The Gateway to Computer Science Excellence
First time here? Checkout the FAQ!
x
+19 votes
3.1k views
Assume that source S and destination D are connected through two intermediate routers labeled R. Determine how many times each packet has to visit the network layer and the data link layer during a transmission from S to D.

(A) Network layer – 4 times and Data link layer – 4 times

(B) Network layer – 4 times and Data link layer – 3 times

(C) Network layer – 4 times and Data link layer – 6 times

(D) Network layer – 2 times and Data link layer – 6 times
asked in Computer Networks by Veteran (342k points) | 3.1k views
0
any good explanation ?

5 Answers

+31 votes
Best answer

C is the answer .

answered by Loyal (5.9k points)
selected by
0
@Mithlesh Can u plz elaborate on why in the router the protocol stack is visited twice.
0
Ok thanks :)
0
As the packet visits the network layer in the routers too, why it is not counted ??
0
Answer to this needs more explaination.
0
give more explanation broooo diagram is clear but why didn't u addd network at routers and why did u count two two times at thr router why can't it be once
+1
both side of router may have different ethernet network or different frame mtu so it has 2 -2 layer of datalink and physical while network layer can handle mtu ,frame size so only 1 network layer
+21 votes

In source,

it is $1$ data link and $1$ network .. now as routers are in network layer
So in

$\text{Router1:}$At first, it goes to network layer like physical$\Rightarrow$DLL$\Rightarrow$network
(then again comes to physical like)$\Rightarrow$DLL$\Rightarrow$physical 

$\text{Router2}:$
Physical$\Rightarrow$DLL$\Rightarrow$network$\Rightarrow$Dll$\Rightarrow$physical

Destination:

Physical$\Rightarrow$DLL$\Rightarrow$Network$\Rightarrow$TCP$\Rightarrow$Application

In both routers after computation in Network layer, it is coming back to physical again...
the reason is signals can only be transmitted with physical layer.

 

So, Network Layer$=4 \text{ Visit}.$

DLL$=6\text{ Visit}.$

answered by Boss (18.5k points)
edited by
+9 votes
(C) Network layer – 4 times and Data link layer – 6 times

Sender Has one network layer and data link layer as receiver but router have 1NL,2DL and 2PL;

So Total NL=1NL(Sender)+2NL*(Router)+1N(Receiver)=4NL

Total DL=1*2DL(Sender+Receiver)+2*2DL(Router=6DL)

Option given as

(C) Network layer – 4 times and Data link layer – 6 times
answered by Loyal (8.6k points)
+5 votes
ans c)
answered by Active (5.2k points)
+5 votes

(C) is the correct option!
For detailed explanation:

answered by Boss (39.2k points)
0
Good Explanation


Quick search syntax
tags tag:apple
author user:martin
title title:apple
content content:apple
exclude -tag:apple
force match +apple
views views:100
score score:10
answers answers:2
is accepted isaccepted:true
is closed isclosed:true

35,527 questions
42,803 answers
121,618 comments
42,166 users