DTMF Issue On Calls (Doc ID 2718596.1)

Last updated on NOVEMBER 20, 2023

Applies to:

Goal

DTMF issues when t.38 is added in add-codecs-on-egress of codec-policy.

#DTMF is not working properly with below Codec Policy

  allow-codecs *
  add-codecs-on-egress G729 PCMU telephone-event T.38
  order-codecs G729 PCMU telephone-event T.38
  packetization-time 20

#DTMF works fine with below codec policy

  allow-codecs *
  add-codecs-on-egress G729 PCMU telephone-event
  order-codecs G729 PCMU telephone-event T.38
  packetization-time 20

Initial Invite SDP details:

Time Description, active time (t): 0 0
Media Description, name and address (m): audio 28434 RTP/AVP 0 101
Media Attribute (a): rtpmap:0 PCMU/8000
Media Attribute (a): rtpmap:101 telephone-event/8000
Media Attribute (a): fmtp:101 0-15

Invite going out of SBC.

Media Description, name and address (m): audio 44490 RTP/AVP 0
Media Attribute (a): rtpmap:0 PCMU/8000
Media Attribute (a): silenceSupp:off - - - -
Media Description, name and address (m): image 41966 udptl t38
Media Attribute (a): T38FaxVersion:0
Media Attribute (a): T38MaxBitRate:14400
Media Attribute (a): T38FaxFillBitRemoval:0
Media Attribute (a): T38FaxTranscodingMMR:0
Media Attribute (a): T38FaxTranscodingJBIG:0
Media Attribute (a): T38FaxMaxBuffer:2048
Media Attribute (a): T38FaxMaxDatagram:256
Media Attribute (a): T38FaxUdpEC:t38UDPREdundancy
Media Attribute (a): T38FaxRateManagement:transferredTCF

Solution

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