Cisco 6200 User Manual
Page 23
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