The Internet Control Message Protocol (ICMP) is a network protocol that is used for network administration and diagnostics. The “ping” utility, which employs an ICMP request and ICMP reply message, is a suitable example. ICMP may send an error message to the source if a specific host or port is inaccessible. Traceroute is another application that makes advantage of ICMP.
Because ICMP messages are contained in IP packets, most people consider it a layer 4 protocol similar to UDP or TCP. ICMP, on the other hand, is usually regarded a layer 3 protocol because it is an integral part of the IP protocol.
The first byte of an ICMP message identifies its type. An ICMP request, for example, uses type 8, while an ICMP reply uses type 0. For destination unreachable notifications, we utilize type 3.
The second byte, code, determines the type of ICMP message being sent. The destination unreachable message, for example, has 16 distinct codes. When you see code 0, it means the destination network was down, and when you see code 1, it means the target host was down.
The third field contains two bytes that are used as a checksum to determine whether or not the ICMP header is corrupt. The remainder of the header is determined by the ICMP message type we’re using.
Let’s have a look at some of the most common ICMP messages in Wireshark to see how they work.
Which application makes use of ICMP (Internet Control Messaging Protocol)?
Ping is an application that uses ICMP messages to report network connectivity and data relay speed between a host and a target computer.
Which application makes use of ICMP (Internet Control Messaging Protocol)? Which NTP DNS rip ping should you use?
The Internet Control Messaging Protocol (ICMP) is used by which application? Explanation: Network devices use ICMP to transmit error signals.
What application makes use of the Internet Control management protocol?
The ICMP protocol is also used to do network diagnostics; the widely used terminal programs traceroute and ping both use it.
What is the most widespread application of the Internet Control Messaging protocol?
For reporting faults and performing network diagnostics, the Internet Control Message Protocol (ICMP) is utilized. When data does not come through as it should, ICMP sends messages from the receiver to the sender as part of the error reporting procedure. ICMP is used in the diagnostic process to send messages that ping and traceroute employ to offer information about how data is transported.
During the operation, which ICMP message is used by the traceroute utility?
The Ping command of the ICMP protocol is used by Traceroute to determine how many distinct devices are present between the machine starting the traceroute and the target. The packet’s time to live value, or TTL, is manipulated by this instruction.
Is ICMP used by traceroute?
A traceroute operates by delivering Internet Control Message Protocol (ICMP) packets to all of the routers involved in the data transfer.
Is ICMP used by ping?
The ping command uses the ICMP messaging protocol, which is arguably the most well-known. An ICMP echo request is sent to the target host when you use the ping command. An echo response is returned by the target host.
What is an ICMP echo scan, and how does it work?
Ping is the most well-known utility that leverages ICMP queries for checking live systems. The idea behind it is simple: ICMP scanning makes queries to hosts and then waits for an echo request to see if the system is still alive.
What does an ICMP echo request entail?
The ping command sends and receives ICMP Echo and Echo Reply packets. When people say they transmitted a ping packet, they are actually referring to an ICMP Echo Request. Both of these texts are self-explanatory. The Echo Request simply states that the packet should be responded to by the host to which it is directed. The ICMP message type that should be used in the reply is Echo Reply. The ping command can specify some data in the Request; whatever data is sent in the Echo Request is returned in the Echo Reply.
Echo Requests and Replies can be used in a variety of ways using the ping command. The ping command, for example, allows you to define the length as well as the source and destination addresses, as well as other data in the IP header. Later in this chapter, in Example 5-6, you’ll get a nice example of the ping command’s capabilities.
FTP and TFTP
In a typical IP network, the File Transfer Protocol (FTP) and the Trivial File Transfer Protocol (TFTP) are two widely used file transfer protocols. FTP is used by most users, while TFTP is used by router and switch managers. Which is “better” depends in part on the task at hand. “Which is supported on the devices that need to transfer the file?” is a more relevant question. Most users today will select FTP over SFTP since it provides more powerful features. However, because the IOS does not support FTP as an application, router administrators choose TFTP.
FTP is a TCP-based tool with various choices and functions, such as the ability to change directories, list files using wildcard characters, transmit multiple files with a single command, and work with a number of character sets and file formats. The basic operation of FTP is more significant in this case. A typical FTP connectionor, to put it another way, connectionscan be seen in Figures 5-15 and 5-16:
An FTP control connection is the connection shown in Figure 5-15. When a user (FTP client) requests to connect to an FTP server, a TCP connection to the well-known port of the FTP server is created (21). The connection is made in the same way that any other TCP connection is made. A user name and password are often required, which the server uses to authenticate the files that are available to that user for read and write permissions. This security is based on the server platform’s file security. The environment from which the client established the FTP connection implies access to files on the client side; this, too, is dependent on the operating system on the client platform. This connection receives all of the commands necessary to govern the transmission of a file, hence the term FTP control connection.
At this stage, the user can use a variety of commands to enable transfer settings, change folders, and list files, among other things. A file is transferred anytime a get or put command is input (or mget or mputm stands for multiple) or the analogous button is selected. A separate TCP data connection is used to transfer the data. The FTP data connection mechanism is depicted in Figure 5-16.
Another TCP connection is made, this time to well-known port 20, as illustrated in Figure 5-16. A file can be sent using this convention without interfering with the control connection. Instead of making a separate control/data connection for each file that needs to be sent, the control connection is formed once. The environment is defined by the control connection, and these settings have an impact on the data connection’s functionality. For example, commands on the control connection can be used to specify the default directory for future transfers, as well as the type of data to be sent (binary or ASCII). The control connection will remain active until the user disconnects it. A separate data connection is formed for each file transfer while the control connection is active.
As demonstrated in Figure 5-16, an additional step helps prevent hackers from breaking in and moving files. Rather than simply making a new connection, the client informs the server via an application layer message with the new connection’s port number. The server will not transfer the file (zzz in this case) over any other data connection than the one to the correct socketthe one with the client’s IP address, TCP, and the server-assigned port number (1031, in this case).
The Trivial File Transfer Protocol (TFTP) is a very basic UDP-based application. One of the reasons for the necessity for such an application (when the more robust FTP is available) is that TFTP requires little RAM to load and program. Such gains appear to be negligible now that incredibly low-cost memory and computation are available. FTP is most likely what you will use if you plan to transfer files from your PC on a regular basis. Cisco, on the other hand, uses TFTP rather than FTP to move files into and out of IOS-based routers and switches.
Because TFTP uses UDP, the transport layer does not have to establish a connection or recover from errors. Application layer recovery is used by TFTP, which embeds a short header between the UDP header and the contents. This header contains instructions such as read, write, and acknowledgement, as well as a numbering scheme for 512-byte data blocks. The data is acknowledged and resent using these block numbers. TFTP sends one block and then waits for an acknowledgement before sending another, equating to a window size of one.
What is the difference between TCP, UDP, and ICMP?
TCP and UDP are for transporting application data (i.e. whatever the app wants), but ICMP is a “control” protocol that sends information about other protocols.
