Cisco AS5800 Specifications download pdf (Page 99)

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Cisco AS5800 Operations, Administration, Maintenance, and Provisioning Guide

DOC-7810814=

Chapter 3 Operations

Verifying Modem Performance

Step 13 Turn off all debug commands:

5800-NAS# undebug all

All possible debugging has been turned off

Initiating and Inspecting a V.90 Test Call

Before you let users dial in to the NAS, initiate and inspect a V.90 test call. V.90 call performance is

heavily dependent upon the telco’s network topology. There are many variables.

Most modem manufactures have unique AT command sets. The AT commands used in the following

procedure may not be supported by your modem. For more information, refer to the following:

• Modem manuals, available online at

http://56k.com/links/Modem_Manuals/

• Modemsite.com’s troubleshooting website, available at

http://808hi.com/56k/trouble1.htm

Step 1 Locate a client PC, client modem, and an analog line.

Step 2 Test your EIA/TIA-232 connection to the client modem:

Parameter #26 Far End Echo Level: -52 dBm

Use this field to detect a near-end digital-to-analog conversion. For

this test, an acceptable value is less than -55 dB.

If you see a high level of far end echo (-55 or higher), a

digital-to-analog conversion probably exists between the NAS and

the switch. This conversion severely impairs modem performance.

Parameter #30 Characters transmitted, received:

70966, 80

The number of characters transmitted and received by the modem.

Line shape:

..............................*

................................*

.................................*

................................*

.................................*

................................*

.................................*

A line shape is the frequency-response graph of the channel.

For this modem loopback test call, there should be no rolloff (even

at the highest frequency). High-end rolloff is characteristic of an

analog-to-digital conversion (not good).

A flat vertical line shape is an ideal V.90 line shape. ISDN uses a

64KB clear channel. No statistical roll off should exist at the low

end or the high end of the spectrum. The spectrum has a Y and X

axis.

The Y axis (vertical) represents frequencies from 150 Hz (top of

chart) to 3750 Hz (bottom of chart) in 150 Hz steps. A flat spectrum

plot is best, it is available for V.34, V.90, and K56Flex.

The X axis (horizontal) represents a normal amplitude. The graph

identifies nulls, bandwidth, and distortion (irregular shape).

Table 3-4 Operational Parameter Descriptions for a Loopback Test Call (continued)

Parameter Description

1 2 ... 94 95 96 97 98 99 100 101 102 103 104 ... 333 334

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Cisco AS5800 Specifications Page 99

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