For a SIP to SIP call flow, when does Cisco Unified Border Element require transcoding resources for DTMF?

Question

Options

• Ainterworking between an OOB method and RFC2833 for flow-around calls
• Binterworking between h245-signalng and rtp-nte
• Cinterworking between an OOB method and RFC2833 for flow-through calls
• Dinterworking between h245-alpha numeric and sip-kpml

• A
  77% (49)
• B
  6% (4)
• C
  14% (9)
• D
  3% (2)

Explanation

Option A is correct because in a flow-around call, media bypasses CUBE entirely - but interworking between an OOB signaling method (like SIP INFO) and RFC 2833 requires CUBE to inject DTMF tones directly into the RTP stream. Since CUBE isn't already in the media path, it must allocate DSP/transcoding resources to reach into that bypassed stream and generate RFC 2833 RTP events.

Option C is wrong (flow-through, not flow-around): when media already flows through CUBE, it can interwork OOB-to-RFC 2833 in software without needing dedicated transcoding resources - the media path is already under CUBE's control.

Option B is wrong because h245-signaling is an H.323 construct, not applicable in a SIP-to-SIP call flow; additionally, both h245-signal and rtp-nte are already RTP-based mechanisms that don't require DSP resources to interwork.

Option D is wrong because h245-alphanumeric and sip-kpml are both pure signaling-layer OOB methods - interworking between them is a signaling translation with no media involvement, so no transcoding resources are needed.

Memory tip: Think "flow-Around needs resources because CUBE is Around the media path." The paradox is that flow-around (no media through CUBE) actually requires transcoding when RFC 2833 is involved, because CUBE must force itself back into the RTP stream to inject tones it wouldn't otherwise touch.

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