realtime networking

[Mack <mack@checkpoint.com>]

Hi.

I consider doing some work on realtime networking protocol over ethernet.
(under linux of course)

1. Has anyone already done something similar ?  I couldn't find anything,
   but I want to be sure before I start working.
2. Any interesting ideas/suggestions for the implementation ?
   Currently, I plan to implement something similar to token-ring over
   ethernet, and have an RT_sendto() function that receives the usual
   staff plus priority for the packet.  Needless to say, all hosts on the
   ethernet are assumed to use this protocol, so under no circumstances
   will there be a collision.   (no arps running around, etc...)
   TCP/IP + arps and the rest of the usual networking staff will work on
   this network although not being realtime, but will not affect the
   realtime communication.  This will be achieved by having IP call
   RT_sendto() whenever sending a packet, and use the lowest priority.
   IP itself cannot be made realtime even if you increase its priority,
   because if the target does not exist in the local arp table, you must
   send arp, get arp reply, and only than transmit your packet.  Also, tcp
   has a retransmit mechanism, which is not a good idea here.   If the
   packet got lost, I dont want an auto retransmit, but an error, letting
   the application know that the packet wasnt sent on time.

Any interesting thoughts about this ?
Will such project be useful for more people, if I do it ?

	Yoav


RT Linux Home Page: http://rtlinux.cs.nmt.edu/~rtlinux