On Tue, 12 Nov 2024 18:25:20 -0500 James Knott <james.knott@jknott.net> wrote:
On 11/12/24 17:54, Lew Wolfgang wrote:
Of course you're correct!
So, what else is new? 😉
48-bits in a MAC address. That makes a bit more sense. After all, /64 is a nice power of two.
It's amazing, Ethernet addressing was developed in 1973. How prescient was Bob Metcalfe and his team to settle on 48-bit addressing! It's funny what one remembers. I recall sitting on the toilet at work in 1976 reading a EDN magazine article talking about how packet switched networks were the wave of the future. It was ten years later when I found myself pulling that yellow Thicknet coax around to set up our first Ethernet subnet. Now look at what we have!
Look up Ethernet Blue Book, to see the first official spec from 1980. However, originally, Ethernet had an 8 bit MAC address, just like ARCnet.
Hmm, both are right. But you're talking about different things. My copy of the blue book says that the destination and source data link addresses are each 6 octets in length and "A station's physical address should be distinct from the physical address of any other station on ANY Ethernet." (p21) But there were obvious physical restrictions for the number of stations that could be connected to a single coax cable of max length 500 m with bee stings at 5 m intervals. The first experimental Ethernet was a single segment that ran at 3 Mbps and had 8 bit addresses, as reported in ETHERNET: DISTRIBUTED PACKET SWITCHING FOR LOCAL COMPUTER NETWORKS. But that was just a convenient size for the first experimental rig, and they recognised that larger addresses were desirable in production.