The FDDI Frame Control byte has a bit that says whether the FDDI frame uses
16-bit MAC addresses (bit is 0) or 48-bit MAC addresses (bit is 1).
The IEEE 802 committee used to allow 16-bit instead of 48-bit addresses.
When ANSI developed FDDI they were just following the 802 committee.
Theoretically 802.3 and 802.5 could use 16-bit addresses too, but, as you
probably know, 16-bit addresses didn't catch on. MAC addresses are 48 bits.
Priscilla
At 05:07 PM 11/23/00, Phil Barker wrote:
>Greetings,
> Reading through CIT course notes Appendix A.
>It states that the Frame Control field indicates the
>size of the address fields i.e variable, this is
>followed by the size of the address fields is 6 bytes.
>
>
>Does anyone know the history behind this ?
>
>I�m guessing that it was being positioned to
>accomodate variable and differing other LAN
>technologies address sizes, such that it could be used
>as a versatile backbone !!!
>
>Any comments ?
>
>Regards,
>
>Phil.
>
>
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