Chapter 1, Problem P23P

a.

Explanation of Solution

Let the pair of packets be A and B.

Given,

• The rate of the first link from server to client is ${\text{R}}_{\text{s}}\text{bps}$.
• The length of the each packet is L bits.
• Packet B starts the transmission only after the completion of transmission of the packet A

b.

Explanation of Solution

When both the packets are sent back to back, the second packet B must cross the input queue of second link before the completion of the transmission of the first packet A.

Then, $\frac{\text{L}}{{\text{R}}_{\text{s}}}\text{+}\frac{\text{L}}{{\text{R}}_{\text{s}}}\text{+}{\text{d}}_{\text{prop}}\text{<}\frac{\text{L}}{{\text{R}}_{\text{s}}}\text{+}{\text{d}}_{\text{prop}}\text{+}\frac{\text{L}}{{\text{R}}_{\text{c}}}$

In the above inequality expression, the left hand side represents the time required by the packet B to cross the input queue of second link before the completion of the transmission of the packet A whereas the right hand side represents the time required by the packet A to complete the transmission on the second link.

If packet B is sent with the delay of time T seconds then,

$\frac{\text{L}}{{\text{R}}_{\text{s}}}\text{+}\frac{\text{L}}{{\text{R}}_{\text{s}}}\text{+}{\text{d}}_{\text{prop}}\text{+}$