PairGain CRA-C User manual

Megabit Modem CRA-C
User Manual
Power
10BASE-TADSL
Manual Number: 425-613-150-02

ii Megabit Modem CRA-C User Manual
Megabit Modem CRA-C User Manual
P/N 425-613-150-02
Revision 02
May 1998
Copyright © 1998. PairGain Technologies, Inc. All rights reserved.
This document contains proprietary information which is protected by
copyright.
Information contained in this document is company private to PairGain
Technologies, Inc. and shall not be modified, used, copied, reproduced or
disclosed in whole or in part without the written consent of PairGain.
PairGain is a registered trademark, and Megabit Modem is a trademark of
PairGain Technologies, Inc.
Other product names mentioned in this manual are used for identification
purposes only and may be trademarks and/or registered trademarks of their
respective companies.
The information in this publication is believed to be accurate in all respects.
However, PairGain Technologies cannot assume responsibility for any
consequences resulting from the use thereof. The information contained herein
is subject to change. Revision to this publication or new additions to it may be
issued to incorporate such changes.

Megabit Modem CRA-C User Manual iii
FCC NOTICE
This equipment has been tested and found to comply with the limits for a
Class B digital device, pursuant to Part 15 of the FCC Rules. These limits are
designed to provide reasonable protection against harmful interference when
the equipment is operated in a commercial environment. This equipment
generates, uses, and can radiate radio frequency energy and, if not installed and
used in accordance with this instruction manual, may cause harmful
interference to radio communication.
However, there is no guarantee that interference will not occur in a particular
installation. If this equipment does cause harmful interference to radio or
television reception, which can be determined by turning the equipment off
and on, the user is encouraged to try to correct the interference by one or more
of the following measures:
•Reorient or relocate the receiving antenna.
•Increase the separation between the equipment and receiver.
•Connect the equipment into an outlet on a circuit different from that
to which the receiver is connected.
•Consult the dealer or an experienced radio/TV technician for help.
Any changes or modifications not expressly
approved by the grantee of this device voids
the user’s authority to operate the equipment.

iv Megabit Modem CRA-C User Manual
DECLARATION OF CONFORMITY
Manufacturer’s name PairGain Technologies, Inc.
and address: 14402 Franklin Ave
Tustin, CA 92780-7013
U.S.A.
declares that
Product name: Megabit Modem CRA-C
conforms to the following
Standards: EN55022 (1987), EN50082-1 (1992),
EN60950 (1994)
Application of Council Directives: 89/336/EEC, 73/23/EEC
I, the undersigned, hereby declare that the equipment specfied above conforms
to the above directives and standards.
Signature:
Roy Stephens,
Director of Quality Assurance
Place: Tustin, CA, U.S.A.
Date: March 16, 1998

Megabit Modem CRA-C User Manual v
USING THIS MANUAL
This manual helps you:
•understand the features of the PairGain®Megabit Modem™ CRA-C
and how the unit operates as a component within a network
•install the Megabit Modem CRA-C
•configure your unit to operate within the network
•contact PairGain if you need additional help
Three types of messages with icons appear in the text:
Notes inform you of special circumstances.
Cautions indicate the possibility of damage to equipment.
Warnings indicate the possibility of personal injury.

Using This Manual
vi Megabit Modem CRA-C User Manual

Megabit Modem CRA-C User Manual vii
CONTENTS
ABOUT THE MEGABIT MODEM CRA-C __________________ 1
About Rate Adaptive Transmission.....................................2
Rate Adaptation..............................................................2
Reach, Data Rate, SNR Margin,
and Noise Environment............................................ 4
INSTALL THE MEGABIT MODEM CRA-C_________________ 7
Unpack and Inspect the Shipment.......................................7
Identify LEDs and Connectors............................................ 9
Front Panel..................................................................... 9
Rear Panel.................................................................... 11
Install the Megabit Modem CRA-C .................................. 12
Connect to the ADSL Line ...........................................12
Connect to the Data Network........................................ 13
Power Up and Check LEDs ..............................................16
CONFIGURE AND VIEW STATUS________________________ 17
Connect to an ASCII Terminal.......................................... 17
How to Log On and Navigate the Menus .......................... 19
How to Configure a Remote Unit...................................... 23
Configure System Settings................................................ 24
Configure ADSL Transceiver ...........................................26
Configuration ............................................................... 26
Reset ADSL Transceiver .............................................. 29
Configure the Bridge/Router............................................. 30
Configure as a Bridge................................................... 31
Configure as a Router................................................... 34
Configure SNMP.......................................................... 38
Reset the Ethernet Bridge............................................. 40
View Status ...................................................................... 41
System Information ...................................................... 41
ADSL Transceiver Status.............................................. 42
Ethernet Bridge Statistics.............................................. 48
Log Out............................................................................ 49

