Newsgroups: comp.dcom.lans.ethernet
Subject: Re: Recommendation required for NIC card
References: <[email protected]> 
William P.N. Smith  writes:

> [email protected] wrote:
> >I need to know if I require any specific kind of NIC card in
> >computer to achieve deterministic communication using Ethernet.
> 
> I'm not sure you _can_ get deterministic communication with Ethernet,
> much less with TCP/IP, much less under WinDoze or Eunuchs.  It's a
> shared medium, hence you will have collisions, and backoffs (and/or
> store/forward in switches) will happen.
> 
> There are some audio-over-ethernet products that claim some kind of
> phase-match, but I'm nearly certain they are not TCP/IP-based.


The real time audio transmission (and other real-time communications 
though Ethernet) systems typically use UDP (standard part of TCP/IP 
protocol stack) or raw ethernet packets. 

With the TCP protocol it is hard to guarantee real-time performance, 
because of retransmission and automatic network speed adaptation 
that TCP does... 

With UDP or raw ethernet, the packet gets quicly to the network 
and to the receiver... it either get there or does not get there 
quicly. No unknown delays on the way... Put time stamp / serial number 
to the packet, so you will know if packets return at out of order 
or too late (discard too late packets).  

-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/