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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

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