The MTU resources are occupied when (). (Multiple Choice)

Question

Options

• AAn IAD user makes an outgoing call through the PRA trunk.
• BA POTS user makes an outgoing call through the PRA trunk.
• CCalls occur between intra IP phone users.
• DThe VU switchboard plays voice files.

• A
  79% (41)
• C
  21% (11)

Explanation

MTU (Media Termination Unit) resources are consumed whenever media streams require processing, transcoding, or special handling at a network boundary or media source.

Options A and B are correct because calls from IAD or POTS users routed through a PRA (Primary Rate Access/ISDN PRI) trunk cross a boundary between the IP domain and the circuit-switched domain - the MTU must handle the media conversion and termination for these calls. Option D is correct because when the VU (Voice Unit) switchboard plays voice files (e.g., announcements or IVR prompts), it actively generates a media stream that requires MTU resources to process and inject into the call.

Option C is the distractor - calls between intra-network IP phone users travel entirely within the IP domain and can use a direct peer-to-peer RTP media path, bypassing the MTU entirely since no transcoding or circuit-domain bridging is needed.

Memory tip: Think of the MTU as a "translator" - it only gets involved when media must cross a network-type boundary (IP ↔ TDM/PRA) or when the system itself must generate media (voice file playback). Pure IP-to-IP calls speak the same language and don't need a translator.

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