Is it possible to build a system that records and stores all conversations of all subscribers of a particular operator?

GSM mobile network equipment allows you to organize the recording and listening of telephone conversations of a specific subscriber - or several dozen subscribers. From this fact, the far-reaching conclusion is very often drawn that operators use this functionality to record and store all the conversations of their subscribers for a certain period of time. In the event that a subscriber becomes the object of close attention of special services, operators, they say, can, upon request, provide available recordings of conversations almost six months ago.

Is it real?

For calculation, you can take publicly available data on the number of calls in the network of one of the largest Russian operators. This operator serves 51.5 million subscribers, who consume an average of 134 minutes of voice traffic per month - and this is most likely only outgoing calls.

Thus, the total duration of calls of all subscribers in one month will be:

51.50 million x 134 minutes = 6.9 billion minutes

After processing and digitization in a mobile phone, the voice signal in the GSM network is transmitted as a digital stream at a speed of 9.6 Kbps. Thus, without additional processing, all calls from subscribers in one month make up a fairly significant amount of information:

6.9Bmin x 60s x 9.6Kb/s / (8b/b) = 514B = 500TB

Now you can think about how difficult (and costly) it will be to build and maintain a system that:

  1. Records outgoing and incoming conversations of all subscribers within a specific network;
  2. Does it enough quickly;
  3. Allows you to easily find any conversation (by caller ID and date, for example);
  4. Allows storage of information for at least three months;
  5. Works with switching equipment any vendor;
  6. Does not create a significant additional load on signaling and voice channels, switch processors and other network equipment, does not affect the network's ability to serve calls;
  7. Sufficiently reliable - for example, records at least 99% of conversations;
  8. Sufficiently safe - does not allow confidential information to be leaked to persons who do not have special permission (sanctions from the prosecutor, for example).

What follows from this:

  1. All conversations are recorded => The system should not be afraid that subscribers are mobile. That is, it must take into account that subscribers move between base stations during a conversation, they can even move to the service area of ​​another switch, they can redirect calls, combine them into conferences, answer several calls at the same time, and so on;
  2. The system is fast enough => Any post-voice processing done before recording for storage should have time to work on the fly;
  3. The ability to find recorded => The system must be equipped with an index / search engine and integrated with a system that stores basic subscriber data - to take into account changes in phone numbers and SIM cards. Data on completed calls should appear in the system without significant delays;
  4. Recorded storage for three months => Based on the above calculations, a minimum of 1500 TB of disk space is required (if not using voice post-processing);
  5. Compatibility with solutions from different manufacturers => A specified interface is required, which is guaranteed to be available from all leading manufacturers of switching equipment;
  6. No significant load => You can not load call processors in switches or channel equipment with tasks that are not typical for them, such as voice compression in MP3;
  7. Reliability => Requires redundancy for communications, power, and hard drives;
  8. Security => A centralized mechanism is needed to manage and control access to recorded information.

In order to be aware of the movements of mobile subscribers and adequately respond to them, the system must connect to switches (and not, say, base station controllers), since it is the switches that are responsible for all the functionality associated with subscriber mobility. A network capable of serving 50 million subscribers will include about 50 average switches.

Now let's see if it is possible to make the system distributed by placing near each MSC not just a storage for the initial accumulation of information, but something more intelligent - for example, a node that satisfies all the formulated requirements at once.

First, let's imagine one of several possible scenarios for servicing a call from subscriber A to subscriber B.

Scenario 1: Throughout the call, subscriber A is in the coverage area of ​​switch X, and subscriber B is in the coverage area of ​​switch Y. In this case, the conversation can be recorded on any of the switches of our choice. If a record is maintained on both switches, then two absolutely identical records will be obtained as a result, and one of them can (and should) be discarded before being stored in the central storage.

Scenario 2: Throughout the call, subscriber A is in the coverage area of ​​switch X, and subscriber B is in the coverage area of ​​switch Y, but the call passes through the intermediate switch Z. The scenario is very similar to the previous one, except that there will be three identical copies of the entry.

