[e2e] A simple scenario. (Basically the reason for the sliding window thread ; -))

Joe Touch touch at ISI.EDU
Mon Jan 22 09:09:22 PST 2007

David Borman wrote:
> Joe,
> You keep missing the point.  The delay*bandwidth between the end hosts
> is sufficiently large that it can not be driven at full speed from
> end-to-end given the window advertised by the host on the ethernet side
> of things.  Even if that host advertised a sufficiently large window,
> the inefficiencies of small packets on the 64K MTU side of the network
> will keep the network from being driven at full speed, not to mention
> the cost of ramping up slowstart using 1.5K byte packets vs. 64K byte
> packets.

This is a contradiction: clearly the splitter needs to keep up with
receiving small packets at rate or it can't sustain emitting the large
packets at full speed. If the splitter can do this, then the destination
can. The fact that it doesn't means this is (by definition) a patch to a
broken system.

Using splitters to patch broken systems is understandable, but it's
still preferable (IMO) to make the splitter visible and run it as a true
proxy, terminating the TCP on both ends properly.

> The splitter in this case is sitting between the two networks,
> transparently connecting what it has effectively turned into two TCP
> connections,

That's the point that's missed, IMO - this isn't "effectively' two TCP
connections; it provides the benefit of two TCP connections without
actually terminating the connections, which means this isn't
'effectively' two, but 'one TCP connection with the performance and
semantics of two'. The former is understandable, but the latter is the


Joe Touch
Sr. Network Engineer, USAF TSAT Space Segment

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