So we've managed to look at real network traffic and parse it completely. We've also taken some ICMP packets, parsed them, and then serialized them right back and we got the exact same result.
So I know what you're thinking - let's just move our way down the stack again - stuff that ICMP packet in an IP packet, then in an Ethernet frame, and then serialize the whole thing.
Right? Wrong.
We need to think about what we're doing. We (a host) are attempting to ping another host. By sending ICMP packets that are inside IPv4 packets that are inside Ethernet frames. That means we need four principal pieces of information.
So I know what you're thinking - let's just move our way down the stack again - stuff that ICMP packet in an IP packet, then in an Ethernet frame, and then serialize the whole thing.
Right? Wrong.
We need to think about what we're doing. We (a host) are attempting to ping another host. By sending ICMP packets that are inside IPv4 packets that are inside Ethernet frames. That means we need four principal pieces of information.