Detection of Corruption in the Statistics FPGA and System Operations on Detecting Corruption

When a bit flip occurs in a DRAM or static RAM (SRAM) of a statistics FPGA of a router functioning as the Session and Resource Control (SRC) or RADIUS client, the router may transmit corrupted accounting statistics to a SRC or RADIUS server. This affects the computation of accounting information for subscriber sessions. You must replace the hardware to resolve the incorrect computation of accounting information caused by the corrupted statistics retrieved from the SRC or RADIUS client.

A parity error check mechanism is introduced in the statistics FPGA of an ES2 4G LM to check whether the statistics is corrupted. The parity error check mechanism checks the parity in both the DRAM and SRAM for all statistics entries. The mechanism populates the parity error status bit of the statistics entry to indicate parity check failure. The parity check failed statistics entries are not updated after the parity error is detected by the mechanism.

Note: The parity error check mechanism is supported only on ES2 4G LMs (with any IOA combination) and is applicable for both the PPP and L2TP subscribers. The parity error check mechanism restricts the available number of bits of a 64 bits packet/byte counter to 60 bits and 32 bits packet counter to 30 bits.

The parity error check mechanism is triggered to check for parity error during the following events:

You can use the fpga-stats-monitoring-enable command to prevent the router from reporting parity check failed user and policy accounting statistics to the RADIUS or SRC server.

Note: The router performs actions (such as subscriber termination) only during interim update or subscriber logout, but not during subscriber login.

Actions Performed on Detecting Parity Error

If you have executed the fpga-stats-monitoring-enable command and parity error is detected, the router performs the following actions for user and policy accounting statistics:

If you have executed the fpga-stats-monitoring-enable command and parity error is detected, the router performs the following actions for statistics other than user and policy accounting statistics:

Note: When the parity error is detected in the multicast statistics on a corresponding interface for a multicast traffic, the unicast packet statistics does not include the actual received unicast packet count as the unicast statistics count is derived from the multicast statistics counter (that is, unicast count = inReceived packets-inMulticast packets).

If you have executed the fpga-stats-monitoring-enable command and parity error is detected, the show ip interface and show ipv6 interface commands display an error message instead of the policy accounting statistics details for the policies whose statistics are corrupted.

If you have not executed the fpga-stats-monitoring-enable command and parity error is detected, the subscribers are not terminated. But, the router sends the older uncorrupted user and policy accounting statistics to the RADIUS or SRC server in all subsequent interim records and also in final accounting record during subscriber logout. Also, the software displays an error message in the output of the show ppp interface command instead of the corrupted user accounting statistics details.

Related Documentation