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 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:

Lawful Interception

Lawful Interception System

PertSol iNterceptor is a Lawful Interception system unified for network operators and telecom service providers which is fully compliant with international standards and has a proven track record. It is a complete solution that is capable of handling both circuit switch and packet switch traffic from both legacies as well as the latest telecom technologies including 2G,OTT Interception,3G, 4G, 5G, IMS,5G Interception, NGN, PSTN, IPLC, IFMS, PS Interception, DPI Interception etc.

The core purpose of iNterceptor is to intercept the traffic and convert intercepted traffic into a format suitable for delivery to National Authorities or Law Enforcement agencies, over a secure network. It can also retain the intercepted traffic for future use by the LEAs compliant with international standards and has a proven track record.

iNterceptor along with PertSol iNteliProbe forms one of the most comprehensive interception solutions available in the market. PertSol iNteliProbe supports capturing 100% of traffic, decoding the traffic from layer 2 to layer 7, and then either transmittal of interception of data and decoded data to the LEAs or its storage for future use. The probes actively support the capture and reconstruction of all non-encrypted IP, and voice traffic this includes reconstruction and capture of VoIP calls, TDM calls, and IP traffic reconstruction.

iNterceptor Lawful Interception is designed to change and adapts as per the latest network upgradation and technologies. It protects investments through its modular setup, accommodating network expansion as well as network changes. It can also integrate with existing Lawful Interception vendors incorporating it into a centrally managed unified solution.

5G Ready Solutions

PertSol works closely with the leading telecom company, MNOs, network equipment providers, and regulators to evolve its products as per the technology and market trends. In its bid to keep track of the market and latest technology, PertSol has upgraded its product as per the 5G standards released by 3GPP in its Release 15. PertSol iNterceptor has also been upgraded to fulfill lawful interception system requirements for both standalone and non-standalone 5G networks.

Technical Specification:

  • Supported Telecom Network & Services:
    • XDSL, Cable, IPLC
    • Email (POP3, SMTP, IMAP, Webmail)
    • IPv4 & IPv6
    • VoIP (SIP, RTP, H.323, SCCP)
    • PoC (Push-to-talk over Cellular)
    • SMS, MMS, Voicemail
    • WLAN
    • IoT, M2M

Services Data Voice Video Call
Messenger Chat SMS VoIP Email Social MediaNetworkPSTN4GIMSIMS2G/3G5GNGNBroadband

Multi-Vendor Support

iNterceptor has an extensive list of modules to support direct integration with major versions of network elements. These modules have proven their worth and stability in the field. PertSol maintains an active relationship with these vendors to keep up to date with new versions of the network equipment, verified with an IOT (Interoperability Test) in the vendor lab where possible. iNterceptor supports all the major NEPs of the world like Nokia, Ericsson, Cisco, Brocade, Alcatel Lucent, ZTE, Huawei, Samsung, Juniper, Genband, Comverse, Arris, Nortel, Open wave, Qualcomm, and many more.

Supported Network Interface

    • Ethernet (1GE, 10GE, 40GE)
    • SDH (STM-1)
    • TDM (E1/T1/J1)
    • ATM
    • ISDN
    • SS7 Interfaces

Output & Delivery Format

iNterceptor supports the following output and delivery formats.

Technical Standards
Some of the main LI standards that iNterceptor complies with are mentioned below:


    • TS 101 671 (Voice)
    • TS 101 331 (Generic)
    • TS 102 232-1, TS 102 232-2, TS 102 232-3, TS 102 232-4, TS 102 232-5, TS 102 232-6
    • TS 103 120
    • TR 103 690 (e-Warrant)


    • J-STD-025A & J-STD-025B
    • T1.724
    • T1.IAS
    • TIA-1066
    • ATIS-10021


    • TS 33.106
    • TS 33.107
    • TS 33.108
    • TS 33.126
    • TS 33.127
    • TS 33.128

Packet Cable 1.5 & 2.0

    • PKT-SP-EM-I08
    • TS 33.107
    • PKT-SP-ESP1.5
    • PKT-SP-ES-DCI-I01
    • PKT-SP-ES-INF-I02
    • CBIS

iNterceptor: Benefits

iNterceptor is capable of handling networks with very high throughput requirements. It can handle multiple 100 Gbps links and is capable of selecting required traffic from these links. PertSol iNteliProbe has been tested and implemented for traffic up to 40 Gbps per probe. The integrity check mechanism periodically checks the network elements and if required corrects the erroneous states. It will query the network element for the placed intercepts and add missing intercepts, remove invalid intercepts, etc. This mechanism is used to detect and correct both network flaws as well as tampering with the interception solution. In case of correction of an erroneous state, this will be notified to the operator.

iNterceptor has a vast range of Input/Output adapters which makes it compatible with all the available access technologies and network equipment of all the major equipment providers. If required, customer-specific Input or Output adapters can be developed.
iNterceptor allows configuration of multiple Input and Output Adapters to be combined in one system and support any situation like inter-working between different technologies or scaling up to include latest technology. Due to iNterceptor’s modularity, telecom operators can leverage their investment for a longer duration and scale up their network with more flexibility.

Due to its design philosophy, iNterceptor can support hybrid networks with equipment from different vendors on same server. When networks grow or change, iNterceptor can easily be extended to cater for the growth in traffic volumes or new types of network elements. Unified solution for all interception requirements of a service provider which is compliant to international standards like 3GPP, ETSI, ATSI, ANSI, CALEA and others. It also complies with local LI regulations of many countries across the world.

Lawful Interception vendors provide a proven and mature solution that continues to benefit from functional enhancement and feature evolution. It has been deployed in varied networks, enabling TSPs / Law Enforcement Agencies to benefit.