Scenario 3: At the beginning of the conversation, subscriber A is in the coverage area of ​​switch X, and subscriber B is in the coverage area of ​​switch Y, and during the conversation they move: subscriber A goes to the service area of ​​the switch T, and the subscriber - to the service area of ​​the switch S. In this case, the complete record of the conversation will have to be assembled from parts. There will be four parts in total, and from them it will be possible to assemble two complete copies of the record in four possible ways.

If we are honored that during the call both subscribers can use conference calling and call hold services, and there can be more than one intermediate switches (moreover, they can change in the process of moving subscribers), then it becomes clear that in the general case to collect a complete record of a conversation, it is necessary to solve the problem of correlating data from different sources. Similar work is done by inter-operator billing systems, whose architecture can be taken as a starting point for designing our hypothetical global listening system. You must choose between two options:

  • Or collect all the accumulated data in some common centralized repository and process it there. This simplifies processing and maintenance, but requires significant processing power in the processing center;
  • Or collect only metadata about the call (who called whom, when) in the central storage and correlate them in order to understand which parts of the call from which switches will give a complete record of the conversation when collected. The records of conversations themselves can be stored distributed. The results of the correlation are used to retrieve parts of a particular conversation from a distributed repository. This approach reduces the requirements for computing power in each specific node of the system, but significantly increases its complexity and makes it difficult to maintain and keep afloat.

For further considerations, let's assume that it is better to store and process information in one central place from the point of view of security and ease of maintenance. But first, the data needs to be delivered there.

For simplicity, let's assume that the load on the switches is distributed evenly and continuously. Accordingly, 500 TB of conversations are distributed among 50 switches, and each has 10 TB of voice traffic per month. To take this amount of information, you need to have a channel with a bandwidth:

10 * 10244 / (3600 s * 24 hours * 30 days) * 8 bits per byte
= 4241943 bps
= 32 megabits per second

Total, we write down 50 such channels in the estimate.

Further, to ensure the proper quality of data storage, you need to have spare media, in the amount of at least 5% of the used media to replace failed ones.

How many hard drives do you need? From 3000 hard drives of 500 GB to 6000 (if we write everything in a row without preprocessing and record each conversation twice - for the caller and the receiver). Accordingly, the reserve is another 150-300 of the same hard drives annually.

In addition, this number of hard drives needs to be combined into an indexed storage with some kind of access user interface. The storage should provide uninterrupted recording of conversations from all switches (at a speed of 1600 megabits per second), updating search indexes on the go, and serving queries to search and retrieve recorded conversations.

Let's not go into the details of the possible architecture of such a repository now. Let's briefly list everything we have counted so far:

  • Media: 3000-6000 500 GB hard drives, or 3 times (roughly) less hard drives, provided that the voice is compressed at 8 kbps mp3 - since the GSM codec already compresses the voice, it will not be possible to achieve more gain. Naturally, instead of the "saved" hard drives, it is necessary to add processors to perform compression;
  • Infrastructure for building 50 communication channels at 32 mbps;
  • Servers that provide an interface to the repository and its functioning (indexing, searching for the necessary records, searching and deleting old records, integration with the subscriber management system);
  • Power supply and climate control for all equipment;
  • Place in the server rooms for placing equipment;
  • Infrastructure for the operation of the entire system (maintenance personnel, warehouses, logistics . )

It is clear that all this is technically feasible. The only question is economic feasibility.

What self-respecting operator would shell out money for all this "luxury" simply because they were insistently asked for it - given that the return on such investments is not https://cars45.com.gh/32At0JfBhE04D31lKccjYfnM will it be? As far as I know, there are no laws anywhere that would oblige operators to provide such a “service”, so it can only be a “persistent request” from the state or law enforcement agencies, but nothing more.

Which operator has the local technical expertise to build and maintain a solution of this magnitude with its own employees? If you think that this is very simple and cost-effective, think about why large telecom operators do not completely create their own billing, financial and ERP systems.

Where are the suppliers and manufacturers of such ready-made solutions for those operators who cannot develop such a system on their own? In the end, information on real-life listening systems is not a secret with seven seals - to make sure of this, it is enough to search the Internet for the keywords "SORM" or "lawful interception".

After answering these questions for yourself, you can decide for yourself whether it is possible to create a system that records all conversations on a mobile phone or not.

Is it possible to build a system that records and stores all conversations of all subscribers of a particular operator?

