reliably detecting the presence of a bridge?

John Levine johnl at
Sat Dec 19 22:52:53 UTC 2015

>I think I have used WiFi terminals ("air ports", "WiFi routers" [spit]) 
>that offer a "bridge" mode, apparently to build a dedicated radio link 
>between two such terminals.

The ones I've seen 

Normally those things are routers, typically with NAT on the wifi
side.  If you put it in bridge mode it is indeed a bridge, passing the
packets back and forth without messing with them.  Depending on which
way you set them up, it might be a wireless link between two wired
networks, or an extra access point with the wire running back to the

>Next objective:  Somebody to 'splain at what happened to the 
>wonderfulness of the OSI model where layer X did not know, could not 
>know, did not care what layer X-1 was, did, or how it did it.

It never actually existed.  If you built your network that way,
passing each packet up and down six or seven layers, it would have
been absurdly slow.  In reality the layers only happen in places where
you can plug in multiple things at one layer, e.g., different physical
connections underneath your IP layer.


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