Explain how traceroute uses ICMP in order to trace the routers along the path to
ID: 3850240 • Letter: E
Question
Explain how traceroute uses ICMP in order to trace the routers along the path to a destination (b) What are the differences between message confidentiality and message integrity? (c) Suppose N people want to communicate with each of N-1 other people using symmetric key encryption. All communication between any two people, i and j, is visible to all other people in this group of N, and no other person in this group should be able to decode their communication. How many keys are required in the system as a whole? Now suppose that public key encryption is used. How many keys are required in this case?Explanation / Answer
a)Explain how traceroute uses ICMP in order to trce the routers along the path to a destination.
ans)
Traceroute is network diagnostic tool for displaying the route and measuring the transit delays of packets of network.
ICMP is a Internet Control message protocol.
in Traceroute uses the the ICMP messages to find the path from source to destination.
when we execute the traceroute <xxxxxxxx.xxx> in source/client, then our/client sending a standard ICMP request message(packet) with ttl field of value of 1 (second/hop )to the target. when this packet is recieved by the first router along the pathit must be dropped because it has no remaining lifetime- the recieving router<yyyyyyyy.yyy> cannot decrement the TTl filed to zero and forward it on.
the recieving router(yyyyyyyyy.yyy) sends an ICMP Time Exceeded/TTl Expired in transit packet back to the client. when client recieves this Time Exceeded packet, the client examines the source IP address in the note the first router along the path.
once first router discoverd. then client increments the TTL value and sends another ICMP request packet with TTL value of 2. these packets are forwarded along the first router. same like first router it will respond with ICMP Time Exceeded packets and repeats this procedure.
client machine increments the TTL field untill it recieves the ICMP Reply message from the target router/machine.
b)What are the differences between message confidentiality and message integrity?
ans)
Message Confidentiality:
two or more hosts communicate securely, typically using encryption. the communication cannot be monitored(sniffed) by the un trusted hosts. the communication between trusted parties is confidential.
Message Integrity:
the message transported has not been tampered with or altered. A message has integrity when the payload sent is the same as the payload received.
Sending a message confidentially does not guarantee data integrity. Even when two nodes have authenticated each other, the integrity of message could be compromised during the transmission of a message.
and we can have integrity of a message without confidentiality.
C)
ans)in Symmetric key encryption every pair need one shared key for both encryption amd decryption. so we have N people.the first person have to communicate to N-1 other needs N-1 keys,
and the second person needs N-2 keys like that the N-1 person needs 1 key.
total keys are required in symmentric key encryption is 1+2+.....+N-1
as N(N-1)/2.
in public key encryption every person uses two keys public and private. public keys knows to everyone and private for themself.
total keys in public key encryption was 2N.
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