root@conexch.UUCP (Larry Dighera) (10/18/88)
I came across the following article, and thought readers of this
news group might be interested in its content.
=============================================================================
The following is Bulletin 5 from Phoenix Techline 602-936-3058
Downloaded on 10/18/87
Not long ago, many data communicators thought that dial-up modem manufacturers
had pushed transmission speeds to the limit with the introduction of 2400 bit
per second (bps) modems. Recently, however, several manufacturers have
creatively combined relatively mature techniques of data transmission with
newer technology and have introduced 9600 bps modems.
Unfortunately, a widely accepted standard for full duplex 9600 bps
transmission as defined by the International Consultative Committee for
Telegraphy and Telephony (CCITT) does not yet exist (the CCITT is currently
considering proposals for a new 9600 bps dial-up standard). This means that
today's 9600 bps modems do not offer cross-manufacturer compatibility. The
CCITT HAS endorsed a half duplex and a full duplex 9600 bps standard, but to
date implementations of these relatively flexible standards have been
proprietary, i.e., even the "standardized" modems from different manufacturers
are not compatible.
All this means that modem users who want to enjoy the dream speed of 9600 bps
must weigh the pros and cons of each 9600 bps technique before committing to a
particular 9600 bps design. This paper was written in an effort to provide
typical modem users with enough technical information and insight that they
will be able to consider the new 9600 bps modems from the position of an
educated consumer and not have to rely on information gleaned from sales
brochures and advertisements. It should be noted that the author, Wes Cowell,
is an employee of USRobotics.
THE ROAD TO 9600
High speed data communications via the dial-up phone network is limited by the
available phone line bandwidth and by random channel impairments. Just as the
diameter of a pipe limits its liquid flow capacity, so does the telephone
channel bandwidth limit its data flow capacity.
The roughly 3000-Hz available in the telephone bandwidth poses few problems
for 300 bps modems, which only use about one fifth of the bandwidth. A full
duplex 1200 bps modem requires about half the available bandwidth,
transmitting simultaneously in both directions at 600 baud and using phase
modulation to signal two data bits per baud. "Baud rate" is actually a
measure of signals per second. Because each signal can represent more than
one bit, the baud rate and bps rate of a modem are not necessarilly the same.
In the case of 1200 bps modems, their baud rate is actually 600 (signals per
second) and each signal represents two data bits. By multiplying signals per
second with the number of bits represented by each signal one determines the
bps rate: 600 signals per second X 2 bits per signal = 1200 bps.
In moving up to 2400 bps, modem designers decided not to use more bandwidth,
but to increase speed through a new signalling scheme known as quadrature
amplitude modulation (QAM).
In QAM, each signal represents four data bits. Both 1200 bps and 2400 bps
modems use the same 600 baud rate, but each 1200 bps signal carries two data
bits, while each 2400 bps signal carries four data bits:
600 signals per second X 4 bits per signal = 2400 bps.
A technique known as adaptive equalization enables 2400 bps modems to adapt to
phone line impairments call-by-call. Essentially, if the modem is experiencing
problems with a noisy line, it looks for a "sweet spot" in the bandwidth and
attempts to avoid troublesome frequencies. This technique makes 2400 bps
modems more tolerant of line noise than their 1200 bps counterparts that use
compromise equalization (a one-size-fits-all approach).
While these advanced modulation and equalization techniques in 2400 bps modems
provide for double the data rate of 1200 bps modems, they also result in a
design at least four times more complex than 1200 bps modems.
Which brings us to the problem of designing a 9600 bps modem.
Jumping to 9600 from 2400 bps is several orders of magnitude more complicated
than going to 2400 from 1200 bps. Telephone network characteristics make it
highly unlikely that success will be had in extending the "data signal
alphabet" (number of bits represented by each signal) beyond four bits per
signal.
Instead, modem designers must increase the bandwidth that is to carry the
signal, and this presents a very big problem. In fact, at speeds of 4800 bps
(1200 signals per second), the transmit and receive channels must be expanded
to the point where they actually begin to overlap. A 9600 bps "band"
requires roughly 90 percent of the available bandwidth, making it impossible
to have two-way communication without the bands interfering with each other.
A helpful analogy to the problem might be to consider a two lane highway:
traffic must flow in both directions simultaneously, but to carry more cars
per unit of time, highway designers must either increase the number of lanes
in each direction or widen the two lanes to accommodate driver error with a
margin of safety. Unfortunately, these options are not available to modem
designers as the available bandwidth is of a fixed size.
With these considerations and limitations in mind, let's examine three basic
ways to accomplish full duplex (two-way) 9600 bps communications: echo
cancellation, virtual full duplex (achieved by half duplex systems), and
asymmetrical frequency division.
ECHO-CANCELLATION
This method solves the problem of overlapping transmit and receive channels.
Each modem's receiver must try to filter out the echo of its own transmitter
and concentrate on the other modem's transmit signal. This presents a
tremendous computational problem that significantly increases the complexity
-- and cost -- of the modem. But it offers what other schemes don't:
simultaneous two-way transmission of data at 9600 bps.
The CCITT "V.32" recommendation for 9600 bps modems includes echo-
cancellation. The transmit and receive bands overlap almost completely, each
occupying 90 percent of the available bandwidth. Measured by computations per
second and bits of resolution, a V.32 modem is roughly 64 times more complex
than a 2400 bps modem. This translates directly into added development and
production costs which means that it will be some time before V.32 modems can
compete in the high- volume modem market.
Despite the fact that V.32 is a recognized standard, it is uneconomical and
unnecessarily complex for personal computer datacomm applications that simply
don't require simultaneous two-way 9600 bps transmission.
HALF DUPLEX SYSTEMS
(Virtual Full Duplex)
Half duplex solutions devote the entire bandwidth to 9600 bps in one direction
at a time, and "ping-pong" the data flow back and forth to simulate full
duplex. This is potentially the simplest scheme. Its performance is
acceptable in data transfer applications that don't involve user interaction,
i.e. file transfers. Even so, advanced error-control protocols that require
ACKnowledgments to be sent in response to received data blocks generate a high
number of "line reversals" which greatly impair overall data throughput. In
short, the benefit of higher speed is so significantly compromised by line
reversals in half duplex sessions that the net gain in data throughput may be
marginal at best.
If users want to operate in an interactive mode, their data must be sent to
the remote computer, the data channel must be reversed, and then the data must
be echoed back. This process results in significant turn-around delays which
can be very frustrating to users.
Half duplex modems of this kind are most often based on CCITT recommendation
V.29 for half duplex 9600 bps transmission on the dial-up network. V.29 based
data pumps used in facsimile systems are available as LSI chip sets, providing
a short-cut to modem manufacturers, particularly to companies that don't
develop their own modem technologies. But the major problem is that the V.29
modulation scheme has been outdated by the fact that it operates in a half
duplex mode and doesn't provide good signal to noise performance. The V.32
recommendation, which operates in a full duplex mode and employs Trellis
Coding Modulation offers greater throughput and a greater immunity to channel
impairments.
To the best of my knowledge, modems employing V.29-based modulation include
products from Racal-Vadic, Comspec, Develcon, Gamma Technology, Microcomm, and
Electronic Vaults, Inc. (EVI). These modems, however, are NOT mutually
signal compatible -- cross-manufacturer compatibility does not exist.
Another modem in the half duplex category, but not based on V.29 modulation,
is the Telebit Trailblazer (R), which uses a proprietary modulation method.
Trailblazer is based on a multi-carrier technique. Conceptually, the
transmission channel is divided into many (512), independent, very narrow
channels (think of our two-lane highway and imagine it as having 512 very
narrow lanes (say, for bicycles) going in one direction and you've got a fair
idea of how Trailblazer divides the bandwidth). The main advantage is that no
receiver adaptive equalizer is needed because each channel is very narrow
compared to the overall channel bandwidth.
