Tag: reply

ICMP WHY

Posted on by lechuck park

From DALL-E with some prompting
The image is an educational diagram explaining different ICMP (Internet Control Message Protocol) messages that indicate problems in TCP/IP network connections. When an “Echo Request” is sent and the network is unable to forward the packet, the ICMP may return various error messages:

  1. “Destination Unreachable” (Type 3) can mean that the network/host/protocol/port is unreachable. The reasons can be varied, such as the route is missing, the host or service on the port is down, or the protocol is blocked by a firewall or NAT (Network Address Translation).
  2. “Time Exceeded” (Type 11) indicates that the time-to-live (TTL) of a packet has reached zero, meaning the packet has taken too long to reach its destination, or fragment reassembly time was exceeded.
  3. “Parameter Problem” (Type 12) points to issues like header errors where certain required information is missing or incorrect.

The diagram also emphasizes the importance of checking ICMP return packets for troubleshooting network issues. It provides a detailed list of ICMP types and codes along with their descriptions to assist in identifying the specific nature of the network problem.

ICMP overall

Posted on by lechuck park

From DALL-E with some prompting
This image succinctly demonstrates the essential functions of the Internet Control Message Protocol (ICMP), emphasizing the protocol’s ability to check network paths and status through simple request and response actions. This includes echo (ping) operations, error messages, network path change suggestions, timing measurements, and IPv6 functionalities, all contributing to the efficiency and performance enhancement of network operations.