Destination Unreachable Message Format
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Questions and Answers

What is the type of the echo-request message?

  • 0
  • 14
  • 8 (correct)
  • 13

    • What is the purpose of sending an echo-request message?

  • To check the host's reachability (correct)
  • To calculate the round-trip time
  • To synchronize the clocks in two different machines
  • To learn the time on a remote computer

    • What is the type of the timestamp-reply message?

  • 13
  • 0
  • 14 (correct)
  • 8

    • What is the code of the timestamp-request and timestamp-reply messages?

    <p>0</p> Signup and view all the answers

    What can be calculated using the timestamp-request and timestamp-reply messages?

    <p>The round-trip time</p> Signup and view all the answers

    What is the purpose of the ping command?

    <p>To check the host's reachability</p> Signup and view all the answers

    What are the two debugging tools that use ICMP for debugging?

    <p>ping and traceroute</p> Signup and view all the answers

    What is required to synchronize the clocks in two different machines using the timestamp-request and timestamp-reply messages?

    <p>The exact transit time</p> Signup and view all the answers

    What is the condition for calculating the round-trip time using the timestamp-request and timestamp-reply messages?

    <p>The exact transit time is known</p> Signup and view all the answers

    Who can send a parameter problem message?

    <p>Both the router and the destination host</p> Signup and view all the answers

    What is the purpose of the redirection message?

    <p>To update the routing table</p> Signup and view all the answers

    What is the type of message for a parameter problem?

    <p>12</p> Signup and view all the answers

    What is the purpose of an echo-request message?

    <p>To ping a message to check if the host is alive</p> Signup and view all the answers

    Who can send an echo-request message?

    <p>Both the router and the host</p> Signup and view all the answers

    What is the response to an echo-request message?

    <p>Echo-reply message</p> Signup and view all the answers

    What is the main purpose of ICMP Query messages?

    <p>Error handling and debugging</p> Signup and view all the answers

    When is a redirection message sent?

    <p>When the packet is sent from the router to the host on the same network</p> Signup and view all the answers

    What are the two types of messages used for error handling and debugging?

    <p>Echo-request and echo-reply</p> Signup and view all the answers

    What does the 'Type' field in the destination unreachable message specify?

    <p>The type of message</p> Signup and view all the answers

    What is the range of the 'Code' field in the destination unreachable message?

    <p>0 to 15</p> Signup and view all the answers

    What happens when the destination does not want to process the request?

    <p>The destination sends a destination unreachable message</p> Signup and view all the answers

    What is the purpose of the source quench message?

    <p>To inform the sender that the datagram has been discarded due to congestion</p> Signup and view all the answers

    What is the type of the source quench message?

    <p>Type 4</p> Signup and view all the answers

    What happens when the router is not able to handle the high data rate?

    <p>The router sends a source quench message</p> Signup and view all the answers

    What is the role of ICMP in the network layer?

    <p>To provide feedback about congestion</p> Signup and view all the answers

    What is the consequence of not having flow control and congestion control in the network layer?

    <p>The sender does not think about the receiver's ability to receive packets</p> Signup and view all the answers

    What should the sender do when it receives a source quench message?

    <p>Stop or slow down the sending of datagrams</p> Signup and view all the answers

    What is the primary function of the Traceroute tool?

    <p>To track the route taken by a packet on an IP network</p> Signup and view all the answers

    What type of messages does Traceroute use?

    <p>ICMP messages</p> Signup and view all the answers

    What happens if the TTL value reaches zero?

    <p>The packet gets discarded</p> Signup and view all the answers

    Why does Traceroute use small TTL values?

    <p>To quickly expire the packet</p> Signup and view all the answers

    What is the purpose of the TTL value in Traceroute?

    <p>To track the route taken by the packet</p> Signup and view all the answers

    What happens when the TTL value is 1?

    <p>The packet gets discarded by router 1</p> Signup and view all the answers

    What is generated by router 1 when the TTL value reaches 0?

    <p>A time-exceeded message</p> Signup and view all the answers

    What is the purpose of the example in the content?

    <p>To illustrate the use of Traceroute</p> Signup and view all the answers

    What is the relationship between the TTL value and the router that generates the time-exceeded message?

    <p>The TTL value is equal to the number of the router that generates the message</p> Signup and view all the answers

    What is the primary purpose of ICMP echo-request and echo-reply messages?

    <p>To perform a ping operation</p> Signup and view all the answers

    Why is ICMP a connectionless protocol?

    <p>Because it does not open a connection with the destination device</p> Signup and view all the answers

    What happens when a device is targeted by an ICMP flood attack?

    <p>The device is overwhelmed with ICMP echo-request packets</p> Signup and view all the answers

    What is the main goal of a ping of death attack?

    <p>To crash the targeted device</p> Signup and view all the answers

    Why is ICMP not associated with a transport layer protocol?

    <p>Because it is a network layer protocol</p> Signup and view all the answers

    What is the consequence of a device receiving a ping packet larger than the maximum allowable size?

    <p>The device freezes or crashes due to a buffer overflow</p> Signup and view all the answers

    What is the main difference between an ICMP flood attack and a ping of death attack?

    <p>The size of the packets used</p> Signup and view all the answers

    Why is ICMP commonly used in DDoS attacks?

    <p>Because it can be used to overwhelm a device with packets</p> Signup and view all the answers

    What is a characteristic of ICMP that makes it vulnerable to DDoS attacks?

    <p>It does not open a connection with the destination device</p> Signup and view all the answers

    Study Notes

    Destination Unreachable Message

    • Type 3 specifies that the destination is unreachable
    • Code (0 to 15) identifies whether the message comes from an intermediate router or the destination itself
    • Code 2 or 3 indicates the destination creates the destination unreachable message
    • The destination sends the destination unreachable message to the source if it does not want to process the request

    Source Quench

    • ICMP provides feedback to the sender to slow down the packet transmission rate
    • The router sends a source quench message (Type 4, Code 0) to inform the sender to reduce the packet transmission rate due to congestion
    • The sender must either stop or slow down the sending of datagrams until the congestion is reduced

    Parameter Problems

    • The router and destination host send a parameter problem message (Type 12, Code 0 or 1) to indicate improper parameter settings

    Redirection

    • Redirection message updates the routing table and informs the sender to use a better route
    • The router sends a redirection message to the host on the same network
    • The host updates its routing table to use the better route

    ICMP Query Messages

    • ICMP query messages are used for error handling and debugging
    • Echo-request (Type 8, Code 0) and echo-reply (Type 0, Code 0) messages check host reachability and operation of IP protocol
    • Timestamp-request (Type 13, Code 0) and timestamp-reply (Type 14, Code 0) messages calculate round-trip time and synchronize clocks

    Debugging Tools

    • Ping uses ICMP echo-request and echo-reply messages to check host reachability
    • Traceroute tracks the route taken by a packet on an IP network from source to destination
    • Traceroute uses ICMP messages and TTL values to determine the location of routers

    How ICMP Works

    • ICMP is a connectionless protocol and does not require a transport layer protocol (TCP/UDP)
    • ICMP does not open a connection before sending a message
    • ICMP does not allow targeting a specific port on a device

    ICMP in DDoS Attacks

    • ICMP flood attack: the attacker overwhelms a targeted device with ICMP echo-request packets, consuming its computing resources
    • Ping of death attack: the attacker sends a ping larger than the maximum allowable size, causing the machine to freeze or crash

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    Related Documents

    ch2.pdf

    Description

    This quiz covers the different fields in a Destination Unreachable message, including Type and Code, and how they are used in network communication.

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