350-801 CLCOR: Implementing and Operating Cisco Collaboration Core TechnologiesDemo

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QuestionQ111

Voice Gateways and Session Border Controllers

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Refer to the exhibit. Which outgoing m-line SDP does Cisco Unified Border Element send to Cisco UCM after it matches the applicable dial peers?

  • A m=audio 16550 RTP/AVP 0 8 18 a=rtpmap:0 PCMU/8000/1 a=rtpmap:8 PCMA/8000/1 a=rtpmap:18 G729/8000/1
  • B m=audio 16550 RTP/AVP 18 0 a=rtpmap:0 PCMU/8000/1 a=rtpmap:18 G729/8000/1
  • C m=audio 16550 RTP/AVP 8 0 18 a=rtpmap:0 PCMU/8000/1 a=rtpmap:8 PCMA/8000/1 a=rtpmap:18 G729/8000/1
  • D m=audio 16550 RTP/AVP 18 0 a=rtpmap:8 PCMA/8000/1 a=rtpmap:0 PCMU/8000/1 a=rtpmap:18 G729/8000/1
Explanation

CUBE filters the outbound codec offer to codecs that are both permitted by the codec voice class and present in the inbound SDP. G.711 A-law is therefore excluded, while G.729 (payload 18) and PCMU/G.711 μ-law (payload 0) remain. When those codecs are present in the incoming SDP, CUBE follows the incoming SDP preference order, yielding payloads 18 0 with the corresponding G.729 and PCMU mappings.

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