Hello everybody,
for a system that uses a Ethernet point-to-point
connection that end-to-end latency should decrease
dramatically when not UDP/IP but "raw" Ethernet frames
are used.
I.e. the data to transfer are directly written into
the Ethernet frame, the Type field in the Ethernet
header
has to be set to be not equal to 0x800. This should
save transmission time and also it should save
software effort as not protocol layers have to be
passed.
Addressing could be based on MAC addresses (or even
broadcasts?).
Did anybody run any tests with something similar to
that?
I did some "ping-pong" tests with connecting two PC
(point-to-point full duplex) using
rtnet (100 MBit Ethernet, eepro100) and I measured a
round-trip delay for 20 byte UDP data
of approx. 110 microseconds, which is not really
low-latency...
The theoretical value for transfering 20 byte twice
via a 100 Mbit/s line is about 3.2 microseconds -
thus the overhead is fairly big and it should be
possible to reduce it.
Any comments on that are highly welcome!
Thanks
Mathias
=====
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Mathias Koehrer - [EMAIL PROTECTED]
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