Troubleshooting guide

B-4
Cisco PGW 2200 Softswitch Release 9.8 Operations, Maintenance, and Troubleshooting Guide
OL-0800-14
Appendix B Troubleshooting Cisco ITP-L Signaling
Cisco ITP-L Signaling Overview
The following sections describe connection management:
• Backhaul Statistics, page B-4
• Backhaul Congestion, page B-4
• Link Status, page B-5
Backhaul Statistics
There are two IP signaling backhaul statistics messages:
• Stats request—Cisco PGW 2200 Softswitch sends this command that to the Cisco ITP-L to request
the Cisco ITP-L to return its MTP Level 1 (MTP1) and MTP2 statistics. The request is always
processed.
The command includes an action value to specify one of three options: (1) return the statistics and
reset the statistics collection, (2) return the statistics, or (3) reset the statistics collection.
• Stats confirmation—Reply sent by the Cisco ITP-L to the Cisco PGW 2200 Softswitch in response
to the stats request command. Sample message trace:
4d10h: MTP2: rcvd Statistics Req-Send&Reset ch=0
Backhaul Congestion
The Cisco ITP-L sends an asynchronous message that includes a congestion indication to the Cisco PGW
2200 Softswitch. The message indicates that the backhaul signaling link is entering (Onset) or exiting
(Abate) congestion.
Sample message trace:
Mar 1 005616.707 MTP2 send Flow Ind ch=0 status=0x0 start congestion
The Cisco ITP-L has two possible types of congestion. Both are determined in the same manner, but
control flow in different directions.
• MTP2 signaling congestion—SS7 congestion that is detected on each SS7 link.
• Backhaul congestion—Pertains to the active Session Manager session.
The percentage of free receive buffers determines the congestion onset and abatement.
• Congestion onset—Indication that the signaling node is congested.
When the number of free receive buffers drops below 20 percent, the Cisco ITP-L sends a backhaul
congestion onset message to the Cisco PGW 2200 Softswitch. At this point, the Cisco PGW 2200
Softswitch holds all backhaul traffic that is destined for the Cisco ITP-L.
• Congestion abate—Indication that congestion has cleared.
When the number of free receive buffers rises above 40 percent, a backhaul congestion abate
message is sent from the Cisco ITP-L to the Cisco PGW 2200 Softswitch. At this point, the Cisco
PGW 2200 Softswitch resumes sending backhaul traffic that is destined for the Cisco ITP-L.