This Document is created based on the Frequently asked questions in the discussions, "How to Troubleshoot the Voice Call Failure in PGW & Media Gateway AS5400? ". This will help you to identify the Call failure when the Call is terminated to the PSTN Carrier using the PSTN Gateway (PGW) and the Media Gateway. Call flow is as follows
PGW <----------> MGW <-----------> PSTN Carrier
When a Call is Routed from the PGW to the PSTN Carrier thru the Media Gateways using E1/T1 carriers, calls can fail in the network due to multiple reasons like E1/T1 related issues, PSTN Operator issues and System related issues.
In order to maintain better uptime and Call Completion Ratio, we need to identify the reason for Call failures. This document covers the Troubleshooting Steps to identify the end-end call failure reasons both at the Media Gateway, PGW level and based on the reasons action can be taken.
Troubleshooting Call Failure
Troubleshooting can be done at both the MGW and PGW. Both the caputures will help analzing the end-end call failure.
1. Using Debugs Running on MGW
Step 1: Enable the Debug on the MGW
# debug voip ccapi inout
Step 2: Make one or more test calls or live calls can be captured to identify the call failure reasons.
Step 3: Capture the "debug voip ccapi inout" output
Using the "debug voip ccapi inout" you get the following Call informations in detail like, Calling Number, Called Number,
Incoming Dial-peer, Outgoing Dial-peer, Trunk group lables, ANI (A Number CLI), ANI type, NPI, Presentation and also the CAUSE VALUE.
This Cause Value well help you to identify the reason for call drop..
Step1:Take the snoop capture in the PGW and on the Wireshark apply the voip call flow
snoop -d bge0 -o /tmp/snoopop.cap
Run using the root user on PGW
Step2: Snoop output taken on bge0 / bge1 will caputure the calls thru the leg. Now Decode the output snoop file on the Wireshark and take the voip call Graph.This will provide the call with SIP-PGW-ISUP call trace
Attached the Sample Wireshark voip call flow output graph with "Call failure reason"
Step3: Using the Wireshark graph you can get the following details as shown in the snapshot attached.