Question B$1$

a$)$ Describe how the CSMA$/$CD access method works, explaining what each part of the

acronym means. Also, the $802\mathrm{.}11$ wireless protocols use $CSM\frac{A}{C}$A instead of

CSMA$/$CD$.$ Explain why Wi$-$Fi does not use CSMA$/$CD$?$

$[5$ Marks$]$

b$)$ Compare and contrast the OSI reference model and TCP$/$IP reference model. $($Use

diagrams to show the correspondence between relevant protocol layers in the two

models$)$

c$)$ Describe the physical construction characteristics of the following transmission media

identifying the differences between them

Twisted pair

Optical fibre cable

$[4$ Marks$]$

d$)$ A Network administrator pings a remote machine and the following is the result. Explain why

the first packet was "request timed out"?

Request timed out.

Reply from $64\mathrm{.}100\mathrm{.}1\mathrm{.}185$: bytes $=32$ time $=185ms$ TTL $=123$

Reply from $64\mathrm{.}100\mathrm{.}1\mathrm{.}185$: bytes $=32$ time $=281ms$ TTL $=123$

Reply from $64\mathrm{.}100\mathrm{.}1\mathrm{.}185$: bytes $=32$ time $=287ms$ TTL $=123$

$[3$ Marks$]$

e$)$ Suppose Host A wants to send a large file to Host B$.$ The path from Host A to Host B

has three links, of rates $R1=5Mbps,R2=2000kbps$ and $R3=1Mbps.$ Assuming no

other traffic in the network, what is the throughput for the file transfer? Explain your

answer.

$[3$ Marks$]$

f$)$ Define the terms Unicasting, Multicasting and Broadcasting?

$[6$ Marks$]$

g$)$ Provide the full name for each of the following acronyms.

ARP

DNS

ICMP

FTPIn the CSMA$/$CD access method, a host requires $2$ t$\_$prop to ensure exclusive access to a transmission channel. Using your own words, please explain what this means and why, in detail. You are reminded of your obligations under the Academic Integrity Policy.