RE: threats ID

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

> > However, TCP is not IP, which is the point of my presentation
> > at Vienna.
> We can hardly disagree. But TCP is not SCTP, UDP, DCCP or ICMP either.
> The systems level argument for a layer 3.5 solution is that it can
cover
> all cases, including ones we have not invented yet.

The flip side of that argument is that different transport layers have
different ways of coping with multiple paths between two nodes.
Currently, TCP does not; SCTP has an integrated support for multi-path;
UDP is a pass-through layer and leaves multi-path handling to the
application; and ICMP just does not care. If multi-path support becomes
important, the transports will evolve, and develop different algorithms
that fit different usage model. It is not hard to see how transports
could use per path RTT measurements and congestion windows to arbitrage
between load balancing, resiliency, and re-sequencing. By imposing a
"3.5" layer, you make an early decision to forestall this evolution.

-- Christian Huitema