ITU-T G.709 optical networks have a layered design (Figure 1-40). This
structure enables localized monitoring that helps you isolate and troubleshoot network problems.
Figure 1-40 Optical Transport Network Layers
1.6.2 Optical Channel Layer
The optical channel (OCh) layer is the outermost part of the OTN and spans from client to client. The
optical channel is built as follows:
1. A client signal such as SDH, Gigabit Ethernet, IP, ATM, fiber channel, or enterprise system
connection (ESCON) is mapped to a client payload area and combined with an overhead to create
the optical channel payload unit (OPUk).
OCh
OCh Layer
OMS
OTS OTS OTS
124067
OMS Layer
OTS Layer
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