From: karl@ddsw1.MCS.COM (Karl Denninger)
Subject: Modem test results (3 models)
Date: Wed, 27 Jan 1993 05:34:06 GMT
Organization: MCSNet, Chicago, IL

I recently conducted a modem evaluation of three modems from ZyXEL, Telebit,
and UDS.  Here are the results; they are quite interesting and
counter-intuitive.  All measurements were made to a T3000 on the remote end 
between two NetBlazers, with one end running to a host system.


Modem			Ping			Best FTP

T3000			180ms/1791ms		4.9Kb/sec
UDS FasTALK 32bx	220ms/2362ms		4.7Kb/sec

ZyXEL U1496E		170ms/3238ms(1)		5.0Kb/sec

Notes:
	Pings were measured with 8 byte packets; 56 byte packets were also
	used with comparable results.  The second number is for a 3000 byte
	"ping" and simulates overloaded links or extreme traffic.  Both sets
	were run for 100 pings and the arithmetic mean taken for the
	extreme test; the short test settled down within 5 pings to a given 
	value on all three models and that is the number reported.

	FTP is of a 125KB text file, repeated three times.  Best data rate
	reported as measured by FTP.  All modems were within .1Kb/sec 
	varience on this test.


(1)	ZyXEL was unable to reasonably work with the load of the large pings
	in this test.  As a result, until that problem is resolved it cannot
	be recommended, despite its <excellent> latency and throughput
	numbers.  The distribution of responses to the overload ping test 
	were wild and uncoordinated around a mean; the assumption is that 
	the modem was having severe trouble with the offered load.  This
	modem would likely misbehave on a heavily-used SLIP or PPP link.

It would appear that the Telebit T3000 was still the best performer overall
of the models tested.  The UDS was quite a disappointment.  I had expected 
better for the price (they're expensive).  Its latency is a killer on 
interactive sessions.

The ZyXEL, while originally promising, proved to be a great disappointment
with the current firmware.  I am awaiting newer firmware and will repeat the
tests when it arrives.  <IF> ZyXEL was to fix the problems here with
overloading, AND fix the ATI0 botch (it returns a alphanumeric string) this 
would be an excellent unit for this kind of use.  As it is, until the 
problems with large transfers are fixed, I simply could not recommend it.
SLIP and PPP links are frequently stuffed to the gills, and the misbehavior
displayed was quite alarming (ping return times ranged from 1700 to 9500 ms 
in the test!)

In a week's testing of actual use the ZyXEL and the UDS both "froze" up
once.  The ZyXEL did it without any indication of trouble, the UDS froze
with a blinking front-panel LED pattern which I'd never seen before.  Both
required power-downs to restore sanity.  

The T3000 (which I've had here for a while) has shown no problems in about 
6 months of use, and has never had to be powered down or reset.

All three modems appear to tolerate bad lines well; the T3000 has tossed 
a user a couple of times where the others have been able to keep the 
connection open.  The T3000, however, does not have the latest firmware
either.

The UDS is the only modem with "current" firmware in it at this instant; I
got new chips this AM.

Looks like, at least for now, that Telebit still has the "golden"
performance in the modem market, at least among these competitors.

--
Karl Denninger (karl@ddsw1.MCS.COM, <well-connected>!ddsw1!karl)
Data Line: [+1 312 248-0900]
Newsgroups: comp.dcom.modems