Greetings Beta Testers!

It's good to be chatting with you all again, I hope everything 
is well with you and your families.

Attached to this message is a new SDL file update for the Courier
desktop modems.   At the present time, there is NO intention of
releasing this code to the public.  This test is only being done
to confirm the effectiveness of the changes we have been making 
since the last public release on 12/2/94.

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DO NOT MAKE THIS SDL FILE AVAILABLE TO ANYONE OUTSIDE THE BETA TEAM!
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Changes and enhancements:

1. Improved V.FC line performance.

2. Improved V.34 compatability.

3. Improved V.32xxx retraining.

4. This code adds the optional "Selective Reject" feature to LAPM 
operation.   This feature enhances throughput by reducing the number 
of data blocks that are re-sent when an error (BLER) occurs.   
Under normal LAPM operation, a BLER results in the transmitter backing 
up to the point where the error occurred and re-sending the errored 
block as well as all subsequent blocks.   Under Selective Reject mode, 
ONLY the errored block is re-sent, subsequent blocks are buffered and 
then processed in sequence after the error has been corrected.   This 
reduction in re-transmitted data provides a substantial increase in 
throughput under noisy conditions.   

Note: Selective Reject may be disabled via S51=64.

5. Increased block size in LAPM mode.  Previous USR implementations of 
LAPM used a block size of 128 bytes, this new code uses a maximum size
of 244 bytes.   The increased block size results in lower overhead, and
increased throughput.  

6. The ATI6 diagnostic screen has an extended "Protocol" field which
displays the actual block and window sizes, and indicates when Selective
Reject has been negotiated.   

7. ARQ LED operation has been modified so that the LED blinks whenever
BLERS are encountered.   Previous code only blinked the light when 
data was being re-transmitted due to BLERS at the remote side.  Now 
that both conditions are being reported, you will notice an increase
in the activity of that light.   

8. MR LED operation has been modified so that the light extinguishes 
when either modem requests a retrain.   Previous code only extinguished 
the light when the local modem made the request.

The main purpose of this special Beta test is to validate the operation
of the new Selective Reject feature, and to ensure compatability with
previous code and competitors products.   Pay close attention to file 
transfer throughputs and ATI6 screens, and be sure to include the
remote modem type and firmware rev in any trouble reports that you may
post.

Again, please do not post this SDL file on any BBS.   It is ONLY for the
use of registered BETA team members.   It is extremely important that
this SDL file does not get into public circulation.   Details of future
public releases have not been determined at this time, and we do not
wish to upset scheduling by a "leak" of this Beta test version.

I will be acting as administrator of this Beta cycle.   The Beta 
conference on the USR BBS will be the only contact point, no fax 
or voice calls unless requested, please.

Thanks, and enjoy!

Joe Frankiewicz

