Exam 300-815 topic 1 question 132 discussion

Supported DTMF-Relay Methods for H323 * H.245 Alphanumeric - DTMF digits are separated from the voice stream and sent through the H.245 signaling channel OOB instead of sent through the RTP channel. The tones are transported in H.245 User Input Indication messages. The H.245 signaling channel is a reliable channel and the packets that transport the DTMF tones are guaranteed to be delivered. All systems that are H.323 Version 2-compliant are required to support the dtmf-relay h245-alphanumeric command. However, support of the dtmf-relay h245-signal command is optional. * H.245 Signal - OOB method which is similar to H.245 alphanumeric, allows passage of the tone duration information, thereby it addresses a potential problem with the alphanumeric method when interworking with other vendor's systems. * Named Telephony Events (NTE) – RFC2833 * Cisco Proprietary RTP https://www.cisco.com/c/en/us/support/docs/unified-communications/unified-border-element/200412-DTMF-Relay-and-Interworking-on-CUBE.html#toc-hId--1486125058

B is correct