With IPHost Network Monitor you can run simple snmp requests against a Nortel device in your network.
x25DteLcnInInterruptPackets
x25 Dte Logical Channel Number In Interrupt Packets
1.3.6.1.4.1.562.2.4.1.90.4.13.1.6
This attribute counts the number of interrupt packets received from the link.
Back to Nortel-Magellan-Passport-X25DteMIB MIB page.
IPHost Network monitor allows you to monitor x25DteLcnInInterruptPackets on Allied Telesis device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Nortel modems right now.