source address (MAC) (SA)
The source address ( SA) is generally understood to be the address of the subscriber who sent the message.
The source address is used wherever data is transmitted from a data source, the Source, to a destination station, which is identified by the Destination Address. The Source Address is entered in the Source Address fields found in the headers ofmedia access methods and in network and transport protocols. It gives the frame a unique association with the sending entity. In the Ethernet frame, the source address is six octets long; in the IP protocol, the source address field comprises four bytes, and 16 bytes for IPv6.