Computer Networking › Section E · The network layer: control plane › Topic E.5
ICMP
IP is best effort and silent about its failures, so the network needs a way to say "that destination is unreachable" or "your packet died here". The Internet Control Message Protocol carries those reports, and ping and traceroute are built on it.
In this topic
- What ICMP is for
- Message format: type, code and evidence
- Common message types
- Ping
- How traceroute uses ICMP
- Worked example: reading a traceroute
- Path MTU discovery
- Worked example: discovering a smaller MTU
- ICMPv6
- Common mistakes to avoid
- Key takeaways
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