350-801 · Question #198
A network administrator with ID0123456789 has determined that a WAN link between two Cisco UCM clusters supports only 1 Mbps of bandwidth for voice traffic. How many calls does this link support if…
The correct answer is D. 12. To calculate the number of simultaneous G.711 calls supported on a 1 Mbps link, the bandwidth consumption per G.711 call (including IP/UDP/RTP overhead) must be determined and then divided into the total available bandwidth.
Question
A network administrator with ID0123456789 has determined that a WAN link between two Cisco UCM clusters supports only 1 Mbps of bandwidth for voice traffic. How many calls does this link support if G.711 as the audio codec is used?
Options
- A15
- B16
- C13
- D12
How the community answered
(25 responses)- A8% (2)
- B12% (3)
- C4% (1)
- D76% (19)
Why each option
To calculate the number of simultaneous G.711 calls supported on a 1 Mbps link, the bandwidth consumption per G.711 call (including IP/UDP/RTP overhead) must be determined and then divided into the total available bandwidth.
15 calls would require 15 * 80 kbps = 1200 kbps, which exceeds the 1 Mbps (1000 kbps) link capacity.
16 calls would require 16 * 80 kbps = 1280 kbps, which significantly exceeds the 1 Mbps (1000 kbps) link capacity.
13 calls would require 13 * 80 kbps = 1040 kbps, which exceeds the 1 Mbps (1000 kbps) link capacity.
A G.711 call requires approximately 80 kbps of bandwidth per call, including IP/UDP/RTP overhead (64 kbps for payload + ~16 kbps for overhead). With a 1 Mbps (1000 kbps) link, the calculation is 1000 kbps / 80 kbps/call = 12.5 calls. Since a fraction of a call cannot be supported, the link supports 12 simultaneous G.711 calls.
Concept tested: Voice codec bandwidth calculation
Source: https://www.cisco.com/c/en/us/support/docs/voice/ip-telephony/7738-bandwidth-consume.html
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