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

rick jones perfgeek at mac.com
Fri Jan 19 08:52:53 PST 2007

> In this scenario, the 1500 byte host may be only offering a window of, 
> say 16K.  The splitter offers a window to the 64K host of something 
> like 512K.  This allows the 64K MTU host to send multiple 64K sized 
> packets, which the splitter then sends out as ethernet size packets to 
> the remote host.  In other words, for a 16K vs. 512K scenario, for 
> each window of data transferred between the 64K host and the splitter, 
> there are 32 windows of data transferred out to the remote hosts.
> Conversely, as 1500 byte packets arrive from the remote host, they are 
> acked and accumulated into larger packets that are then transferred 
> over the 64K MTU network in larger packets.

Apart from calling it a splitter, superficially at least that resembles 
what some 10G NICs can do today, albeit with some explicit 
knowledge/assistance by the stack.  Large send has the stack(host) 
giving the NIC(splitter) a large "segment" which the NIC(splitter) 
resegments for the link.  Those flow across the ethernet to the other 
NIC(splitter) which if it has Large Receive Offload enabled will 
"upsegment" the ethernet-sized traffic and give larger segments to the 
receiving stack(host).

rick jones
there is no rest for the wicked, yet the virtuous have no pillows

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