Computer Networks: Routing Protocols, ICMP Packet Encapsulation, and Convergence Properties

Running head: COMPUTER NETWORKS
SIT 202 Computer Networks
Name of the Students
Name of the University
Author’s Note

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COMPUTER NETWORKS
Answer to Question 1:
Step#1: Source and destination address in outgoing packet from PC1 to remote server
Source Address – 192.168.10.7 /24
Destination address – 209.165.200.226 /27
Step#2: Explanation of how the router keeping track on the incoming packet from
remote server and forwards to the correct sources with private IP inside the company host by
using router entries.
On receiving the data packet from the remote server the L2 header information is
removed and the destination IP address is checked. The route for reaching the destination IP
address is checked from the prefix and if it is found the Mac address of the interface used for
communication and the destination Mac address is attached with the packet as source and
destination address and the packet is forwarded. The routing table is analysed for finding the
route and if there is no routes available the packet is dropped. The following steps are

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COMPUTER NETWORKS
performed by the router after receiving the packet from the remote server and are given as
follows:
Step#1: Routing
A routing table is recorded by the router listing all the possible routes that can be used
for forwarding a data packet in the network with the details of the physical interface used for
establishing the connection. The network routes are learned by the router by static or dynamic
configurations. On receiving a data packet the layer 2 information are removed and layer 3
information are added for maintaining a track on the delivery of the data packet to the
destination address.
Step#2: Forwarding
On the selection of the routing interface the packets are moved using switching
procedure. Adjacency tables are used for the transmission of the data packets to the next hop
address.
Step#3: Encapsulation
The layer 3 information is used for the encapsulation and it does not changes until the
packet is delivered to the destination address. The layer 2 information can change based on
the medium of transmission and number of hops it passes.

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Answer to Question 2:
1) How IP packet is created from ICMP packet at PC-A, i.e., describe the encapsulation of
the ICMP payload into an IP packet (indicating values of relevant IP header fields).
The ICMP is a protocol that is used for reporting the errors in the network used for the
successful delivery of the data packets in the network. An IP header is used for the
encapsulation of the ICMP data and transmission of the message as a datagram. The entire IP
header of the original message is contained in the ICMP message. The header of the ICMP
packet appears after the IPv4 /IPv6 header and is identified by protocol no. 1.
The above diagram is used for the demonstration of the ICMP message format. The
first 8 bit is used for the identification of the message type, followed by the second 8 bit
which is used transmission of the header file. The payload is used for the identification of the
path used by the sender after receiving the ICMP message. The payload helps in