Calculate how many IP phone calls can be sent across a 64 kbps Frame Relay link that uses the
A.
729 codec being sampled 50 times a second, 20 bytes a sample, and has 6 bytes of Frame Relay header overhead with no checksum and uses header compression.
B.
3
C.
4
D.
5
E.
7
Explanation:
this is wrong, answer is D
bandwith = ((20bytes + 6bytes) * 50) * 8bit = 10400 b/s = 10,4 kbps
64kbps / 10,4kbps = 6.1 the maximum is 5 ( answer D)
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You forgot the compressed header:
bw= (20+6+2)*50)*8)= 11200 = 11,2 (look at bandwidth per call table cRTP & G.729)
64/11,2 = 5,7 –> maximum calls is 5 (your answer was correct though)
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What about layer 3 header of 40 bytes? will it not be used?
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the question say “header compresion with no checksum” so is 2 bytes.
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