What Is Internet Control Message Protocol icmp ) What Are The Functions Of This

What is ICMP


The Internet Protocol is the principal communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet.

The Internet Protocol (IP) is a protocol or set of rules, for routing and addressing packets of data so that they can travel across networks and arrive at the correct destination. Data traversing the Internet is divided into smaller pieces, called packets. IP information is attached to each packet, and this information helps routers to send packets to the right place. Every device or domain that connects to the Internet is assigned an IP address and as packets are directed to the IP address attached to them, data arrives where it is needed.

Once the packets arrive at their destination, they are handled differently depending on which transport protocol is used in combination with IP. The most common transport protocols are TCP and UDP.


The Internet Control Message Protocol is a supporting protocol in the Internet protocol suite. It is used by network devices, including routers, to send error messages and operational information .

The Internet Control Message Protocol (ICMP) is a network layer protocol used by network devices to diagnose network communication issues. ICMP is mainly used to determine whether or not data is reaching its intended destination in a timely manner. Commonly, the ICMP protocol is used on network devices, such as routers. ICMP is crucial for error reporting and testing, but it can also be used in distributed denial of service attacks(DDoS attacks)

What is ICMP used for?

The primary purpose of ICMP is for error reporting. When two devices connect over the Internet, the ICMP generates errors to share with the sending device in the event that any of the data did not get to its intended destination. For example, if a packet of data is too large for a router, the router will drop the packet and send an ICMP message back to the original source for the data.

A secondary use of ICMP protocol is to perform network diagnostics; the commonly used terminal utilities traceroute and ping both operate using ICMP. The traceroute utility is used to display the routing path between two Internet devices. The routing path is the actual physical path of connected routers that a request must pass through before it reaches its destination. The journey between one router and another is known as a ‘hop,’ and a traceroute also reports the time required for each hop along the way. This can be useful for determining sources of network delay.

The ping utility is a simplified version of traceroute. A ping will test the speed of the connection between two devices and report exactly how long it takes a packet of data to reach its destination and come back to the sender’s device. Although ping does not provide data about routing or hops, it is still a very useful metric for gauging the latency between two devices. The ICMP echo-request and echo-reply messages are commonly used for the purpose of performing a ping.

Unfortunately network attacks can exploit this process, creating means of disruption such as the ICMP flood attack and the ping of death  attack.

How does ICMP work?

Unlike the Internet protocol IP ICMP is not associated with a transport layer protocol such as TCP or UDP. This makes ICMP a connectionless protocol: one device does not need to open a connection with another device before sending an ICMP message. Normal IP traffic is sent using TCP, which means any two devices that exchange data will first carry out a TCP handshake to ensure both devices are ready to receive data. ICMP does not open a connection in this way. The ICMP protocol also does not allow for targeting a specific port on a device.

What happens when ICMP is turned off?

With ICMP disabled, the host will not be aware of the most optimal route to the destination — causing the host to send data through excessive network devices, consuming unnecessary resources which leads to the reduction of network performance.

Internet Control Message Protocol (ICMP) Parameters

  • Type 0 — Echo Reply.
  • Type 1 — Unassigned.
  • Type 2 — Unassigned.
  • Type 3 — Destination Unreachable.
  • Type 4 — Source Quench (Deprecated)
  • Type 5 — Redirect.
  • Type 6 — Alternate Host Address (Deprecated)
  • Type 7 — Unassigned.

What Are the Benefits of Internet Control Message Protocol?

Computer networks provide unlimited uses for today’s society. A network administrator’s responsibility consists of always being able to track a problem when it happens on the network. To perform their jobs effectively, they rely on a vast amount of tools and expertise. One such tool is ICMP protocol. This protocol is integrated with IP protocol, which is the basic makeup of a network and allows requests to be sent out and information to be sent back to the administrator.

Diagnostic Utility

ICMP protocol helps network administrators by assisting them in diagnosing networking issues. Most issues that arise, like server outages or computer failure, are determined with two helpful commands. These commands are PING and TRACERT. An administrator uses PING to send a request from the local computer he uses to another computer or server. This request travels across the network and, once it reaches the other machine, a reply gets sent back to the original computer letting the administrator know that the communication was received. TRACERT performs the same function as PING. This tool will display the path that the request takes across the network so the administrator can view where the breakdown on the network occurred.

Network Speed

Network speed provides users with the access on demand that they require in order to accomplish their task on the network or Internet. Many times administrators run into situations where users complain about Internet pages, as well as network resources, taking too long to load. ICMP protocol provides administrators with the ability to send timed requests across the network, which determines if the network has a bottleneck slowing down access. Most acceptable time spans come back under 100 milliseconds; anything more usually signifies a problem either on the network or the resource a user attempts to access. This type of slow-down is called slow throughput.

Network Layer

Every network has multiple layers that actually make up the entire network, from the computers and servers that operate on the network, to even the pieces you do not see–like the Network layer which helps ICMP protocol actually function. The network layer builds the backbone of the Internet and all networks that transfer any type of data requests. Since the network layer plays such an important part of the network, having the ICMP protocol run on this layer allows the protocol to detect problems that arise and helps track down the source so the administrator can correct the issue(s) right away.

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