ICMP enables network devices to communicate errors and exceptions. ICMP messages have two components: type and code. The class identifies the message category, and the code indicates subtypes within that category. Network tools and protocols such as ping and traceroute use ICMP.
Unlike other IP packets, ICMP requires no handshake or formal connection between two devices to transmit data. Instead, ICMP operates in the IP layer.
Error Detection (ICMP in Networking Communication)
When a network device encounters an error that prevents IP packet transmission, it reports the problem to the message’s source with an ICMP error message. IP doesn’t have a built-in error-reporting mechanism, so ICMP fills in the gap.
In addition to error reporting, ICMP provides feedback about the network connection status between two devices. This information helps troubleshoot issues and maintain network connectivity.
The ICMP header includes the type of error message and a code defined by the Internet Assigned Numbers Authority (IANA). These two bits provide a pointer to the byte location in the original IP packet that caused the error, making it easier for the receiving network device to identify the issue.
For example, if a packet of data is too large for a router, it will drop the box and send an ICMP error message to inform the transmitting device of the size issue.ICMP also facilitates network diagnostic tools like traceroute and ping, which report how long data travels between two specified locations by sending a series of ICMP echo requests and echo reply messages. However, ICMP can also hurt network performance through attacks such as the Smurf attack and the ping of death, which bombard network equipment with ICMP requests and echo reply messages that overwhelm the system and prevent normal functionality. Understanding how ICMP works in your network and what are the uses of ICMP is important because malevolent actors can exploit it for denial-of-service attacks.
Flow Control (ICMP in Networking Communication)
Network administrators use ICMP to troubleshoot various types of problems. For example, if the rate at which data is transmitted from two devices exceeds what one can handle, it can cause congestion. To remedy this, ICMP sends messages to the sending device with information about the problem. This feedback allows the device to adjust its transmission rate and avoid data congestion.
ICMP also helps diagnose problems with the path data takes between two devices. For instance, when a device does not receive a response to its echo request, it can determine that the message never reached its destination and retransmit the information. This feature is especially useful in finding out which devices were slowing down data transfer along the way.
For those interested in how networks operate, ICMP includes information about each hop data travels to reach its destination. Using the traceroute and ping commands, network professionals can find out how long a packet took to travel from its source to its destination, for instance.
Each ICMP message comprises four parts: type, code, checksum and content. Each class represents a different category of network error, such as destination unreachable or routing table inconsistent. The ICMP message also includes the complete IP header from the original message, which allows the target system to determine which precise packet failed.
Source Quench (ICMP in Networking Communication)
When network devices send data at high speeds, it is common for the gateway to have limited buffer space. If this capacity is reached, the router discards any incoming data packets. This is called congestion control. A device may also send an ICMP message to the data source to indicate that it has sensed congestion.
This message is a Type 4 with code 0 and indicates that a router cannot queue any more data packets and asks that the sender decrease the rate at which it sends data. Unlike a router advertisement, this message does not carry any other information about the congestion.
ICMP has many other types and codes that serve a variety of purposes. For example, a device may use the traceroute function to find out how long data travels from one device to another.
To prevent these attacks, you must have a well-defined security strategy. The goal of the security plan should be to detect a wide range of attacks and mitigate them promptly. To do this, you need a solution capable of monitoring traffic across multiple layers and identifying threats.
Destination Unreachable (ICMP in Networking Communication)
ICMP is an error-reporting protocol that network devices use to communicate. It is not used regularly in end-user applications such as ping, but it is important to know about it for troubleshooting and maintaining Internet connections. Each ICMP message contains a pointer to the location of the problem in the original IP data packet. This helps the receiving device pinpoint which portion of the ICMP message is responsible for the problem.
For example, a router may send a Destination Unreachable message to the source of a data packet when it can’t forward the packet because it is too large. The message will include the code of the type of ICMP message the router generated and additional information, such as the next-hop link’s MTU size.
Using this information, a network administrator can diagnose the problem. Another popular ICMP function is the ability to measure how long a packet travels between two points. This is known as a traceroute and can be useful in identifying the devices that slow down network traffic. In addition to measuring the amount of delay, a traceroute can also determine which routers are involved in the route and the amount of time that has passed since each hop. This is invaluable when troubleshooting network issues such as packet loss and routing problems.