[e2e] Header length field in IP header

[Charles M. Hannum]

On Thursday 23 September 2004 13:22, Saad Biaz wrote:
> The header length HL of IP header has 4 bits.
> Normally, the header length HL would be a number from 5 (no options) to
> 15. Since the IP header is at least 5, I wonder if the field HL can take
> the values 0, 1, 2, 3, or 4 to mean something else. If it takes such values
> (0-4), what is the meaning?

Mostly that every(?) existing implementation will simply drop the packets.