VoIP – Introduction

Voice traffic has been the main telecom service in OTT VOIP since the inception of mobile telephony. It is still relevant and is increasing as well in this day and age of mobile data and IP-based technology.

VoIP Calls can be captured by a lawful interception system at an ISP and distributed to authorized Lawful Interception. VoIP Interception is a term used to describe when a provider delivers audio over an IP network (such as the internet), by passing the traditional operator’s network completely.

VoIP providers are a growing factor within telecommunications networks, with advances in technology such as smartphones, high-speed IP networks, and open-source platforms all fueling the increase in adoption rates.

VoIP – Lawful Interception

Lawful Interception of VoIP is a complex process with challenges like :

  • Many parties are typically involved in transporting data over the Internet.
  • Target source & destination identities of the information flow are embedded within the overall flow of data.
  • Target & Non-target data are tightly intermingled in the bit flows at numerous points throughout the Internet.
  • The separation of applications and relevant data from the overall data stream.
  • Lack of standards implementations.
  • There are limited network elements which can provide IRI and CC of the target.

Overcoming the above challenges and complying 100% to international standards PertSol offers non- intrusive passive interception approaches for the interception of VoIP calls. Supporting real time fanout of voice calls for LEA’s over SIP or E1.

Our Solution support various type of interception traffic for OTT platforms used IMS domain (IP Multimedia Subsystem):

  • Voice calls (VoIP)
  • Video calls
  • Video conferencing
  • Call forwarding or multi-participant calls
  • SMS
  • Data Flow

The PertSol’s iNtercepter solution support both Mass and Target centric interception of the traffic depending upon the MNO’s network and requirement:

  •  Interception via SBC
  • Interception via Edge routers
Passive Interception

In Passive Interception, PertSol uses its iNteliProbe which functions as an LI Access Point and investigates the tapped traffic data.

PertSol’s iNteliProbe is the state of the art passive probes providing interception support for vast range of protocols, network type, filtering capabilities, metadata analysis etc.

Advance Features:

  • Support for 100Gbps duplex traffic in single probe.
  • Support L2 to L7 network traffic filtering and Analysis.
  • Deep packet inspection (DPI) for traffic to provide InSite info like Apps detail, URL categorization etc.
  • Support more than 10,000 concurrent VoIP calls.
  • Automated re-provisioning for detecting network changes.
  • Stealthily intercept the traffic without revealing its identity.

It requires passive taps at appropriate point like SBC or Edge routers to mirror the complete traffic. LIM Generic functional architectural solution flow for interception:

Enabling cities worldwide to access lifesaving location technology

Situation Analysis
Building solutions for a better quality of life.
Pert Telecom Solutions (PertSol) creates best-in-class custom software applications and offers professional project management services. With offices in Mumbai and Gurugram, India, PertSol focuses on innovation for telecoms and government agencies.
PertSol’s expertise lies in Telecom Core Network (TCN), Telecom Compliance Management (TCM) and Internet of Things (IoT) solutions. In TCN and TCM services, PertSol’s technology helps telecom service providers effectively and efficiently run their networks while ensuring compliance with regulatory requirements. Increasingly, PertSol is using this expertise to design locationbased services (LBS) for telecom companies to integrate into their offerings.
Making the world more secure.
PertSol began developing LBS solutions, believing they could make the world a safer place in the face of rapid urbanization. LBS solutions can help with emergency call tracking, effective fleet management, location-based advertising and other locationbased, value-added services.
Fulfilling the need for a global partner.
Given the number of “smart cities” projects worldwide that are helping improve urban living, PertSol’s goal was to launch its LBS solution, called iLocator, quickly. The one major hurdle to overcome was the need for an original equipment manufacturer (OEM) partner with global services and an open-architecture approach to help launch iLocator. Moreover, the PertSol team wanted the peace of mind that while it focused on developing solutions, its OEM partner would be committed to designing an in-market solution that would differentiate iLocator, increasing its potential for success.
Design Partnership
Partnering with Dell Technologies OEM Solutions.
Working together, OEM Solutions assisted PertSol in designing and implementing the iLocator platform, which includes Dell EMC PowerEdge servers, PowerScale storage, networking solutions and OptiPlex desktops. “From the start, Dell Technologies OEM Solutions was committed to the success of PertSol’s iLocator,” says Gurjot S Sandhu, director and chief business officer at PertSol.
Making LBS intelligent across the world with OEM Solutions.
  • Ensuring class-leading solution performance to help differentiate iLocator from competing solutions.
  • Sharing engineering expertise with the PertSol team to maximize the efficiency of development processes.
  • Assisting PertSol in launching iLocator globally.
  • Helping PertSol’s customers deploy iLocater faster, saving 7-9 months on average.
“Dell Technologies OEM Solutions’ technical support was critical during deployment, and together we ensured iLocator was tested and validated to meet the high standards of telecom companies and government agencies worldwide.”
The partnership between Dell Technologies OEM Solutions and PertSol created a new in-market iLocator design for the platform’s global audience. Support from OEM Solutions included the following:
Gurjot S Sandhu
Director and Chief Business Officer
Pert Telecom Solutions
Ensuring cities are safer.
Bharat Sanchar Nigam Limited (BSNL), which owns one of the largest telecom networks in India, is deploying iLocator to support location-based services for all of its mobile networks. iLocator will help BSNL pinpoint the locations of its mobile subscribers across India and will be able to share it with Law Enforcement Agencies for national security, Emergency Services for sending rescue/relief teams and other location-based applications for the commercial use of location services.
Expanding to increase safety in growing populations.
PertSol is now leveraging OEM Solution’s global program management to expand iLocator into Africa and South America. Comments Sandhu, “Multiple engagements are under way for iLocator as telecom companies use LBS to deliver social good among growing populations and pinpoint callers’ positions, which can mean the difference between life and death.”

