A customer is deploying a SIP IOS gateway for a customer who requires that in-band DTMF relay is first priority and out-of-band DTMF relay is second priority.
Which IOS entry sets the required priority?
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A. B. C. D.A.
The correct answer is C. sip-notify dtmf-relay rtp-nte.
Explanation:
DTMF (Dual-Tone Multi-Frequency) is a method used to transmit digits during a call, such as when you press keys on your phone to enter numbers or make selections. There are two ways to relay DTMF: in-band and out-of-band.
In-band DTMF relay sends DTMF tones in the same audio stream as the voice call. Out-of-band DTMF relay sends DTMF tones in a separate signaling channel. In general, out-of-band DTMF is preferred because it is more reliable and doesn't interfere with the voice quality of the call.
However, some systems may require in-band DTMF for compatibility reasons. In this case, you can specify the priority of DTMF relay types using the dtmf-relay command in IOS.
The four options given in the question are different combinations of DTMF relay types: rtp-nte, sip-notify, cisco-rtp, and sip-kpml.
The correct answer is C. sip-notify dtmf-relay rtp-nte because it specifies that SIP NOTIFY messages should be used for out-of-band DTMF relay (sip-notify) and if that is not possible, in-band DTMF relay using RTP Named Telephony Events (rtp-nte) should be used as a fallback. This meets the customer's requirement of in-band DTMF being the first priority and out-of-band DTMF being the second priority.
Option A (dtmf-relay rtp-nte sip-notify) is the same as option C but with the order of the parameters reversed. This would still work but doesn't match the requested order.
Option B (dtmf-relay cisco-rtp) only specifies in-band DTMF using Cisco's proprietary RTP (Real-time Transport Protocol) implementation.
Option D (dtmf-relay sip-kpml cisco-rtp) specifies out-of-band DTMF using SIP KPML (Key Press Markup Language) as the first priority and in-band DTMF using Cisco RTP as the second priority. This does not match the requested priority order.