tep@tots.UUCP (Tom Perrine) (08/28/90)
I am working on a system that will require "real-time" data transfer from a Sun IPC to a 386 PC-clone (20 or 25 MHz) via Ethernet. For us, in this case, "real-time" means 500-1000 byte packets, 10 per second, from the Sun to the PC. The PC and Sun will be on a dedicated Ethernet, i.e. *nothing* else on that wire. I'm planning to use UDP to communicate between the Sun-side application and an application on the PC written using the PC-NFS Programmer's Toolkit. Unfortunately, someone has convinced people around here that PC-NFS "won't do real-time" and that we must "write our own Ethernet protocol stack" to get the performance we need. :-( Obviously, I am looking for performance ammunition to avoid this incredible folly. Does anyone have any performance info on applications written using the PC-NFS Programmer's Toolkit? Or, failing that, has anyone used any other application-callable library for MS-DOS that will let me use UDP at this data rate? HELP! Tom Perrine (tep) |Internet: tep@tots.Logicon.COM Logicon |UUCP: nosc!hamachi!tots!tep Tactical and Training Systems Division |-or- sun!suntan!tots!tep San Diego CA |GENIE: T.PERRINE "Harried: with preschoolers" |+1 619 455 1330 Home of the _Tower Operator Training System_ as seen in the SunTech Journal.
ljm@OBELIX.TWG.COM (09/05/90)
>I am working on a system that will require "real-time" data transfer >from a Sun IPC to a 386 PC-clone (20 or 25 MHz) via Ethernet. For us, >in this case, "real-time" means 500-1000 byte packets, 10 per second, >from the Sun to the PC. The PC and Sun will be on a dedicated >Ethernet, i.e. *nothing* else on that wire... > >Unfortunately, someone has convinced people around here that PC-NFS >"won't do real-time" and that we must "write our own Ethernet protocol >stack" to get the performance we need. :-(... With our *TCP* stack, on a 25 Mhz clone, you can get ~600 1000 byte packets/second -- with UDP you can melt the wire. Note that this PC to PC, a SUN (at least with a stock protocol stack) can't keep up. With this in mind, I would find it very, very difficult to believe that SUN's PC-NFS will have any trouble at all transmitting just 10 packets/second. enjoy, leo j mclaughlin iii The Wollongong Group ljm@twg.com
jbvb@FTP.COM (James B. Van Bokkelen) (09/05/90)
Transfer rates significantly less than 10 packets/sec are relatively easy to achieve if you have a sufficiently lousy Ethernet interface (e.g. 3C501) and offer a big TCP window to a fast host afflicted with the standard 4.2bsd TCP retransmit algorithm. Leo is describing a tuned situation with good hardware. Your prophet of doom has probably seen a pathological situation with bad hardware. Writing your own relaible protocol on both ends of the connection is a lot of effort. Perhaps your prophet of doom would be appeased by the use of one of the freeware TCP/IP stacks, which would allow you to tinker starting from a working baseline.... James B. VanBokkelen 26 Princess St., Wakefield, MA 01880 FTP Software Inc. voice: (617) 246-0900 fax: (617) 246-0901