[e2e] overlay over TCP

[Joe Touch]

David P. Reed wrote:
> Anyone know of any experiments that have involved overlay networks that 
> run over TCP virtual circuits, but which try to avoid some of the 
> application-layer problems of reliable in-order delivery?

Yes. They suffer from TCP's inability to do a true 'push' - i.e., since 
there is no correlation between writes and TCP segments, it's frequently 
the case that such use has significant 'stalls', either waiting for 
packet aggregation (if NAGLE is on, which it should not be, though), or 
for ACK compression.

They've been used for years for tunnels at the application layer. The 
phrase "TCP tunnel" gets half a million hits in Google, and some of 
those on the first page are even relevant.

It'd be better to use DCCP for such tunnels, though, if you want 
in-order, TCP-friendly, but also want some sort of segment-boundary 
semantics preserved at the API.

Joe
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