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Cisco ONS 15600 SDH Reference Manual, Release 9.0
78-18400-01
Chapter 7 Circuits and Tunnels
7.10 Automatic Circuit Routing
The ONS 15600 SDH supports both automatic and manual J1 path trace monitoring to detect and report
the contents of the 16-byte path trace message (nonterminated) for the designated path.
•
Automatic—The receiving port assumes that the first J1 string it receives is the baseline J1 string.
•
Manual—The receiving port uses a string that you manually enter as the baseline J1 string.
Note
When J1 path trace is enabled on a two-fiber MS-SPRing circuit, CTC will not retrieve the path trace
information from the card view Maintenance > Path Trace tab.
7.10 Automatic Circuit Routing
If you select automatic routing during circuit creation, CTC routes the circuit by dividing the entire
circuit route into segments based on protection domains. For unprotected segments of circuits
provisioned as fully protected, CTC finds an alternate route to protect the segment, creating a virtual
SNCP. Each segment of a circuit path is a separate protection domain. Each protection domain is
protected in a specific protection scheme including 1+1, SNCP, or MS-SPRing.
The following list provides principles and characteristics of automatic circuit routing:
•
Circuit routing tries to use the shortest path within the user-specified or network-specified
constraints.
•
If you do not choose fully path protected during circuit creation, circuits can still contain protected
segments. Because circuit routing always selects the shortest path, one or more links and/or
segments can have some protection. CTC does not look at link protection while computing a path
for unprotected circuits.
•
Circuit routing does not use links that are down. If you want all links to be considered for routing,
do not create circuits when a link is down.
•
Circuit routing computes the shortest path when you add a new drop to an existing circuit. It tries to
find the shortest path from the new drop to any nodes on the existing circuit.
7.10.1 Bandwidth Allocation and Routing
Within a given network, CTC routes circuits on the shortest possible path between source and destination
based on the circuit attributes, such as protection and type. CTC considers using a link for the circuit
only if the link meets the following requirements:
•
The link has sufficient bandwidth to support the circuit.
•
The link does not change the protection characteristics of the path.
•
The link has the required time slots to enforce the same time slot restrictions for MS-SPRing.
If CTC cannot find a link that meets these requirements, an error appears.
ASAP STM-N ports
Yes
No
ASAP Ethernet ports
Yes
Yes
Table 7-6
ONS 15600 SDH Cards Supporting J1 Path Trace (continued)
Card
Receive
Transmit
