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

By Cisco · Question Mode

QuestionQ225

Media and QoS

An engineer deploys a new Cisco UCM-based telephony system with these requirements:

  • Local Ethernet bandwidth is calculated from the total bandwidth per call.
  • A G.736 codec is used.
  • The bit rate is 64 kbps.
  • The codec sampling interval is 10 ms.
  • The voice payload is 160 bytes per 20 ms.

What Ethernet bandwidth size is required for each call?

  • A 31.2 kbps
  • B 38.4 kbps
  • C 55.2 kbps
  • D 87.2 kbps
Explanation

A 160-byte payload transmitted every 20 ms creates 50 packets per second. On Ethernet, the 160-byte payload plus 40 bytes of IP/UDP/RTP headers and 18 bytes of Ethernet Layer 2 overhead totals 218 bytes per packet. At 50 packets per second, this requires 87.2 kbps. Cisco’s matching 64-kbps codec profile with 10-ms samples and a 160-byte payload per 20 ms also specifies 87.2 kbps Ethernet bandwidth per call.

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