Recall that ATM uses 53-byte p_

Recall that ATM uses 53-byte packets consisting of 5 header bytes and 48 payload bytes. Fifty-three bytes is unusually small for fixed-length packets; most networking protocols (IP, Ethernet, frame relay, and so forth) use packets that are, on average, significantly larger. One of the drawbacks of a small packet size is that a large fraction of link bandwidth is consumed by overhead bytes; in the case of ATM, almost 10 percent of the bandwidth is "wasted" by the ATM header. In this problem we investigate why such a small packet size was chosen. To this end, suppose that the ATM cell consists of P bytes (possibly different from 48) and 5 bytes of header.

a. Consider sending a digitally encoded voice source directly over ATM. Suppose the source is encoded at a constant rate of 64 kbps. Assume each cell is entirely filled before the source sends the cell 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. Calculate the store-and-forward delay at a single ATM switch for a link rate of R=155 Mbps (a popular link speed for ATM) for L= 1,500 bytes,and for L= 48 bytes.

c. 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= 48 (corresponding to an ATM cell).
d. Comment on the advantages of using a small packet size.

Recall that ATM uses 53-byte p

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