Further, in the Trailblazer modulation scheme, the modulation rate in each
narrow channel can be changed somewhat independently. Trailblazer is
different from many other modems in that the decision to fall back to lower
speeds is built into the modem protocol, rather than controlled by the user's
computer port. It is claimed that in the face of channel impairments,
throughput can be adapted gracefully to channel conditions. Traditional
modulation systems would have to fall back in larger steps. But there are
three inherent MAJOR problems:
1) The turn-around delay is very long compared to conventional modulation
techniques because data must be sent in large blocks. A typed character may
take several seconds to be echoed back to the system that sent it. As a
result, the system fails to achieve the illusion of full duplex and is not
really suited to interactive online sessions.
2) The Trailblazer receiver cannot "track" carrier "phase jitter" (phase
jitter can be thought of in terms of "phase shift": think of how the whine of
a race car goes from higher to lower as it passes the viewer -- the frequency
of the sound is said to be "shifted" or "jittered"). Instead of cancelling
out phase jitter (which is commonly encountered on long distance calls) the
Trailblazer can only respond by lowering throughput to gain more immunity to
phase jitter.
3) The ability to transmit at the maximum rate when subject to channel
impairment is considerably less than for conventional modems. There is one
notable exception: the multiple channel technique offers extremely good
immunity to impulse noise because the impulse energy is distributed over
narrow channels. While conventional modems can achieve similar results
through special coding or filtering techniques they rarely implement such
methods.
ASYMMETRICAL FREQUENCY DIVISION
When one considers the nature of most PC datacomm applications, it is realized
that most applications are interactive, involving manual (typed) data entry
from one end and data file transmission from the other end.
Few, if any, PC users can justify using an expensive 9600 bps channel to carry
their typed characters when they realize that 300 bps translates to 360 words
per minute. Assuming one could type 100 words per minute, even a 100 bps
transmission channel would be sufficient.
On the other hand, file transfer should take advantage of the tremendous speed
of the microprocessor. Serial ports are often set at data rates in excess of
19,000 bps.
Considering these inherent characteristics, a communications scheme that
incorporated a high speed and a low speed channel would be best suited for
most PC datacomm applications.
Remembering the highway analogy (higher speeds mean wider lanes), one can see
how such a method would grant modem designers a large portion of the
available bandwidth for a 9600 bps channel and still leave enough room to
accommodate a narrow 300 bps channel without any channel overlap.
By utilizing two discreet channels, such a modem would avoid costly, complex
echo-cancellation schemes. And, because the channels carry data in both
directions simultaneously, the communications link is a true full duplex
connection. This means that data entered at one system would be almost
instantaneously echoed back -- eliminating the frustrating turn-around delay
experienced in half duplex sessions.
USRobotics has developed just such a modem. It passes data in one direction
using the V.32 modulation technique (a very robust method that is very immune
to phone line impairments) but employs only a 300 bps channel in the opposite
direction so that the channels do not overlap and echo-cancellation is not
necessary.
The use of the high-speed channel by the two modems is based on data demand.
In most applications, however, "channel swapping" will not be required. For
interface elegance, the modems employ a 4K buffer that allow them to perform
data rate conversion: sending and receiving speeds remain constant between the
modem and the computer -- it is only in between the modems that transmitted
and received data run at different speeds.
For interactive sessions, users are assigned the low-speed channel while the
data sent to them (long mail messages, menus, files, etc.) in the 9600 bps
channel.
For file transfer sessions, the data blocks that make up a file are sent in
the 9600 bps channel while the corresponding ACKnowledgments are returned in
the 300 bps channel. An asymmetric frequency division scheme is ideal for
file transfer where large data blocks (usually several hundred bytes in
length) are transmitted in the high-speed channel and the ACKs (usually only
a few bytes in length) are carried in the low-speed channel.
If a user switches from an interactive mode to file transfer and then back to
interactive mode, the high speed channel is dynamically and automatically
assigned to the system with the greatest data demand.
A BRIEF COMPARISON
Three options exist for data communicators who desire to operate at 9600 bps:
1) V.32-type modems offer a full duplex connection but do so by virtue of
echo-cancellation. This technique is so complex, and has proven so difficult
to employ, that the cost for such modems will remain prohibitively high and
their implementation a delicate task for some time to come.
2) Half duplex modems (either V.29 or multi-carrier) offer 9600 bps but the
turn-around delay inherent in half duplex links severely compromise overall
throughput. This degradation of throughput, however, can be more than offset
by data compression techniques assuming the modems in question support
identical compression protocols and are operating on relatively "clean" phone
lines. Both half duplex methods suffer disproportionate degradation on
"noisy" lines: the V.29 modems must spend more and more time in line reversals
as detected data errors increase, and the multi-carrier modems must sacrifice
throughput to gain noise immunity.
3) Asymmetrical Frequency Division offers 9600 bps communications in a true
full duplex implementation. By efficiently utilizing the available bandwidth,
these modems provide users with high speed file transfer capabilities and fast
response in interactive sessions. Because the transmit and receive data
channels do not overlap, expensive echo-cancelling techniques are unnecessary
making these modems economically efficient.
IN CONCLUSION
Until a widely recognized standard is agreed upon by the standards community,
and implemented by several manufacturers, modem buyers must weigh the benefits
and detriments of each 9600 bps scheme.
V.32 would be best where symmetrical, full duplex, synchronous communication
is desired (for example, dial-up HDLC links between multiplexers) and where
the user can modify his software to accommodate non-"AT" command-driven
modems.
V.29 modems would be likely solutions where absolute lowest price is required
and conformance to an international standard (in a very limited sense) is
desired.
Multi-carrier transmission schemes are well-suited to applications that
require maximum one-way throughput and where circuit conditions are known to
be good. This transmission method is also ideally suited for circuits where
immunity to impulse noise is paramount.
Users who most often work with one-way file transfers (PC-to-PC) or with real-
time applications may opt for an Asymmetrical Frequency Division scheme, which
is suited equally well for either application. The elegant approach to the
frequency division (avoiding overlapping bandwidths) also allows these modems
to present a very economical ratio between dollars and bps.
Potential high-speed-modem buyers should also consider the aspects of ease-of-
use, ease-of-implementation, and downward compatibility with existing
implemented standards (the CCITT's V.22bis for 2400 bps, Bell 212A for 1200
bps, and Bell 103 for 200 bps).
POST SCRIPT
Many modem users have voiced confusion and consternation about the lack of
compatibility between modem manufacturers at speeds greater than 2400 bps.
Modem manufacturers have embraced the Bell 212A and 103 standards for 1200 and
300 bps. In these post-divestiture days, however, Bell no longer sets modem
standards in the U.S. and hence, U.S. modem manufacturers have turned to the
CCITT as a definitive source for standards. The industry-wide acceptance of
the CCITT's V.22bis standard for 2400 bps is the best example of this shift.
The CCITT recommendations V.29 and V.32 for 9600 bps have not resulted in
compatible implementations. It is important to remember that V.29 was
originally developed as a four-wire full duplex leased-line modem and has
since been adapted by various manufacturers to encompass half duplex dial up
applications. Other problems with V.29 are that it compromises transmission
speed and is poor for interactive sessions. V.32 is proving to be
prohibitively complex and exceptionally difficult to implement (driving
development and production costs up).
Recognizing the need for an alternative to the V.32 recommendation, the CCITT
has requested proposals from modem manufacturers.
Presently, two proposals are being considered by the CCITT. One is the multi-
carrier scheme developed and sponsored by Telebit. The other is an
Asymmetrical Frequency Division scheme developed and sponsored by USRobotics.
--
USPS: The Consultants' Exchange, PO Box 12100, Santa Ana, CA 92712
TELE: (714) 842-6348: BBS (N81); (714) 842-5851: Xenix guest account (E71)
UUCP: conexch Any ACU 2400 17148425851 ogin:-""-ogin:-""-ogin: nuucp
UUCP: ...!uunet!turnkey!conexch!root || ...!trwrb!ucla-an!conexch!rootpete@octopus.UUCP (Pete Holzmann) (10/20/88)
The US Robotics [marketing] employee who wrote that article could hardly
be called an unbiased source of information... He didn't mention a few
of the nice advantages of competing technologies, or disadvantages of
his own...
1) V.32 modulation is simply not as robust as PEP in the real world. PEP
gets much higher data rates on real world impaired lines most of
the time. An disadvantage of both V.32 and USR techniques.
2) PEP gets much more than 9600 baud on good lines, even without data
compression. An advantage for Telebit.
