Problem $6(14$ marks$)$: The figure below illustrates the Internet Protocol operation for data exchange between host A on LAN $1$ and host B on LAN$2,$ where both LANs are interconnected by a wide area network $($WAN$)$ using legacy Frame Relay technology. The two LANs use distinct data link layer protocols.

a$)$ For each one of the indicated times $t_i,$iin$\{1,2,$dots,$16\},$ show the format of the corresponding PDU.

b$)$ Consider an IP datagram with the following content: IP header $=20$ octets, TPC header $=20$ octets, TPC payload $=412$ octets. Suppose that due to WAN limitations$,$ the maximum size of IP datagrams cannot exceed $268$ octets, requiring fragmentation of this IP datagram into two

Course: ECSE $308$

Winter $2022$

Page number: $\frac{3}{4}$

segments. Illustrate the format of each segment and indicate the corresponding values of the following parameters: data length, segment offset, and more bit.

c$)$ Suppose that the WAN is identified with a Class C network number $204\mathrm{.}228\mathrm{.}18,$ and that a total of $4$ LANs $($with subnet numbers ranging from $0$ to $3)$ are attached to it$.$

Give the subnet mask of the Frame Relay WAN in dotted decimal notation.

Give the extended network number $($i$.$e$.,$ subnet number$)$ of LAN $2$ in dotted decimal notation.

Assuming that $B$ is given host number $6,$ give its complete IP address in dotted decimal.