Troubleshooting guide

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Cisco Broadband Local Integrated Services Solution Troubleshooting Guide
OL-5169-01
Chapter 4 Troubleshooting with Call Flows
Call Flow Analysis
The call flow can fail at a number of different points. To troubleshoot this problem, perform the
following steps:
Step 1 Trap the message exchange between the Call Agent and originating or terminating MTAs and compare
it to the reference call flow. Determine whether CRCX or MDCX messages are receiving return NAK
messages. The MTAs may NAK for the following reasons:
• The Call Agent is attempting to create a connection (CRCX) for a line that already has an RTP
session active. This can happen if the Call Agent and MTA get out of sync (less likely to happen
with an MTA than a TGW). Somehow, an RTP session from a previous call was not torn down.
See the MTA troubleshooting procedures for how to verify active RTP sessions or line state.
If the MTA shows an RTP session already active on the terminating line, it may require a reset.
• The SDP parameters are not understood by the MTA. Check the SDP parameters in the trapped
message against the reference call flow.
NTFY - off-hook, xsactionID-001
ACK - xsactionID=002
RQNT - play dial tone, collect digits
with map, xsactionID=002
ACK - xsactionID=001
Call Agent
Originating MTA
NTFY - diaed digits = 732-345-0909,
xsactionID=003
ACK - xsactionID=003
CRCX, half duplex, xsaction ID=004
ACK - xsactionID=004, SDP params A
MDCX, half duplex, SDP params B,
xsactionsID=006
ACK - xsactionID=006
CRCX, full duplex, SDP params A,
ring, ringbackxsaction ID=005
ACK - xsactionID=005, SDP params B
Terminating MTA
104550
RTP Session Establishment
Ringbacktone