Question $2$

$($a$)$ The IPv$4$ packet header is shown in Figure $2\mathrm{.}1$ below. The bits allocated to each field are

shown at the top of the frame.

Figure $2\mathrm{.}1$

$($i$)$ For a transmitted packet the entry of the IHL field in the header reads $1101.$ If the

Options contain $30$ bytes of data, does this packet need a padding? If not, explain

why. If yes, how big is a padding? What is a maximum data length in Options? List

any three functions which are implemented in the Options field of IPv$4$ datagram.

$($ii$)$ List and briefly describe the five main schemes used for assigning IP addresses.

$($iii$)$ A router in the network which uses CIDR addressing has the following base

addresses BA$1$ and BA$2$ and the corresponding destinations in its routing table:

Base Address

BA$1$: $142\mathrm{.}17.\frac{56\mathrm{.}0}{22}$

Destination

BA$2$: $142\mathrm{.}17.\frac{60\mathrm{.}0}{22}$

CSEE

Two packets with the IP addresses IP$1=142\mathrm{.}17\mathrm{.}63\mathrm{.}20$ and IP$2=142\mathrm{.}17\mathrm{.}59\mathrm{.}40$

arrive to the router. Explain, to which destination$($s$)$ these packets will be routed.

$($b$)$ An IPv$4$ network shown in Figure $2\mathrm{.}2$ consists of two hosts H$1$ and H$2$ and two routers R$1$

and R$2.$ The link H$1-$R$1$ has maximum transmission unit $($MTU$)$ MTU$1=1200$ bytes, the

link R$1-$R$2$ has MTU$2=600$ bytes, and the link R$2-$H$2$ has MTU$3=596$ bytes. The

network uses a non$-$transparent fragmentation. The application layer of the host $H1$

generates $1160$ bytes of data which are given to the transport layer for a reliable

transmission to the host $H2.$

$($i$)$ Is fragmentation of the packet required in this case? Explain your answer.

$($ii$)$ In case the packet is fragmented, calculate the payload of each fragment.

$($c$)$ The dependence of the congestion window $W_c($in kilobytes$)$ on the transmission time $t($in

units of RTT$)$ for a congested internet is shown in Figure $2\mathrm{.}3,$ where it was assumed that

the maximum cacment ciza MCS $-1$ lilohute