VVX and Soundpoint not sending DTMF when telephone-event not lowercase

[Anonymous]

We made some calls from Polycom phones (Soundpoint 4.0.13 and VVX 5.6.0.17325) into reConServer and observed that the phones  were not sending any RFC 2833 RTP packets when DTMF keys were pressed.  Packet sniffer only shows regular size RTP packets coming from the phone.

I looked at the SDP answer from reConServer and compared that to SDP from other applications like Asterisk.  I noticed that in the SDP from reConServer, the encoding name "TELEPHONE-EVENT" is uppercase.  I tweaked the reCon code to send it as lowercase and then the Polycom phones recognize the encoding and the DTMF presses work.

RFC 4855 suggests that the encoding names should not be considered case sensitive:

https://lists.cs.columbia.edu/pipermail/sip-implementors/2012-July/028555.html

   Note that the payload format (encoding) names defined in the RTP
   Profile [4] are commonly shown in upper case.  Media subtype names
   are commonly shown in lower case.  These names are case-insensitive
   in both places.  Similarly, parameter names are case-insensitive both
   in media type strings and in the default mapping to the SDP a=fmtp
   attribute.

Therefore, while we can work around this easily by adapting the reSIProcate and sipXtapi stacks to send "telephone-event" in lowercase, it is a bug in the Polycom implementation and it would be helpful to fix it for future releases.  While the majority of implementations write telephone-event in lowercase, there may be other encoding names that appear in future where implementations are not so consistent and Polycom users may trip up on this.

[SteffenBaierUK]

Hello @pocock,

welcome back to the Polycom Community.

First of all 5.6.0 is no longer supported. We only support the current Software aka 5.8.1 -1 which would be 5.8.0

If you insist on using 5.6.x you should use 5.6.4 instead.

If this is still the same issue please report this into Polycom via the Support Portal.

Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.

Best Regards

Steffen Baier

Polycom Global Services

[Anonymous]

Thanks for the fast reply, I'm happy to test with the current firmware and report back.

[Anonymous]

Tested with 5.8.1.7278 and the problem appears to be unresolved

[SteffenBaierUK]

Hello @pocock,

verifying an issue is not something we can do via the Polycom community as we need to look at Logs, Wireshark Captures and exchange direct communication with you as the user.

In addition we cannot commit to any SLA's / Service Line Agreements via the community either.

In order to raise a support ticket you need to work with your Polycom reseller as they need to do this for you.

End Customers are unable to open a ticket directly with Polycom support.

If this is some sort of an Internet discounter providing your MAC address or your Polycom devices serial will enable us to look up who would be able to support you. This may not be who you purchased the Polycom device from.

If the unit is no longer within warranty please be prepared to Pay Per Incident / PPI. This is all outlined in detail here

Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.

Best Regards

Steffen Baier

Polycom Global Services