GSM mobile network equipment allows you to organize the recording and listening of telephone conversations of a specific subscriber - or several dozen subscribers. From this fact, the far-reaching conclusion is very often drawn that operators use this functionality to record and store all the conversations of their subscribers for a certain period of time. In the event that a subscriber becomes the object of close attention of special services, operators, they say, can, upon request, provide available recordings of conversations almost six months ago.

Is it real?

For calculation, you can take publicly available data on the number of calls in the network of one of the largest Russian operators. This operator serves 51.5 million subscribers, who consume an average of 134 minutes of voice traffic per month - and this is most likely only outgoing calls.

Thus, the total duration of calls of all subscribers in one month will be:

51.50 million x 134 minutes = 6.9 billion minutes

After processing and digitization in a mobile phone, the voice signal in the GSM network is transmitted as a digital stream at a speed of 9.6 Kbps. Thus, without additional processing, all calls from subscribers in one month make up a fairly significant amount of information:

6.9Bmin x 60s x 9.6Kb/s / (8b/b) = 514B = 500TB

Now you can think about how difficult (and costly) it will be to build and maintain a system that:

  1. Records outgoing and incoming conversations of all subscribers within a specific network;
  2. Does it enough quickly;
  3. Allows you to easily find any conversation (by caller ID and date, for example);
  4. Allows storage of information for at least three months;
  5. Works with switching equipment any vendor;
  6. Does not create a significant additional load on signaling and voice channels, switch processors and other network equipment, does not affect the network's ability to serve calls;
  7. Sufficiently reliable - for example, records at least 99% of conversations;
  8. Sufficiently safe - does not allow confidential information to be leaked to persons who do not have special permission (sanctions from the prosecutor, for example).

What follows from this:

  1. All conversations are recorded => The system should not be afraid that subscribers are mobile. That is, it must take into account that subscribers move between base stations during a conversation, they can even move to the service area of ​​another switch, they can redirect calls, combine them into conferences, answer several calls at the same time, and so on;
  2. The system is fast enough => Any post-voice processing done before recording for storage should have time to work on the fly;
  3. The ability to find recorded => The system must be equipped with an index / search engine and integrated with a system that stores basic subscriber data - to take into account changes in phone numbers and SIM cards. Data on completed calls should appear in the system without significant delays;
  4. Recorded storage for three months => Based on the above calculations, a minimum of 1500 TB of disk space is required (if not using voice post-processing);
  5. Compatibility with solutions from different manufacturers => A specified interface is required, which is guaranteed to be available from all leading manufacturers of switching equipment;
  6. No significant load => You can not load call processors in switches or channel equipment with tasks that are not typical for them, such as voice compression in MP3;
  7. Reliability => Requires redundancy for communications, power, and hard drives;
  8. Security => A centralized mechanism is needed to manage and control access to recorded information.

In order to be aware of the movements of mobile subscribers and adequately respond to them, the system must connect to switches (and not, say, base station controllers), since it is the switches that are responsible for all the functionality associated with subscriber mobility. A network capable of serving 50 million subscribers will include about 50 average switches.

Now let's see if it is possible to make the system distributed by placing near each MSC not just a storage for the initial accumulation of information, but something more intelligent - for example, a node that satisfies all the formulated requirements at once.

First, let's imagine one of several possible scenarios for servicing a call from subscriber A to subscriber B.

Scenario 1: Throughout the call, subscriber A is in the coverage area of ​​switch X, and subscriber B is in the coverage area of ​​switch Y. In this case, the conversation can be recorded on any of the switches of our choice. If a record is maintained on both switches, then two absolutely identical records will be obtained as a result, and one of them can (and should) be discarded before being stored in the central storage.

Scenario 2: Throughout the call, subscriber A is in the coverage area of ​​switch X, and subscriber B is in the coverage area of ​​switch Y, but the call passes through the intermediate switch Z. The scenario is very similar to the previous one, except that there will be three identical copies of the entry.

Scenario 3: At the beginning of the conversation, subscriber A is in the coverage area of ​​switch X, and subscriber B is in the coverage area of ​​switch Y, and during the conversation they move: subscriber A goes to the service area of ​​the switch T, and the subscriber - to the service area of ​​the switch S. In this case, the complete record of the conversation will have to be assembled from parts. There will be four parts in total, and from them it will be possible to assemble two complete copies of the record in four possible ways.