3) USR HST modems simply don't connect at high speed on slightly impaired
lines. I had *lots* of trouble with a semi-local connection
between Cupertino and Palo Alto... about 10 miles away, and we
aren't exactly in a telephone service backwater! :-(
Some of his information is simply untrue... The current PEP protocol does
not have a "several second" response time delay for typed characters; it
isn't truly instant, but it is very good!
Am I biased? Probably- I've used both HST and PEP modems, and PEP modems
win hands down in the real world. It is hard to be unbiased!
Pete
--
OOO __| ___ Peter Holzmann, Octopus Enterprises
OOOOOOO___/ _______ USPS: 19611 La Mar Court, Cupertino, CA 95014
OOOOO \___/ UUCP: {hpda,pyramid}!octopus!pete
___| \_____ Phone: 408/996-7746lmb@vsi1.UUCP (Larry Blair) (10/20/88)
In article <9515@conexch.UUCP> root@conexch.UUCP (Larry Dighera) writes:
=I came across the following article, and thought readers of this
=news group might be interested in its content.
=
=1) The turn-around delay is very long compared to conventional modulation
=techniques because data must be sent in large blocks. A typed character may
=take several seconds to be echoed back to the system that sent it. As a
=result, the system fails to achieve the illusion of full duplex and is not
=really suited to interactive online sessions.
Wrong! My TB+ has nearly full-duplex response in interactive mode. I've
also tried running uucp between two TB's running PEP w/o the spoofing,
and while it's not blazingly fast, the turn-around is no where near even
one second. I'd be interested in hearing the accurate figure from Telebit,
but I would guess that it is somewhere around 150ms.
--
Larry Blair ames!vsi1!lmb lmb%vsi1.uucp@ames.arc.nasa.govrls@telebit.UUCP (Richard Siegel) (10/21/88)
In a recent article, Larry wrote: > Wrong! My TB+ has nearly full-duplex response in interactive mode. I've > also tried running uucp between two TB's running PEP w/o the spoofing, > and while it's not blazingly fast, the turn-around is no where near even > one second. I'd be interested in hearing the accurate figure from Telebit, > but I would guess that it is somewhere around 150ms. > And yes, he is right, our spec for turnaround time is 120 msec + or - 30 ms plus the actual line delay (about 60 msec for a cross country call). I think that the original poster probably had a very old TrailBlazer that only had one packet size (the long packets of 136 ms). ========================================================================== Richard Siegel Phone: (415) 969-3800 Product Manager UUCP: {sun,uunet,ames,hoptoad}!telebit!rls Telebit Corporation ARPA: telebit!rls@ames.ARPA "We are, after all, professionals"...HST ==========================================================================
dtynan@sultra.UUCP (Der Tynan) (10/21/88)
With respect to the above article (please refer back - it's too long to
include), I found it pure ad-copy. It was neither informative nor objective.
In summary; What other people have done is OK, but it's wrong. For a *real*
solution, buy *USRobotics*. That's an OK argument for something that seeks
to persuade a potential customer. Something, however, that promises to give
an insight into the dizzying world of modems, it's not. My personal opinion
is that dividing up the bandwidth into multiple channels is an improvement
over two distinct hi-speed/lo-speed channels. Why? Because the Trailblazer
*could* split the channels thusly. Or, perhaps, devote 256 to each direction,
producing 2400 bidirectional. Adaptively configuring channels based on data
flow in both directions *has* to be better. What if I remotely read news?
Every ten seconds or so, I hit ' ' or 'n'. Surely I don't need 300 baud for
that? What about uucp? Is 300 baud enough for all those 'g' acknowledge
packets? Anyway, like I said, that's just my opinion. USR would be better
served by producing something a little less biased, and hence a lot more
believable.
- Der
--
Reply: dtynan@sultra.UUCP (Der Tynan @ Tynan Computers)
{mips,pyramid}!sultra!dtynan
Cast a cold eye on life, on death. Horseman, pass by... [WBY]paul@morganucodon.cis.ohio-state.edu (Paul Placeway) (10/21/88)
I have another problem with asymmetrical frequency division. For file transfer, 9600 one way and 300 the other is fine, unless you are running something like SLIP and doing simultaneous FTP in both directions. In that case, both channels will have a full load, and AFD will just fall apart and give between 2400 and 4800 bps throughput (depending on how smart the modem is). It seems to me that the Telebit protocol will suffer less from this. Besides, the Telebit protocol seems to still have room to grow. Assuming an optimal line, giving 512 channels through it, at 30 baud per channel, 2 bits per baud, that gives an effective total bandwidth of 30720 bps. Assuming that they can squeeze more bits/baud or more baud/channel, speeds can go up from there. Besides, it's more resistant to limited bandwidth connections; just don't use the channels you don't have. Of course, I'm not authoritative, just giving my $.02... -- Paul
dlr@daver.UUCP (Dave Rand) (10/22/88)
In article <2590@sultra.UUCP> dtynan@sultra.UUCP (Der Tynan) writes: >What about uucp? Is 300 baud enough for all those 'g' acknowledge packets? No. Each 70 bytes transmitted needs 6 bytes of ACK. This is an 8.6 % "backchannel", or 822 bps at 9600 outgoing. 300 bps is a 3.1% backchannel. -- Dave Rand {pyramid|hoptoad|sun|vsi1}!daver!dlr
phil@diablo.amd.com (Phil Ngai) (10/22/88)
It's funny, but in the midst of all these people who love Trailblazers I have to say I think the TB is not perfect for applications like reading news. I find the delay from my keystrokes objectionable. (I was using a brand new TB+ with the "quick turnaround hack".) The USR method sounded very attractive to me. 300 baud is perfect for my keystrokes. I don't know about noise immunity, that may be a problem with USR's protocol, but we have had V.29 modems between California and Texas and that seemed to work out ok so I think V.29 will probably work on most phone lines. -- "In the West, to waste water is not to consume it, to let it flow unimpeded and undiverted down rivers. Use of water is, by definition, beneficial use." (from _Cadillac Desert_)
alexis@ccnysci.UUCP (Alexis Rosen) (10/23/88)
In article <25339@tut.cis.ohio-state.edu> paul@morganucodon.cis.ohio-state.edu (Paul Placeway) writes: >Besides, the Telebit protocol seems to still have room to grow. >Assuming an optimal line, giving 512 channels through it, at 30 baud >per channel, 2 bits per baud, that gives an effective total bandwidth >of 30720 bps. Assuming that they can squeeze more bits/baud or more >baud/channel, speeds can go up from there. I'm no expert on this, but isn't the top limit for phone lines about 20kbps, based on Shannon's equation? (This doesn't count compression, of course.) This assumes that phones still operate between 300 and 3300 hertz, and that the S/N ratio is 100:1. As far as I recall, this is an absolute number, unaffected by modulation schemes. I got the numbers from Cole's Computer Communications, 1982. ---- Alexis Rosen alexis@dasys1.UUCP or alexis@ccnysci.UUCP Writing from {allegra,philabs,cmcl2}!phri\ The Big Electric Cat uunet!dasys1!alexis Public UNIX {portal,well,sun}!hoptoad/
wtm@neoucom.UUCP (Bill Mayhew) (10/27/88)
I've used both of these modems. Both are very good units. Both are very well constructed. Both offer excellent noise rejection characteristics. The main difference is that the Trailblazer modem through the use of its internal uucp ACK generation achieves transfer rates that average around 1100 char/sec between our site here in Ohio and scooter in California. The USR modem was limited by the fact that it the 300 bps allocated to the reverse channel is not enough to transmit the ACK within the minimum time. The trailblazer can also in effect ACK the packet before it has actually reached the other end, ensuring continuous filling of the xmit buffer. With the USR modem you have to eat the turnaround time of the other host + line turn around (not modem turn around, since the reverse channel is already available). A long distance call might have about 50 mS delay; add to that whatever the overhead of the other host is. Our uucp transfers over a good quality phone line with the USR ran about 450 - 500 char/sec. The icing on the cake is the internal compression in the TB+. The one place that USR whips the Trailblazer is cost, but that margin has been cut back with the recent introcution of the Telebit Junior (my name for it), model T1000. The people on the FIDO network are just about as religious about USR modems as we Unix denizens are about Trailblazers. --Bill
