Self doubt on Ethernet LAN

Question

Are the below formulas for correct w.r.t ethernet LAN?

efficiency :

PD = propagation delay

TD = transmission delay

L = frame size

$\eta =\frac{1}{1 + 6.44(\frac{ pd }{ td })}$ 

throughput:

$= \frac{L}{RTT}$

If they are wrong please provide correct ones.

Comments

correct tuhin.

---

Thanks Rupendra. Can you please look into the below  question and tell why the above formula was not used while calculating $\eta$

https://gateoverflow.in/3838/gate2005-it-75

Here they have used instead this:

$\eta$ = td / ( td + pd)

---

It is 1 / (1 + 5.44 a) instead of 1 / (1 + 6.44 a) for ethernet technology.. U may go through the section 4.3.3 of the Computer Networks textbook of Tanenbaum(5th edition) for more clarity..

---

@Tuhin Dutta , it is so because time slot is defined clearly .Hence total time is found based on that solely . Actually the result which u have mentioned considers contention in the medium whereas the question which u have commented does not do so as it has not kept into account the time taken due to contention..

---

Thanks Habib for the correction and explanation.

---

When do we use $\eta = 1/(1+6.44a)$ and when do we use $\eta = 1/(1+2a)$ {a = pd/td}. I am very confused between efficiency, throughput, utilization...please help!

---

1 / (1 + 5.44 a) : This is correct. Follow it if the efficiency of Ethernet LAN is needed otherwise for sliding window or stop-and-wait use W / ( 1 + 2a) or 1/(1 + 2a).

---

Thanks!