IPDR Management


With a tremendous surge in mobile data usage & shift in the telecom industry from voice to data, all service providers are moving towards an IP network that delivers voice, data, video & mobile applications. Therefore, to safeguard the public from threats like cyber-crime, cyberbullying, cyber terrorism etc. & to help LEAs with their investigations, Regulatory Authorities across the globe have recommended TSPs/ISPs to gather metadata information of their users which may help LEAs with their investigations & Intelligence generation.

In addition, this info can also help enterprises for building future growth strategies including trading, buying, and selling data to gain insights and drive profits. MetaData generated is being used to create predictive models, automated processes, and predictive analytics for the subscriber database.

Tracing IP addresses to subscriber devices and their actual users can be very detrimental in investigating and fighting modern-day crimes. In the current scenario, with everyone leaving a digital footprint finding the source IP address, TCP port number, date, and time of session can lead to criminals.

Therefore, service providers need an IPDR System / IP Log Management System in their network which shall support Government Agencies by gathering and managing IPDR (Internet Protocol Detail Record) logs of the subscribers and help provide the data which can become the building block of LEAs’ investigations & intelligence generation.


IPDR Management Platform

PertSol iSecureHL is a fully automated IPDR management system that offers consistent and high-quality IP Logs across the operator’s network domains. It is a web-based system that fetches data from various sources like Internet Traffic, GTP traffic, CGNAT Logs, AAA traffic, etc., and stores them in the form of IPDR. It helps telecom CSPs and LEAs in protecting the public against Cybercrime by providing IPDRs.

iSecureHL in combination with PertSol iNteliProbe deliver the most comprehensive monitoring solutions. It can simultaneously monitor Internet Traffic for the control plane and User plane. Packets can be captured via interface cards that support 10G, 40G, 100G interfaces. It is also capable of decoding captured traffic from layer 2 to layer 7.


Solution With Excellent Capabilities


VoLTE Lawful Interception

VoLTE – Introduction

VoLTE Lawful Interception has been the main telecom service since the inception of mobile telephony. It is still relevant and is increasing as well in this day and age of mobile data and IP-based telecom technology. In Evolved Packet System (EPS), which is completely IP-based technology, delivering voice service can only be realized using either Circuit-Switched Fallback (CSFB) or Voice over LTE (VoLTE).
While CSFB offers voice services to LTE interception users without utilizing IMS by temporarily moving the user from the LTE network to a legacy network i.e. 2G/3G system which can then serve voice calls over a circuit-switched network. Whereas VoLTE is a digital packet voice service that is delivered over IP via an LTE access network utilizing IMS (IP Multimedia Subsystem) technology.


VoLTE: Lawful Interception

Lawful Interception of VoLTE is a complex process as a VoLTE call invokes two systems, i.e. EPC and IMS. Moreover, there are multiple network elements in these two systems that can provide IRI and CC of the target. PertSol offers two different approaches for the interception of VoLTE calls depending upon the MNO’s network and requirements:

i. By Interception of EPC nodes
ii. By Interception of both EPC and IMS nodes

Lawful Interception through EPC Nodes

MNO’s which already has an existing LI solution for its IMS system can use this approach. In this approach, PertSol will provide its LI solution (iNterceptor) which will intercept the EPC traffic (including VoLTE) by integrating with the EPC nodes (Intercept Access Points) like MME, SGW and PGW. It also facilitates the VoLTE interception for inbound roamers using S8HR interception as explained in below section. 

Lawful Interception through EPC & IMS Nodes

PertSol iNterceptor can also be implemented as a combined LI solution for both IMS and LTE network of an MNO. This approach will involve integration with IMS IAPs in addition with the EPC IAPs explained in the first approach.

The IMS access points that will be integrated for VoLTE interception are CSCF, BGF, TAS and MGW.

Lawful Interception: VoLTE Roaming Scenario

VoLTE roaming can be carried out using two ways, as defined in 3GPP specifications:

i. Local Breakout (LBO): Local Breakout mechanism requires the visited network to have an IMS system in its network. In LBO the roaming user is connected to the PDN-GW of the visited network and all the traffic is transported via visited network’s PDN-GW, without using the PDN-GW of home network.

ii. S8 Home Routing (S8HR): S8HR makes use of the home network PDN-GW and does not require the visited network to have an IMS system. The roaming user traffic is to the PDN-GW of home network, via S-GW of visited network, which then forwards it to the IMS network for completing the call.

