A) Consider the following network links: G1 8.8.8.8 L1 10.0.0.5 X1 216.34.181.48

Question

A) Consider the following network links: G1 8.8.8.8 L1 10.0.0.5 X1 216.34.181.48 L2 10.0.1.7 X2 216.34.181.45 G2 130.102.72.8 i) For each source and destination below, fill in the table of how many source IP addresses, destination IP addresses and destination MAC addresses will be involved in the transport of a UDP message travelling from source to destination? 3 marks] Source Dest Number of Number of Number of Source IPs Destination Destination IPs MACs Ll 2 2 X2 ii) There is an upper limit on the number of nodes bctween L2 and X2 if they are to communicate. What determines this upper limit? 2 mark iii) If X1 and X2 had their IP addresses changed to 192.168.1.1 and 192.168.1.2 respectively; what els

Explanation / Answer

Answer:-

A) IP Address is the logical address of the network card on our device. Subnet mask is the symbol of 1's in the network bits and 0's in the host bits.

If a computer wants to send a message to other computer, then how will the computer know that the destination is in the same network or a different network? Since the source, will have the destination IP address, the source will and its own subnet mask with the IP of destination. Now the result is the network ID of destination with respect to source.

And likewise, it will and its own IP address with its own subnet mask to get its own network ID. Now, it will compare both network ids. If they are equal, then they are present in same network else they are present in a different network. Now, If the source and destination are present in same network, source will directly send message to destination else to default router of the network.

i)Source: L1 Dest: L2

In the figure both L and L2 are present in same network.

Hence, L1 will directly send message to L2

Number of source IP's = 1

Number of destination IP's = 1

Number of Destination Mac's = 1

Source = L2 Dest: X2

In the figure, both L2 and X2 are present in different network.

In between there are four routers.

So, the route is L1-> R1, R1->R2, L2->R2,R2->R3, R3->R4, R4->X2

The, IP address is added by Network layer. The source IP address is always IP of L1 and destination IP address is always IP of X2

But, MAC address is not always same. Since it is added by Data Link Layer, it changes when the hops change.

So, the Number of Source IP's = 1

Number of destination IP's = 1

Number of Destination MAC's = R1, R2.R3, R4, X2 = 5

ii) The upper limit is actually depends on the TTL (Time to leave).

This is the maximum of hop count to reach destination. Here, it is 5

iii) If X1 and X2's IP addresses are changed to 192.168.1.1 and 192.168.1.2 respectively, both of them can still be present in the same network.

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