If we are honored that during the call both subscribers can use conference calling and call hold services, and there can be more than one intermediate switches (moreover, they can change in the process of moving subscribers), then it becomes clear that in the general case to collect a complete record of a conversation, it is necessary to solve the problem of correlating data from different sources. Similar work is done by inter-operator billing systems, whose architecture can be taken as a starting point for designing our hypothetical global listening system. You must choose between two options:

  • Or collect all the accumulated data in some common centralized repository and process it there. This simplifies processing and maintenance, but requires significant processing power in the processing center;
  • Or collect only metadata about the call (who called whom, when) in the central storage and correlate them in order to understand which parts of the call from which switches will give a complete record of the conversation when collected. The records of conversations themselves can be stored distributed. The results of the correlation are used to retrieve parts of a particular conversation from a distributed repository. This approach reduces the requirements for computing power in each specific node of the system, but significantly increases its complexity and makes it difficult to maintain and keep afloat.

For further considerations, let's assume that it is better to store and process information in one central place from the point of view of security and ease of maintenance. But first, the data needs to be delivered there.

For simplicity, let's assume that the load on the switches is distributed evenly and continuously. Accordingly, 500 TB of conversations are distributed among 50 switches, and each has 10 TB of voice traffic per month. To take this amount of information, you need to have a channel with a bandwidth:

10 * 10244 / (3600 s * 24 hours * 30 days) * 8 bits per byte
= 4241943 bps
= 32 megabits per second

Total, we write down 50 such channels in the estimate.

Further, to ensure the proper quality of data storage, you need to have spare media, in the amount of at least 5% of the used media to replace failed ones.

How many hard drives do you need? From 3000 hard drives of 500 GB to 6000 (if we write everything in a row without preprocessing and record each conversation twice - for the caller and the receiver). Accordingly, the reserve is another 150-300 of the same hard drives annually.

In addition, this number of hard drives needs to be combined into an indexed storage with some kind of access user interface. The storage should provide uninterrupted recording of conversations from all switches (at a speed of 1600 megabits per second), updating search indexes on the go, and serving queries to search and retrieve recorded conversations.

Let's not go into the details of the possible architecture of such a repository now. Let's briefly list everything we have counted so far:

  • Media: 3000-6000 500 GB hard drives, or 3 times (roughly) less hard drives, provided that the voice is compressed at 8 kbps mp3 - since the GSM codec already compresses the voice, it will not be possible to achieve more gain. Naturally, instead of the "saved" hard drives, it is necessary to add processors to perform compression;
  • Infrastructure for building 50 communication channels at 32 mbps;
  • Servers that provide an interface to the repository and its functioning (indexing, searching for the necessary records, searching and deleting old records, integration with the subscriber management system);
  • Power supply and climate control for all equipment;
  • Place in the server rooms for equipment placement;
  • Infrastructure for the operation of the entire system (maintenance personnel, warehouses, logistics . )

It is clear that all this is technically feasible. The only question is economic feasibility.

What self-respecting operator would shell out money for all this "luxury" simply because they were insistently asked for it - given that the return on such investments is not https://cars45.com.gh/32At0JfBhE04D31lKccjYfnM will it be? As far as I know, there are no laws anywhere that would oblige operators to provide such a “service”, so it can only be a “persistent request” from the state or law enforcement agencies, but nothing more.

Which operator has the local technical expertise to build and maintain a solution of this magnitude with its own employees? If you think that this is very simple and cost-effective, think about why large telecom operators do not completely create their own billing, financial and ERP systems.

Where are the suppliers and manufacturers of such ready-made solutions for those operators who cannot develop such a system on their own? In the end, information on real-life listening systems is not a secret with seven seals - to make sure of this, it is enough to search the Internet for the keywords "SORM" or "lawful interception".

After answering these questions for yourself, you can decide for yourself whether it is possible to create a system that records all conversations on a mobile phone or not.

Is it possible to build a system that records and stores all conversations of all subscribers of a particular operator?

