Essay 16ELC004: Communications Networks – The Hidden-Station Problem – TCP Transmission – Networking Assignment Help

Assignment Task:

1. Answer the following questions:
a) What are the layers in the 5-layer network?

b) Explain why the CSMA/CD protocol is not used in WiFi.

c) What is the ‘hidden-station’ problem? Which protocol can be used to solve this problem?

d) Which layer realizes reliable transmission? Suggest a way to realize reliable broadcast (i.e. transmission from one source to multiple destinations).

e) Suppose a host receives the following frame
1011111100
If the generator polynomial is XP3P+XP2P, will this frame pass the CRC check? [4 marks]

f) At a transmission rate of 10 Mbs-1 (M =106 here) and propagation speed of 200 meters/μs, how many metres of cable is the 1-bit delay equivalent to?

c) A company’s network is assigned an IP address block as:
192.96.144.128/25.

What is the maximum number of hosts the company can have with the assigned IP addresses?

What is the equivalent subnet mask for this company’s network?

Determine whether the following IP addresses are for this company or not.
i. IP1: 192.96.144.144
ii. IP2: 192.96.144.96

3. This question considers TCP transmission:
a) The data bytes in one TCP transmission are numbered with 2 bits. The receiving window size is 3.

Suppose at one time, the receiving window is at bytes ‘1RbR’, ‘2RbR’ and ‘3RbR’, where the subscripts are used to indicate different bytes. For example, bytes ‘1RaR’ and ‘1RbR’ are different data bytes, though they are both numbered as ‘1’.

Determine whether the following transmission windows (highlighted in shades) are allowed or not, and justify your answers.

b) A TCP transmission is based on a 1G bps link (G = 109), and the transmission window size is 65535 bytes. The confirmation ‘ACK’ is sent only after all data in a transmission window have been received. Suppose all data and ACK can be received successfully in the first round (i.e. no re-transmission occurs).

Obtain the throughput of this TCP link (or the amount of data transmitted per second).

c) Suppose that one mobile communication link in a WiFi network is based on TCP protocol. It is known that TCP supports full-duplex, while WiFi networks operate in half-duplex mode. Specify whether this communications is full-duplex or half-duplex.