david@wiley.UUCP (David Hull) (10/28/88)
In article <299@telebit.UUCP> rls@telebit.UUCP (Richard Siegel) writes: >And yes, he is right, our spec for turnaround time is 120 msec + or - 30 ms >plus the actual line delay (about 60 msec for a cross country call). > >I think that the original poster probably had a very old TrailBlazer that only >had one packet size (the long packets of 136 ms). Another possibility is that he was using some curses-based program with the "wrong" termcap entry. When I first started using my TrailBlazer, I found that the delay between typing a character in 'vi' and having it echoed was terrible: around half a second. I found that if I changed the termcap entry from "ic=7\E1@" to "im=\E[4h:ei=\E4l" it improved the interactive response tremendously. Curses sends the "ic" (insert character) string for each character inserted, while it only sends "im" (insert mode) at the beginning and "ei" (end insert mode) at the end of a series of characters. The extra traffic with "ic" must have interacted badly with the TrailBlazer's turnaround algorithm to make for very slow interactive performance. So if your terminal supports an insert mode, use it! -David P.S. Before anyone suggests it, removing the 7 ms of padding from "ic" didn't make any noticable difference. -- --------------------------------------- David Hull TRW Inc. Redondo Beach, CA ...!{uunet,cit-vax,trwrb}!wiley!david david%wiley.uucp@csvax.caltech.edu
David@cup.portal.com (David Michael McCord) (11/01/88)
I don't know why this conference isn't named comp.dcom.telebit-lovers. It ought to be. To dredge up my old opinions on the topic, neither the USR or the Telebit is worth a damn when it comes to global networking, or when supporting most real-world communications applications (SNA/SDLC, X.25, etc.). The Telebit product does not even support synchronous transmission, not to mention the disadvantages of getting yourself locked into a modem vendor's proprietary modulation technique. I say this in this forum because perhaps there are some readers who will appreciate exposure to points of view not so parochial. It would be easy for someone not knowledgeable about telecommunications to believe, by reading this conference, that the Telebit or USR or whatever is the cat's pajamas. There are some very serious reasons why, if you invest in Telebit or USR, you are throwing your money away. Speaking as a data and voice telecommunications professional with many years of experience and the salary to back it up, I say that V.32 modems are going to smash the vendor-proprietary types in the marketplace within a year. Why? Because any large corporation using modern networking (eg, SNA/SDLC, X.25, etc.) is buying V.32, not Telebit or USR. And these are the customers telecomm manufacturing vendors pay attention to. Consequently, if you invest in V.32, you are still going to be able to use it five years from now; long after the HST and Telebit schemes fade away and disappear due to lack of market support. The USENET community has done itself a disservice to let itself fall into the trap it is now in. It should be fun to watch as you netadmin types have to replace your equipment with new modems, be they V.32 or whatever PEP variation is officially adopted by the CCITT (hint: it will not be compatible with your current Trailblazers). I am glad I am not going to have to stand up in front of my managers and ask for more money to redress my past bad decisions. It's your choice. David@cup.portal.com
tsmith@usna.MIL (Tim G. Smith ) (11/01/88)
In article <10711@cup.portal.com> David@cup.portal.com (David Michael McCord) writes: > >I don't know why this conference isn't named comp.dcom.telebit-lovers. It >ought to be. > >To dredge up my old opinions on the topic, neither the USR or the Telebit is >worth a damn when it comes to global networking, or when supporting most >real-world communications applications (SNA/SDLC, X.25, etc.). The Telebit >product does not even support synchronous transmission, not to mention the >disadvantages of getting yourself locked into a modem vendor's proprietary >modulation technique. Try reading page 2-17 in the Commands_and_Registers_Reference_Manual from Telebit. It is entitled "SDLC Support". Many of us using the TB don't give a crap about your "real-world communications applications" we only care about our "real-world communications applications". Ever stop to think that they might be different? >I say this in this forum because perhaps there are some readers who will >appreciate exposure to points of view not so parochial. It would be easy for >someone not knowledgeable about telecommunications to believe, by reading >this conference, that the Telebit or USR or whatever is the cat's pajamas. >There are some very serious reasons why, if you invest in Telebit or USR, you >are throwing your money away. I don't consider the TB to be the cat's pajamas, I simply have an application where the TB is without a doubt the best product available. I have other applications where I use X.25 and others where I plan on using V.32. I try and pick the best solution for each problem. >Speaking as a data and voice telecommunications professional with many years >of experience and the salary to back it up, I say that V.32 modems are going >to smash the vendor-proprietary types in the marketplace within a year. Why? >Because any large corporation using modern networking (eg, SNA/SDLC, X.25, >etc.) is buying V.32, not Telebit or USR. And these are the customers >telecomm manufacturing vendors pay attention to. Consequently, if you invest >in V.32, you are still going to be able to use it five years from now; long >after the HST and Telebit schemes fade away and disappear due to lack of >market support. So what if V.32 takes us all by storm and I replace my TBs- they have still been cost effective and worth using. Yes it is true that the vendors only pay attention to large corporations. Perhaps that is why that TB has so many loyal customers- because they treat all of their customers well instead of ignoring the academic and government market (which is a pretty large and lucrative market). There are quite a few folks who have had TBs for quite some time now and have had their LD and online bills reduced significantly. Folks were using TBs for a long time before V.32 could be bought. There are still many V.32 modems that can only talk modems from the same manufacturer. So the original V.32 modems were just about as proprietary as the TB. >The USENET community has done itself a disservice to let itself fall into the >trap it is now in. It should be fun to watch as you netadmin types have to >replace your equipment with new modems, be they V.32 or whatever PEP >variation is officially adopted by the CCITT (hint: it will not be compatible >with your current Trailblazers). I am glad I am not going to have to stand >up in front of my managers and ask for more money to redress my past bad >decisions. Many people expect communications gear to be short lived. Many of us are happy to get a year or two out of gear before it is obsolete. Many people have also saved enough money on their LD and OL bills that the a pair of Telebits (at about $1400 for the pair) is cheaper than one V.32 (at the regular price a pair of TB's is generally cheaper than one V.32). Many folks don't have time to sit around waiting for the standards- we want products that work today- not products that will be available RSN. One other minor point-- try using a V.32 modem to call the busiest mail relaying machine in the country (uunet if you don't know) and see what kind of modems they use. It is worth a lot of folks the money to buy a modem compatible with uunet's no matter what the cost. >It's your choice. >David@cup.portal.com Indeed it is and many of us are very happy with our choice. Perhaps in the future you should ask some of the folks for the technical and financial reasons that they bought TBs instead of jumping in and telling us that we all are idiots because you say so and you are "Mr Professional Well Payed Data Communications Expert". Also one last thing- I am not sure of how the V.32 modems adjust for poor quality lines but I have yet to see as good a scheme as TB's. Standard disclaimer: The Navy doesn't pay me enough for me to speak for them. I speak for me and me alone.