Contents
viii Megabit Modem CRA-C User Manual
NETWORK AND MANAGEMENT OVERVIEW____________ 51
MAC Layer Bridging and Spanning Tree Protocol............51
Static IP Routing...............................................................53
Megabit Modem CRA-C IP Addresses..........................59
Management Protocols......................................................61
SNMP...........................................................................61
Megabit Modem CRA-C SNMP Agent .........................62
MIB and Trap Support..................................................63
Network Configuration and Image Code Download ..........64
BOOTP.........................................................................64
TFTP ............................................................................66
Encapsulation Protocols....................................................66
TECHNICAL SPECIFICATIONS _________________________ 67
TECHNICAL ASSISTANCE______________________________ 69
World-Wide Web..............................................................69
FTP ..............................................................................69
LIMITED WARRANTY _________________________________ 71
GLOSSARY____________________________________________ 73

Megabit Modem CRA-C User Manual 1
ABOUT THE MEGABIT MODEM CRA-C
The PairGain®Megabit Modem™ CRA-C uses Asymmetric Digital
Subscriber Line (ADSL) technology to provide, on a single pair telephone line,
a multi-megabit Ethernet connection between the subscriber and the service
provider. The Megabit Modem CRA-C transmits data up to 3.16 Mbps from a
service provider and receives data up to 1.08 Mbps from a subscriber. The
Megabit Modem CRA-C is rate adaptive; its speed is adjusted to the maximum
attainable data rate depending on distance and line condition. Additionally,
ADSL technology allows ordinary telephone service to coexist with the
high-speed data service on the same wire pair.
The rate-adaptive Megabit Modem allows the service provider to deliver the
best possible data rate for any subscriber. Typically, a subscriber closest to the
provider receives the highest data rate available, while subscribers farther
away receive data at a lower transmission rate.
The Megabit Modem CRA-C has field-proven Carrierless
Amplitude-modulation and Phase-modulation (CAP) line coding.
The 2-dimensional, 8-state Trellis coding with Viterbi decoding and
the Reed-Solomon forward-error-correction provide robust transmission
in harsh environments.
Use the Megabit Modem CRA-C for application solutions, particularly those
requiring high-speed transmission to the subscriber, such as:

Internet access

remote Local Area Network (LAN) access

telecommuting
•small office or home office
Other features of the Megabit Modem CRA-C include:

embedded Simple Network Management Protocol (SNMP) agent

IEEE 802.1d transparent MAC level bridging with Spanning Tree
protocol support

static IP routing to provide secure access to the Internet

BOOTP and TFTP to download software

10BASE-T Ethernet port for connection to an Ethernet LAN

line port for Rate-adaptive ADSL single-pair connection
•console port for maintenance and management

About the Megabit Modem CRA-C
2 Megabit Modem CRA-C User Manual
Use the Megabit Modem CRA-C with these other PairGain products:
•Megabit Modem CRA (at subscriber site)
•S1 Network Interface Device (network interface at subscriber site)
About Rate Adaptive Transmission
The following definitions are useful for understanding the operation of the
Megabit Modem:
•Bit Error Rate (BER) is the ratio of received bits that are in error
relative to the total number of bits received, measured over time.
For example, 10-7 BER means that on average one error occurs per
107bits received.
•Signal to Noise Ratio (SNR) is the ratio (typically expressed in dB) of
the received signal power to the received noise power. It is a measure
of the quality of the transmission. The theoretically achievable BER
can be extrapolated from the measured SNR.
•Margin (SNR margin) is the amount of degradation in SNR that the
system can tolerate under the current conditions and still achieve a
10-7 BER. A margin of 6 dB, for example, would mean that the SNR
can degrade by 6 dB and still provide a performance of 10-7 BER. The
PairGain Megabit Modem CRA-C has a margin configuration option
that defaults to 6 dB, but may be set anywhere between -3 dB to 9 dB.
•Reach is the longest loop length that the system can support with
a given margin and a BER of less than 10-7 at the given data rate.
Rate Adaptation
With PairGain's rate adaptive technology, the Megabit Modem CRA-C
can automatically adjust to the fastest speed possible, given the transmission
distance and line conditions. Alternatively, the provider can manually set
the modem to a specific rate. The available data rates are:
•downstream (transmit) rates: 3.168 Mbps, 2.528 Mbps, 2.208 Mbps,
1.888 Mbps, 1.568 Mbps, 1.248 Mbps, 928 Kbps, 608 Kbps
•upstream (receive) rates: 1.080 Mbps, 944 Kbps, 808 Kbps, 672 Kbps,
536 Kbps, 400 Kbps, 264 Kbps, 82.66 Kbps

