Cisco Systems ATA 188, ATA 186 rtpcatch Limitations, Possible Cause for Failure, Analysis, 6-19

Chapter 6 Configuring and Debugging Fax Services

Debugging the Cisco ATA 186/188 Fax Services

Possible Cause for Failure

•Cisco fax relay option is not disabled on the gateway.

Example 6-10 Fax Pass-through Mode Failure

---------- FAX Summary 1			----------
[	33]<3.200=>2.53>	Codec G729
[	39]<2.53=>3.200>	Codec G729
[	562]<2.53=>3.200>	NTE	PT 101, EVT	34: Modem Mode, ANSam tone Detected (RFC2833)
[	563]<2.53=>3.200>	NTE	PT 101, EVT	34: Modem Mode, ANSam tone Detected (RFC2833)
[	565]<2.53=>3.200>	NTE	PT 101, EVT	34: Modem Mode, ANSam tone Detected (RFC2833)
[	566]<2.53=>3.200>	Codec G711u/D
[	568]<2.53=>3.200>	NTE	PT 101, EVT	34: Modem Mode, ANSam tone Detected (RFC2833)
[	580]<3.200=>2.53>	Codec G711u/D

Analysis

•<3.200> is the originating Cisco ATA, and <2.53> is the terminating gateway.

•Both sides initially use G.729.

•<2.53> gateway sends NTE signaling packets, then upspeeds to G.711µ-law.

•<3.200>The Cisco ATA switches to G.711µ-law also, but never sends NTE signaling packets.

•Fax transmission fails because <2.53> gateway does not receive any NTE packets, and it drops the fax call.

Possible Cause for Failure

•The Cisco ATA does not support the NTE signaling method and requires that the gateways use the NSE signaling method.

rtpcatch Limitations

•rtpcatch performs optimally when analyzing capture files containing only one VoIP session.

•rtpcatch detects only G.711A, G.711µ-law, G.723, G.729, T.38, Cisco fax relay, modem pass-through with or without redundancy packets, RTCP packets and NSE packets.

•rtpcatch can handle a maximum of 20 prserv ports using the -port option.

•rtpcatch may not detect T.38 packets correctly.

Cisco ATA 186 and Cisco ATA 188 Analog Telephone Adaptor Administrator’s Guide (SCCP)

Ol-3141-01 6-19