GSM mobile network equipment allows you to organize the recording and listening of telephone conversations of a specific subscriber - or several dozen subscribers. From this fact, the far-reaching conclusion is very often drawn that operators use this functionality to record and store all the conversations of their subscribers for a certain period of time. In the event that a subscriber becomes the object of close attention of special services, operators, they say, can, upon request, provide available recordings of conversations almost six months ago.

Is it real?

For calculation, you can take publicly available data on the number of calls in the network of one of the largest Russian operators. This operator serves 51.5 million subscribers, who consume an average of 134 minutes of voice traffic per month - and this is most likely only outgoing calls.

Thus, the total duration of calls of all subscribers in one month will be:

51.50 million x 134 minutes = 6.9 billion minutes

After processing and digitization in a mobile phone, the voice signal in the GSM network is transmitted as a digital stream at a speed of 9.6 Kbps. Thus, without additional processing, all calls from subscribers in one month make up a fairly significant amount of information:

6.9Bmin x 60s x 9.6Kb/s / (8b/b) = 514B = 500TB

Now you can think about how difficult (and costly) it will be to build and maintain a system that:

  1. Records outgoing and incoming conversations of all subscribers within a specific network;
  2. Does it enough quickly;
  3. Allows you to easily find any conversation (by caller ID and date, for example);
  4. Allows storage of information for at least three months;
  5. Works with switching equipment any vendor;
  6. Does not create a significant additional load on signaling and voice channels, switch processors and other network equipment, does not affect the network's ability to serve calls;
  7. Sufficiently reliable - for example, records at least 99% of conversations;
  8. Sufficiently safe - does not allow confidential information to be leaked to persons who do not have special permission (sanctions from the prosecutor, for example).

What follows from this:

  1. All conversations are recorded => The system should not be afraid that subscribers are mobile. That is, it must take into account that subscribers move between base stations during a conversation, they can even move to the service area of ​​another switch, they can redirect calls, combine them into conferences, answer several calls at the same time, and so on;
  2. The system is fast enough => Any post-voice processing done before recording for storage should have time to work on the fly;
  3. The ability to find recorded => The system must be equipped with an index / search engine and integrated with a system that stores basic subscriber data - to take into account changes in phone numbers and SIM cards. Data on completed calls should appear in the system without significant delays;
  4. Recorded storage for three months => Based on the above calculations, a minimum of 1500 TB of disk space is required (if not using voice post-processing);
  5. Compatibility with solutions from different manufacturers => A specified interface is required, which is guaranteed to be available from all leading manufacturers of switching equipment;
  6. No significant load => You can not load call processors in switches or channel equipment with tasks that are not typical for them, such as voice compression in MP3;
  7. Reliability => Requires redundancy for communications, power, and hard drives;
  8. Security => A centralized mechanism is needed to manage and control access to recorded information.

In order to be aware of the movements of mobile subscribers and adequately respond to them, the system must connect to switches (and not, say, base station controllers), since it is the switches that are responsible for all the functionality associated with subscriber mobility. A network capable of serving 50 million subscribers will include about 50 average switches.

Now let's see if it is possible to make the system distributed by placing near each MSC not just a storage for the initial accumulation of information, but something more intelligent - for example, a node that satisfies all the formulated requirements at once.

First, let's imagine one of several possible scenarios for servicing a call from subscriber A to subscriber B.

Scenario 1: Throughout the call, subscriber A is in the coverage area of ​​switch X, and subscriber B is in the coverage area of ​​switch Y. In this case, the conversation can be recorded on any of the switches of our choice. If a record is maintained on both switches, then two absolutely identical records will be obtained as a result, and one of them can (and should) be discarded before being stored in the central storage.

Scenario 2: Throughout the call, subscriber A is in the coverage area of ​​switch X, and subscriber B is in the coverage area of ​​switch Y, but the call passes through the intermediate switch Z. The scenario is very similar to the previous one, except that there will be three identical copies of the entry.

Scenario 3: At the beginning of the conversation, subscriber A is in the coverage area of ​​switch X, and subscriber B is in the coverage area of ​​switch Y, and during the conversation they move: subscriber A goes to the service area of ​​the switch T, and the subscriber - to the service area of ​​the switch S. In this case, the complete record of the conversation will have to be assembled from parts. There will be four parts in total, and from them it will be possible to assemble two complete copies of the record in four possible ways.

