bob@MorningStar.Com (Bob Sutterfield) (11/03/90)
With version 7 of the ROMs, the Telebit T2500 supports V.42bis compression over a V.42-corrected V.22bis, V.22, or 212A (2400 or 1200bps) connection. V.42bis and V.42 are not documented as supported over a V.32 (9600bps) connection. There's no change documented in the modem's maximum serial interface speed (S51=5 sets 19200bps). So it appears that, for now at least, one can't run a T2500 at 38400bps, blasting V.42bis-compressed data though a V.42-corrected stream over a V.32 connection. Darn. Or am I missing something? Also, has anyone played with the new V.32 protocol spoofing support? Is it worth the trouble, or mightn't one just as well use PEP, since only another Trailblazer at the other end of the wire would be able to do the in-modem spoofing anyway?
cec@cup.portal.com (Cerafin E Castillo) (11/07/90)
My experience with V.32 protocol spoofing is that it gains you about
10% throughput, otherwise it's not worth the hassle. You do need
two TELEBIT modems with the right firmware to do the spoofing.
BTW, did you notice any TELEBIT fanfare in the introduction of this
new feature? Goes to show you what they think about it, as well. I
thought this strange; when V.42/V.42bis has more pull than V.32
protocol spoofing.
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===============================================================================cpcahil@virtech.uucp (Conor P. Cahill) (11/07/90)
In article <35670@cup.portal.com> cec@cup.portal.com (Cerafin E Castillo) writes: >My experience with V.32 protocol spoofing is that it gains you about >10% throughput, otherwise it's not worth the hassle. You do need >two TELEBIT modems with the right firmware to do the spoofing. There are reasons for this. The biggest benefit of protocol spoofing is that it doesn't cause a half duplex channel to be switched around. With a full duplex channel (which v.32 is), you loose this benefit all-together. I'm suprised that you would even get a steady 10% throughtput increase because the way that uucp works (with the sliding windows) the acks come back while the next packets are being transmitted, so there shouldn't be any waiting. I guess that they cut out some of the uucp packet overhead, since both sides know what is going on. -- Conor P. Cahill (703)430-9247 Virtual Technologies, Inc., uunet!virtech!cpcahil 46030 Manekin Plaza, Suite 160 Sterling, VA 22170