The Request for Comment (RFC) system
Describe the structure of RFC documents and explain the significance of the terms
‘must’, ‘should’ and ‘may’ in the RFC context. What relationships can exist between
different RFC documents?
RFC is a computer concept that is established by the IETF that explaining the basics of internet engineering. This concept helps in linking some of the internet activities such as businesses transactions and many others. The RFC contain a chain of computer commands that controls most of the internet activities. The main purpose for the RFC establishment is to allow room for more notes on ARPANET (Anders, 45). The RFC work in line with the given internet protocols to execute commands or instructions given. ‘Must’ and ‘may’ are used in the RFC programming to give commands and instructions based on the task to be executed. ‘Must’ give authenticity or vitality of the action to be taken. It only applies to cases where verification is needed. May on the other hand gives options from which clients are to choose from . In this case, a client or program user can choose to skip the procedure to avoid future complications. Issuing commands in this case is done through codes that are understandable and related to computer language. This computing practice was invented by one of the computer wizards some years back by the name Steve Crocker.
Find the RFC that describes the (ver 4) Internet Control Message Protocol (ICMP)
on the Internet. Describe the method used to find it, the location of the document
and the numbers and broad content of any RFCs which are related to it.
The RFC used in describing the Internet Control Message Protocol is the RFC 792. I found this through typing Internet Control Message protocol in google. In the list of the results I got, from www.ietf.org/rfc/rfc792.txt, I realized that there are two types of RFC best use in describing ICMP. These are the RFC 792 and RFC 777. I took RFC 792 because the RFC 777 was more of obsolete as stated in the website. The RFC 792 was in normal font colour hence it had obsoleted the RFC 777.
The information provided by the RFC 792 comes out as the compliment of the information provided by the RFC 777. The type 777 only gave less detailed information about the ICMP without such details like the echo replies and request. However, the RFC 972 contained all these information giving out more clarity on the ICMP. In addition, the RFC 972 contains all the information found in the RFC 777 hence I found it as the best description for the ICMP (Miller, 941).
Describe, using the current (ver 4) ICMP RFC, how the ICMP protocol works and include a description of the ICMP message field and a summary of the defined types of ICMP message. (2 marks)
The definition of the ICMP remains within the RFC 792 acting as a communication protocol occurring in the presence of IP protocol implementation on two connected system. it works in providing information to the sender on the problems occurring during TCP/IP implementation while also giving information about the internet settings. The working of the ICMP involves the ping program which first creates a normal healthy IP header and followed by adding the ICMP header to that. In present format, the ICMP packet type is represented by the first byte while the second by represents the Code (Anders, 34). Combining the Type and Code helps in giving information about the characteristics of a problem exhibited in the internet.
The ICMP consist of three message types usually sent including time exceeded message, echo message, and routing related messages. The time exceeded message represents the message type which occurs when there is reduction of the TTL to zero in the presence of processed datagrams. The occurrence of the time exceeded message is accompanied by the router which specializes in processing the datagram to decrease the TTL to zero. The time exceeded message normally symbolizes that there is occurrence of routing loops in the TCP/IP implementation. Consequently, it is crucial during the TCP/IP implementation.
The echo message is also crucial for the TCP/IP implementation since it helps in tracing the route followed by a packet to another host from a known host. This makes the echo messages to be described as message type which gives the information about the status of other hosts. The components that help the echo messages to achieve its functions include the echo request and echo reply. The third message type, which is Routing relatd messages, helps in providing information about a certain problem during the TCP/IP implementation. The Routing related messages include destination unreachable, router advertisement, redirect and router solicitation (Anders, 34).
Describe how ICMP can be used to create a program that can report the route taken by a packet from one host to another. (1 mark)
The ICMP aids in the creation of a ping program or a trace program that can then help in reporting the route taken by he packet. The ping program works on the mechanism of creating a normal healthy IP header which helps in sendin the ICMP packets with the type 8 (Echo Request) to the targeted host (Anders, 42). The echo produced by the Ping is what helps in giving information about the route taken. The ‘echo request’ by ping program means that the involved person is manipulating the target to offer the reply packet by the Echo. The reply helps the computer to interchange the destination IP addresses and the source of the IP addresses followed by incorporating the optional information received (Greene & Smith, 140). This helps in getting the reply back to the persons involved in reporting about the routes. In the course of reporting about the route, there is also a need for the IP header to substitute the 8 found in the ICMP Type Filed and put a 0. The zero acts as a echo reply. The packet received gives a chance to store the time for the reception. The time can then help when there is need for comparison with the time taken by the sent Echo Request. The comparison allows for checking off the information about the trips made while also helping in gauging the dependability of the route (Anders, 34).
Choose non-zero values for the parameters required in an ICMP(ver 4) ECHO message (choose 32 bits of data) and compute the checksum. Change a random bit in the ICMP message and show how the checksum can be used by the receiver to detect the error. Full details of the checksum calculations must be given. (1 mark)
At the sending node
Non zero values implies that the Code is zero while the value of Type is 8. The value for identifier is 1.
Combining the type and code
00001000 0000000
Where the 0 represents the code while 1 is the identifier.
For the checksum
00000000 00000000
This result to a sequence of 01000000 010000000
Giving rise to a data of 01000000 010000000 00000000 01000000
On the receiving node
Type and code will be the same with that at the sending node 00001000 0000000
While the checksum will be 01110111 01011110
This leads to getting the complementing sum as 11111111 11111111
Consequently, the resulting checksum indicates that an error occurred because of the presence of 1(Greene & Smith, 140).
Suggest an application for the ICMP timestamp message indicating briefly how it
would be implemented. (1 mark)
The ICMP timestamp usually applies when there is need of a time synchronization. The implementation of the ICMP timestamp involves setting the Type at 13 while the code should be at zero. Further, there is need for setting the reply of the timestamp to be at the same level with the request of the timestamp. This occurs through the application of the identifier which helps in determining the perfect value for the match. Further, an individual will also need to use the sequence number in order to match the request and the reply. To get the amount of millisecond recorde immediately after the midnight UT, there is need to incorporate the 32 bits timestamp length which helps in transimission of the required data (Greene & Smith, 140). Provide the recorded time does not occur in milliseconds, then the subject can make use of any time within timestamp. This will only occur when there is presence of a high order bit set in ordr to give out a non-standard value in the timestamp (Anders, 34).
Works cited
Anders, and Carol. A clear look at tax software. The CPA Journal (May): 2009.20-29.
Miller, Mark A. Internet Technology Handbook: Optimizing the Ip Network. Hoboken, NJ: Wiley-Interscience, 2004. Print.
Greene, Barry R, and Philip Smith. Cisco Isp Essentials. Indianapolis, IN: Cisco Press, 2002. Print.
