RE: Layer 3.5 is actually layer 4

["Christian Huitema" <huitema@windows.microsoft.com>]

> > UDP being a special case
> > there will be other special cases for non-TCP protocols including
> > ones we have not invented yet
> 
> UDP is a special case because it doesn't provide reliability or
> congestion control. There is no reason why UDP should necessarily be a
> special case for multihoming. The only reason to make it a special
case
> would be because UDP interactions are often very short-lived.

Thinking of UDP as a transport protocol is misleading. UDP is not really
a transport protocol, it is a pass-through. It only performs one of the
classic TP functions: multiplexing. The idea is to provide the
application with a "raw" service from the network. Transport functions
such as reliability are commonly provided as part of the application, or
a layer inside the application (e.g. RPC, RTP). In a multi-homed
environment, the application will also handle multi-homing.

-- Christian Huitema