The quota system
----------------

The quota system works with OpenSER data sources. It enforces usage limits
for post-paid accounts. 

The system is based on collected statistics and its accuracy is never 100%.
Variations between actual usage and quota limits depends on the number and
moment of calls that were still in progress during the block operation for
users who exceeded their quota. On a platform basis the fraud is minimized
even if the system is not 100% accurate.

The quota system builds incremental statistics with usage information from
the normalized SIP sessions, it compares the curent usage with the monthly
quota assigned by administrator and blocks the accounts in the SIP Proxy
when the quota is exceeded. The system will not stop in real-time ongoing
calls but provides in practice a perfect protection against fraudulent usage
on a platform basis.

The quota system does not impose a high load on the CDR database by using an
efficient caching and a memcached server. The usage data is incrementally
updated during the normalization process thus offloading the server from
scanning the whole CDR table at each checking interval. The process is able
to check the quotas for 100K users in less then 60 seconds.

To start/stop memcache server used by the quota system use:

/etc/init.d/cdrtool stopmemcache
/etc/init.d/cdrtool startmemcache

Memcached can be manually downloaded from http://www.danga.com/memcached or
is automatically installed during debian package installation. Beware that
memcached server has no built in security, for this reason is advisable to
configure it to listen only on a private network interface.

The quota is checked by a cron job:

/var/www/CDRTool/scripts/SER/quotaCheck.php

To check the current quota usage run:

/var/www/CDRTool/scripts/SER/quotaShowAccounts.php

To check if the cached quota is in sync with the stored CDRs use run:

/var/www/prj/dnshosting/CDRTool/scripts/SER/quotaCompareUsage.php

At the beginning of each month the current quota usage is reset and all users
are unblocked by this cron job:

/var/www/CDRTool/scripts/SER/quotaReset.php

When quota is exceeded email notifications are sent to the end-user and a
copy to the system administrator. To customize the email message subject,
body and other header fields you must create some entries in
cdrtool.settings table. See CDRTool/setup/mysql/custom_notifications.mysql
for an example.