dave@arnold.UUCP (Dave Arnold) (11/01/88)
David@cup.portal.com (David Michael McCord) writes: > > I say that V.32 modems are going > to smash the vendor-proprietary types in the marketplace within a year. Would somebody else please comment on this. -- Dave Arnold (dave@arnold.UUCP) Work: Volt Delta Resources Phone: (714) 921-7635 Home: 26561 Fresno street, Mission Viejo, Ca 92691
rls@telebit.UUCP (Richard Siegel) (11/02/88)
In article <10711@cup.portal.com>, David@cup.portal.com (David Michael McCord) writes: > > To dredge up my old opinions on the topic, neither the USR or the Telebit is > worth a damn when it comes to global networking, or when supporting most > real-world communications applications (SNA/SDLC, X.25, etc.). The Telebit > product does not even support synchronous transmission, not to mention the ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Actually, Telebit does manufacture a product, the T2000, which supports the SNA/SDLC modes. It is functionally a superset of the TrailBlazer Plus, with the addition of SNA/SDLC support. So you can have all of the advantages (at least as we at Telebit see them :-) of PEP, and SNA/SDLC support for your IBM machines. I don't usually talk much about it, because this newsgroup has generally expressed little interest in that area. David's other points about V.32 as an emerging standard are well taken, but (and here come's the bias!) I think that it won't quite deteriorate that quickly or as severely. I don't want to start another V.32 vs. Telebit debate. This newsgroup has seen enough of that. Let's all sit back and see what happens! Thanks for your interest, David! Regards, ========================================================================== Richard Siegel Phone: (415) 969-3800 Product Manager UUCP: {sun,uunet,ames,hoptoad}!telebit!rls Telebit Corporation ARPA: telebit!rls@ames.ARPA "We are, after all, professionals"...HST ==========================================================================
lmb@vsi1.UUCP (Larry Blair) (11/02/88)
In article <10711@cup.portal.com> David@cup.portal.com (David Michael McCord) writes: >I don't know why this conference isn't named comp.dcom.telebit-lovers. It >ought to be. Here on Usenet, we call them "newsgroups". >There are some very serious reasons why, if you invest in Telebit or USR, you >are throwing your money away. I guess all those people who bought PC/XTs six or seven years ago threw their money away too:-). After all, how much is an XT worth now. >Speaking as a data and voice telecommunications professional with many years >of experience and the salary to back it up, I say that V.32 modems are going >to smash the vendor-proprietary types in the marketplace within a year. So what? Meanwhile we're supporting a level of communication with 2 $700 modems that would have required a bank of slow modems and tied up half of our serial ports. >Because any large corporation using modern networking (eg, SNA/SDLC, X.25, >etc.) is buying V.32, not Telebit or USR. And these are the customers >telecomm manufacturing vendors pay attention to. Consequently, if you invest >in V.32, you are still going to be able to use it five years from now; long >after the HST and Telebit schemes fade away and disappear due to lack of >market support. Rubbish. You are confusing one type of application with another. It is true that 5 years from Telebit won't be selling Trailblazers. You may even be right that V.32 will supersede PEP as a standard. So what? I'll bet you that 5 years from now V.32 will look like ancient history, superseded by V.42 and then V.52 and your hardwired V.32 modems will be a whole lot more useless than the various software controlled modems that will be able to adapt. >The USENET community has done itself a disservice to let itself fall into the >trap it is now in. It should be fun to watch as you netadmin types have to >replace your equipment with new modems, be they V.32 or whatever PEP >variation is officially adopted by the CCITT (hint: it will not be compatible >with your current Trailblazers). I am glad I am not going to have to stand >up in front of my managers and ask for more money to redress my past bad >decisions. My boss is thrilled with the benefits we have received from having the TB's. If they were obsoleted today, he would still be happy. $1,600 dollars well spent. Can you say the same for your $1,500 per modem V.32's? What good is an overpriced modem that won't talk to anyone? I wonder how much anguish you suffer when buying a car. $20,000, and five years from now it won't be worth very much. You fail to understand that ANY piece of high tech equipment has a limited usefulness. Our Sun-3/160, which looked like a wonder machine 2 years ago, is already getting long in the tooth. In two more years, you won't be able to give it away (anyone want a VAX 780 gathering dust in our computer room?). Is the Trailblazer the perfect modem? No. I want one that will run 38.4kb fullduplex on very noisy lines while spoofing every known protocol. Meanwhile, my TB does its job, netnews and email transfers via uucp. -- Larry Blair ames!vsi1!lmb lmb%vsi1.uucp@ames.arc.nasa.gov
limonce@pilot.njin.net (Tom Limoncelli) (11/02/88)
I really can't believe that the discussion is about systems that
aren't going to be any good "5 years from now". Have any of you
considered what things will be like in five years? Try to remember
what you were doing in 1982. I know where I was. I was almost
creaming over my Commodore-64 because it had a 40 column screen.
Right now I don't have a modem. Really! I use a phone system that
offers simultanious voice and data (data is non-blocking at any bps
rate... I use 19.2K bps... brag... brag...) as long as I stay on site.
If I dial off-site I connect through a modem pool of modems (ok, I
admit it, I do *use* some modems, but I don't have one within a 1/4
mile of me). The phone system is all digital and under the phone sits
a little IBX<->async interface.
My point is that the only thing you can predict about the future is
that you can't predict anything about the future. Hopefully within 5
years my computer will speak directly to the phone and there will be
protocals for other sites with similar phone systems to allow me to
talk to each other like it was one big system.
Actually, in 5-10 years I hope to not need to use computers at all. I
just want to be able to talk to a little box and have it answer me on
a screen (or voice... if it detects I'm not looking at the screen) :-)
...but that's discussion for a different news group.
Five years is a lot of time.
-Tom
--
Tom Limoncelli -- Student Network Supervisor
Drew University, Box 1060, Madison NJ 07940 -- 201-408-5389
new->> tlimonce@drunivac.Bitnet -- limonce@pilot.njin.net
"The opinions expressed are mine... just mine."
"Network Theory? Just say node!"mrm@sceard.UUCP (M.R.Murphy) (11/02/88)
In article <10711@cup.portal.com> David@cup.portal.com (David Michael McCord) writes: | |I don't know why this conference isn't named comp.dcom.telebit-lovers. It |ought to be. Well, comp.dcom.telebit-admirerers, anyhow :-) | |To dredge up my old opinions on the topic, neither the USR or the Telebit is |worth a damn when it comes to global networking, or when supporting most |real-world communications applications (SNA/SDLC, X.25, etc.). The Telebit |product does not even support synchronous transmission, not to mention the Yeah, it does. At least some of 'em do. [most of remainder deleted after Glaring Error Detector trigger...] |appreciate exposure to points of view not so parochial. It would be easy for Parochial, who's parochial? [deleted...] |There are some very serious reasons why, if you invest in Telebit or USR, you |are throwing your money away. It's not an investment, it's a tool to be used until a better tool comes along. | |Speaking as a data and voice telecommunications professional with many years |of experience and the salary to back it up, I say that V.32 modems are going Wow. |to smash the vendor-proprietary types in the marketplace within a year. Why? |Because any large corporation using modern networking (eg, SNA/SDLC, X.25, And we all know that large corporations with high-paid telecommunications professionals are the only arbiters... [deleted...] |etc.) is buying V.32, not Telebit or USR. And these are the customers |telecomm manufacturing vendors pay attention to. Consequently, if you invest |in V.32, you are still going to be able to use it five years from now; long |after the HST and Telebit schemes fade away and disappear due to lack of |market support. NBL. And again, it's not an investment. | |The USENET community has done itself a disservice to let itself fall into the |trap it is now in. It should be fun to watch as you netadmin types have to |replace your equipment with new modems, be they V.32 or whatever PEP |variation is officially adopted by the CCITT (hint: it will not be compatible |with your current Trailblazers). I am glad I am not going to have to stand |up in front of my managers and ask for more money to redress my past bad |decisions. I make bad decisions frequently; then I try to learn from them. | |It's your choice. Thank you. | | |David@cup.portal.com Why a post from portal rather than from a large corporation:-) -- Mike Murphy Sceard Systems, Inc. 544 South Pacific St. San Marcos, CA 92069 ARPA: sceard!mrm@nosc.MIL BITNET: MURPHY@UCLACH UUCP: ucsd!sceard!mrm INTERNET: mrm%sceard.UUCP@ucsd.ucsd.edu
pavlov@hscfvax.harvard.edu (G.Pavlov) (11/02/88)
In article <10711@cup.portal.com>, David@cup.portal.com (David Michael McCord) writes: > > To dredge up my old opinions on the topic, neither the USR or the Telebit is > worth a damn when it comes to global networking, or when supporting most > real-world communications applications (SNA/SDLC, X.25, etc.). "Typical business communications applications" would be the more honest phrasing. Lots of us have been in the "real world" for a long time and do not need to "support" SNA/SDLC, etc. If I do, then I will buy the necessary hardware/software. But it would not be very intelligent of me to slow down current communications simply be- cause sometime in the future I may need to interface with a different en- vironment. > > There are some very serious reasons why, if you invest in Telebit or USR, you > are throwing your money away. > As with anything else, "it depends on your application". > ... any large corporation using modern networking (eg, SNA/SDLC, X.25, > etc.) is buying V.32, not Telebit or USR.... It would be more accurate to say "current IBM" than "modern". > ... And these are the customers > telecomm manufacturing vendors pay attention to. > So I should go to a vendor who is focused on someone else's concerns and applications ???? Five years ago, the above could have been written as "And these are the customers computer manufacturing vendors pay attention to". One of the reasons Sun has gone from zero to $1 billion during that time. No, $1B doesn't hold a candle to IBM's $50+B. That's not the point. > The USENET community has done itself a disservice to let itself fall into the > trap it is now in. It should be fun to watch as you netadmin types have to > replace your equipment with new modems, be they V.32 or whatever PEP > variation is officially adopted by the CCITT (hint: it will not be compatible > with your current Trailblazers). I am glad I am not going to have to stand > up in front of my managers and ask for more money to redress my past bad > decisions. > 1. depending on who one talks to, it is not clear that any equipment will have to be replaced any time soon; 2. the replacement is likely to be considerably more powerful than V.32; 3. it is a heck of a lot easier to ask for "more money" if one didn't spend very much in the first place. greg pavlov, fstrf, amherst, ny
W8SDZ@WSMR-SIMTEL20.ARMY.MIL (Keith Petersen) (11/03/88)
There has been a lot of talk about Telebit and USR HST modems becoming
obsolete when the new CCITT standard is adopted.
