The protocols explicit probe the first hop router on the network for
upnp capabilities. In their model of a home gateway/LAN there is no
"internal" routing, the world is bridged, so the signaling should not
damage routing transparency.
But just imposing that model removes transparency. Maybe I have a router
between my wireless and wired Ethernets. That's a reasonable thing to
do--say, if the wired segment is 100Mbps and is carrying high-bandwidth
{broad|multi}cast traffic. Or maybe I have a substantial number of home
appliances with network connections, and I don't trust their software to
be secure, so I put them in a DMZ, like this:
(Internal LAN) <--> (Firewall A) <--> (DMZ LAN) <--> (Firewall B) <-->
(Outside world)
/===============================================================\
|John Stracke |Principal Engineer |
|jstracke(_at_)incentivesystems(_dot_)com |Incentive Systems, Inc. |
|http://www.incentivesystems.com |My opinions are my own. |
|===============================================================|
|If God had not given us duct tape, it would have been necessary|
|to invent it. |
\===============================================================/