| Introduction | | | | Administration Function (ADMF) This function handles |
| Lawful Intercept (LI) is a requirement placed upon | | | | the serving of interception orders and communicates |
| service providers to provide legally sanctioned official | | | | with the IIFs and MF though an Internal Network |
| access to private communications. In the existing Public | | | | Interface. |
| Telephone Network, Lawful Intercept is performed by | | | | Implementing LI within an VoIP Network |
| applying a physical 'tap' on the telephone line of the | | | | One of the primary problems faced when managing |
| target in response to a warrant from a Law | | | | VoIP calls is the separation of the signalling and media |
| Enforcement Agency (LEA). However, Voice over IP | | | | streams. It is quite possible that the two streams may |
| (VoIP) has enabled the mobility of the end-user, so it is | | | | take completely different paths through the network. In |
| no longer possible to guarantee the interception of calls | | | | addition, even when they do pass through the same |
| based on tapping a physical line. | | | | device, it may not be aware of the relationship |
| Whilst the detailed requirements for LI may differ from | | | | between the streams. Some devices within the |
| one jurisdiction to another, the general requirements | | | | network are however specifically designed to |
| are the same. The LI system must provide transparent | | | | understand and manage the separate signalling and |
| interception of specified traffic only and the subject | | | | media streams - session border controllers. Typically |
| must not be aware of the interception. The service | | | | located at the borders of the network, they receive |
| provided to other users must not be affected during | | | | Intercept Related Information from the signalling stream |
| interception. | | | | and Contents of Communication directly from the |
| Architecture Overview | | | | media stream. |
| Although the detail of LI may vary from country to | | | | Conclusion |
| country we can describe the general requirements and | | | | It has become clear that VoIP services will be |
| also explain much of the common terminology used. | | | | expected to provide Lawful Intercept capabilities to the |
| The primary purpose of the service provider network | | | | same level experienced in the PSTN. The FCC in |
| is to enable private communications between | | | | North America has mandated that both emergency |
| individuals; any LI functionality built into the network | | | | calls and Lawful Intercept must be available. Whilst not |
| must not affect the normal service to those individuals. | | | | all countries mandate this capability, any network |
| The interfaces between the PTN and the Law | | | | operator building a publicly available voice or multimedia |
| Enforcement Monitoring Facility (LEMF) are | | | | over IP service today will need to plan a network |
| standardised within a particular territory. | | | | which is flexible enough to implement these regulatory |
| LI deals with two 'products', these are: | | | | services in the future. |
| - Contents of Communications (CC): exactly what it | | | | Terminology |
| sounds like, the voice, video or message contents. | | | | ADMF Administration Function |
| - Intercept Related Information (IRI): information about | | | | CALEA Communications Assistance for Law |
| the source and destination of the call etc. European | | | | Enforcement Act |
| requirements are often based on the ETSI standards. | | | | CC Contents of Communication |
| In North America CALEA (Communications | | | | ETSI European Telecommunications Standards |
| Assistance for Law Enforcement Act) requires | | | | Institute |
| operators to provide LI capabilities. The network | | | | HI Handover Interface |
| architecture and handover specifications are based on | | | | IIF Internal Intercept Function |
| the PacketCable(TM) surveillance model, however the | | | | INI Internal Networks Interface |
| architectures are very similar. | | | | IRI Intercept Related Information |
| Basic Elements of LI in a Public Telecom Network | | | | LEA Law Enforcement Agency |
| There are three primary elements required within the | | | | LEMF Law Enforcement Monitoring Facility |
| public network to achieve Lawful Intercept, these are: | | | | LI Lawful Interception |
| - An Internal Intercept Function (IIF) located in the | | | | MF Mediation Function |
| network nodes. | | | | PSTN Public Switched Telephone Network |
| - A Mediation Function (MF) between the PTN and | | | | PTN Public Telecom Network |
| LEMF. | | | | VoIP Voice over IP |
| - An Administration Function (ADMF) to manage | | | | References |
| orders for interception in the PTN. | | | | ETSI TS 101 332 v1.1.1 (2001-08) Telecommunications |
| Internal Intercept Function (IIF) These functions are | | | | security; Lawful Interception (LI) Requirements of Law |
| located within the network nodes and are responsible | | | | Enforcement Agencies ETSI TR 101 943 V1.1.1 |
| for generating the Intercept Related Information (IRI) | | | | (2001-07) Telecommunications security; Lawful |
| and Contents of Communications (CC). | | | | Interception (LI); Concepts of Interception in a Generic |
| Mediation Function (MF) This function clearly delineates | | | | Network Architecture |
| the PTN from the LEMF. It communicates with the IIFs | | | | ETSI TS 101 671 V2.8.1 (2003-11) Telecommunications |
| using Internal Network Interfaces (INIs) which can be | | | | security; Lawful Interception (LI); Handover interface for |
| proprietary. The MF communicates to one or more | | | | the lawful interception of telecommunications traffic |
| LEMFs through locally standardized interfaces: the | | | | PKT-SP-ESP1.5-I01-050128; PacketCable(TM) 1. |
| Handover Interfaces (HI2 and HI3). | | | | |