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The Connection Success Rate (CSR) is an important metric for tracking and measuring the stability of
a dial service. The CSR is defined by the number of modems that successfully train up and go in to
connected state. In addition to the CSR, you must track and analyze additional areas. For example,
SNMP MIBs can be used to measure the success rate for items such as PPP, AAA, and IP negotiation.
To collect the CSR service level counters, inspect the connection success and failure rate by using
modem OIDs or the show modem Cisco IOS command. SNMP, rather than the Cisco IOS CLI, is the
preferred method to collect these counters. SNMP can scale to support large numbers of access servers.
The following graphs show the DS0s and PPP sessions in use for 70,000 modem users calling in to a
dial-up service at a large university. The graphs are taken from one Cisco AS5300 in a large dial-up
modem pool.
The jagged saw-tooth pattern at the top of the graph indicates a telephone-switch hunt group for the dial
lines passing by the access servers. A "jump up" occurs each time the hunt group passes by a different
T1 line. For a hunt group that rotates in a round-robin fashion, a jagged saw-tooth pattern is normal.
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