Hi there
On 10/09/16 13:37, Nicolas George wrote:
Le quintidi 25 fructidor, an CCXXIV, Rob van der Putten a écrit :
So the question should have been 'Is delayed ack disabled'.
I have a hard finding decent information on the subject, so I did a bit of
experimentation;
I send tiny bits of data (two bytes at a time) to a little echo server. As
it turns out, the use of delayed acks and therefore nagle, depends on the
time between sending the bits of data and the RTT.
I do not think you can really test delayed ACK with an echo server: the
principle of delayed ACK is to leave a little time to the application to
send a reply, because then the ACK can be bundled with the reply, saving a
packet.
With an echo server, the reply comes immediately, never letting the delay
for the ACK expire.
I use netcat6. From man nc;
nc6 --continuous --exec cat -l -p <port>
So the data goes from nc to cat and then back to nc.
Timestamps (epoch.microseconds) are dumped to a file on transmission and
to an other file on reception of the 'echo'. Further check with tcpdump.
Experiment on LAN and experiment over DSL;
When the time between the bits of data is larger then the RTT, data is
send at two bytes per TCP packet.
Regards,
Rob
