Retro networking / WAN communities

[Paul Koning]

> On Apr 11, 2022, at 6:35 PM, Grant Taylor via cctalk <cctalk at classiccmp.org> wrote:
> 
> On 4/11/22 4:18 PM, Cameron Kaiser via cctalk wrote:
>> Were there ever actual true 10b2 switches?

DECbridge-90: AUI or 10Base2 to 10Base2.

> ...
> IMHO an unmanaged switch is an evolution of a bridge.  Or in the past, I used to say (a very long time ago) a switch was was three or more ports and a bridge was exactly two ports.  --  Probably inaccurate in some way.  But it worked for the conversation at the time.

That's not accurate.

"Switch" is a marketing term invented by certain companies that wanted to pretend their products were different from (and better than) other people's bridges.  

It never was true that bridges are specifically two port devices.  Yes, the very first few models (DEC's DECbridge-100 for example) were two port devices, as was one whose manufacturer I no longer remember that bridged Ethernet over a satellite link (InterLAN?).  But the standard never assumed that, neither the original DEC one nor its later 802.1d derivative.  To pick one example, the DECbridge-500 is a four port bridge: FDDI to 3 Ethernets.  The DECbridge-900 is a 7 port bridge: FDDI to 6 Ethernets.  Neither, at the time when DEC introduced them, were called or described as anything other than bridges.

The marketeers who flogged the other term also tried to use it to claim it referred to other supposed improvement, like cut-through operation.  That was an oddball notion that never made much sense but some people seemed to like doing it in the 10 Mb and 100 Mb era.  Of course it doesn't work for any mixed media, and at higher speeds the difficulty goes up while the benefits, if they ever were meaningful in the first place, shrink to microscopic values.  For sure it hasn't been heard of in quite a while.  I forgot the name of the company, mid 1980s I think, that made a big fuss over "cut through" and I think may also have been the inventer of the term "switch".  Cisco bought them at some point.

Also: neither "bridge" nor "switch" by itself implies either managed or unmanaged.  I think DEC bridges were generally unmanaged, though that was mostly because no management standards existed yet.  I wasn't around when SNMP became a big deal so I don't know if DEC adopted it when that happened.

	paul