If we are honored that during the call both subscribers can use conference calling and call hold services, and there can be more than one intermediate switches (moreover, they can change in the process of moving subscribers), then it becomes clear that in the general case to collect a complete record of a conversation, it is necessary to solve the problem of correlating data from different sources. Similar work is done by inter-operator billing systems, whose architecture can be taken as a starting point for designing our hypothetical global listening system. You must choose between two options:

  • Or collect all the accumulated data in some common centralized repository and process it there. This simplifies processing and maintenance, but requires significant processing power in the processing center;
  • Or collect only metadata about the call (who called whom, when) in the central storage and correlate them in order to understand which parts of the call from which switches will give a complete record of the conversation when collected. The records of conversations themselves can be stored distributed. The results of the correlation are used to retrieve parts of a particular conversation from a distributed repository. This approach reduces the requirements for computing power in each specific node of the system, but significantly increases its complexity and makes it difficult to maintain and keep afloat.

For further considerations, let's assume that it is better to store and process information in one central place from the point of view of security and ease of maintenance. But first, the data needs to be delivered there.

For simplicity, let's assume that the load on the switches is distributed evenly and continuously. Accordingly, 500 TB of conversations are distributed among 50 switches, and each has 10 TB of voice traffic per month. To take this amount of information, you need to have a channel with a bandwidth:

10 * 10244 / (3600 s * 24 hours * 30 days) * 8 bits per byte
= 4241943 bps
= 32 megabits per second

Total, we write down 50 such channels in the estimate.

Further, to ensure the proper quality of data storage, you need to have spare media, in the amount of at least 5% of the used media to replace failed ones.

How many hard drives do you need? From 3000 hard drives of 500 GB to 6000 (if we write everything in a row without preprocessing and record each conversation twice - for the caller and the receiver). Accordingly, the reserve is another 150-300 of the same hard drives annually.

In addition, this number of hard drives needs to be combined into an indexed storage with some kind of access user interface. The storage should provide uninterrupted recording of conversations from all switches (at a speed of 1600 megabits per second), updating search indexes on the go, and serving queries to search and retrieve recorded conversations.

Let's not go into the details of the possible architecture of such a repository now. Let's briefly list everything we have counted so far:

  • Media: 3000-6000 500 GB hard drives, or 3 times (roughly) less hard drives, provided that the voice is compressed at 8 kbps mp3 - since the GSM codec already compresses the voice, it will not be possible to achieve more gain. Naturally, instead of the "saved" hard drives, it is necessary to add processors to perform compression;
  • Infrastructure for building 50 communication channels at 32 mbps;
  • Servers that provide an interface to the repository and its functioning (indexing, searching for the necessary records, searching and deleting old records, integration with the subscriber management system);
  • Power supply and climate control for all equipment;
  • Place in the server rooms for equipment placement;
  • Infrastructure for the operation of the entire system (maintenance personnel, warehouses, logistics . )

It is clear that all this is technically feasible. The only question is economic feasibility.

What self-respecting operator would shell out money for all this "luxury" simply because they were insistently asked for it - given that the return on such investments is not https://cars45.com.gh/32At0JfBhE04D31lKccjYfnM will it be? As far as I know, there are no laws anywhere that would oblige operators to provide such a “service”, so it can only be a “persistent request” from the state or law enforcement agencies, but nothing more.

Which operator has the local technical expertise to build and maintain a solution of this magnitude with its own employees? If you think that this is very simple and cost-effective, think about why large telecom operators do not completely create their own billing, financial and ERP systems.

Where are the suppliers and manufacturers of such ready-made solutions for those operators who cannot develop such a system on their own? In the end, information on real-life listening systems is not a secret with seven seals - to make sure of this, it is enough to search the Internet for the keywords "SORM" or "lawful interception".

After answering these questions for yourself, you can decide for yourself whether it is possible to create a system that records all conversations on a mobile phone or not.

Is it possible to build a system that records and stores all conversations of all subscribers of a particular operator?

GSM mobile network equipment allows you to organize the recording and listening of telephone conversations of a specific subscriber - or several dozen subscribers. From this fact, the far-reaching conclusion is very often drawn that operators use this functionality to record and store all the conversations of their subscribers for a certain period of time. In the event that a subscriber becomes the object of close attention of special services, operators, they say, can, upon request, provide available recordings of conversations almost six months ago.

