FAILURE Returned by MSP -> 0xFFFFFFE

Symptom

Calls in the IP to TDM direction cannot be established, and you see the following error logged in the gateway diagnostics trace:

[DspRoot ] Error FAILURE Returned by MSP -> 0xFFFFFFE8

In addition, the following alarm gets logged:

[Alarm ] Init ALARM |9| - id:[0] info:[0x0] txt:[Media session open failed]

You also see the call failure logged to the gateway call log with an end result of 'Internal Server Error'.

[CallLog ] Event Direction: From VoIP Network 
[CallLog ] Event Start Time: . . . 
[CallLog ] Event End Time: . . . 
[CallLog ] Event Inbound: [. . .->. . .] 
[CallLog ] Event Outbound: [1:10005] 
[CallLog ] Event End Reason: VoIP: Internal Server Error

Reason for the issue

This issue’s signature is typical of the IP application requesting the use of a DTMF payload type that is incompatible with one that the gateway can accept. 

This issue has been observed, for example, when connecting a Dialogic 2000 Media Gateway Series (DMG2000) to an Avaya SES IP connectivity server. 

Fix / Solution

Configure the IP side of the connection to use a DTMF digit payload type of 101 instead of the value currently being used.

You can see the value being used by reviewing the SDP block of the IP request being made to the gateway. An example is shown below:
 

01 [VoIP ] Prot ---->INVITE sip:10005@135.64.192.31;transport=tcp SIP/2.0
02 [VoIP ] Prot Route: <sip:135.64.192.31;lr;transport=tcp>
03 [VoIP ] Prot From: sip:Messageing%20Server@135.64.192.31;tag=fc2d43bbb6f0fb44
04 [VoIP ] Prot To: sip:10005@135.64.192.31
05 [VoIP ] Prot Call-ID: d2168fb5c412647b
06 [VoIP ] Prot CSeq: 1 INVITE
07 [VoIP ] Prot Max-Forwards: 70
08 [VoIP ] Prot User-Agent: User Agent Name
09 [VoIP ] Prot Supported: 100rel, timer, replaces, join
10 [VoIP ] Prot Allow: INVITE, CANCEL, BYE, ACK, PRACK, SUBSCRIBE, NOTIFY, REFER, OPTIONS
11 [VoIP ] Prot Contact: <sip:135.64.192.184;transport=tcp>
12 [VoIP ] Prot Session-Expires: 240;Refresher=uac
13 [VoIP ] Prot Min-SE: 240
14 [VoIP ] Prot Content-Type: application/sdp
15 [VoIP ] Prot Via: SIP/2.0/TCP 135.64.192.184;branch=z9hG4bK44c96b3ae41a9744
16 [VoIP ] Prot Content-Length: 182
17 [VoIP ] Prot
18 [VoIP ] Prot v=0
19 [VoIP ] Prot o=- 1 1 IN IP4 135.64.192.184
20 [VoIP ] Prot s=-
21 [VoIP ] Prot c=IN IP4 135.64.192.184
22 [VoIP ] Prot t=0 0
23 [VoIP ] Prot m=audio 7056 RTP/AVP 8 0 127
24 [VoIP ] Prot a=rtpmap:8 PCMA/8000
25 [VoIP ] Prot a=rtpmap:0 PCMU/8000
26 [VoIP ] Prot a=rtpmap:127 telephone-event/8000

The value in question here can be seen on line 26 of the Invite above. The value being requested is 127. This value is a reserved payload type used internally within the gateways DSP firmware and therefore is not available for use with external devices.

Workaround

The only current workaround is to alter the payload type used by the IP application. It is recommended to use the value of 101 for DTMF digit events, as that is an established standard and has been found to work with the Dialogic 1000 and 2000 Media Gateway Series. 

Glossary of Acronyms / Terms

SIP - Session Initiation Protocol
SES - Sip Enablement Services
DTMF - Dual Tone Multi Frequency
DSP - Digital Signal processor
SDP - Session Description Protocol