Question
Consider the figure below (which is similar to Figure 7.7). A sender begins sending packetized audio periodically at t = 1. The first packet arrives at the receiver at t = 8.
a.What are the delays (from sender to receiver, ignoring any playout delays) of packets 2 through 8? Note that each vertical and horizontal line segment in the figure has a length of 1, 2, or 3 time units.
b. If audio playout begins as soon as the first packet arrives at the receiver at t = 8, which of the first eight packets sent will not arrive in time for playout?
c. If audio playout begins at t = 9, which of the first eight packets sent will not arrive in time for playout?
d. What is the minimum playout delay at the receiver that results in all of the first eight packets arriving in time for their playout?
Answer
a)
Given data:
A sender begins sending packetized audio periodically at t = 1. The first packet arrives at the receiver at t = 8.
The following delays (from sender to receiver, ignoring any playout delays) of packets 2 through 8 by using given figure.
|
Packet |
Packets generated |
Packet recieved |
Delay=Packet received – Packet generated |
| 1 | 1 | 8 | 7 |
| 2 | 2 | 9 | 7 |
| 3 | 3 | 12 | 9 |
| 4 | 4 | 12 | 8 |
| 5 | 5 | 12 | 7 |
| 6 | 6 | 15 | 9 |
| 7 | 7 | 15 | 8 |
| 8 | 8 | Not received yet | >8 |
b)
Given data:
If audio playout begins as soon as the first packet arrives at the receiver at t = 8.
The following table represents the find out exepecte received packet time of packets 2 through 8 by using given figure.
|
Packet |
Packets generated |
Packet recieved |
Exepected received packet time |
| 1 | 1 | 8 | 8 |
| 2 | 2 | 9 | 9 |
| 3 | 3 | 12 | 10 |
| 4 | 4 | 12 | 11 |
| 5 | 5 | 12 | 12 |
| 6 | 6 | 15 | 13 |
| 7 | 7 | 15 | 14 |
| 8 | 8 | Not received yet | 15 |
The packets 3,4 6,7 and 8 are the packet received time is greater than the expected packet received from the above table. So, packets 3, 4, 6, 7, and 8 packets sent will not arrive in time for playout.
c)
Given data:
Assume audio playout begins at t = 9.
The following table represents the find out exepecte received packet time in audio playout begins at t = 9:
|
acket |
Packets generated |
Packet recieved |
Exepected received packet time |
| 1 | 1 | 8 | 9 |
| 2 | 2 | 9 | 10 |
| 3 | 3 | 12 | 11 |
| 4 | 4 | 12 | 12 |
| 5 | 5 | 12 | 13 |
| 6 | 6 | 15 | 14 |
| 7 | 7 | 15 | 15 |
| 8 | 8 | Not received yet | 16 |
The packets 3,6 and 8 are the packet received time is greater than the expected packet received from the above table. So, packets 3, 6, and 8 packets sent will not arrive in time for playout at t=9.
d)
Assume the minimum playout delay at the receiver at t=10.
The following table represents the find out exepecte received packet time in audio playout begins at t = 10:
|
Packet |
Packets generated |
Packet recieved |
Exepected received packet time |
| 1 | 1 | 8 | 10 |
| 2 | 2 | 9 | 11 |
| 3 | 3 | 12 | 12 |
| 4 | 4 | 12 | 13 |
| 5 | 5 | 12 | 14 |
| 6 | 6 | 15 | 15 |
| 7 | 7 | 15 | 16 |
| 8 | 8 | Not received yet | 17 |
There no packets are the packet received time is greater than the expected packet received from the above table. So, no packets sent will not arrive in time for playout.