Is it real?

For calculation, you can take publicly available data on the number of calls in the network of one of the largest Russian operators. This operator serves 51.5 million subscribers, who consume an average of 134 minutes of voice traffic per month - and this is most likely only outgoing calls.

Thus, the total duration of calls of all subscribers in one month will be:

51.50 million x 134 minutes = 6.9 billion minutes

After processing and digitization in a mobile phone, the voice signal in the GSM network is transmitted as a digital stream at a speed of 9.6 Kbps. Thus, without additional processing, all calls from subscribers in one month make up a fairly significant amount of information:

6.9Bmin x 60s x 9.6Kb/s / (8b/b) = 514B = 500TB

Now you can think about how difficult (and costly) it will be to build and maintain a system that:

  1. Records outgoing and incoming conversations of all subscribers within a particular network;
  2. Does this fairly quickly;
  3. Allows you to easily find any conversation (by caller ID and date, for example);
  4. Allows you to store information for at least three months;
  5. Works with any vendor's switching equipment;
  6. Does not create significant additional load on signaling and voice channels, switch processors and other network equipment, does not affect the network's ability to serve calls;
  7. Reasonably reliable - for example, records at least 99% of conversations;
  8. Sufficiently secure - does not allow confidential information to be leaked to persons who do not have special permission (sanctions from the prosecutor, for example).

What follows from this:

  1. All conversations are recorded => The system should not be afraid that subscribers are mobile. That is, it must take into account that subscribers move between base stations during a conversation, they can even move to the service area of ​​another switch, they can redirect calls, combine them into conferences, answer several calls at the same time, and so on;
  2. The system is fast enough => Any post-voice processing done before recording for storage should have time to work on the fly;
  3. The ability to find recorded => The system must be equipped with an index / search engine and integrated with a system that stores basic subscriber data - to take into account changes in phone numbers and SIM cards. Data on completed calls should appear in the system without significant delays;
  4. Recorded storage for three months => Based on the above calculations, a minimum of 1500 TB of disk space is required (if not using voice post-processing);
  5. Compatibility with solutions from different manufacturers => A specified interface is required, which is guaranteed to be available from all leading manufacturers of switching equipment;
  6. No significant load => You can not load call processors in switches or channel equipment with tasks that are not typical for them, such as voice compression in MP3;
  7. Reliability => Requires redundancy for communications, power, and hard drives;
  8. Security => A centralized mechanism is needed to manage and control access to recorded information.

In order to be aware of the movements of mobile subscribers and adequately respond to them, the system must connect to switches (and not, say, base station controllers), since it is the switches that are responsible for all the functionality associated with subscriber mobility. A network capable of serving 50 million subscribers will include about 50 average switches.

Now let's see if it is possible to make the system distributed by placing near each MSC not just a storage for the initial accumulation of information, but something more intelligent - for example, a node that satisfies all the formulated requirements at once.

First, let's imagine one of several possible scenarios for servicing a call from subscriber A to subscriber B.

Scenario 1: Throughout the call, subscriber A is in the coverage area of ​​switch X, and subscriber B is in the coverage area of ​​switch Y. In this case, the conversation can be recorded on any of the switches of our choice. If a record is maintained on both switches, then two absolutely identical records will be obtained as a result, and one of them can (and should) be discarded before being stored in the central storage.

Scenario 2: Throughout the call, Subscriber A is in the coverage area of ​​Switch X and Subscriber B is in the coverage area of ​​Switch Y, but the call passes through the intermediate Switch Z. The scenario is very similar to the previous one, except that there will be three identical copies of the entry.

Scenario 3: At the beginning of the conversation, subscriber A is in the coverage area of ​​switch X, and subscriber B is in the coverage area of ​​switch Y, and during the conversation they move: subscriber A goes to the coverage area of ​​switch T, and the subscriber goes to the coverage area switch S. In this case, the complete record of the conversation will have to be assembled from parts. There will be four parts in total, and from them it will be possible to assemble two complete copies of the record in four possible ways.