In my opinion it is not a poor business choice to purchase whatever
high speed technology is now available IF you save enough on telephone
connect charges to pay for the modems.
Here's an example: As Engineering Manager of a TV Broadcast station in
a large market I spent $10,000 to purchase some special videotape
equipment which will save the station $30,000 *each year* in videotape
costs. The equipment will become obsolete in about three years, but
during that time $90,000 (minus the original $10,000 purchase price)
will have been saved.
When the equipment becomes obsolete there will be no problem
explaining why it has to be replaced in such a short time.
--Keith Petersen
Arpa: W8SDZ@WSMR-SIMTEL20.ARMY.MIL
Uucp: {ames,decwrl,harvard,rutgers,ucbvax,uunet}!wsmr-simtel20.army.mil!w8sdzDavid@cup.portal.com (David Michael McCord) (11/03/88)
For those who responded to my previous posting, you may be interested to know that Network World this week had an short blurb about a company that will be offering a V.32 chip set in OEM quantities for $150/ea. They went on to say that by this time next year, it was expected that modems based on this design would be offered at retail for $750 or less. I was gratified to see this confirmation of my statement that V.32 was going to smash the telebit/hst/etceteras "within a year". And I thought I was going out on a limb! Heh heh. David@cup.portal.com
brian@cbw1.UUCP (Brian Cuthie) (11/04/88)
In article <KPETERSEN.12443404284.BABYL@WSMR-SIMTEL20.ARMY.MIL> W8SDZ@WSMR-SIMTEL20.ARMY.MIL (Keith Petersen) writes: >There has been a lot of talk about Telebit and USR HST modems becoming >obsolete when the new CCITT standard is adopted. > >In my opinion it is not a poor business choice to purchase whatever >high speed technology is now available IF you save enough on telephone >connect charges to pay for the modems. > [lot's of supporting argument deleted] There is an even simpler argument for buying Telebit TB+s now. It goes like this: Since the current cost of a V.32 modem is > $1500 and a TB+ can be had for as little as $600 the real question is: do you think the cost of V.32 will fall by more than $600 in the next year. If the answer is yes, then you could own a TB+ now and a v.32 in one year (when somebody on the other end has them anyway) and still spend LESS money than if you bought a V.32 now. Couple this argument with the fact that a LARGE majority of uucp sites currently have TB+ modems and you see that buying a V.32 now is just a good way to spend unecessary $$. -brian -- Brian D. Cuthie uunet!umbc3!cbw1!brian Columbia, MD brian@umbc3.umd.edu
mml@srhqla.UUCP (Michael Levin) (11/04/88)
In article <10711@cup.portal.com> David@cup.portal.com (David Michael McCord) writes: > >To dredge up my old opinions on the topic, neither the USR or the Telebit is >worth a damn when it comes to global networking, or when supporting most >real-world communications applications (SNA/SDLC, X.25, etc.). The Telebit >product does not even support synchronous transmission, not to mention the >disadvantages of getting yourself locked into a modem vendor's proprietary >modulation technique. > Right. After all, the BELL 212 standard isn't a 'vendor's proprietary modulation technique', is it?? I mean, BELL doesn't ring one, does it?? As to CCITT- they don't mean a damn thing in the US. We have NEVER been observant of European standards- the CCITT has been around for a VERY long time, and we go on about our business. Without their help. CCITT is a very important organization when looking at a conglomeration of 15 countries whose TOTAL market size is barely equal to the US. So I don't think I would be ringing the death-knolls for Telebit just yet. . . >There are some very serious reasons why, if you invest in Telebit or USR, you >are throwing your money away. What are they?? > >Speaking as a data and voice telecommunications professional with many years >of experience and the salary to back it up, I say that V.32 modems are going Gee- do you want to tell us what you make?? I've been making buckets of money as a 'telecommunications professional' for over a decade. With the history of this business, I don't think I'd forecast the V.32 winner just yet. Not to say that V.32 isn't a contender, just that it hasn't won yet. >The USENET community has done itself a disservice to let itself fall into the >trap it is now in. It should be fun to watch as you netadmin types have to >replace your equipment with new modems, be they V.32 or whatever PEP >variation is officially adopted by the CCITT (hint: it will not be compatible >with your current Trailblazers). I am glad I am not going to have to stand Yeah- you might have to replace an EPROM for $50. That's a lot less than what you'd have to do if you bought V.32, and it doesn't catch on. >up in front of my managers and ask for more money to redress my past bad >decisions. > You take life too seriously-- unless you have a crystal ball, or you are precognitive, you CAN'T predict what the marketplace is going to do. I can tell you that, thus far, I have run into dozens of admins who have bought, or are buying, Telebit. I haven't talked to even ONE who has bought V.32. >It's your choice. And yours. I hope, for your sake, that V.32 doesn't die out-- or you will have to be justifying a bad decision. Mike Levin -- +----+ P L E A S E R E S P O N D T O: +------+-*-*-*-*-*-*-*-* | Mike Levin, Silent Radio Headquarters, Los Angeles (srhqla) | No room for a * | Path:{aeras|csun|denwa|magnus|pacbell|telebit}!srhqla!levin |'snappy remark'* +-------------------------------------------------------------+-*-*-*-*-*-*-*-*
rick@seismo.CSS.GOV (Rick Adams) (11/04/88)
Why do you presume that Telebit won't buy those chips and then run PEP on top of V.32 allowing "twice" the speed of the current implementation. The T3000.... 24kbps asymetrical PEP... Why not? And it could be V.32 compatible as a fall back. Are they still going out of business? --rick
kaufman@polya.Stanford.EDU (Marc T. Kaufman) (11/04/88)
In article <10711@cup.portal.com> David@cup.portal.com (David Michael McCord) writes: >Because any large corporation using modern networking (eg, SNA/SDLC, X.25, >etc.) is buying V.32, not Telebit or USR... > ...I am glad I am not going to have to stand >up in front of my managers and ask for more money to redress my past bad >decisions. There is an old saying around large corporations, one which might have some relevance to the above argument: "No one was ever fired for buying IBM" Buy safe and save for retirement. Marc Kaufman (kaufman@polya.stanford.edu)
dtynan@sultra.UUCP (Der Tynan) (11/04/88)
In article <10805@cup.portal.com>, David@cup.portal.com (David Michael McCord) writes: > > They went on to say that by this time next year, it was expected that modems > based on this design would be offered at retail for $750 or less. > > I was gratified to see this confirmation of my statement that V.32 was going > to smash the telebit/hst/etceteras "within a year". And I thought I was going > out on a limb! Heh heh. > > David@cup.portal.com I wasn't going to reply to your last (and stupid) posting. I bit back all the smart remarks. Then, you put this up for perusal. I mean, please!!! On the average, you seem to have two 'jokes' in every posting. The last time, you said that you were a 'telecommunications expert, with the salary scale to prove it.' Really. Shall we get into a salary war here? Who do you think subscribes to this network? This is not your average Portal BBS. If you want to impress teenagers with your 'experience', then keep your distribution local, or post messages to local bulletin boards, but PLEASE keep your condescending attitude out of this forum. When you said you worked for a "big tele- communications company", I stopped and thought for a minute. What company would sacrifice big gains today, for the promise of something better "within a year". Then it came to me. You work for ROLM (now IBM). Who else would pay a salary to a turkey. While you are playing around at 300 baud, the rest of us will do some *real world* communicating. But wait!!! There's more!!! Don't buy a V.32 "next year", because someone will have promised a V.EVEN-BETTER, and you wouldn't want to invest in an archaic standard, now would you? For a supposed professional, you do seem to place an awful lot of faith in what the trade-rags have to say, now don't you? In fact, maybe soon your boss will fire you, and replace you with a subscription to "Network World". When you're anywhere *near* the cutting edge, the stuff that is printed in the trade-rags is old news and incorrect. Hmmm. Network world. Weren't they the people who told us that IBM's token ring would rule the world "within a year". That controllers would be available at your local 