Re: Routing issue?
Hi David,toggle quoted messageShow quoted text
This very article says "Note that these tests are done with squelched receiver for convenience of triggering the data logger, normal operation is with open squelch wich the TNC-X supports."
I think by the very sentence the author really means his practice won't affect the validity of his conclusion.
" I still argue that squelch is NOT the same as the DCD recognition. "
I never said squelch is the same as the DCD recognization. I said DCD is an RS-232 counterpart of CS (carrier sensing in medium access control protocols).
"TXDelay and TNC"
See more details in my previous reply to Bill. It is complicated, but I believe the status quo of TNC design can be improved to be more friendly to bi-directional IP traffic.
"802.11, OFDM and DTN"
802.11b uses BPSK,QPSK,QAM16 and QAM64. 802.11a, 802.11g, 802.11n etc. use OFDM which in turn uses BPSK,QPSK,QAM as its sub-channel building blocks. It is kind of distractive to get into such details. What I meant by referring to 802.11 is that the 802.11 radios carrier-sensing latency (of ALL 802.11-conforming radios) is very short (measured by 1024micro-seconds ~1ms) and its impact to the IP protocol stack is negligible. If this assumption is true for all (or most) ham radios, I guess we don't need squelch in ham radios as well.
My research group worked with Kevin Fall's DTN group some years ago. It is a different topic. Delay-tolerant basically means that the "store-and-forward" packet switching (which is the reason of inventing the TCP/IP Internet when circuit-switching telephone network was the only option in 1960s) can have an alternative approach by emphasizing on the "store" part. As the hardware storage technology gives us cheap TB harddrives, we can go around to collect all data and store as much as we can, then forward them when the network is available. This approach is not friendly to data traffic with real-time constraints.
James Kong, KM6JNN
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