If we are honored that during the call both subscribers can use conference calling and call hold services, and there can be more than one intermediate switches (moreover, they can change in the process of moving subscribers), then it becomes clear that in the general case to collect a complete record of a conversation, it is necessary to solve the problem of correlating data from different sources. Similar work is done by inter-operator billing systems, whose architecture can be taken as a starting point for designing our hypothetical global listening system. You must choose between two options:

  • Or collect all the accumulated data in some common centralized repository and process it there. This simplifies processing and maintenance, but requires significant processing power in the processing center;
  • Or collect only metadata about the call (who called whom, when) in the central storage and correlate them in order to understand which parts of the call from which switches will give a complete record of the conversation when collected. The records of conversations themselves can be stored distributed. The results of the correlation are used to retrieve parts of a particular conversation from a distributed repository. This approach reduces the requirements for computing power in each specific node of the system, but significantly increases its complexity and makes it difficult to maintain and keep afloat.

For further considerations, let's assume that it is better to store and process information in one central place from the point of view of security and ease of maintenance. But first, the data needs to be delivered there.

For simplicity, let's assume that the load on the switches is distributed evenly and continuously. Accordingly, 500 TB of conversations are distributed among 50 switches, and each has 10 TB of voice traffic per month. To take this amount of information, you need to have a channel with a bandwidth:

10 * 10244 / (3600 s * 24 hours * 30 days) * 8 bits per byte = 4241943 bps = 32 megabits per second

Total, we write down 50 such channels in the estimate.

Further, to ensure the proper quality of data storage, you need to have spare media, in the amount of at least 5% of the used media to replace failed ones.

How many hard drives do you need? From 3000 hard drives of 500 GB to 6000 (if we write everything in a row without preprocessing and record each conversation twice - for the caller and the receiver). Accordingly, the reserve is another 150-300 of the same hard drives annually.

In addition, this number of hard drives needs to be combined into an indexed storage with some kind of access user interface. The storage should provide uninterrupted recording of conversations from all switches (at a speed of 1600 megabits per second), updating search indexes on the go, and serving queries to search and retrieve recorded conversations.

Let's not go into the details of the possible architecture of such a repository now. Let's briefly list everything that we have counted so far:

  • Media: 3000-6000 500 GB hard drives, or 3 times (roughly) less hard drives, provided that the voice is compressed at 8 kbps mp3 - since the GSM codec already compresses the voice, it will not be possible to achieve more gain. Naturally, instead of the "saved" hard drives, it is necessary to add processors to perform compression;
  • Infrastructure for building 50 communication channels at 32 mbps;
  • Servers that provide an interface to the repository and its functioning (indexing, searching for the necessary records, searching and deleting old records, integration with the subscriber management system);
  • Power supply and climate control for all equipment;
  • Place in the server rooms for equipment placement;
  • Infrastructure for the operation of the entire system (maintenance personnel, warehouses, logistics . )

It is clear that all this is technically feasible. The only question is economic feasibility.

What self-respecting operator would shell out money for all this "luxury" simply because they were insistently asked for it - given that there will be no return on such investments https://cars45.com.gh/32At0JfBhE04D31lKccjYfnM? As far as I know, there are no laws anywhere that would oblige operators to provide such a “service”, so it can only be a “persistent request” from the state or law enforcement agencies, but nothing more.

What self-respecting operator would shell out money for all this "luxury" simply because he was insistently asked for it - given that the return on such investments is not https://cars45.com.gh/32At0JfBhE04D31lKccjYfnM https://cars45.com.gh/32At0JfBhE04D31lKccjYfnM will? As far as I know, there are no laws anywhere that would oblige operators to provide such a “service”, so it can only be a “persistent request” from the state or law enforcement agencies, but nothing more.

Which operator has the local technical expertise to build and maintain a solution of this magnitude with its own employees? If you think that this is very simple and cost-effective, think about why large telecom operators do not completely create their own billing, financial and ERP systems.

Where are the suppliers and manufacturers of such ready-made solutions for those operators who cannot develop such a system on their own? In the end, information on real-life listening systems is not a secret with seven seals - to make sure of this, it is enough to search the Internet for the keywords "SORM" or "lawful interception".

After answering these questions for yourself, you can decide for yourself whether it is possible to create a system that records all conversations on a mobile phone or not.