The beauty of Ethernet is that it's simple. "Ethernet" has evolved considerably, and continues to do so. It's not really fair to make comments about it's sociability and talk about it as if it were still in the state it was 20 years ago: "Ethernet doesn't scale because of collisions and exponential backoff" We got around large collision domains by replacing hubs with switches, effectively shrinking the collision domain to the link between the host and the switch (and only in half-duplex). "Ethernet doesn't scale because of large amounts of broadcast traffic." We started to introduce multicast, and multicast-aware switches in IPv4; in IPv6 there is no broadcast traffic. We won't be able to scale networks up until we can turn off IPv4, but once we can IPv6 will be able to grow much larger in terms of per-LAN. The best practice of no more than 512 per broadcast domain will seem very outdated at that point; especially when you add in multicast flood protection, the available bandwidth goes up, and performance of network interfaces improves. The link you pointed to is talking about flat networks of tens of thousands of hosts; that might be excessive right now... But I can certainly see an IPv6-only LAN (with some filtering to make sure ARP and IPv4 traffic is dropped at the port) scaling easily to thousands of hosts with today's hardware. I know the post is a little off topic; but as someone who's met Metcalfe several times I think it's only fair to not make Ethernet out to be the only thing preventing scaleability of networks. On Wed, Jun 15, 2011 at 1:04 PM, <sthaug@nethelp.no> wrote:
Ethernet is not designed for huge LANs. If you want that you need to make significant changes - http://www.cl.cam.ac.uk/~mas90/MOOSE/
Hm:
"Our object is to design a communication system which can grow smoothly to accommodate several buildings full of personal computers and the facilities needed for their support."
Ethernet: Distributed Packet Switching for Local Computer Networks Robert M. Metcalfe and David R. Boggs Communications of the ACM Volume 19 Issue 7, July 1976
So let's change it slightly: Ethernet is not designed for huge broadcast domains.
How big is huge? To some degree it depends on how broadcast "chatty" the protocols used are - but there's also the matter of having a size which makes it possible to troubleshoot. Personally I'd prefer an upper limit of a few hundred computers.
Steinar Haug, Nethelp consulting, sthaug@nethelp.no
-- Ray Soucy Epic Communications Specialist Phone: +1 (207) 561-3526 Networkmaine, a Unit of the University of Maine System http://www.networkmaine.net/