networking - IP Header: Total Length vs. Internet Header Length -

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i have questions w.r.t. ip header.

if correct, total length field shows length of overall packet. internet header length (ihl) shows length of header , whether options set or not.

my question why ihl field needed if there total length field shows total length?

regards

with ipv4, header length variable. ihl pointer start of packet payload. without this, unable know payload starts.

ipv6 has fixed header size, ihl unnecessary, , doesn't exist.


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