About the Megabit Modem CRA-C
Megabit Modem CRA-C User Manual 3
The Megabit Modem CRA-C can be set to any one of three modes that
determine how the data rate is selected. It is important to note that rate
adaptation occurs only during startup. The Megabit Modem CRA-C will
not change its data rate while the link is up. The three startup modes are:
•Full startup always: In the full startup mode, the system figures out
the highest upstream and downstream data rates it can support under
the current line conditions, with a margin greater than or equal to the
configured margin. This is done during every ADSL startup attempt.
The system will always attempt a full startup where it will set a
transmission rate up to the maximum specified. It determines this rate
by assessing the signal quality data (line length and noise conditions,
for example) and the margin configuration setting. It then comes up
in the highest available rate based on this information.
•Session startup: In session startup mode, the system uses the data
rates set during a previous full startup, rather than re-assessing the
signal quality data. In this mode the system performs a full startup
upon every powerup or reset and would also revert back to a full
startup attempt when a session startup is not successful for 30 seconds.
•Fixed data rate: In a fixed-rate mode (fixed data rate), the user
programs both the upstream and the downstream data rates using the
Transceiver Configuration Menu. The user can select from available
data rates shown above. Another configuration parameter is the
startup SNR margin that is also configurable using the Transceiver
Configuration Menu. The system will attempt to come up to the
programmed data rates with a margin greater than or equal to the
configured margin. Failure to complete startup with the desired
margin results in repeated attempts to accomplish it.
When a connection is lost in any mode (the cable disconnected, for example),
the system attempts reconnection as if it has been reset.

About the Megabit Modem CRA-C
4 Megabit Modem CRA-C User Manual
Reach, Data Rate, SNR Margin, and Noise Environment
The maximum transmission rate of the Megabit Modem CRA-C is determined
by distance, SNR margin, and the condition of the line (wire gauge, condition
noise environment). Figure 1 shows the relationship between reach and data
rate for a given set of conditions. The plots can be used to determine the
achievable reach at a given data rate, or they may be used to determined the
achievable data rates at a given distance. In all of the cases except the no
noise case, a margin of 6 dB was allocated above the SNR that provides a Bit
Error Rate (BER) of 10-7.
These line conditions fall within the range of the plots shown in Figure 1:
•no noise (0 dB margin)
•low noise (−140 dBm-Hz Additive White Gaussian Noise (AWGN))
•24 ISDN lines in the same binder group
•24 HDSL lines in the same binder group
•24 ADSL lines in the same binder group
•10 T1 lines in an adjacent binder group
•one T1 line in the same binder group
The performance shown is "typical" for PairGain Megabit
Modem CRA products. Due to variations in environment and
test setup, PairGain does not guarantee performance to the
figures shown.
One of the configuration options in the Megabit Modem CRA-C is the
startup margin setting. This setting defaults to 6 dB but may be set from
-3 dB to 9 dB. The modems will attempt to come up at the programmed
margin setting. Setting the margin high allows for a cushion against changing
line conditions and impulse noise. Setting the margin low provides less
protection but allows the modems to come up at a higher data rate (if in the
rate-adaptive modes) or at a longer loop length (if in the fixed data rate mode).
The default setting of 6 dB is recommended and provides an overall BER
better than 10-10. Reducing the setting to 0 dB will only provide a BER of
less than 10-7 and is not recommended.

About the Megabit Modem CRA-C
Megabit Modem CRA-C User Manual 5
Figure 1. Reach for a Rate Adaptive ADSL Megabit Modem

About the Megabit Modem CRA-C
6 Megabit Modem CRA-C User Manual

Megabit Modem CRA-C User Manual 7
INSTALL THE MEGABIT MODEM CRA-C
Install the Megabit Modem CRA-C using these sections:
For information about this topic Go to page
Unpack and inspect the shipment 7
Identify LEDs and connectors 9
Install the Megabit Modem CRA-C 12
Power up and check LEDs 16
Unpack and Inspect the Shipment
Upon receipt of the equipment:
1Unpack each container and visually inspect it for signs of
damage. If the equipment has been damaged in transit,
immediately report the extent of damage to the transportation
company and to your sales representative. Order replacement
equipment if necessary.
2Check the contents to the packing list to ensure complete and
accurate shipment. If the shipment is short or irregular, contact
your sales representative. If you must store the equipment for a
prolonged period, store the equipment in its original container.
The shipping carton contains, in addition to the Megabit Modem CRA-C and
this manual, the cables described in Table 1.

