Hot answers tagged ipv4
4
The short answer is yes - the IPv4 spec says its necessary, and so it is, at least for compatibility purposes.
The long answer is that some layer 2 transports will pad a datagram if it's under a particular size. the IP length header is important when this occurs, so that the layer two padding can be discarded.
2
This is probably an off-topic question, but I clearly remember asking the same question some 25 years ago in university when we discussed TCP/IP in networking 101.
The 2 answers I got then and which still makes sense where:
"At the time TCP/IP v4 was designed it was far from certain there wouldn't be an extension to IPv4 in the future that would make it ...
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