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
To troubleshoot the problems in this scenario, perform the following steps:
Step 1 Trap the message exchange between the Call Agent, the originating MTA, and trunk gateway, and verify
it against 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 trunk gateway get out of sync. Somehow, an
RTP session from a previous call was not torn down, though the Call Agent thinks the trunk endpoint
is idle. (See your trunk gateway’s troubleshooting procedures for verifying active RTP sessions or
trunk state.) If the trunk gateway that an RTP session already active on the trunk, it may be necessary
to reset the individual trunk state.
• The SDP parameters are not understood by the TGW. 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
PSTN Switch
104551
RTP Session Establishment
Ringbacktone
SS7 Initial Address
Message (IAM)
SS7 Address Complete
Message (ACM)