[e2e] Is a non-TCP solution dead?

[David P. Reed]

At 11:47 AM 3/31/2003 -0800, Mark Handley wrote:
>This raises a higher level issue: to what extent is a wireless link
>error a sign of congestion?

Relating this to my other mail:  in the RF medium, any number of 
communications can happen simultaneously.   Congestion of a sort (too many 
signals impinging on a single receiver antenna) results in a link error, 
but this depends significantly on the systems design of the receiver and 
its assumptions about the kinds of signals that may concurrently be 
transmitted.

There are many more dimensions of adaptation in the RF medium to adapt to 
variations in end-to-end bitrate demand.  These are extraordinarily 
interesting dimensions, far more so than mere rate control.  Simple 
examples include power control, rate adaptation, frequency adaptation, 
antenna steering, reconfiguration of network repeaters into new topologies, 
etc.   Many of these are not mere "link level" adaptations, but can involve 
the whole wireless network topology.

Given that the entire capacity of a wireless system varies tremendously 
depending on demand, one cannot layer wireless networks in the traditional 
way by assuming a set of independent fixed capacities at the physical level 
and then managing capacity above that layer as if the networks consist of 
fixed capacity links.

Thus Hari Balakrishnan's comment implying that partitioning wireless 
networks into a link layer and an end-to-end layer are misleading.   I 
personally suspect that end-to-end approaches are far more important for 
managing latency, throughput, etc. than he'd suggest.   But those 
end-to-end approaches will need to be worked out in a context that includes 
a better abstraction of the tradeoffs than has been traditionally used in 
modeling wired networks.