Hello Justone,
After re-reading your post, perhaps it does belong here, after all.
If you think back to the original thick net (802.5) Ethernet, every station was connected to the "cloud" (actually, to the thick coaxial cable) via an AUI cable and an external transceiver. That is, an attachment unit interface cable that extended to a transceiver device that mounted directly onto the coax through a vampire tap.
The distance limit on this AUI might have been 50 meters, say. Not exactly sure anymore, but that's not important. 50 m sounds about right. Why not 1500 meters? The fact is, however, that it was a short extension from the PC or terminal to the coax, which represented the cloud, and that the station was not a part of the cloud. Rather, it was attached to it.
If I take a form of Ethernet (shared or switched, makes no matter) and extend it to the residence over a twisted pair, or coax, or wireless, or fiber optic link, I have the same thing. The only thing that changes is the relative distance of the attachment, and maybe some sublayers within the physical layer. I can extend this same thinking to a neighborhood hub, or switch for that matter, and make my attachment even shorter. Maybe as short as the one that was originally used on thick coax in the office.
Now, if I want to be completely free to enter this ether at any point on the cloud I can do so. Why not? Are you suggesting that a service order and the installation of a medium to the side of my home, which must necessarily follow, is anti-ethernet?
The fact that it is switched v. shared is another area where I feel it is inconsequential today, especially when we use Layer 3 switching, where we resolve to an IP address that is being advertised by my very own end point (even if I do have to go through a DHCP or a NAT occasionally).
You reach a conclusion, which I can partially agree with, except that I don't think you've followed through all the way on certain issues:
Justone:
"Finally, I can't agree with your point:"
FAC:
"Which, when you look at what a switched port is, is nothing radically different in principle, although the newer ports are backed up with a lot more intelligence and speed, with some of them looking at the upper layers for instructions, to boot..."
Justone:
"It is clear from the above quotes from the 1976 papers, that the authors believed there as a radical difference between shared access and point to point links with switching. I believe this patented difference made Meltcale famous and a multi-millionaire from the royalties."
I almost view this as a non sequitur, except that I think I know where you're coming from. My first impulse is to ask, How could the early pioneers of Ethernet, and the greater 'Net, twenty-five years ago have taken such a negative position as you suggest against switched Ethernet, if switched Ethernet didn't come into play until the Nineties?
Unless, of course, you are drawing an analogy to the PSTN type of switched, which is in another league altogether, and therefore doesn't belong.
BTW, this is one of the reasons I like to view historical readings such as you've presented. The volumetric and timeliness requirements of those laboratory folks at that stage of the Internet's growth were almost quaint by today's standards, wouldn't you agree? Their notions about store and forward, for example? How does this play against today's caching models, where information is not only stored, but updated from time to time, sometimes on cue, to keep it fresh? Another example of how the 'Net is both evolving, on the one hand, and devolving, on the other, at the same time.
And their expectations of what the network could, or should, deliver, were also limited by the developments of the day, just as ours are today.
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I just read a great piece by Judy Estrin (ex-Precept, then ex-Cisco, and now head of Packet Design), btw, where she devotes a part of her interview to the potential evils of MPLS, when it is taken to places where, in her opinion, it oughtn't oughta be. And for some of the same reasons that you have cited, centering on the tensions between switched and end to end, shared. Briefly, she cites how initially MPLS was viewed as a means of reconciling the mapping of ATM and IP to one another, but how since those early days it's been viewed as a panacea for all ills. Great stuff. It's in the January Cook Report on Internet, if you can get your hands on a copy.
FAC |
