ROPE Language Reference - "$ip_ihl"

The "$ip_ihl" register contains the header length value from the packet being inspected. This is a read-only, integer value.

RFC_791 descibes this value as follows..

IHL:  4 bits

 Internet Header Length is the length of the internet header in 32
 bit words, and thus points to the beginning of the data.  Note that
 the minimum value for a correct header is 5.

See Also

RFC_791, $ip_check, $ip_daddr, $ip_dont_frag, $ip_frag_off, $ip_id, $ip_protocol, $ip_saddr, $ip_tos, $ip_tot_len, $ip_ttl, $ip_version