Consider the transmission delay and the queuing delay in a router buffer using t
ID: 674602 • Letter: C
Question
Consider the transmission delay and the queuing delay in a router buffer using the relationships given in Problem P-13 in Chapter 1 of Kurose and Ross 6th edition.[Problem P-13: Suppose N packets arrive simultaneously to a link at which no packets are currently being transmitted or queued. Each packet is of length L and the link has a transmission rate R. What is the average queuing delay for the N packets? Now suppose that N such packets arrive to the link every LN/R seconds. What is the average queuing delay of a packet?] Suppose packets are 500 bytes long and 10 packets arrive each second. The data rate of the link is 100,000 bits per second.
a. What is the transmission delay for a packet? Give your result in seconds.
b. What is the expected queuing delay for a packet? Give your result in seconds
Explanation / Answer
Transmission Rate = 100,000 bits = 12,500 bytes/second = 12.5 KiloBytes
Rate = 12,500 bytes per second
10 packets = 5000 bytes long
first second : 10 packets arrive:
500 bytes = 1 packet
12,500 bytes = 25 packets
hence, Sustaining capacity = 25 packets
Time in Seconds
Number of packets arrived
size (bytes)
Time taken at the Transmission Rate of (12,500 bytes per second) in seconds = Transmission Delay
1
10
5000
5000/12500 = 0.4
2
20
10,000
10,000/12,500 = 0.8
3
30
15,000
15,000/12,500 = 1.2
4
40
20,000
20,000 / 12,500 = 1.6
5
50
25,000
25,000/12,500 = 2
Hence 0.04 seconds per packet
a) Transmission delay per packet = 0.04 micro seconds
a) 0.4 / 10 = 0.04
0.8 / 20 = 0.04
2 / 50 = 0.04
Hence Transmission delay per packet = 0.04 micro seconds = 4 E -8 seconds
b) Average Queuing delay (QD) per packet = 1 / ( pps – arrvRate)
where pps = Capacity in Number of packets per second,
arrvRate = Average arrival rate of packets
Queuing Delay = QD = 1 / ( 25 - 10 ) = 1 / 15 = 0.06667 seconds
Explanation:
Types of delays:
Types of Networks for data transmission
Types of protocols:
Time in Seconds
Number of packets arrived
size (bytes)
Time taken at the Transmission Rate of (12,500 bytes per second) in seconds = Transmission Delay
1
10
5000
5000/12500 = 0.4
2
20
10,000
10,000/12,500 = 0.8
3
30
15,000
15,000/12,500 = 1.2
4
40
20,000
20,000 / 12,500 = 1.6
5
50
25,000
25,000/12,500 = 2
Hence 0.04 seconds per packet
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