http://www.cs.unc.edu/Courses/comp249-s02/lectures/comp249_s02_3/sld011.htm
As can be seen, the TCP packet does NOT have the ethernet card's MAC address in the format. The only way this data can be transferred to the destination is for the application to place the MAC address in the data. The MAC address (Media Access Control) is part of the Link Level layer of the 7 layer ISO networking model (layer 2, I believe.) Since lower layers "encapsulate" the upper layers, information pertaining to lower layers are not carried forward when that layer is "stripped" away by the receiving (or routing) devices. In fact, once you traverse from an ethernet environment to some other environment, the MAC address becomes irrelevant. (The above link is part of a slide show which might be of interest to some.) :o) Rich Cloutier SYSTEM SUPPORT SERVICES President, C*O www.sysupport.com ----- Original Message ----- From: "Rodent of Unusual Size" <[EMAIL PROTECTED]> To: "Greater New Hampshire Linux Users" <[EMAIL PROTECTED]> Sent: Tuesday, March 19, 2002 11:17 PM Subject: MAC at TCP level > 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? > > TIA.. > -- > #ken P-)} > > Ken Coar, Sanagendamgagwedweinini http://Golux.Com/coar/ > Author, developer, opinionist http://Apache-Server.Com/ > > "Millennium hand and shrimp!" > > ***************************************************************** > To unsubscribe from this list, send mail to [EMAIL PROTECTED] > with the text 'unsubscribe gnhlug' in the message body. > ***************************************************************** > ***************************************************************** To unsubscribe from this list, send mail to [EMAIL PROTECTED] with the text 'unsubscribe gnhlug' in the message body. *****************************************************************
