>I've read in some books that the physical layer (L1) of the OSI model deals >with the logical functions of putting the 1's and 0's onto a wire and not >the physical act of doing so, and I've read other books that state that the >physical layer deals with not only putting 1's and 0's onto a wire, but also >the mechanical make-up of a wire, the electrical voltage of a wire, >hardware,. etc. > >Which is true? >
The formal OSI model, as specified in ISO 7498, specifies the interface to the medium, but not the medium itself. Remember that the group that wrote the original document was dominated by telecom people, who make a strong distinction between customer and provider. In 1986 or so, I participated in meetings between ISO/CCITT and IEEE folk, who were trying to harmonize the models. IEEE began by sort of indirectly specifying the medium in terms of its electrical characteristics, and eventually started specifying the cable and connectors. Things like Cat5 were done by different bodies such as EIA. By the time ISO started issuing stack specifications such as ISO 10000, the medium was included for LANs. No one ever went back, however, and amended 7498, the way they did for connectionless communications, routing, etc. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=35565&t=35544 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
