ICMP: Internet control message protocol
Used by hosts & routers to communicate network-level information such as:
- Error reporting: unreachable host, network, port, protocol
- Echo request/reply (used by ping)
ICMP can be seen as network-layer “above” IP:
- ICMP messages carried in IP datagrams
- ICMP message: type, code, plus first 8 bytes of IP datagram causing error
Figure 20 Type and Code fields in ICMP message
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This resource was developed as part of an Erasmus+ project, funded with support from the European Commission under grant agreement 2016-1-SE01-KA203-22064.
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- The University of Borås, Sweden
- The University of the Highlands and Islands, Scotland
- The University of Alcalá, Spain
- Digital Connections, Scotland
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