gandrews@netcom.COM (Greg Andrews) (02/16/91)
In article <1991Feb15.164415.19733@rwwa.COM> witr@rwwa.COM (Robert W. Withrow) writes: > >In the case of Telebit modems, for PEP and Direct V.32 (but not V.42 >LAP-M) connection, the modem ``spoofs'' the `g' protocol, and thus the >pacing (aka flow-control) is performed by the modem in this way. > Protocol support for uucp (or kermit or x/ymodem) is available only in two modes: PEP and V.32/MNP. "Direct V.32" (by which I understand you to mean V.32 without error control) does not have protocol support. > >With other modems (and telebit modems using LAP-M), the pacing is done >by the two computers via the `g' protocol. In cases where the >DTE-to-modem bit rate is higher than the modem-to-modem bit rate, >modern modems generally have enough buffer capacity to run UUCP `g' >protocol without using *any* DTE-to-modem flow control! > OTOH, the modem-to-DTE flow control can still have its little say. If the uucp data exceeds the modem's XOFF threshold, the modem will send an XOFF, causing an alarm on many systems. My info on the buffering in Telebit modems says the modem sends an XOFF after there are 30-40 bytes in the buffer. Since uucp "g" can spit out 192 bytes (3 x 64) the computer may be able to fill the buffer past the threshold when there's a large difference between the DTE speed and the connection speed (such as 19200/2400 or 19200/1200). The above is on links without error control. MNP or LAP-M links may have different thresholds. PEP links have completely different thresholds. > >I have my DTE speed set at 38400 BPS, >and have successfully performed UUCP `g' to other modems operating at >2400, 4800, and 9600 BPS. > 38400? Hope you're using a T1600 (or a non-Telebit modem). <smile> -- .-------------------------------------------. | Greg Andrews | gandrews@netcom.COM | `-------------------------------------------'
witr@rwwa.COM (Robert W. Withrow) (02/18/91)
In article <24307@netcom.COM> gandrews@netcom.COM (Greg Andrews) writes: >Protocol support for uucp (or kermit or x/ymodem) is available only >in two modes: PEP and V.32/MNP. "Direct V.32" does not have protocol support. Everyone I talk to tells me something different on this (including Telebit tech support! Everyone agrees that spoofing is performed in PEP mode, but no-one can agree on which other modes do spoofing. >OTOH, the modem-to-DTE flow control can still have its little say. Not when you have disabled *all* flow control (as I stated in my post). Depending on the modem (and I *dont* use Telebit modems), there seems to be enough buffer space to support UUCP (with *all* DTE-Modem flow control turned off) without lost packets, even when the DTE-Modem data rate is greater than the Modem-Modem data rate. This is a purely empiracle estimate on my part thought... -- --- Robert Withrow, R.W. Withrow Associates, Swampscott MA 01907 USA Tel: +1 617 598 4480, Fax: +1 617 598 4430, Uucp: witr@rwwa.COM