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Adding a PVC connection to an IDQ1 fails with a message that the PVC connection limit is exceeded

Publication Date:  2012-07-25 Views:  79 Downloads:  0

Issue Description

The fault occurs to an OptiX OSN 3500 NE of V100R003. When engineers attempt to configure an ATM cross-connection for an IDQ1 on the NE, a message with an error code of 39839 is returned. The message indicates that the VC connection limit is exceeded. As a result, the configuration fails. 

Alarm Information


Handling Process

1. There is no reference to an interface-based VC connection limit.
2. Check the interface attributes on the T2000. It is found that the interface supports up to two VPIs by default. Engineers suspect that the interface can assign a maximum of two VPIs to the PVC connections by default. Coincidently, the PVC connections on the interface use two VPIs and the new PVC connection that fails to be configured has a third VPI.
3. Attempt to modify the limit. The attempt, however, fails even when the interface does not carry any ATM connection.
4. Deactivate all the ATM connections on the board, and then modify the limit to 3.
5. Add the new PVC connection. The addition succeeds. 

Root Cause

An IDQ1 supports up to 2,048 VC connections. The IDQ1, however, carries only 68 PVC connections. Therefore, the PVC connection limit of the board is not exceeded. Engineers suspect that the interface has a VC connection limit. 


An interface supports up to two VPIs by default. This limit is too low and is prone to be exceeded. Therefore, before configuring ATM services, prepare a detailed service plan. If you adapt the limit to a service after running certain services, the adaptation adversely affects the running services.