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Nokia Services Architecture study materials
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Nokia Services Architecture practice questions

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Question 1Fixed access

In a Nokia fixed access network, which protocol is used by an ONT to obtain its management IP address and the address of the configuration server during initial bring-up?

  1. SNMP GetRequest issued by the ONT to the OLT management address
  2. PPPoE session negotiated directly with the BNG before ONT registration
  3. RADIUS accounting started from the OLT before ranging completes
  4. DHCP with vendor-specific option 43/125 carried over the service VLAN Correct answer.

Explanation

ONTs are typically provisioned through DHCP, where vendor-specific options (such as option 43 or 125) point the device to the correct ACS or configuration server. This happens before or alongside registration, so the ONT learns both its address and its management target in one exchange. RADIUS, SNMP polling and PPPoE are not used by the ONT to discover its configuration server at bring-up.

Question 2Fixed access

Which statement best describes the role of the Nokia ISAM OLT in a GPON fixed access deployment?

  1. It acts as the BNG terminating all subscriber IP sessions and applying per-subscriber QoS policies
  2. It provides the optical splitter function that divides one feeder fiber into many drop fibers
  3. It functions as the DHCP server allocating addresses to every residential gateway in the network
  4. It terminates GPON physical layer and OMCI, aggregates subscriber traffic, and connects upstream to the aggregation network Correct answer.

Explanation

The OLT terminates the GPON physical layer, manages ONTs through OMCI, aggregates their traffic and hands it upstream toward aggregation and the BNG. It does not itself terminate subscriber IP sessions, act as the DHCP server, or perform passive optical splitting. The splitter is a passive component in the outside plant.

Question 3Fixed access

A technician needs to view the current registration state and ranging distance of a specific ONT on a Nokia ISAM. Which command family is the appropriate starting point?

  1. show equipment ont
  2. show gpon onu Correct answer.
  3. show service sap
  4. show interface ip

Explanation

On Nokia ISAM platforms the GPON ONT/ONU operational state, including registration and ranging information, is inspected through the GPON ONU command family. Equipment commands cover shelves and cards, IP interface commands cover L3 interfaces, and SAP commands cover service access points rather than ONT registration.

Question 4Fixed access

What is the primary purpose of OMCI in a GPON fixed access network?

  1. To synchronize timing between the OLT and the core network clocks
  2. To carry Ethernet frames between the OLT and the BNG over the aggregation network
  3. To encrypt subscriber traffic between the ONT and the OLT at layer two
  4. To manage and configure the ONT from the OLT through a defined management channel Correct answer.

Explanation

OMCI is the ONT Management and Control Interface defined for GPON, allowing the OLT to configure, monitor and manage ONT functions over a dedicated management channel. It does not carry subscriber data, provide encryption, or distribute core timing. Those functions belong to other protocols and layers.

Question 5Fixed access

In Nokia fixed access terminology, what does a service VLAN (S-VLAN) primarily identify?

  1. A customer service instance carried across the access and aggregation network Correct answer.
  2. The physical PON port number on the OLT line card
  3. A single subscriber's PPPoE session identifier
  4. The OMCI management entity identifier of an ONT

Explanation

The S-VLAN tags a customer service instance so it can be identified and forwarded consistently across the access and aggregation network. It is a service-level identifier, not a subscriber session identifier, a physical port number, or an OMCI entity. PPPoE session IDs and OMCI entity IDs operate at different layers.

Question 6Fixed access

Which Nokia ISAM feature allows a single physical port to serve multiple service providers with isolated forwarding and separate management views?

  1. Multi-service access with per-service SAPs and VPLS or VPRN contexts Correct answer.
  2. VLAN stacking with a single global service profile
  3. Port isolation with MAC flooding disabled
  4. Static ARP entries per provider

Explanation

Multi-service access on the ISAM lets one physical port carry several services, each bound to its own SAP and mapped into a separate VPLS or VPRN context for isolation. Port isolation, stacking with one global profile, and static ARP do not give providers independent forwarding and management separation. The service contexts provide the required isolation.

Question 7Fixed access

An operator wants to verify that a newly created VPLS service on a Nokia ISAM has its SAP correctly bound to the intended GPON ONT. Which approach is most appropriate?

