IPv4 Protocol Notes
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Version
Only 4 bits, this field determines the how the rest of the packet is treated
HLen
HLen is the header length and is specified as the number of 32 bit words. Thus the header is at most 480 bits (2^4 - 1) * 32. Normally this value is 5 because we don't specify any options varibles.
TOS
Length
Ident
Flags
Offset
TTL
Protocol
Checksum
SourceAddr
DestinationAddr
Options(Variable)
Pad (Variable)