Bulletins from the Pacific Packet Radio Society - page 069

"Excuse me, but I'd like to see how I came to decision!" "What do you, I mean me, mean by that? The VADCG group has chosen HDLC, and AMRAD is working on an ADCCP package. Even TAPR is looking at a subset of the IEEE-802 LLC (logical link control)." "Look again... How often do you guys read those standards? The first two bit-oriented protocols were never designed for local area network use. They were meant for a primary point to link to one or more secondary points, on a dedicated line. Which groups send a continuous stream of frame flags or "breaks" down the line when the primary's not transmitting?" "Well that's just a stupid thing to do on a radio channel. Of course none of us block the channel!" "Yet you'll find that in the HDLC standard. Never mind. Answer this then: All of the protocols involved presume the address of the primary, and so ALL addresses are that of the secondary, receiving station. I don't recall that the above-mentioned groups are placing the receiving station ID in their packet address space at all." "Well, that's true. The ID used is always that of the sending station instead." "That's right.So none of you hams are using some fundamental aspects of these protocols. It's a good thing too." "Why do you say that?" "You guys are misusing these protocols to let you get onto the radio channel with packets. You change the standard around to reflect the fact that there's a repeater on channel who will be instrumental in routing the packets, based on initialization schemes using the control field. The medium is not one of a primary in control of slaved secondary stations. It's one of multiple primaries, or nodes, all with the power to initiate conversations at will." "OK, so we don't run HDLC, or ADCCP or what-ever. But notice that I said TAPR is using a sub-set of LLC, a brand new protocol DESIGNED for local area networking! I think we have the jump on all the other groups!" "Think again Charlie. What you guys will be using is a dynamically-assigned, single byte addressing scheme with both the sender and receiver ID in the packet header. That allows a balanced mode of operation, but ADCCP and a few other protocols allow balanced modes without double addressing anyway. Your problem is that the IEEE standard also calls for a "medium access layer" sittings smack dab between the physical and link layers, and that layer is more complicated than anything any of the ham groups have come up with yet! I think you'll find that using a protocol designed for a 1OMb/s link would be just as bad as using one for point-to-point. All groups are justified in using whatever "subset" of whatever protocol they want, since there is no standard designed for slow packet radio channels!" "Sigh.. I guess we're not at the point yet of defining a universal standard for balanced-mode transmissions on a shared medium that doesn't lend itself to simultaneous collision detection, true?" "I'm glad you said that... Sounds like you hams have a lot of work ahead of you in figuring out what will work best. Keep up with protocols BASED-ON, but not compatible with, the standards already out, and the controller chips will help you out financially. The IEEE will have some standards for broadband coaxial cable networks in the near future, and the head-end translator looks a lot like a repeater Keep up the experimentation 11 "OK. Now can I

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