  1. Check the VPLS service SAP list and confirm the SAP is associated with the correct ONT and service VLAN Correct answer.
  2. Reboot the OLT line card and observe whether the service comes back up
  3. Ping the ONT management address and assume success proves the SAP binding
  4. Read the OMCI MIB dump and search for the VPLS service name

Explanation

Verifying the SAP binding requires inspecting the VPLS service definition and confirming that the SAP references the intended ONT and service VLAN. A successful ping only proves management reachability, a line card reboot is disruptive and inconclusive, and OMCI MIB dumps do not contain VPLS service names. The service SAP list is the authoritative check.

Question 8Fixed access

During GPON activation, an ONT is discovered but remains in an unconfigured state because no matching ONT profile is found. What is the most likely corrective action?

  1. Assign an appropriate ONT profile or pre-provision the serial number so the ONT can be configured Correct answer.
  2. Disable OMCI encryption on the OLT line card
  3. Change the S-VLAN tag on the aggregation uplink
  4. Increase the upstream bandwidth allocation on the PON port

Explanation

When an ONT is discovered but not configured, the OLT has no profile to apply to it. Assigning a matching ONT profile or pre-provisioning the serial number allows the OLT to push configuration through OMCI. Bandwidth allocation, OMCI encryption settings and uplink VLAN tagging do not resolve a missing profile match.

Question 9Fixed access

A subscriber reports no connectivity while the ONT shows registered and the service SAP is up. Which layer should be investigated first to determine whether the issue is in the access or the aggregation domain?

  1. The OMCI software image version on the ONT
  2. The DHCP or PPPoE session state toward the BNG Correct answer.
  3. The temperature alarm history on the OLT line card
  4. The optical budget at the ONT receive interface

Explanation

With the ONT registered and the SAP up, the access layer is functioning, so the next step is to check whether the subscriber session reached the BNG through DHCP or PPPoE. Optical budget, OMCI image version and temperature alarms concern the access layer and would not explain a fault that begins beyond a working SAP. Session state reveals whether the problem lies upstream.

Question 10Fixed access

What is the function of the Nokia ISAM uplink port in a fixed access deployment?

  1. It terminates the OMCI management channel for each ONT
  2. It provides the optical interface to the passive splitters in the field
  3. It performs the ranging measurements for newly discovered ONTs
  4. It connects the access node to the aggregation or metro network for upstream traffic Correct answer.

Explanation

The uplink port carries aggregated subscriber traffic from the access node toward the aggregation or metro network. PON ports connect to the passive splitters, OMCI termination happens on the PON side, and ranging is a GPON function on the PON interface. The uplink is the northbound connection of the node.

Question 11Fixed access

An operator needs to apply different upstream bandwidth guarantees to two ONTs sharing the same GPON port. Which mechanism achieves this?

  1. Increasing the OMCI polling interval on the OLT
  2. Per-ONT DBA or traffic shaping profiles referenced by the ONT configuration Correct answer.
  3. Static MAC address filtering on the aggregation uplink
  4. A single global shaper applied to the whole PON port

Explanation

Upstream bandwidth guarantees are enforced through DBA or traffic shaping profiles that are referenced per ONT, allowing differentiated treatment on a shared PON port. A single global shaper cannot differentiate between ONTs, MAC filtering does not allocate bandwidth, and OMCI polling intervals affect management traffic only. Profiles provide the per-ONT control.

Question 12Fixed access

Which statement accurately distinguishes a VPRN from a VPLS service on a Nokia ISAM?

  1. VPRN provides layer-three routed service contexts, while VPLS provides layer-two bridged service contexts Correct answer.
  2. VPRN and VPLS both operate exclusively at layer one and differ only in naming
  3. VPRN is only used for management traffic, while VPLS carries all subscriber data
  4. VPRN provides layer-two bridged service contexts, while VPLS provides layer-three routed contexts

Explanation

A VPRN is a layer-three routed service context, whereas a VPLS is a layer-two bridged service context. This distinction determines how subscriber traffic is forwarded and where routing occurs. The reversed description, the management-only claim and the layer-one claim all misstate the roles of these services.

Question 13Fixed access

A GPON port shows repeated ONT deactivation events with varying ranging distances for the same ONT. Which cause is most plausible?

  1. The ONT profile has the wrong OMCI software version assigned
  2. The optical link has excessive loss or a dirty connector causing intermittent ranging failures Correct answer.
  3. The BNG has exhausted its DHCP address pool
  4. The VPLS service is bound to the wrong S-VLAN

Explanation

Intermittent deactivations with unstable ranging distances point to a physical-layer problem, such as excessive optical loss or a contaminated connector. Profile version mismatches, VLAN misbinding and DHCP exhaustion would not produce varying ranging measurements. Ranging stability depends on a clean, adequately powered optical link.

