Rodent of Unusual Size <[EMAIL PROTECTED]> writes:

> I'm not real conversant with the various packet formats.
> Is there anything at the TCP packet level that might include
> the MAC address of either endpoint?  If so, I rather guess
> it isn't used, but I'm not even sure it exists.  In other
> words, is the MAC address completely inaccessible in a WAN
> environment using TCP, or only by convention?

The MAC address is not visible at the TCP level. Ethernet was developed
at Xerox as a full networking solution, but its most common uses these 
days is vestigial, merely  acting as a physical transport underneath IP.
IP can sit transparently on top of Ethernet, ATM, FDDI, serial line, and
many others. 

There's even an old April Fools gag about running IP over a system of 
carrier pigeons:

    Request for Comments: 1149 - 1 Apr 1990
    A Standard for the Transmission of IP Datagrams on Avian Carriers

    Request for Comments: 2549 - 1 Apr 1999
    IP over Avian Carriers with Quality of Service


-- 
John Abreau / Executive Director, Boston Linux & Unix 
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