Retro networking / WAN communities

[Paul Koning]

> On Apr 12, 2022, at 10:44 AM, Todd Goodman <tsg at 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 at 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