The rapidly growing telecommunications industry has posed
some of the big challenges for operators in the country. Call Data Records (CDR)
archiving is one the biggest challenges that telcos are facing today. For the
purpose of compliance and national security, telecom companies need to keep CDR
for a long term, so that when required it can aid in investigations by police
and other agencies to detect criminal activities.
By the end of October 2009, the telecom subscriber base in
India reached the 525.65 mn mark. The numbers increased from 509.03 mn
subscribers in September 2009, registering a 3.3% increase. With this change,
the overall teledensity in India reached 44.9%.
For the wireless segment, the subscriber base increased by
16.67 mn. The subscriber base rose from 471.73 mn in September 2009 to 488.40 mn
at the end of October 2009, at a monthly growth rate of 3.6%. The wireless
teledensity stands at 41.7%. The wireline subscriber base again witnessed a
decline in the subscriber base. The drop this month has been of 0.05 mn, from
37.31 mn in September 2009 to 37.25 mn at the end of October 2009. Keeping the
CDR of such a huge subscriber base, and producing it on time, is one the key
challenges faced by operators.
Call Detail Record
A CDR is a computer record produced by a telephone exchange containing
details of a call that passed through it. It is the automated equivalent of the
paper toll tickets that were written and timed by operators for long distance
calls in a manual telephone exchange.
"CDR is a fundamental part of the telecom system. One has to
store data in such a way that it is there for a long period of time, and that it
can be decoded fast whenever required," says Rajat Mukarji, chief corporate
affairs officer, Idea Cellular.
A call detail or data record contains the 'number' making the
call, the 'number' receiving the call, when the call started (date and time),
and the duration of the call. It also records the type of call-voice and SMS.
The other information not necessarily required for billing the call may be
included such as the amount charged for the call, the identifier of the
telephone exchange writing the record, a sequence number identifying the record,
additional digits on the number used to route or charge the call, the result of
the call (whether it was answered, busy, etc), the route by which the call
entered the exchange, the route by which the call left the exchange, any fault
condition encountered, and any facilities used during the call (such as call
waiting or call diversion).
Call accounting software is generally used to retrieve and
process the CDR data. This system can be called a billing support system (BSS)
and in this system the price of the call will be calculated. Billing CDRs can be
used to support the operations of a telephone company by providing information
on faulty calls and measures of the amount of traffic taken along particular
routes.
DoT Regulations
As per the Department of Telecommunications guidelines, issued on April 15,
2009, the SPs should make arrangements for monitoring simultaneous calls by the
government security agencies. The hardware at SP's end and the software required
for monitoring calls should be engineered and provided, installed and maintained
by the SP at its own cost. Keeping in view of the large number of subscribers
and additional 8-12 mn being added every month, the cost of CDR goes up.
The interface requirements as well as the features and
facilities-as defined by the authorities-should be implemented by the SPs for
both data and voice. Presently, SPs should ensure suitable redundancy in the
complete chain of monitoring equipment for trouble-free operations and
monitoring at least 210 simultaneous calls for seven security agencies.
"SEBI has also put in a request for having access to CDR. And
the government is considering to give access to the authority. The number of
agencies having access to CDR could grow to eight," says a senior official of a
leading mobile operator pleading anonymity.
Along with the monitored calls, database of called or calling
party, mobile or PSTN numbers should be maintained. The record should also have
time, date, duration of interception, and location of target subscribers. At
present, cell ID should be provided for location of the target subscribers.
Further, authorities may issue directions from time-to-time on precision of
location, based on technological developments, and integration of GPS which is
binding on the SP.
Challenges
Usually CDR is offloaded from the billing system on a regular basis (usually
linked to the billing cycle) and needs to be kept in a system that not only
protects the data from mutation and corruption; but also in a way, whereby
telecom companies are able to find this data easily whenever needed. Many a
times, investigative agencies approach telecom companies in order to know about
call records of specific customers which they require in a short span of time
(sometimes even hours). This means that this data cannot be offline. Also, since
this data is old and hardly accessed, telecom companies will save a lot of money
by compressing it. Encrypting this data is usually required as it contains
sensitive personal information. The EU mandates telecom companies to encrypt CDR
data under data privacy laws.
"Capacity of the server is the key challenge for CDR
archiving, keeping in view of the number of subscribers going up and at the same
time call cost going down. A new project on CB-CDR is underway which will solve
our problem," says AK Dinkar, GM operations, MTNL, Mumbai.
A lot of things can go wrong when data is stored over a long
period of time like corruption, accidental deletion, etc. The system should have
provisions to detect any corruption in data and heal the data automatically, so
that when the investigative agencies ask for the data, it can be searched and
read easily. Ability to apply retention policy (write-once-read-many) is
definitely a great feature to have in the system which will protect the CDR from
being modified after it is created.
Many telecom companies keep the CDR data on tier-3 (typically
a bunch of SATA drives), thinking that they are keeping the data online (for
quick search and recovery). And at times on the 'cheapest' disk; but what these
organizations do not realize is that the real cost in keeping CDR for long term
is the backup cost. Even the cheapest SATA drives will require backup data and
that's where the real cost lies. CDR data is not even changing and backing up
information (incremental and full) that never changes and it is a waste of
resources and money. This is where storage solutions designed for archiving
information help in reducing the cost of storing CDR for a long term while
de-risking it by ensuring data immutability, availability and search.
Akhilesh Shukla
akhileshs@cybermedia.co.in