The internet is generally built on the implicit contract of "TCP-friendly flow control". If your homegrown protocol backs off slower than TCP, some router configurations will drop your packets first.
There is no general policy against non-TCP packets of course, as lots of important internet services are non-TCP. Just flows that don't respond to congestion.
It's not a vendor specific thing, all the major router vendors provide ways of doing this.
> If your homegrown protocol backs off slower than TCP, some router configurations will drop your packets first.
I think that's only if you're being less responsive to congestion signals (drops, ECN marks), and you're using more than a fair share of bandwidth or trying to use any available bandwidth. Fixed but low rate flows (eg. VoIP) shouldn't be penalized until the link is congested with so many flows that the VoIP is trying to use more than 1/N of the bandwidth.
There is no general policy against non-TCP packets of course, as lots of important internet services are non-TCP. Just flows that don't respond to congestion.
It's not a vendor specific thing, all the major router vendors provide ways of doing this.
(Note: router != your home NAT box)