10.2. Call Detail Recording
Without even being told, Asterisk assumes that
you want to store CDR information. Quite a smart machine, yes?
By default, Asterisk will create a
CSV file and place it in the
folder /var/log/asterisk/cdr-csv/.
To the naked eye, this file looks like a bit of a mess. If,
however, you separate each line according to the commas, you will
find that each line contains information about a particular call,
and that the commas separate the following values:
accountcode
-
Assigned if the application SetAccount(
) is used, or if configured for the channel in the channel
configuration file (i.e., sip.conf). The account code is assigned on a
per-channel basis.
src
-
Received Caller*ID (string, 80 characters).
dst
-
Destination extension.
dcontext
-
Destination context.
clid
-
Caller*ID with text (80 characters).
channel
-
Channel used (80 characters).
dstchannel
-
Destination channel, if appropriate (80
characters).
lastapp
-
Last application, if appropriate (80
characters).
lastdata
-
Last application data (arguments, 80
characters).
start
-
Start of call (date/time).
answer
-
Answer of call (date/time).
end
-
End of call (date/time).
duration
-
Total time in system, in seconds (integer), from
dial to hangup.
billsec
-
Total time call is up, in seconds (integer),
from answer to hangup.
disposition
-
What happened to the call (ANSWERED,
NO ANSWER, BUSY).
amaflags
-
What flags to use (DOCUMENTATION,
BILL, IGNORE, etc.), specified on a per-channel
basis, like accountcode. AMA flags stand for
Automated Message Accounting flags, which are somewhat standard
(supposedly) in the industry.
userfield
-
A user-defined field, maximum 255
characters.
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CDRs can also be stored in a database. Asterisk
currently supports SQLite, PostGreSQL, MySQL, and unixODBC. The
configuration details for these databases will not be covered in
this book, but they are outlined in the Asterisk source code, under
the doc/ subdirectory. (For
licensing reasons, cdr_mysql is in
asterisk-addons.) Many people
prefer to store their CDRs in a database because this makes it
easier to query them for specific information, such as billing or
toll fraud. We can use the CDR applications to manipulate the
current CDR from the dialplan (adding information to the custom
field, for example).
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10.2.1. CDR Challenges
While Asterisk will happily store information
about any calls that pass through it, it cannot store information
it is not given. For example, if you have SIP devices that are
allowed to reinvite, once Asterisk has finished setting up the
calls, the devices will no longer need its assistance. Whether or
not those devices subsequently report call detail information back
to it is something Asterisk is unable to control. If CDRs are
important, make sure your IP devices are not allowed to
reinvite.
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