What can be the answer for this question -- Datapath through 3 routers

[22990atinesh]

Homework Statement

An IP machine Q has a path to another IP machine H via three IP routers R1, R2, and R3.
Q—R1—R2—R3—H
H acts as an HTTP server, and Q connects to H via HTTP and downloads a file. Session layer
encryption is used, with DES as the shared key encryption protocol. Consider the following four
pieces of information:

[I1] The URL of the file downloaded by Q
[I2] The TCP port numbers at Q and H
[I3] The IP addresses of Q and H
[I4] The link layer addresses of Q and H

Which of I1, I2, I3, and I4 can an intruder learn through sniffing at R2 alone?

(A) Only I1 and I2
(B) Only I1
(C) Only I2 and I3
(D) Only I3 and I4

Homework Equations

The Attempt at a Solution

As Router works only at Network Layer (which is on top of link layer) of TCP/IP Protocol Stack. Hence option (d) seems appropriate. But correct ans is (c) how

 

[jedishrfu]

you can't encrypt the tcp numbers as they are used to rout your data. You need the host # and port # to talk to the machine after that every else can be encrypted.

 

[22990atinesh]

you can't encrypt the tcp numbers as they are used to rout your data. You need the host # and port # to talk to the machine after that every else can be encrypted.

@jedishrfu then what ans would you suggest.

 

[jedishrfu]

What answer does it match?

 

[rezeew]

is that possible?The correct answer is (A) Only I1 and I2.

An intruder at R2 can only see the IP addresses and TCP port numbers of the packets passing through it. The URL of the file downloaded, as well as the link layer addresses of Q and H, are not visible at the network layer. The URL and link layer addresses are only visible at the application and data link layers respectively, which are higher layers in the TCP/IP protocol stack. Therefore, the intruder can only learn the URL and TCP port numbers through sniffing at R2.