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Technology Stocks : COM21 (CMTO) -- Ignore unavailable to you. Want to Upgrade?

To: lml who wrote (1649)	2/2/2000 12:03:00 AM
From: Mark Laubach	Read Replies (2) \| Respond to of 2347

"downstream transmission itself vs MAC packets" Here's two examples of timing derivation: DOCSIS uses a MAC level message called a SYNC message containing a timestamp value. This is sent out periodically and accurately by the CMTS. It is a normal message contain a header and data. The modem receives this message and evaluates the time stamp and "tickles" is clock. I believe most implementation do this in hardware and intercept SYNC message before being passed to the CPU so as to avoid any interrupt latency/jitter issues. The clock in the modem is used to control the timing of upstream transmissions. Com21 uses a method where the baud rate (or symbol rate) of the transmissions of the downstream raw modulation symbols are used to keep the modem's upstream timing clocks synchronized. Both protocols use additional MAC management messages to "range" the station so that each modem shares the same sense of time on the upstream. I think you have the rest of it thought through correctly. Yes, I think that the cost to implement new programmable technology, such as seen via the URL you passed is very interested, but coming in late on the volume / cost curves that ASICs for broadband are experiencing now. I'm in favor of it, so we'll have to find a way to work it into the industry. Mark