clemon@lemsys.UUCP (Craig Lemon) (06/24/91)
So after all of this discussion it would seem that the best modem
to get for throughput, good reliability and future compatibility would be a
V.32bis/V.42bis box right? Also, refresh my memory, what is the bis on
V.32? The 14400 carrier instead of 9600? (I know that V.42bis is data
compression).
Also again, will the "throughput upto" value for a V.32bis/V.42bis
modem be the 38400 number that I've seen floating around. Of course, that
would be a manufacturer's statement, I realize that real throughput doesn't
get that high.
--
Craig Lemon - Kitchener, Ontario. Amiga B2000 UUCPv1.13D.
clemon@lemsys.UUCP lemsys!clemon@xenitec.on.ca | Please Mail any binaries
xenitec!lemsys!clemon@watmath.waterloo.edu | to 'files' at this site
..!uunet!watmath!xenitec!lemsys!clemon | instead of 'clemon'bob@MorningStar.Com (Bob Sutterfield) (06/25/91)
In article <clemon.4926@lemsys.UUCP> clemon@lemsys.UUCP (Craig Lemon) writes:
what is the bis on V.32?
It's French for "second try" or "once more around the track" or some
such. I took Greek, not French...
The 14400 carrier instead of 9600?
Right.
Also again, will the "throughput upto" value for a V.32bis/V.42bis
modem be the 38400 number that I've seen floating around.
If V.42bis is a 4x compression under optimal conditions, one might
expect that one would only get optimal throughput if a V.32bis modem
were fed data at 4*14400=57600, which is half again as fast as 38400.
I'm not familar with any UNIX implementations with any numbers higher
than 38400 in <sys/ttydev.h>, but (a) it's probably coming someday,
(b) with custom hardware and accompanying tty drivers and ioctls you
could probably do it already, (c) some UARTs and UNIX interrupt
handlers might not be able to keep up with the data if it's really
flowing at that rate, and (d) non-UNIX systems will probably be able
to do this sooner than it becomes "standard" for async tty drivers on
"standard" UNIX (whatever that means :-).tnixon@hayes.uucp (06/25/91)
In article <clemon.4926@lemsys.UUCP>, clemon@lemsys.UUCP (Craig Lemon) writes: > [W]hat is the bis on V.32? The 14400 carrier instead of 9600? Yes. The difference between V.32bis and V.32 is that V.32bis supports, in addition to V.32's 4800 and 9600 speeds, 7200, 12000, and 14400 bps. V.32bis also supports "rate renegotiation", which allows the modems to rapidly (1/10th of a second) change speeds in response to changing line conditions, without going through a full retrain as required in V.32 (5 seconds or more). > Also again, will the "throughput upto" value for a V.32bis/V.42bis > modem be the 38400 number that I've seen floating around. Of course, that > would be a manufacturer's statement, I realize that real throughput doesn't > get that high. Most of the V.32bis/V.42bis modems I've seen so far still have a maximum DTE interface speed of 38400. This is adequate for nearly all applications. The main benefit of V.32bis is in being able to achieve 38400 on more different types of data, since it only needs to get about 2.2-to-1 compression (38400/14400/1.22) instead of 3.3-to-1 (38400/9600/1.22). [The 1.22 factor is the improvement achieved by the error control protocol itself through stripping of start and stop bits, less protocol framing overhead.] It's possible for text data, which is compressible at around 3.3-to-1, to achieve 57600bps on a V.32bis/V.42bis modem, but I've only heard of one modem that supports that rate (AT&T Paradyne). -- Toby Nixon, Principal Engineer | Voice +1-404-840-9200 Telex 151243420 Hayes Microcomputer Products Inc. | Fax +1-404-447-0178 CIS 70271,404 P.O. Box 105203 | UUCP uunet!hayes!tnixon AT&T !tnixon Atlanta, Georgia 30348 USA | Internet tnixon%hayes@uunet.uu.net
bill@camco.Celestial.COM (Bill Campbell) (06/25/91)
In <clemon.4926@lemsys.UUCP> clemon@lemsys.UUCP (Craig Lemon) writes:
: So after all of this discussion it would seem that the best modem
:to get for throughput, good reliability and future compatibility would be a
:V.32bis/V.42bis box right? Also, refresh my memory, what is the bis on
:V.32? The 14400 carrier instead of 9600? (I know that V.42bis is data
:compression).
I may well be doing it wrong, but the best data rates I've been
able to get recently using real data (pre-compressed) and V.42bis
modems is about 600cps. This is between a couple of UDSV3242B
modems with interface speed locked at 38,400 on Specialix 8-port
boards. My PEP modems regularly get 1400-1700cps with interface
locked at 19,200.
I get similar speeds (600cps) between the UDS and my T1600 with
both locked @ 38.4.
I've seen reports of transfer rates > 1,400 cps with V.42bis
(Stuart Lynne on a SLIP connection). Is this because of the
compression or is there something I'm missing that will get real
speed with V.42bis on compressed data?
Bill
--
INTERNET: bill@Celestial.COM Bill Campbell; Celestial Software
UUCP: ...!thebes!camco!bill 6641 East Mercer Way
uunet!camco!bill Mercer Island, WA 98040; (206) 947-5591albers@ka3ovk (Jon Albers) (06/27/91)
In <1099@camco.Celestial.COM> bill@camco.Celestial.COM (Bill Campbell) writes: >I may well be doing it wrong, but the best data rates I've been >able to get recently using real data (pre-compressed) and V.42bis >modems is about 600cps. This is between a couple of UDSV3242B >modems with interface speed locked at 38,400 on Specialix 8-port >boards. My PEP modems regularly get 1400-1700cps with interface >locked at 19,200. Bill, here's my uutraf stats for a couple of my sites: Remote -----------K-Bytes----------- ----Hours---- --Avg CPS-- --Files-- Host Recv Sent Total Recv Sent Recv Sent Recv Sent ------ --------- --------- --------- ------ ------ ----- ----- ---- ---- wb3ffv 10666.2 2489.5 13155.7 2.7 0.6 1086 1095 130 75 nstar 11270.4 14.2 11284.6 2.4 0.0 1283 2289 136 48 barn 6049.5 1045.7 7095.2 1.4 0.3 1230 1062 32 56 infopro 861.0 1.7 862.7 0.2 0.0 1236 2252 20 6 Note that for small amounts of data, uutraf's numbers don't make sense, but for larger amounts of data, it seems realistic. These are all news feeds, which are 16-bit compressed batches. The site 'nstar' is via V.42/V.42bis. The others are via Trailblazers in PEP mode. I haven't gotten the high rates that larry@nstar has given on the net (1750 cps, I think). The I/O card here is a Digiboard PC/i16, which uses Z80SIOs. Jon -- | Jon Albers, IRS, Information Systems Management, Support and Installation. | | Office Symbols: ISM:S:S:SI voice: (202/FTS)535-3729 Packet: KA3OVK@N4QQ | | UUCP:(media|teemc|tcsc3b2|ki4pv)!ka3ovk!albers ARPA: JALBERS@SIMTEL20 |