Ascend Archive
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Re: (ASCEND) v90 slowdowns
On Friday, August 07, 1998 14:02 Derek Vadala <derek@usfca.edu> wrote:
>> I just upgraded our max 6000's to v90 ( and in turn 6.1.3 )
>> and some of our users are reporting strange slowdown
>> issues. It seems that most of them using v90 either connect
>> at around 45k/bps or about 50k/bps.
>>
>> Now, the 45k/bps connections seem to work flawlessly
>> and yield a very solid throughput of about 5.5k/sec with
>> very few errors or slowdowns. However, it is reported
>> that when a 50k/bps connection is established there are
>> "long pauses" between bursts of data transfer and that
>> the overall effect is a throughput of about 1k/sec less
>> than the 45k/bps connections. Is this a known issue
>> or something others have experienced?
I think you may find that this problem is typically due
to some kind of modem retraining. A way to possibly
demonstrate this in the most simple terms is to use a
modem that has external LED's ... make your connection,
and cause a continuous stream of data to occur
(ping, ftp, whatever).
Your line quality may be degrading - I've seen modems
do this whereby all transmissions cease whilst the modems
renegotiate, and then things take off from the point at
which they pause. Some modems even have stats to
tell you this; I think even the cheap 3Com/USR Sportster
modem has stats that will tell you the number of times
it retrained during a connection (you can connect to
the modem afterwards and use ATI commands to get
the stats).
The key is that during this retrain type operation,
no data passes ... that's the long pause (often as
long as it typically takes to make the initial connection,
i.e., what you hear when the speaker is on). And that
long pause of course diminishes the overall bit rate
(or throughput) in bps.
These kinds of problems on our end have basically
diminished since we went to the 6.1.3 code on the
MAX 4000 boxes and instructed our clients to upgrade
their modems to the manufacturer's latest v.90 code.
That's not to say you're not really having problems
with telephone line quality ...
Bob McCormick
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