Cisco 6200 User Manual

Page 23

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78-5296-02

10/02/98

Hardware Description

1

Cisco 6200 User Guide

1-23

In the downstream direction, 11 rates are available ranging from 640 kbps to 7.168 Mbps. In the
upstream direction, 9 rates are available, ranging from 91 kbps to 1.088 Mbps.

The modems on the CAP SLC train in sequence, first downstream, then upstream. Each modem first
acquires the line. Then it tests the signal quality on the line by measuring the signal-to-noise ratio
(SNR). It adds a preset margin, 6 dbm, to the SNR, and compares the resulting value to a table. If
the value is acceptable, the modem trains at the configured rate. If not, the modem repeats the
process, using the next lower transmission rate. The modem keeps trying to train indefinitely until it
is successful.

Statistics

The SLC gathers signal quality statistics for network management purposes. It sends this
information to the management system via the master SNMP agent. The SLC reports each of the
following statistics to the management system for both upstream and downstream traffic:

Number of nonidle cells transmitted downstream

Number of nonidle upstream cells received with valid header checksum

Number of upstream cells received with invalid header checksum

Number of errored seconds (this is the number of seconds in which at least one header checksum
error or loss of cell delineation is observed), both upstream and downstream

Figure 1-10

SLC 8CAP Operation

Cisco

6200

ADSL

modem

SLC

Port 1

Port 2

Port 3

Port 8

ATM

12690

Public

telephone

network

POTS

splitter

POTS
splitter

Contention

and

arbitration

Cell

filter

CAP

transceiver

NTC

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