7-11, for $3.95 (including tax), and that ALL banking would be done at home via local-area-networks :-) Aren't they related to such pillars of journalism as PC-world, who seriously believe that unless it's got I-B-M on the front, no-one will buy it? Particularly in the world of Personal Computers. Ah yes! And for this they pay your HUGE salary :-) You can stick with your V.32 if you want. I once say a cartoon of Andrew Logie Baird (the inventor of television) sitting in front of a prototype TV. The screen is blank. His wife is talking to a neighbour; "He's waiting for someone to invent programs". I can just see you now, with your $750 V.32 modem; "someone, ANYONE, talk to me! please!!!". As it happens, by the way, the Telebit modem uses DSP technology. The actual protocol is in software. It should be feasable to upgrade the thing to V.99999 if that's really what you want. The bottom line here, is V.32 is 9600 baud BIDIRECTIONAL. A bidirectional modem ain't worth the power consumption in the USENET world. But hey, you're a telecom expert... you already knew that didn't you... :-) - Der ps: my criticism of Rolm is well-founded -- that's what they use here :-( -- Reply: dtynan@sultra.UUCP (Der Tynan @ Tynan Computers) {mips,pyramid}!sultra!dtynan Cast a cold eye on life, on death. Horseman, pass by... [WBY]
james@bigtex.cactus.org (James Van Artsdalen) (11/04/88)
In <10805@cup.portal.com>, David@cup.portal.com (David Michael McCord) wrote: > I was gratified to see this confirmation of my statement that V.32 > was going to smash the telebit/hst/etceteras "within a year". There are two fundemental problems you simply haven't addressed. 1. V.32 modems are substantially slower than the Trailblazer over clean lines. I regularly see 1400cps over local connections, and no local connections do worse than 1000cps except on rare occassions. My Tokyo link also stays up over 1000cps. The V.32 modems are limited to 878cps using uucp, and no more than 960cps using something like Zmodem. 2. V.32 appears to have no error handling. Some people may implement MNP or something like it, but the fact is that two V.32 modems may or may not talk well with each other. There's also a question of how gracefully mildly impaired lines are handled: how does V.32 back off? I may well buy a couple of V.32s in the next year or so for SLIP applications. But I'll always have a TB+ for bulk news & mail traffic, because I just can't afford to increase my line usage and costs by 30% or more. > And I thought I was going out on a limb! Well, basically, you are. Think more like a buyer and less like a member of a standards committee. The TB+ certainly has its quirks, but the fact is that it is cheaper than V.32 to buy *and operate* and will remain so indefinitely because of the high speed of the TB+. -- James R. Van Artsdalen james@bigtex.cactus.org "Live Free or Die" Home: 512-346-2444 Work: 338-8789 9505 Arboretum Blvd Austin TX 78759
jim@eda.com (Jim Budler) (11/05/88)
In article <10711@cup.portal.com> David@cup.portal.com (David Michael McCord) writes:
%
%I don't know why this conference isn't named comp.dcom.telebit-lovers. It
%ought to be.
%
%To dredge up my old opinions on the topic, neither the USR or the Telebit is
%worth a damn when it comes to global networking, or when supporting most
%real-world communications applications (SNA/SDLC, X.25, etc.). The Telebit
%product does not even support synchronous transmission, not to mention the
%disadvantages of getting yourself locked into a modem vendor's proprietary
%modulation technique.
Wrong. Simple enough answer? Telebit TB+ revision 4.0 supports SDLC. Older
TB's can get ROM upgrades.
%
%Speaking as a data and voice telecommunications professional with many years
%of experience and the salary to back it up,
That's nice for you. This entire obnoxious statement was unnecessary.
% I say that V.32 modems are going
%to smash the vendor-proprietary types in the marketplace within a year. Why?
%Because any large corporation using modern networking (eg, SNA/SDLC, X.25,
%etc.) is buying V.32, not Telebit or USR. And these are the customers
If X.25 were cheaper than phones in the US, like in Europe, I *might*
agree. But I think this whole argument is a clone of the old "any large
corporation is buying XXX, and who cares what the small companies do".
It may be news to many but there are a h**l of a lot more small companies
who need to communicate than there are large companies. So 30 large companies
each set up large communication networks, each buying hundreds of modems, and
or leased lines, and/or X.25 links. 30 times hundred adds up to 3000 each,
a significant number. 3600 smaller sites each buy 2, this adds up to 7200, also
a significant number.
%telecomm manufacturing vendors pay attention to. Consequently, if you invest
%in V.32, you are still going to be able to use it five years from now; long
%after the HST and Telebit schemes fade away and disappear due to lack of
%market support.
%
Uh, I think my modem will last five years, and still work then. If
you modems are working, and communication is working, why change it? The
old 'newer toy' philosophy?
%The USENET community has done itself a disservice to let itself fall into the
%trap it is now in. It should be fun to watch as you netadmin types have to
%replace your equipment with new modems, be they V.32 or whatever PEP
%variation is officially adopted by the CCITT (hint: it will not be compatible
%with your current Trailblazers). I am glad I am not going to have to stand
Why not? And even if not, that's what ROM swaps are for. I doubt Telebit
will have any trouble making the TB V.32 compliant if the standards really
go that way. It is after all just software controlled signal processing.
%up in front of my managers and ask for more money to redress my past bad
%decisions.
%
If my modems last more than a year, and meet our communication needs for
that period of time, I wont have to worry about anything.
%It's your choice.
Yep.
%
%David@cup.portal.com
--
uucp: {decwrl,uunet}!eda!jim Jim Budler
internet: jim@eda.com EDA Systems, Inc.henry@utzoo.uucp (Henry Spencer) (11/05/88)
In article <10805@cup.portal.com> David@cup.portal.com (David Michael McCord) writes: >... Network World this week had an short blurb about a company that >will be offering a V.32 chip set in OEM quantities for $150/ea. Well, me lad, I've got this bridge that just might interest you... :-) Talk is cheap. Let's see if they can actually do it. Some very big companies have had to eat similar boasts in the past. (Look up Intel's claims about how quickly Ethernet was going to become dirt cheap, for example.) -- The Earth is our mother. | Henry Spencer at U of Toronto Zoology Our nine months are up. |uunet!attcan!utzoo!henry henry@zoo.toronto.edu
steve@ivucsb.UUCP (Steve Lemke) (11/05/88)
In article <Nov.1.14.57.38.1988.17380@pilot.njin.net> limonce@pilot.njin.net (Tom Limoncelli) writes: }Right now I don't have a modem. Really! I use a phone system that }offers simultanious voice and data (data is non-blocking at any bps }rate... I use 19.2K bps... brag... brag...) as long as I stay on site. }If I dial off-site I connect through a modem pool of modems (ok, I }admit it, I do *use* some modems, but I don't have one within a 1/4 }mile of me). The phone system is all digital and under the phone sits }a little IBX<->async interface. Yes, isn't the IBX system a wonderful system? When I worked at Apple in Cupertino this past summer, I, too was hooked up to internal things at 9600 baud, as well as outside things like GEnie (and therefore AppleLink) through a direct pad to Geisco. Apple's VAX was available, as well as a bank of 1200 and another bank of 2400 baud modems. There are also ADIs (Async Data Interfaces) and Sync ones that go much faster than 9600, for things like bridging networks and so forth... I can't wait to get back and see what fun things they're doing with it! Every user of the IBX system also has voicemail now (something like 6000 people?) - slick stuff. }Five years is a lot of time. Yep, just thinking about what computing will be like then is mind-boggling. Working for A (note, I didn't say "the" but "a", implying that there will be many) company that will be right in the midst of it all is the thrill of a lifetime! } Tom Limoncelli -- Student Network Supervisor } Drew University, Box 1060, Madison NJ 07940 -- 201-408-5389 } new->> tlimonce@drunivac.Bitnet -- limonce@pilot.njin.net ----- Steve Lemke ------------------- "MS-DOS (OS/2, etc.) - just say no!" ----- Internet: steve@ivucsb.UUCP; lemke@apple.COM AppleLink: LEMKE ----- uucp: pyramid!comdesign!ivucsb!steve CompuServe: 73627,570 ----- alt.uucp: {decwrl!}sun!apple!lemke GEnie: S.Lemke ----- Quote: "What'd I go to college for?" "You had fun, didn't you?"
