[LARTC] Packets being coallesced

[LARTC] Packets being coallesced

[Ed W]

Here's a peculiar one.  I'm trying to simulate some speed effects due to 
varying sized packets so I have written a quick perl app which spits out 
packets of a fixed size (<1500 bytes).  What I'm finding is the despite 
apparently turning off nagle and everything else I can think of I still 
notice that when the receiver isn't keeping up that the sending side 
(linux 2.6.11) is coalescing the packets and sending fewer large packets...?

Is this a known and expected thing to do, or am I likely suffering some 
buffering effects in my perl app?

Note: I am observing the effect based on tcpdump traces, so I can 
clearly see when it's sending the expect 1000 byte packets, and when 
it's suddenly packing them altogether into max MTU sized packets.  Note 
also that it's *sending* them like this, it's not just the the receiver 
is buffering and receiving them like this...

Seems odd to me?

Ed W
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