Ian, at 03:46 on Dec 09 1996, you wrote to Bill Grimsley...

BG> That still doesn't explain the 4000cps which was physically
BG> seen here on one particular 1.5Mb file transfer between
BG> David's Courier and mine (and which was witnessed by
BG> Russell Brooks at the time).

IS> Using Binkley?  With LAPM?  With what file transfer 
IS> protocol?  Terminate with ymodem-g, now I could believe it 
IS> saying that .. :)

Yeah, me too!  In fact, it was done with BOTH QmodemPro (under an OS/2 MDOS
session) and TE/2 under native OS/2, 33k6 Courier to Courier connects, LAPM
256b frames with SREJ active, and I'm also pretty sure that I used Ymodem-g
as the protocol.  The really interesting thing is that as Russ was here,
I'd been extolling the virtues of OS/2 for comms (he's since changed to
OS/2 :)), and at one stage, right in the middle of one large file transfer,
the WPS crashed (my fault), yet the active comms session was not affected
at all!

IS> No modem that complies with V.34 does anything 'unique' with 
IS> frame sizes, and most modern modems will respond to a request 
IS> for larger than default frames.

BG> Dunno, when I call Rockwells, most aftecall stats show the
BG> frame size as being 128 bytes, and only a handful indicate
BG> 256 byte frames or SREJ, so I'm not convinced that this
BG> applies to "most" modems just yet.

IS> The Courier probably requests, but doesn't demand it.

Much the same as 64-State Trellis coding then.  If it's available, the
Courier uses it, but if not, it simply reverts to 16-S, like most Rockwells
use.

IS> I'm not quite sure of the intricacies of the 
IS> request/acknowledgement of these (optional) parameters.
IS> I seem to recall you could fiddle with options on some 
IS> Rockwells - you certainly can with V.42bis dictionaries etc.  

Same as the Courier, although as I virtually never transfer uncompressed
data, I didn't bother playing with BLTZ's parameters at all.

IS> Tell me, do the calls you refer to above have compression 
IS> enabled or not?  (Sometimes V.42bis will negotiate the 
IS> larger 256 byte frames, I understand).

Like most Couriers, mine was configured with BTLZ active, but not MNP5.

IS> "9.2.3  Maximum number of octets in an information field (N401)
[ ... ]
IS> Phew.  It's all like that .. very precise, but very verbose.  

Not to mention being close to indecipherable.  :)

IS> The MNP4 spec (annex A) is as think as a brick to read, compared even to 
IS> V.42 proper .. but I'll have a go ..

Don't forget that it's actually a recommendation rather than a spec per se.

IS> .. half an hour later .. sorry, more research will be needed 
IS> to make head or tails of the possible header sizes for MNP 
IS> .. there are just so many options .. LAPM is a lot easier to follow.

I'm glad you seem to think so.  If that data had some application in my own
industry, I'd probably make some sort of an effort to become conversant
with it, but it really is awfully long-winded otherwise...

IS> If you've access to a postscript printer, and ink and paper 
IS> for 74 pages, freq V42-PS.ZIP (270K) and try figuring it out 
IS> yourself :)  BTW, if you do, make sure V.42bis is enabled, 
IS> so you might tell me if we get 256-byte frames?

Appreciate the offer, but as I'm currently "between" Couriers, I
doubt this el-cheapo GVC does anything unique from other Asian Rockwell
clones.

BG> Still reckon the 4000cps I saw with Russ was genuine...  :)

IS> Show me a Binkley log segment - it should be repeatable, no?  :)

I doubt it's possible under Binkley, as I've never seen 4000cps on anything
other than smaller files, where the logging is relatively error-prone.  Nor
does it use Ymodem-g, and I can't try repeating it with this GVC, as
(unlike the Courier) it won't connect any faster than 28k8 with Dave's
Courier, even though it's definitely a 33k6 modem.  :(

IS> Recall that the maximum _theoretical_ throughput was 1728cps, with NO file 
IS> transfer protocol overheads (i.e raw continuous transmission with NO 
IS> transfer protocol blocking / crcs at all).

I have certainly never disputed those figures either.

IS> 1728cps at 14400 = 4032cps at 33600.  4000cps at 33600 = 
IS> 1714cps at 14400.  Believe it when I see it ..

Time to buy yet another Courier, and a decent stopwatch, methinks.

(Russ:  Might be a good time to trot around one of your spare Couriers, so
we can prove or disprove its 4000cps capabilities once and for all).

Regards, Bill

--- MsgedSQ/2 3.50