dave@onfcanim.UUCP (Dave Martindale) (11/06/88)
Even if V.32 modems were available today at the same price as a Trailblazer, and compatibility issues were fixed so that any V.32 modem would talk to any other, the Trailblazer would still be the better choice for uucp. Its throughput is 1400 cps, not 960, and the uucp spoofing helps get real transfer rates that are close to the maximum. The V.32 spec will never match this. Of course, faster modems will come along, making the existing Trailblazers obsolete, but then they'll make the V.32 modems obsolete at the same time. How will you explain to your boss that you spent more money for a lower- performance modem in the name of "standards" and then had to replace it at the same time anyway? By the way, I was talking to someone from Telebit at SIGGRAPH this summer. They have apparently already demonstrated 28000 bps on a voice channel, using a more powerful signal processor than is in current Trailblazers. So it's quite possible that in a few years the modem of choice for upgrading from a Trailblazer will be another Telebit product. It will likely talk to the existing Trailblazers too.
phile@lgnp1.MASA.COM (Phil Eschallier) (11/07/88)
In article <10805@cup.portal.com>, David@cup.portal.com (David Michael McCord) writes: [deleted ...] > > They went on to say that by this time next year, it was expected that modems > based on this design would be offered at retail for $750 or less. > > I was gratified to see this confirmation of my statement that V.32 was going > to smash the telebit/hst/etceteras "within a year". And I thought I was going > out on a limb! Heh heh. > > David@cup.portal.com after following this discussion on the tb+/hst vs. the v.32 modems, i am reasonably sure that no one is doubting that the v.32 modems will eventually replace the tb+. in fact, i am sure the v.32 will blow away the telebit!! what you can not sell me on is the fact it was a bad decision to purchase the tb+ ... the uucp sites lgnp1 is connected to primarily use the tb+. in the 4 months that i have had the modem, it has easily paid for itself in phone bill savings!! even it were obsolete now, i have still saved money by buying it!! in addition, come the time next year when these v.32 modems are "more affordable", i doubt that every uucp site currently using the tb+ will rush out and get the new modems, atleast not immediately!! look how long the ibm-pc/xt has held on ... phil eschallier phile@lgnp1.masa.com
rick@pcrat.UUCP (Rick Richardson) (11/08/88)
In article <16680@onfcanim.UUCP> dave@onfcanim.UUCP (Dave Martindale) writes: >They have apparently already demonstrated 28000 bps on a voice channel, >using a more powerful signal processor than is in current Trailblazers. >So it's quite possible that in a few years the modem of choice for upgrading >from a Trailblazer will be another Telebit product. It will likely talk >to the existing Trailblazers too. It was easy to cost justify the `blazer, non-standard and all, when the older technology was 2400 and the blazer promised up to 18000. Nobody gets that, of course, (I see around 12000 using AT&T into UUNET, *much* less if I use SPRINT). So lets take the published limits and figure that real users will get 2/3 of what is claimed. That puts the 'blazer++ at around 18000 usable. Only 50% more bandwidth. That would probably mean that I couldn't justify upgrading FROM a 'blazer+ to a 'blazer++ unless the price was dirt cheap (unlikely). But the 'blazer++ would be very attractive to the 2400 baud holdouts. So, you can see that there will be a large imbedded base that probably won't switch based on savings alone. And a group of converts that will switch, but only *if the 'blazer++ can talk to the imbedded base*. "Likely" isn't good enough. It "must" talk to existing 'blazer+'s. -- Rick Richardson | JetRoff "di"-troff to LaserJet Postprocessor|uunet!pcrat!dry2 PC Research,Inc.| Mail: uunet!pcrat!jetroff; For anon uucp do:|for Dhrystone 2 uunet!pcrat!rick| uucp jetroff!~jetuucp/file_list ~nuucp/. |submission forms. jetroff Wk2200-0300,Sa,Su ACU {2400,PEP19200} 12013898963 "" \r ogin: jetuucp
dave@onfcanim.UUCP (Dave Martindale) (11/14/88)
In article <610@pcrat.UUCP> rick@pcrat.UUCP (Rick Richardson) writes: >In article <16680@onfcanim.UUCP> dave@onfcanim.UUCP (Dave Martindale) writes: >>They have apparently already demonstrated 28000 bps on a voice channel, >>using a more powerful signal processor than is in current Trailblazers. > >It was easy to cost justify the `blazer, non-standard and all, when >the older technology was 2400 and the blazer promised up to 18000. >Nobody gets that, of course, (I see around 12000 using AT&T into UUNET, >*much* less if I use SPRINT). Rick misunderstands the theoretical maximum throughput of current Trailblazers. Telebit says that the current modulation technique gives just over 18000 bps total (on a clean line0, but some of that bandwidth is used up for protocol and error-control information passed between the modems. Telebit quotes an actual throughput of user data of 14000 bps, after all overhead is subtracted. So not even Telebit claims that you will see more than 1400 cps. 1200 cps is a pretty respectable portion of 1400. (Note that the UUCP packet overhead does not get accounted for here, since with UUCP spoofing the packet overhead won't get transmitted between the modems. Thus the 1400 cps theoretical throughput is all available for real data. *However*, to get 1400 cps through the modem, the host has to send or receive characters at 1400 * 70/64 = 1531 cps). Anyway, I assumed that the Telebit rep was talking about 28000 bps of user data, exactly twice the current rate. Thus, real throughput should also double, if the host can keep up.
rick@pcrat.UUCP (Rick Richardson) (11/15/88)
In article <16715@onfcanim.UUCP> dave@onfcanim.UUCP (Dave Martindale) writes: >Trailblazers. Telebit says that the current modulation technique gives >just over 18000 bps total (on a clean line0, but some of that bandwidth >is used up for protocol and error-control information passed between >the modems. Telebit quotes an actual throughput of user data of 14000 >bps, after all overhead is subtracted. So not even Telebit claims that > >Anyway, I assumed that the Telebit rep was talking about 28000 bps of >user data, exactly twice the current rate. Thus, real throughput >should also double, if the host can keep up. I assumed that Telebit was still quoting raw speeds. Page 1-1: "Using PEP, Trailblazer can transmit or receive asynchronous data at speeds of up to 18,000 bps over dial-up telephone lines". We know this number should be 14,000 from the technical discussion. But the marketroids will still be saying 18,000 (or 28,000???). Yet another obfuscation technique, like disk drive manufacturers quoting MFM formatted capacities for small drives, but unformatted capacities for large drives. Only this case, in reverse??? -- Rick Richardson | JetRoff "di"-troff to LaserJet Postprocessor|uunet!pcrat!dry2 PC Research,Inc.| Mail: uunet!pcrat!jetroff; For anon uucp do:|for Dhrystone 2 uunet!pcrat!rick| uucp jetroff!~jetuucp/file_list ~nuucp/. |submission forms. jetroff Wk2200-0300,Sa,Su ACU {2400,PEP19200} 12013898963 "" \r ogin: jetuucp