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Cisco ATA 186 and Cisco ATA 188 Analog Telephone Adaptor Administrator’s Guide for MGCP (version 3.0)
OL-4803-01
Chapter 6 Configuring and Debugging Fax Services
Debugging the Cisco ATA 186/188 Fax Services
Step 3 At the DOS prompt of this directory, enter the following command:
:>rtpcatch <cap_file> [<prefix>] [options]
–
<cap_file> is the NAI Sniffer capture file.
–
<prefix> is the prefix prepended to the output filenames.
Output Files
The output files of rtpcatch include a summary file and audio stream files.
The summary file is <prefix>.sum if <prefix> is specified, otherwise it is file.sum.
Stream files are labeled with an integer tag beginning with 00. Stream files are also tagged with the
extension pcm for G.711A/G.711µ-law, 723 for G723.1, 729 for G729, t38 for T.38, and cfr for Cisco
Fax Relay.
Options
rtpcatch options include:
• -fax—to output the fax events for a connection.
The output includes "FAX summary 1" as the interleaved event list for all directions, and "FAX
summary 2" as the event list for each direction. The reported events include voice codec change,
NSE signalling, and fax relay events.
• -port <port0> <port1>—to discard any packets sent from/to this port.
If the NAI Sniffer capture file includes Cisco ATA prserv packets, these packets can interfere with
rtpcatch analysis. Some prserv packets might be interpreted as NTE or NSE events. To prevent
such interference, you can either disable debugging output on the Cisco ATA (do this by setting the
Nprintf configuration parameter to 0), configure your NAI Sniffer to filter out the prserv packets,
or run rtpcatch with the -port options.
Note rtpcatch works best for analyzing a single VoIP session. Command-line options can be entered in any
order.
Example of rtpcatch
The section contains an example of using rtpcatch and includes an explanation of its output:
Output
C:\>rtpcatch faxpassthru -fax
[ 25]open file: 00.723, (G723) 2.213:10000 => 2.116:10002
[ 26]open file: 01.723, (G723) 2.116:10002 => 2.213:10000
[ 29] <00> 1 silence pkts from TS 1760 (seq# 3)
[ 42] <00> 2 silence pkts from TS 4400 (seq# 9)
[ 47] <00> 2 silence pkts from TS 5600 (seq# 11)
[ 55] <00> 2 silence pkts from TS 7760 (seq# 15)
[ 101]open file: 02.pcm, (G711u) 2.116:10002 => 2.213:10000
[ 106] <02> 2 lost pkts from seq# 39
[ 107]open file: 03.pcm, (G711u) 2.213:10000 => 2.116:10002
[ 110] <03> 1 silence pkts from TS 19440 (seq# 41)