Nortel DMS-250 - Troubleshooting

3-4 D-channel handler
297-2521-106 Standard 23.01 March 2001
To run the continuity test, perform the following steps.
1 Go to the PRADCH level of the MAP terminal. The full path name is:
MAPCI;MTC;TRKS;TTP;PRADCH
2 Enter the POST command to post the DCH associated with the DS-1 to
test.
3 Ensure the D-channel is looped back at the far end. To do so, use the
LOOPBK SET command at the far-end switch.
4 Enter the CONT command with the external (EXT) option to run the
external continuity test.
5 At the far end, remove the loopback with the LOOPBK REMOVE
command.
Troubleshooting
Check the following if the DCH is in lockout (LO):
• Baud rate (field DCHRATE)—datafilled at the local end (in Table
TRKSGRP) may not match that at the far end of the DS-1 channel.
• NETWORK setting—The DMS-250 switch is considered to be the
network in the layer 2 protocol. This means that entry IFCLASS in Table
TRKSGRP must be set to NETWORK. Other datafill may cause LO.
• DS-1 channel configuration—If local parameter IFCLASS in Table
TRKSGRP is set to USER, verify the remote DS-1 channel
configuration.
• Appropriate card type—The DS-1 channel may not be supervised by the
appropriate NT6X50 DS-1 card type.
• Layer 1 setup—may be set up incorrectly. Both sides of the DS-1
channel may not be set for the same frame format (either standard or
extended).
• Frame synchronization—The DCH does not send any messages to the
far end unless it has frame synchronization with the far end. Use a
protocol analyzer to verify frame synchronization.
Also refer to “Restoring service to the DCH,” in Chapter 10, “Service
verification.”
Test equipment
A protocol analyzer can be used to monitor a DS-1 channel. Analyzers are
normally used to check layer 1. However, analyzers can be used to check
whether layer 2 HDLC flags are being transmitted. HDLC flags must be
transmitted from both sides of the DS-1 channel when operating at a rate of
64 kbit/s. This check can be made after the DCHs are ready for service.