1999/12/21

			ComOS 4.1c2 Interim Release Note 
 

_______________ Introduction

The Lucent Technologies InterNetworking Systems ComOS(R) 4.1c2 interim
software release is now available for the PortMaster(R) 4 Integrated
Access Concentrator.

This release is provided at no charge to all Lucent customers.

This release note applies only to the PortMaster 4 and documents
updates to the modem code. All other features are identical to those in
ComOS 4.1c1.

NOTE: This interim software release is recommended only for customers
who are experiencing the problems described and are unable to wait for
the next maintenance release.

Before upgrading, thoroughly read "Limitations" and "Upgrade
Instructions."

NOTE: If you downgrade from ComOS 4.1c2 to ComOS 4.0.3c2 or earlier, 
you must perform the downgrade process twice because of changes in the
nonvolatile memory layout in ComOS 4.1c2.

_______________ Contents

Introduction
Modem Bugs Fixed in ComOS 4.1c2
ComOS 4.1c2 Limitations
Upgrade Instructions
Technical Support
 

_______________ Modem Bugs Fixed in ComOS 4.1c2

The following bugs are fixed in ComOS 4.1c2.

________Code Fixed for Sega Dreamcast Game

New modem code for the Sega Dreamcast video game modem has been
implemented. As a result, the PortMaster switches to buffered mode more
quickly -- after 10 seconds rather than after 40 seconds.

This quicker mode change allows the PortMaster to conduct Link Access
Procedure for Modems (LAPM) negotiation and detect open distributed
processing (ODP) failures if it receives an exchange identification
(XID) within 10 seconds. Otherwise, the PortMaster uses the Microcom
Networking Protocol (MNP) or buffered code.

________V.8 Logic Improvements

V.8 modem negotiation logic has been modified to check for the V.90 or
V.34 data rate before falling back to V.32.

Previously, some modems completed V.8 negotiation and falsely triggered
the PortMaster to use V.32. By checking for V.90 or V.34 first, the
PortMaster now ensures that only V.32 modems connect at V.32 rates.

________V.8bis Logic Improvements

V.8bis logic has been improved to force PCTEL modems to V.90.

PCTEL modems do not set the V.90 bit during V.8bis negotiations, but
set a proprietary bit instead. If the PortMaster detects that this
proprietary bit is set on a PCTEL client modem, it uses V.90 rates.

One drawback is that a PCTEL modem set for K56flex will fail V.90 and
fall back to V.34.

________K56flex Improvements

K56flex code has been improved to better handle rate renegotiations
with Rockwell client modems.

________LAPM Suspension during Rate Changes and Retrains

To reduce the number of disconnections, the PortMaster now suspends all
LAPM negotiations and data transfers during rate changes and retrains,
and also resets timers.

The Link Access Procedure for Modems (LAPM) is the final and
highest-layer phase of V.90 modem negotiation that occurs during the
process of connecting to a communications server:

1. Packets received from the OSI data link layer of the transmitting
device traverse the LAPM layer during modem V.90 negotiation and
undergo compression and error control.

2. Once the packets are compressed, they are transferred down through
the V.90 layers to the physical transport layer and received by the
modem on the other end.

3. The receiving modem then passes the packets back up to the V.90
layer of LAPM on the receiving device.

4. The LAPM layer checks the packet header for errors and decompresses
the packet data before passing the packet to the OSI data link layer of
the receiving device.

Packet transmission rate is determined at the lower V.90 layers.
Because no packets can be transferred from a higher layer while the
lower layers are busy determining the speed of transfers, the
PortMaster suspends LAPM activity during this time.

________LAPM Selective Reject Support

The PortMaster now supports selective reject to improve throughput for
modem clients that support this feature.

Selective reject is an important throughput adjustment that allows
modems to retransmit only frames that arrive with an error, to conserve
precious bandwidth and time.

For example, suppose that the PortMaster and a client modem agree on a
window size of five frames. The first frame from the client arrives
correctly, the second frame arrives in error, and subsequent frames
arrive without error.  Modems without selective reject (most modems)
will retransmit  frames 2 through 5, but a modem with selective reject
retransmits only frame 2 and then continues on to transmit frame 6 and
subsequent frames. The PortMaster now supports this feature.

________Line Improvements

Poor upstream connections, NO EC (no error control), and No Connect
problems on lines with more than one analog-to-digital conversion and
other lines that do not support V.90 have been fixed.

________A-Law V.90 Transmission Increase

Maximum digital modem transmission for A-law V.90 has been 
increased to -9dBm from -12dBm, to reduce the rate changes for A-law 
modem clients in Europe.

________Loss-of-Carrier Detection Improvement

Modems now detect loss of carrier for V.90 calls over T1 lines with
foreign exchange station (FXS) or foreign exchange office (FXO)
interfaces (Loop Start Lines).

