JMS@ARIZMIS.BITNET.UUCP (02/09/87)
Since most postings on INFO-VAX are questions, here are some answers which might resolve some problems regarding heartbeats. Consider two Ethernet networks, and a piece of fiber optic cable between. The configuration we tried was : Ether1 - American Photonics RL1000 (Heartbeat disabled) Transceiver - DELNI - LAN Bridge 100 - American Photonics RL5000 Fiber Optic Modem - Fiber Optic Cable - AP RL5000 - DELNI - RL1000 - Ether 2 No matter what the configuration of hearbeats or DELNIs or whatever, the ONLY configuration that would work is having TWO RL1000 transceivers. For many types of equipment, particularly something as touchy and new as a LanBridge 100, you simply cannot mix and match manufacturers. A LAN Bridge in this configuration would not work if it had an RL1000 on one side and an H4000 on the other, no matter what the Heartbeat settings. Even stranger, LAT traffic would work in some configurations, while DECnet traffic would NOT. Realize that the "standards" are anything but. There are three separate standards for what we call Ethernet, two from the original 3-company consortium (Digital/Xerox/ and was it Intel?) and one from the real standard-makers, IEEE. There are known as, respectively, Ethernet Version 1, Ethernet Version 2, and IEEE 802.3. There are significant differences, but 'hearbeat' is the least well understood and the most often bandied about. Heartbeat is NOT an Ethernet signal; it is a signal (like DTR/CTS/RTS/DSR) between the transceiver and the computer (or whatever), carried on the collision detect lines, that indicates that the equipment is alive and powered up (get it? Heartbeat? like the doctors use?) The requirements for heartbeat DIFFER between V1, V2, and IEEE 802.3. The H4000 transceiver is a Ethernet V1-era transceiver, which means that it always returns heartbeat. The DELNI is a real problem, since it passes on heartbeat when it gets it from a transceiver (GLOBAL mode) and generates it itself when it's in LOCAL mode. +-------------------------------+ | Joel M Snyder | BITNET: jms@arizmis.BITNET | Univ of Arizona Dep't of MIS | ArizoNET: MRSVAX::JMS | Tucson, Arizona 85721 | Pseudo-PhoneNET: (602) 621-2748 +-------------------------------+ ICBM: 32 13 N / 110 58 W (std. disclaimer in re: nobody taking anything I say seriously) "Sure looks like Plant Food to me !" - Seymour, and Audrey II