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Ringing tone generation


We have a problem with SAP BCM version. For some external calls there is no ringing tone played for the agent.

We are using SIP trunk for outgoing calls.

I have checked the tcpdump of such call and there is only 180 Ringing sent to BCM. No audio channels are opened until call is answered. As BCM is last SIP endpoint then it should generate ringing tone to agent when Ringing is received.

There are options in Global Switching Settings to enable ringing tone in CDT for all outgoing calls. That is not a solution because then on most calls agent will hear double ringing tone or ringing+busy at the same time.

Another option is to use MRS ringing tone for that specific trunk but that will result also double ringing tone for most of the calls.

Can anyone comment this from SAP side?

Best regards

Madis Malv

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  • Posted on Nov 10, 2015 at 09:48 AM

    Hi Madis,

    it seems at this point you are running into an issue not only with where the ringing tone is played (which by default would be in the CDT, or with the Switching setting you mentioned from MRS.)

    But the fact you get two tones shows me that you also get a ringing tone from the trunk, which is not uncommon as well. So as soon as you CDT opens a connection and plays the ringing tone, you hear the tone generated by CDT as well as the tone coming from trunk.

    Keep in mind, the call is not yet connected and one might wonder why audio from trunk might be heard at all.

    This is an option what also allows to hear certain carrier announcements in certain call situations. The setting you are looking for is related to Early Media.

    You have to allow early media so the ringing tone from the trunk, as one is obviously sent, is allowed as audio prior (or earlier) than the call connect. So you only want the CDT to play ringing tone for internal calls.

    What I found in some situations with older Audiocodes gateways is that besides Early Media being set up for the trunk, it has to be set up properly in the Audiocodes gateways as well.

    You did not tell if the trunk was provided by some sort of gateway or immediately by some carrier, but I think those are the settings to check.

    Sometimes wireshark SIP/VoIP Call analysis will also show telltale signs of what is going on here, like audio flowing with no previous connect.



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    • Hi,

      I found the whole ringing tone part quite messy lately, if you have the possibility of multiple ringing tone sources. Trying to "tidy up" things and limit everything to one source did not work all the time.

      We found the detailled settings now highly depend on the carrier and the type of connection you got. Some provide a Ringing Tone, some do not. (This is valid especially for carrier SIP trunks, as with analog or ISDN lines usually a Ringing Tone is Provided and should be used. In this case the gateway, e.g. an Audiocodes Mediant, has to be set up for Early Media as well.)

      So as a conclusion, for me it seems depending on what the carrier provides, which sometimes seems to be a SIP Trunk comming right of a Gateway and providing Early Media, you need to use Early Media for everything to work fine. Now to have the SAP Contact Center behave as the respective SIP RfC calls for and provided the carier does not use Early Media and no Ringing Tone is sent, you have to make sure to disable Early Media in SAP Contact Center, pay attention especially to the Trunk settings, as it seems here Early Media is enabled by default.

      This enabled seems to work fine in most cases, but you may want to switch it of. Beeing switched of, from my experience it worked like you expected, except for no Audio beeing routed until connect and the Ringing tone beeing generated.

      You may want to do a Wireshark trace on the carrier trunk connection and simulate some normal and some carrier announcement situations. The VoIP Analysis should give you some good directions on what needs to be handled (e.g. Is there already some RTP stream comming in before we actually have a connection.)



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