Install the Megabit Modem CRA-C
8 Megabit Modem CRA-C User Manual
Table 1. Cables for Megabit Modem CRA-C
Item Description Function
Straight-through
Category 3 cable Black unshielded twisted-pair (UTP)
cables terminated with
RJ-45 connectors.
Connects the Megabit Modem
CRA-C Ethernet MDI-X port
to a network device with an
MDI port.
Cross-over
Category 5 cable Yellow UTP cable terminated with RJ-45
connectors.
Connects the Megabit Modem
CRA-C Ethernet MDI-X port
to a network device with an
MDI-X port.
ADSL cable Gray UTP cable
terminated with RJ-11
and RJ-45 connectors.
Connects the Megabit Modem
CRA-C to the ADSL line.
Console cable Flat, silver, eight-wire
cable with RJ-45
connectors at each end.
Plugs into the Console port to
connect the Megabit Modem
CRA-C to an ASCII terminal.
Do not use as a 10BASE-T
Ethernet cable.
Console adapter A rectangular DB-9 (F)
to RJ-48 adapter with
two captive mounting
screws.
Optional. Connects the
Megabit Modem CRA-C to an
ASCII terminal for
configuration and viewing
status.
Power supply An AC to DC power
supply that plugs into
the power outlet.
Provides primary power to the
Megabit Modem CRA-C and
establishes a safety ground.
Do not tamper with the power supply safety
prong. It is a critical element for the secondary
lightning protection provided within the Megabit
Modem CRA-C. If you tamper with the safety
prong, you risk serious injury.

Install the Megabit Modem CRA-C
Megabit Modem CRA-C User Manual 9
Identify LEDs and Connectors
The Megabit Modem CRA-C front panel has LEDs that show status for power
and data transmission. The rear panel has external interface connectors and a
power switch.
Front Panel
Figure 2 and Table 2 describe the LEDs on the Megabit Modem CRA-C
front panel.
Figure 2. Megabit Modem CRA-C Front Panel

Install the Megabit Modem CRA-C
10 Megabit Modem CRA-C User Manual
Table 2. Front Panel LEDs
LED Mode Description
Power Green Indicates power is on.
10BASE-T
LINK Green
Off
Ethernet connection up.
Ethernet connection down.
TX Green
Off
Transmit activity at port.
No transmit activity at port.
COL Green
Off
Collisions occurring on the port.
No collisions occurring on the port.
ADSL
SYNC Solid green
Flashing green
Off
Normal operation.
Training in progress.
Megabit Modem CRA not synchronized with
Megabit Modem CRA-C.
STAT Solid green
Flashing green
Normal operation.
Test/Alarm condition exists.
MAR Solid green
Flashing green
Margin is above threshold.
Margin is below threshold.

Install the Megabit Modem CRA-C
Megabit Modem CRA-C User Manual 11
Rear Panel
Figure 3 and Table 3 describe the Megabit Modem CRA-C rear panel features.
Figure 3. Megabit Modem CRA-C Rear Panel
Table 3. Rear Panel Components
Name Function
POWER connector 6-pin mini-DIN type port that supplies power to Megabit
Modem CRA-C.
Do not connect any other wall-plug supply to the
Megabit Modem CRA-C unit, otherwise, you can
permanently damage the unit.
ON/OFF switch Toggle switch used to turn modem ON and OFF.
CONSOLE port RJ-45 connector (RS-232 compatible) used to connect an
ASCII terminal for configuring the Megabit Modem(s).
10BASE-T
MDI-X port RJ-45 MDI-X (cross-over) port used to connect the Megabit Modem CRA-C to a 10BASE-T port of a data network device.
ADSL port RJ-48 port used to connect the Megabit Modem CRA-C to the
ADSL transmission line.

Install the Megabit Modem CRA-C
12 Megabit Modem CRA-C User Manual
Install the Megabit Modem CRA-C
Complete the steps in the order listed to install the Megabit Modem CRA-C:
•connect to the ADSL line
•connect to the data network
Connect to the ADSL Line
The Megabit Modem CRA-C requires a single pair of telephone wires to
connect the subscriber to the service provider. One wire is the Tip
and the other is the Ring. See Table 4 for pinouts. Connect the Tip and Ring
wires to your Megabit Modem CRA-C:
1Plug the RJ-45 connector of the ADSL cable (gray) into the
ADSL port on the Megabit Modem CRA-C rear panel (Figure 4).
2Connect the RJ-11 connector to the ADSL line.
Figure 4. Connecting to the ADSL Line