kunkee@ficc.uu.net (randy kunkee XNX MGR) (11/17/89)
Question: If you only want to connect two systems together, via Ethernet, it seems that it should be possible to do this simply with a transceiver cable properly adapted to rearrange the signals. We have some special situations in which this would be desireable (ie. much cheaper). Does anybody sell such an adaptor? If this can't be done, could someone explain to me why not, or why you MUST have a transceiver? Please reply via e-mail. If requested, I will post a summary. Thanks in advance. -- Randy Kunkee Ferranti International Controls Corporation 12808 W. Airport Blvd. Sugar Land, TX 77478 UUCP: uunet!ficc!kunkee ph: (713) 274-5132
eriks@yunexus.yorku.ca (Eriks Rugelis) (11/20/89)
>Question: If you only want to connect two systems together, via Ethernet, >it seems that it should be possible to do this simply with a transceiver >cable properly adapted to rearrange the signals. Transceivers do more than 'just put the signal on the medium'. The actual collision detect mechanism lives in the transceiver and not in the controller. Without CD you no-longer have CSMA/CD and Poof! it's not Ethernet anymore :-) >We have some special >situations in which this would be desireable (ie. much cheaper). Does >anybody sell such an adaptor? What you're looking for is a multi-port transceiver with a very small number of ports (i.e. 2). American Network Connections sells something called an ANC-10 that does exactly that. They used to charge only a bit less than the price of two normal transceivers for one 2-port job. There may be other vendors that have similar products. -- --- Voice: Eriks Rugelis E-Mail: eriks@libra.yorku.ca Ma Bell: 416/736-5257 x.2688 UUCP: yunexus!eriks Last resort: eriks@yulibra.NETNORTH Snail: York University, 4700 Keele St., North York, Ontario, Canada. M3J 1P3
dixon@gumby.paradyne.com (0000-Tom Dixon(0000)) (11/29/89)
In article <7014@ficc.uu.net> kunkee@ficc.uu.net (randy kunkee XNX MGR) writes: >Question: If you only want to connect two systems together, via Ethernet, >it seems that it should be possible to do this simply with a transceiver >cable properly adapted to rearrange the signals. We have some special >situations in which this would be desireable (ie. much cheaper). Does >anybody sell such an adaptor? This is not impossible. It is the AUI equalvilent of a cross DTE cable. You don't have to worry about losing collision detection because each machine xmits directly into the reciever of the other machine. I am not sure exactally how to wire it up, but it is not impossible. Happy Searching... Tom Dixon AT&T Paradyne, Largo, FL uunet!pdn!dixon
pat@hprnd.HP.COM (Pat Thaler) (12/02/89)
> In article <7014@ficc.uu.net> kunkee@ficc.uu.net (randy kunkee XNX MGR) writes: > >Question: If you only want to connect two systems together, via Ethernet, > >it seems that it should be possible to do this simply with a transceiver > >cable properly adapted to rearrange the signals. We have some special > >situations in which this would be desireable (ie. much cheaper). Does > >anybody sell such an adaptor? > > This is not impossible. It is the AUI equalvilent of a cross DTE cable. > You don't have to worry about losing collision detection because > each machine xmits directly into the reciever of the other machine. In normal CSMA/CD operation, it is not necessary to have full duplex operation of the MAC. That is, the DTE does not have to be capable of simultaneous receive and transmit. Most DTEs aren't and wiring this way would cause dropped packets. There are other problems. In normal CSMA/CD operation, the transmitted signal appears on the receive pair (loopback). Many DTEs check for this either at power-on with a loopback test or every time a packet is transmitted. They will sense loss of loopback as an error condition and may stop transmitting in response. Also, the transceiver is suppose to activate the collision signal after each transmission (SQE test). If the SQE test message is not received, some DTEs will stop transmitting. (Since early Ethernet implementations did not do SQE tests, some DTEs will ignore the lack of SQE test or will only report it as an error.) > > I am not sure exactally how to wire it up, but it is not impossible. > Happy Searching... You can not eliminate a transceiver with a passive cable, it takes some active components. > > Tom Dixon > AT&T Paradyne, Largo, FL > uunet!pdn!dixon > ---------- Pat Thaler
dd@ariel.unm.edu (dd) (12/06/89)
In article <6784@pdn.paradyne.com> dixon@gumby.paradyne.com (0000-Tom Dixon) writes: >In article <7014@ficc.uu.net> kunkee@ficc.uu.net (randy kunkee XNX MGR) writes: >>Question: If you only want to connect two systems together, via Ethernet, >>it seems that it should be possible to do this simply with a transceiver >>cable properly adapted to rearrange the signals. We have some special >>situations in which this would be desireable (ie. much cheaper). Does >>anybody sell such an adaptor? > >This is not impossible. It is the AUI equalvilent of a cross DTE cable. >You don't have to worry about losing collision detection because >each machine xmits directly into the reciever of the other machine. Collision detection is EXTREMELY important, since the interface cards generally depend on this for "serializing" access to packet buffers. I have tried to get this to work, to no avail. All is not lost however: The ANC division of Niravoice (or maybe they have changed their name, I dunno. Anybody else know?) sells a gadget called the ANC-10 AUI-to-AUI adapter for ~$180 (the last time I checked). It does exactly what you want. Has lots of good diagnostic lights too. Mail me if you need additional info. I am not associated with the company, but am a satisfied customer. -- Don Doerner dd@ariel.unm.edu University of New Mexico CIRT 2701 Campus Blvd, NE Albuquerque, NM, 87131 (505) 277-8036