charlie@oblio.UUCP (Charlie Richardson) (03/19/87)
Is there such a thing as an Ethernet null modem cable which allows you to connect any TWO machines directly, i.e. from the xceiver port on one system to the port on the other WITHOUT using a transceiver? The systems in question are full IEEE 802.3 xceiver specifications. Our East Coast tech support engineer swears he has seen a cable reputed to be such a thing. It seems to me that it might be possible with TCP/IP only; you could connect the differential transmit lines of one port to the receive lines of the other. The only joker in the deck would be how to handle collision detect; maybe you don't have to worry about it since TCP/IP protocol would NAK the packet and ask for another if garbled. ... or is this theory a crock???? Please help out with comments, "crock" responses, or whatever! Thanks. Charlie Richardson Counterpoint Computers, Inc. , San Jose, CA Voice: (800) CPC-TALK UUCP: ...![nsc,hplabs]!oblio!charlie
mouse@mcgill-vision.UUCP (03/28/87)
In article <383@oblio.UUCP>, charlie@oblio.UUCP (Charlie Richardson) writes: > Is there such a thing as an Ethernet null modem cable which allows > you to connect any TWO machines directly, i.e. from the xceiver port > on one system to the port on the other WITHOUT using a transceiver? > It seems to me that it might be possible with TCP/IP only; you could > [theory] What could the protocol you're using possibly have to do with it? I can't see that it could matter whether you're using IP, XNS, ND, Chaosnet, or whatever. What am I missing? > The only joker in the deck would be how to handle collision detect; If there's any contention when they both try to transmit at once then you handle it same as on a regular Ethernet. If there's no contention then data can flow both directions and you just wire the collision detect down to a constant logic signal, whichever way means "no collision". Am I just exposing my ignorance of Ethernet or is this really no problem? der Mouse Smart mailers: mouse@mcgill-vision.uucp USA: {ihnp4,decvax,akgua,utzoo,etc}!utcsri!musocs!mcgill-vision!mouse think!mosart!mcgill-vision!mouse ARPAnet: think!mosart!mcgill-vision!mouse@harvard.harvard.edu