On 4/12/2022 10:50 AM, Paul Koning wrote:
On Apr 12, 2022, at 10:44 AM, Todd Goodman <t...@bonedaddy.net> wrote:
On 4/12/2022 10:12 AM, Paul Koning wrote:
On Apr 12, 2022, at 9:56 AM, Todd Goodman via cctalk <cctalk@classiccmp.org>
wrote:
...
The big difference in my mind between bridge and switch is:
* Switches learn what port given MACs are on and only sends unicast
traffic destined for that MAC address on that port and not all
* Bridges send unicast traffic to all ports
Absolutely not. The only standard device that forwards unicast to all ports is
the repeater. I don't know of any packet forwarding device that sends unicast
traffic to all ports; certainly no such thing can be found in any standard.
Learning was introduced by DEC in the DECbridge 100 (along with spanning tree);
IEEE later standardized this, with some small mods, in 802.1d.
paul
You snipped the part where I said except for ports that should not receive the
traffic due to blocked ports from the Spanning Tree Protocol in 802.1d and that
if that fails you end up with a broadcast storm.
Well, I didn't mention STP in 802.1d specifically because I thought it was
obvious.
Bridges were useful even after switches arrived to allow monitoring of traffic
on any port of the bridge. It was useful before switches got port mirroring
and even after as it didn't require any configuration.
Yes, I snipped part of what you said, but that doesn't affect my point.
Learning has always been part of what bridges do. It's a core part of the DEC bridge
spec, and a core part of the DECbridge-100 functionality. It is the reason why Tony
Lauck and George Varghese invented the "timer wheels" scheme for keeping 8000
timers in constant time.
A device that doesn't do address learning and floods unicast frames is not a bridge but
rather a non-standard piece hardware. I don't actually know if anyone ever implemented
such a device. Certainly I've never seen one or built one myself, even though what I
built was called "bridge".
paul
I'm not talking about pre-standard DEC devices.
I can show you a standard commodity bridge from multiple vendors right
now that will allow you to monitor unicast traffic destined for other
ports just by plugging in to one of the other ports on the bridge.
I don't have my 802.1d spec I implemented a bridge from in the 90s
But whatever, I've used that capability a lot over the years on a lot of
different bridges so have nothing more on the topic
Todd
