Bit order == byte order??

[Frank Solensky]

In sys/netinet/ip.h, the first octet of the ip header structure tests the byte ordering to determine the ordering of the header length (ip_hl) and version (ip_v) fields.

My question: that always works?  While my reading of the language specification document leaves both the ordering of the bits within a byte and the bytes within a longer field as implementation choices, the two are independent of each other.

I haven't run into a CPU where this assumption was proven incorrect. It just surprised me to see that recently