Cisco Systems 186, 188 manual Rtpcatch Limitations, Example 7-9 Fax Pass-through Mode Failure

Chapter 7 Configuring and Debugging Fax Services

Debugging the Cisco ATA 186/188 Fax Services

Example 7-9 Fax Pass-through Mode Failure

---------- FAX Summary 1			----------
[	37]<2.53=>3.200>	Codec G723
[	39]<3.200=>2.53>	Codec G723
[	143]<3.200=>2.53>	Codec G711u/D
[	144]<3.200=>2.53>	NSE	PT 100,		EVT 192: Up-Speed, CED tone Detected
[ 1602]<3.200=>2.53>		NSE	PT 100,		EVT 192: Up-Speed, CED tone Detected
[ 1604]<2.53=>3.200>		Codec G711u/D
[ 1820]<2.53=>3.200>		NSE	PT	96,	Cisco Fax Relay
[ 1966]<2.53=>3.200>		NSE	PT	96,	Cisco Fax Relay

Analysis

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

•The Cisco ATA upspeeds to G.711µ-law and sends G.711 upspeed NSE signaling packets.

•The <2.53> gateway upspeeds to G.711µ-law and then sends Cisco fax relay event packets.

Possible Cause for Failure

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

Example 7-10 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.

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

OL-3410-01 7-19