A tecnologia de «network slicing» 5G cria tanto desafios como oportunidades no que diz respeito ao cumprimento dos requisitos de interceção legal. O «network slicing» é uma das capacidades distintivas da arquitetura 5G Standalone (SA). Ao criar partições de rede logicamente isoladas numa infraestrutura física partilhada, os operadores podem adaptar as características de conectividade — latência, largura de banda, fiabilidade e segurança — aos requisitos específicos de diferentes serviços, aplicações ou grupos de clientes. No que diz respeito à interceção legal, o «network slicing» introduz complicações significativas e, paradoxalmente, potenciais simplificações. Compreender como o «slicing» afeta a definição de alvos, a execução e a implementação da interceção legal é essencial para qualquer operador que esteja a implementar ou a planear uma rede 5G SA.
This article examines the intersection of network slicing and lawful interception, covering the technical architecture, the challenges for target identification and interception execution, the potential benefits that slicing can offer for Operações LI, and the practical steps operators should take to ensure compliance in a sliced network environment.
Como o Network Slicing 5G afeta a LI
In a 5G SA network, a network slice is a logically isolated end-to-end network that includes specific configurations of radio access, transport, and core network resources. Each slice is identified by a Single Network Slice Selection Assistance Information (S-NSSAI) value and is designed to meet particular service requirements. For example, one slice might be optimised for ultra-reliable low-latency communication (URLLC) for industrial control, another for massive IoT (MIoT) sensor networks, and a third might provide enhanced mobile broadband (eMBB) for consumer smartphones.
Do ponto de vista da rede central, cada fatia pode ter as suas próprias instâncias dedicadas de determinadas funções de rede — tais como a SMF, a UPF e a PCF — ou pode partilhar instâncias de funções de rede com outras fatias. O grau de isolamento entre fatias é configurável e depende da estratégia de implementação do operador e dos requisitos da fatia. Esta flexibilidade constitui uma vantagem fundamental do «slicing», mas também introduz complexidade para as funções que precisam de operar além dos limites das fatias, incluindo a interceção legal.
A single subscriber may simultaneously use services across multiple slices. A smartphone user might have their voice traffic routed through one slice, their video streaming through another, and their IoT companion device connected through a third. Each slice may have its own UPF, its own PDU session, and its own IP addressing. Which slice carries which traffic is decided by the device’s route selection policy (URSP), within the slices the network allows, selected with the help of the NSSF and the subscription data in the UDM.
Complicações associadas à orientação para a LI
Network slicing complicates LI targeting in several ways. The most fundamental complication is that a target’s traffic may be spread across multiple slices, each potentially served by different UPF instances. A single interception order must result in the capture of all the target’s communications, regardless of which slice they traverse. This requires the operator to equip every network function that can serve the target, including dedicated per-slice SMFs and UPFs, with LI functions, and to provision the task to all of them.
Target identification in a sliced environment is more complex than in a non-sliced network. The same subscriber may appear with different session contexts, different IP addresses, and different QoS characteristics depending on which slice is serving a particular communication flow. Every interception point tags its X2/X3 records with the task’s XID, so the mediation function delivers every session in every slice under the same LIID, and the IRI tells the LEA which slice (S-NSSAI) each session used.
The dynamic nature of slice allocation adds further complexity. Slices can be created, modified, and terminated dynamically, and a target’s traffic may move between slices as service requirements change. If the task was provisioned only to the network functions of some slices, a change in the target’s subscribed slices (which the UDM reports as IRI) can leave a gap, and the administration function must extend the task to the SMFs of the new slices. Provisioning every SMF that can serve the target avoids this, because UPF interception is then triggered per session.
Another complication arises from the potential for different slices to be operated by different entities. In some business models, an enterprise or vertical industry partner may operate its own slice on the operator’s infrastructure, potentially with its own network functions and operational management. The question of who is responsible for lawful interception within such a slice — the infrastructure operator, the slice tenant, or both — is a regulatory and contractual question. In most frameworks the answer follows the service: whoever provides a publicly available communications service over the slice carries the LI obligation. A private enterprise slice that is not offered to the public is usually out of scope, and the infrastructure operator remains responsible for the parts of its network that serve public services. Contracts must reflect this, and the operator must keep its LI functions secure even in slices it does not manage.
Como a segmentação pode simplificar o LI
Despite these complications, network slicing can also offer potential benefits for lawful interception. The logical isolation of slices means that traffic within a slice is already segregated from traffic in other slices. If the target can only use certain slices, the administration function can provision the task only to the network functions of those slices (3GPP TS 33.127, clause 5.3.5.5), which keeps the number of provisioned interception points small.
Slicing can also enable more granular interception. Instead of intercepting all of a target’s traffic — which in a modern smartphone environment can include significant volumes of background data, software updates, and other non-relevant traffic — slicing could potentially allow the interception to be focused on specific service types or communication flows. In practice, however, limiting interception to particular slices is generally not an option: national rules such as § 5(2) TKÜV in Germany require a complete copy of the target’s communications. Where an order covers only certain services, the standards provide service scoping by service type, not by slice.
From a security perspective, the isolation between slices can provide additional protection for the LI function. By deploying LI components within a dedicated, secure slice — or by ensuring that LI traffic between network functions and the plataforma de mediação is carried on a separate, isolated transport path — operators can enhance the confidentiality and integrity of the interception process. Slice isolation can help, but LI functions still need their own protected trust domain. In virtualised networks 3GPP requires them to meet ETSI GS NFV-SEC 012 (TS 33.126, R6.6-160).