S8 Home Routing (S8HR) is the preferred VoLTE roaming architecture of most of the mobile network operators as it does not dependent on the IMS system of the visited network. PertSol offers two ways of intercepting VoLTE calls for inbound roamer in S8HR roaming scenario:

i. Active Interception – By using BBIFF functionality of SGW

ii. Passive Interception – By intercepting S8 interface

S8HR Active Interception

PertSol iNterceptor is capable of intercepting the VoLTE calls of inbound roamer by providing LI Mirror IMS State Function (LMISF). For active interception of VoLTE calls, the SGW shall support BBIFF functionality (Bearer Binding Intercept and Forward Function). This approach is as per 3GPP TS 33.107 specifications and the recommendations of GSMA PRD IR.65. It requires implementation of proprietary interfaces Xia / Xib. Moreover this approach can also be extended to 5G with minor changes.

S8HR Active Interception
S8HR Passive Interception

In S8HR Passive Lawful Interception, PertSol uses its iNteliProbe which functions as an LI Access Point and investigates the traffic data tapped from the S8 interface between S-GW of the visited network and PDN-GW of the home network. It requires passive taps at the appropriate point in the VPLMN to duplicate the complete S8 traffic. This approach can also be used for 5G (N9 interface) or 5G Interception.

S8HR Passive Interaction
iNterceptor Benefits

Hosted GMLC Provider

An Approach to improve location identification success ratio of PSAP/Emergency service callers

Presently, the PertSol iLocator GMLC Provider sends a request to the TSP’s LBS platform for the caller’s location. The location coordinates availability depends on TSP’s LBS platform. The caller’s location can be fetched only if, the TSP has the information generated at its LBS platform. Getting LBS issues resolved at TSP end has been a major challenge in the past months. TSPs compliance is not meeting DOT guidelines in which the failure rate of non-getting lat-longs is more.

A solution to this is “PertSol’s Hosted GMLC or iGMLC” which generates the location of the distressed caller by querying the TSP’s network and locating the caller. GMLC in telecom stands for Gateway Mobile Location Centre. It enables offering Location Based Services(LBS) to mobile
subscribers roaming across several Mobile Network Operator’s Radio Access Networks, regardless of the type of access (GERAN, UTRAN or E-UTRAN). It is an independent service that is integrated with the TSPs network over a secured communication channel. A GMLC can query the TSP network to generate the location of the distressed caller.

iGMLC or hosted GMLC would be an evolved version of present LBS solution

PertSol shall adopt a novel method for location retrieval as per the TSPs network type and architecture. iGMLC can be installed at TSPs premises or at Dial 112 / 100 Data centre, whichever is suitable to the TSP/ Department. We have implemented a similar solution for BSNL North zone.

Current Limitations: Non-Compliance of DoT Guidelines

The emergency services are long-suffering due to TSP issues. TSPs’ are not able to meet the LBS standards as per DOT guidelines in which the failure rate of getting lat-longs is much more than the guidelines. This non-compliance is gravely impacting the emergency services where a timely response is imperative to ensure that help reaches the distressed caller in time. Moreover, the penalties for non-compliance are being imposed on the vendors who are availing TSPs services.

For the past several months, PertSol has been continuously working with TSP teams to improve and maintain better LBS performance. But in spite of our rigorous follow up there is a continuous drop in Performance. In PertSol endeavor to help TSPs improve their LBS performance, it has observed many issues which were regularly shared with their technical team as well for resolution. However, there is still a very big gap between the level of services being offered and the service level expected by the Emergency Services.

Some of the common error that PertSol observed are highlighted below:

Request failed since service subscription is in pending state TimeOut Error MSISDN not subscribed to service Cell Id Error

Position method failure System failure.

Network Failure Subscriber switch off/Not latched

TSP’s Average Performance Month Wise
*PertSol hosted GMLC is integrated with BSNL network for PSAP/Emergency services location identification.
PertSol Hosted GMLC Approach

PertSol’s Hosted GMLC approach will help TSPs’ achieve the desired LBS results as per DoT mandate. PertSol will deploy its iGMLC either at PSAP’s premise or at TSP’s premise and will identify location of the distress caller. It will ensure that TSP’s fulfil the compliance by providing location intelligence as per the standards defined by the regulators.

Some of the key highlights of the proposed iLocator PertSol’s GMLC platform are:

‣ This solution would be able to achieve a higher success rate of 95% to 100%, serving maximum distressed citizens in the state.

‣ There would be no dependencies on TSPs for error resolution or follow-ups to find LBS error resolutions. We shall be handling the issues by ourselves with minimum dependency on the TSPs.

‣ With SDR (Subscriber Data Record) made available online it would be a perfect combination to build a foundation of a robust PSAP system at emergency locations.

Benefits of TSP's