________Timeout Errors Fixed

The PortMaster now informs certain modem clients of the proper LAPM 
window size to use, fixing some LAPM timeout errors that occurred in 
previous releases.

Window size determines how many packets are sent before the other LAPM
partner can report that it received the bits and frames sent correctly.
The two modems must agree on this number. Sending a single frame of 128
bytes to the client and waiting for the client to acknowledge is less
efficient than sending multiple frames and waiting for a single
acknowledgement.

For example, suppose the PortMaster is set for a window size of three
frames and the remote device expects a window size of four.  When the
PortMaster sends three frames and waits, the remote modem waits for a
fourth frame before acknowledging. Disagreement about window size can
cause timer expiration or even disconnection. This problem has now been
corrected for certain clients.

_______________ ComOS 3.8.2c4 Limitations

* Lucent is still fixing some problems with Rockwell HCF and Cirrus
Logic modems. If you experience any difficulties with modems, verify
that the client modem is running the latest firmware. Then refer to
http://www.livingston.com/tech/bulletin/comos-modem.html. If these
instructions do not help, contact Lucent NetCare(R) technical support.

* A PCTEL modem set for K56flex in its proprietary bit will be
incorrectly identified as being set for V.90 by the PortMaster. As a
result, the modem will fail V.90 negotiations with the PortMaster and
will fall back to V.34 rates.

_______________ ComOS 4.1c2 Limitations

All nonmodem limitations are the same in ComOS 4.1c2 as they
were in ComOS 4.1c1.

A PCTEL modem set for K56flex in its proprietary bit will be 
incorrectly identified as being set for V.90 by the PortMaster. As 
a result, the modem will fail V.90 negotiations with the PortMaster
and will fall back to V.34 rates.

_______________ Upgrade Instructions

You can upgrade your PortMaster 4 using PMVision 1.8 or later, or 
pmupgrade 4.3 from PMTools. Alternatively, you can upgrade using the 
older programs pminstall 3.5.3, PMconsole 3.5.3, or PMconsole for 
Windows 3.5.1.4, or later releases. You can also upgrade using TFTP 
with the "tftp get comos" command from the PortMaster command line
interface.

See ftp://ftp.livingston.com/pub/le/software/java/pmvision18.txt for
installation instructions for PMVision 1.8.

*** CAUTION! If the upgrade fails, do NOT reboot! Contact
*** Lucent NetCare technical support without rebooting.

The upgrade process on the PortMaster 4 erases the configuration area
from nonvolatile memory and saves the current configuration into
nonvolatile memory. Never interrupt the upgrade process, or loss of
configuration information can result. This upgrade does not otherwise
affect your stored configuration in the PortMaster 4.

The installation software can be retrieved by FTP from
ftp://ftp.livingston.com/pub/le/software/, and the upgrade image
can be found at ftp://ftp.livingston.com/pub/le/upgrades/:

ComOS	Upgrade Image	Product
______	_____________	____________
4.1c2 	pm4_4.1c2 	PortMaster 4

________________________________________________________________________

        Copyright and Trademarks

Copyright 1999 Lucent Technologies. All rights reserved.

PortMaster, ComOS, ChoiceNet, and NetCare are registered trademarks of
Lucent Technologies. PMVision, IRX, PortAuthority, and NavisRadius are
trademarks of Lucent Technologies. All other marks are the property of
their respective owners.

	Notices

Lucent Technologies makes no representations or warranties with respect
to the contents or use of this publication, and specifically disclaims
any express or implied warranties of merchantability or fitness for any
particular purpose. Further, Lucent Technologies reserves the right to
revise this publication and to make changes to its content, any time,
without obligation to notify any person or entity of such revisions or
changes.

	Contacting Lucent NetCare Technical Support

Lucent NetCare Professional Services provides PortMaster technical
support via voice or electronic mail, or through the World Wide Web at
http://www.livingston.com/. Specify that you are running ComOS 4.1c2
when reporting problems with this release.

Internet service providers (ISPs) and other end users in Europe, the
Middle East, Africa, India, and Pakistan should contact their authorized
Lucent NetCare sales channel partner for technical support; see
http://www.livingston.com/International/EMEA/distributors.html.

For North America, the Caribbean and Latin America (CALA), and Asia
Pacific customers, technical support is available Monday through Friday
from 7 a.m. to 5 p.m. U.S. Pacific Time (GMT -8). Dial 1-800-458-9966
within the United States (including Alaska and Hawaii), Canada, and
CALA, or 1-925-737-2100 from elsewhere, for voice support. For email
support, send to support@livingston.com (asia-support@livingston.com 
for Asia Pacific customers).

