Question

12. The following questions relate to the protocol used to manage the health of the network and allow network devices to communicate to each other to keep network traffic flowing freely. An example of a common command that uses this protocol is ‘ping’. (10 marks total)

    1. What is the name of this protocol? (1 mark)

    2. What layer of the TCP/IP network model does this protocol belong? (1 mark)

    3. What is the command used to display a path that network traffic takes across a network? (2 mark)

    4. Name a feature of this protocol that is used to map this path mentioned above, and briefly explain how the Tracert function works. (1 + 5 = 6 marks)

Answer 1

The name of this protocol is ICMP that is Internet Control Message Point. The Purpose of ICMP is for error reporting, it is used for sending control and error messages. This protocol is used by network devices such as routers to send error messages. It is also used to determine whether data is reached to the destination or not in a timely manner.

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The ICMP protocol resides in the layer 3 of the TCP/IP network model that is the Internet layer or the Network layer. As it's job is to send error messages and to determine wheter data is reached to the destination from the source or not it resides in the layer 3 and as being in the network layer the ICMP are carried by the IP packets not the data packets. They are sent through IP datagrams.

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One of the common application utilities of ICMP is to map out or trace the path that the data packet can take. This is done through traceroute or tracert command. For UNIX OS traceroute is used and for Windows OS tracert is used. It is the command used to display a path that network traffic takes across a network.

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Feature of this protcol is the traceroute feature that can trace the present and future paths for a data packet to travel. In order to trace the expected and present path of the data packet empty data packets is used by tracert to accomplish this task. The Initial data packet is assigned a TTL value of 0. TTL stands for Time To Live, TTL limits how long data can live in an IP network. Every packet of data is assigned a TTL value. Every time a data packet reaches a hop, the TTL value is decreased by one. When the first router recieves the data packet it is then dropped and ICMP message is transmitted back to the source computer, first router location is known via this. After the initial data packet is sent out and returned, the next data packet is then sent out with a TTL value of 1. Once the next router receives this particular data packet, it will decrease the value by -1 and it will be returned with another ICMP message, thus revealing the identity of the second router. This process will repeat until the data packets either reach the destination device or it reaches the maximum number of hops.Traceroute measures the time between when the data is sent and when the ICMP message is received back, from this the RTT value is calculated. At the end after the completion of the this process traceroute or tracert gives us the number of hops to the destination device, the RTT length for each hop, and the device name and IP address for each hop.