In this problem, we explore the use of small packets for Voice-over IP applicati

Question

In this problem, we explore the use of small packets for Voice-over IP applications. One of the drawbacks of a small packet size is that a large fraction of link bandwidth isconsumed by overhead bytes.

a.Consider sending a digitally encoded voice source directly. Suppose the source is encoded at a constant rate of 128 kbps. Assume each packet is entirely filled before the source sends the packet into the network. The time required to fill a packet is the packetization delay. In terms of L, determine the packetization delay in milliseconds.

b.Packetization delays greater than 20 msec can cause a noticeable and unpleasant echo. Determine the packetization delay for L = 1,500 bytes (roughly corresponding to a maximum-sized Ethernet packet) and for L = 50 (corresponding to an ATM packet).

c.Comment on the advantages of using a small packet size.

Explanation / Answer

A) .
(L /128×1024)x1000

B)
(1500 x 8/128×1000)x1000 is the packetization delay. (50×8/128×1000)x1000 is the ATM.

C).
Store-and-forward delay is small for both cases of typical ATM link speeds. Store-and-forward delay, too is less when small packet size is used.

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