Normas 3GPP para LI em redes segmentadas
The 3GPP LI architecture for 5G, defined in TS 33.127 and TS 33.128, addresses network slicing explicitly. 3GPP’s LI requirements (TS 33.126) are technology-neutral: interception must be complete regardless of how the network is built, and that includes slicing. TS 33.127 and TS 33.128 add slice-aware provisioning and report slice information (S-NSSAI) in the IRI. On X1, a task names the target and, optionally, the service types to intercept. Slices are not an X1 parameter. Instead, the administration function decides which network functions, and therefore which slices, receive the task (3GPP TS 33.127, clause 5.3.5.5), and the X2 and X3 interfaces carry xIRI and xCC from interception points in any slice to the MDF, which turns them into IRI and CC for delivery.
The standards define that the AMF, which handles the target’s registration and mobility management, is a key interception point for slice-related IRI. When a target registers with the network and is allocated to one or more slices, the AMF generates IRI events that include the slice information. CC interception in the UPF is triggered per PDU session: the SMF serving that session, which holds the LI task, instructs its UPF over the internal LI_T3 interface. The operator must therefore make sure every SMF that can serve the target, in every slice, carries the task and that every UPF supports LI_T3 and X3.
The UDM is itself an interception point: it reports changes to the target’s subscribed slices as IRI. To keep coverage complete as slices change, the LI administration function learns about new SMFs and UPFs from the operator’s management and orchestration systems when they are instantiated, and from the System Information Retrieval Function (SIRF) in the NRF when they register and are ready for traffic (3GPP TS 33.127, clauses 5.3.5.3 and 5.3.6).
Implicações práticas para os operadores
Operators deploying 5G SA networks with slicing capabilities should address LI requirements from the earliest stages of slice design and deployment. Several practical steps are recommended. First, ensure that your LI system is aware of the slice architecture and can dynamically discover and configure interception points within any slice. This requires integration between the LI administration function and the operator’s orchestration systems and the NRF-based System Information Retrieval Function (SIRF), so that new SMFs and UPFs are provisioned as they are created.
Second, verify that the UPFs deployed within each slice support the LI_T3 trigger and the X3 interface for content delivery to the LI mediation function, and that the SMFs serving those slices support the IRI point of interception and the CC triggering function. If a slice uses a UPF that does not support X3, the operator will have a gap in its interception capability for traffic traversing that slice. This is a procurement requirement that should be included in all UPF vendor specifications.
Third, develop procedures for handling interception orders that span multiple slices. The LI operations team must understand how to provision tasks that cover all of a target’s slice allocations and when the administration function has to extend a task to the network functions of additional slices. Automation of this process is highly recommended, as manual configuration across multiple slices is error-prone and slow.
Em quarto lugar, abordar as dimensões de governação e contratuais da LI em fatias partilhadas ou operadas pela empresa. Se terceiros operarem fatias na sua infraestrutura, as responsabilidades relativas à interceção legal devem ser claramente definidas nos acordos comerciais e devem estar em conformidade com os requisitos regulamentares de cada jurisdição relevante.
Conclusão
A segmentação de rede no 5G SA apresenta tanto desafios como oportunidades para a interceção legal. A distribuição do tráfego de um alvo por várias fatias, a natureza dinâmica da atribuição de fatias e a possibilidade de operação de fatias por terceiros complicam o processo de interceção. Ao mesmo tempo, o isolamento lógico e a granularidade do corte podem oferecer novas abordagens para uma intercepção direcionada e eficiente. Para as operadoras, a chave reside em abordar os requisitos de interceção legal de forma proativa na conceção das fatias, garantir que os seus sistemas de interceção legal sejam compatíveis com as fatias e dinamicamente adaptáveis, e estabelecer uma governação clara das responsabilidades de interceção em ambientes de fatias multi-inquilino. Ao fazê-lo, as operadoras podem cumprir as suas obrigações de conformidade, ao mesmo tempo que tiram partido de todo o potencial do particionamento de rede 5G.
Looking ahead, the evolution of network slicing toward more dynamic, intent-based models will further increase the complexity of LI in sliced environments. Future networks may feature slices that are created and destroyed on demand, with resources allocated and released in real time based on service demands. The LI system must evolve alongside these capabilities, maintaining comprehensive interception coverage even as the underlying network topology changes continuously. Operators that invest in flexible, standards-compliant Soluções LI today will be better prepared to adapt to these future developments and to maintain uninterrupted compliance as their 5G networks mature.
À medida que as implementações de 5G com segmentação de rede amadurecem, os desafios relacionados com a interceção irão evoluir. As operadoras devem conceber a sua arquitetura LI de 5G com segmentação de rede tendo em conta a escalabilidade futura.
Artigos relacionados
Para mais informações sobre temas relacionados, consulte estes artigos:
- Interfaces X1/X2/X3 em 5G: a arquitetura 3GPP LI explicada
- eSIM e interceção legal: O que a arquitetura RSP significa para a conformidade
- DNS encriptado (DoH/DoT) e o seu impacto nas capacidades de interceção legal
Recursos externos
Os seguintes recursos externos fornecem contexto adicional e documentação oficial:
