[asterisk-users] T38 negotiation, the last step !

[Steve Underwood]

Klaus Darilion wrote:
> Xavier Cardil schrieb:
>   
>> Hi, I've managed to get HYLAFAX---->T38MODEM----->
>> ASTERISK---->CISCOAS5400 working, but when they are negotiating asterisk 
>> drops a message telling "Unknown RTP codec 96 received from gateway" Do 
>> somebody know how to fix it ? 
>>
>> Thank you !
>>
>>
>>
>> << [ TYPE: Control (4) SUBCLASS: Ringing (3) ] [SIP/GWCISCO5400O-600bfcc8]
>> << [ TYPE: Control (4) SUBCLASS: Answer (4) ] [SIP/GWCISCO5400O-600bfcc8]
>> << [ TYPE: Null Frame (5) SUBCLASS: N/A (0) ] [SIP/GWCISCO5400O-600bfcc8]
>> << [ TYPE: Null Frame (5) SUBCLASS: N/A (0) ] [SIP/GWCISCO5400O-600bfcc8]
>> << [ TYPE: Control (4) SUBCLASS: T38/Negotiation Requested (19) ] 
>> [SIP/GWCISCO5400O-600bfcc8]
>> << [ TYPE: Null Frame (5) SUBCLASS: N/A (0) ] [SIP/GWCISCO5400O-600bfcc8]
>> [Jul 16 17:50:39] NOTICE[2736]: rtp.c:1739 ast_rtp_read: Unknown RTP 
>> codec 96 received from '192.168.3.163'
>>     
>
> Is '192.168.3.163' the Cisco GW? If yes, then it is probably an NSE 
> packet. NSE is a Cisco proprietary FaxoverIP solution and uses per 
> default payload types 96 and 97 to signal a changeover from VoIP to FoIP.
>
> Probably you have to configure the Cisco GW to use T.38 instead of NSE 
> for FoIP.
>   
When did RFC2833 become a proprietary Cisco spec?

The NSEs just signal the startup of FAX. You still need to switch into 
T.38 to actually exchange the FAX.

Steve