Question 14Fixed access

Which Nokia ISAM construct is used to associate a subscriber's traffic with a specific service instance at the ONT-facing interface?

  1. An IP filter applied to the uplink port
  2. A SAP defined on the PON interface with the matching encapsulation Correct answer.
  3. A RADIUS accounting policy on the line card
  4. A static route in the base routing instance

Explanation

A SAP on the PON interface, with the matching encapsulation such as a VLAN tag, binds subscriber traffic to a service instance. IP filters on the uplink, static routes and RADIUS accounting policies serve other purposes and do not associate ONT traffic with a service. The SAP is the fundamental binding construct.

Question 15Fixed access

An engineer must confirm that an ONT's management traffic and its subscriber data traffic are separated. Which design element accomplishes this on a Nokia ISAM?

  1. Enabling MAC learning on all PON ports
  2. Disabling OMCI on the ONT
  3. Placing management and subscriber traffic in distinct VLANs and service contexts Correct answer.
  4. Using the same S-VLAN for both traffic types with priority tagging

Explanation

Separating management and subscriber traffic requires distinct VLANs mapped to distinct service contexts so the two traffic types are forwarded independently. Sharing an S-VLAN with priority tagging does not provide separation, enabling MAC learning does not isolate traffic types, and disabling OMCI would break ONT management. Distinct contexts are the correct design.

Question 16Fixed access

A Nokia ISAM must support both residential HSI and business VPN services on the same PON port. Which combination of service constructs best meets this requirement?

  1. A single VPLS for all traffic with no per-service tagging
  2. Separate SAPs per service mapped into distinct VPLS or VPRN contexts, with a common uplink Correct answer.
  3. One VPRN for all subscribers with static host routes per ONT
  4. A single SAP with all traffic forwarded to the BNG untagged

Explanation

Supporting mixed residential and business services requires separate SAPs per service, each mapped into its own VPLS or VPRN context, while sharing the uplink. A single untagged service cannot separate the offerings, a single VPRN with static host routes does not isolate layer-two residential traffic, and an untagged SAP removes the ability to distinguish services. The per-service SAP model provides the needed separation.

Question 17Fixed access

Which sequence correctly describes the order of operations when a new ONT is brought into service on a Nokia ISAM GPON port?

  1. ONT ranging and registration, OMCI configuration from the OLT, then service SAP binding and traffic forwarding Correct answer.
  2. ONT ranging and registration, service SAP binding, then OMCI configuration from the OLT
  3. Service SAP binding, ONT ranging and registration, then OMCI configuration from the OLT
  4. OMCI configuration from the OLT, service SAP binding, then ONT ranging and registration

Explanation

The ONT must first range and register on the PON, after which the OLT configures it through OMCI, and only then can the service SAP be bound and traffic forwarded. Binding a SAP before the ONT is known would leave it unattached, and OMCI configuration cannot precede registration because the management channel does not yet exist. The correct order follows the dependency chain.

Question 18Fixed access

An operator observes that upstream traffic from one ONT is being dropped at the OLT despite a valid SAP. Which factor is most likely to explain the drop when the downstream path works?

  1. The downstream OMCI encryption key is expired
  2. The ONT serial number is not pre-provisioned
  3. The upstream DBA or shaper profile for that ONT is misconfigured or too restrictive Correct answer.
  4. The S-VLAN is missing on the aggregation uplink

Explanation

When downstream works but upstream is dropped, a misconfigured or overly restrictive upstream DBA or shaper profile is the most likely cause, since it governs upstream grants and shaping. An expired downstream key, missing pre-provisioning or a missing uplink S-VLAN would typically affect both directions or prevent activation entirely. The asymmetry points to upstream bandwidth control.

Question 19Fixed access

A provider needs to guarantee that business traffic on a shared PON is prioritized over residential best-effort traffic during congestion. Which approach is most appropriate on a Nokia ISAM?

  1. Assigning all business ONTs to the same S-VLAN as residential ONTs
  2. Increasing the OMCI polling rate for business ONTs
  3. Disabling DBA on the PON port to reserve full bandwidth
  4. Applying classification and scheduling with distinct forwarding classes per service on the PON and uplink Correct answer.

Explanation

Prioritizing business traffic during congestion requires classification into distinct forwarding classes with appropriate scheduling on both the PON and the uplink. OMCI polling rates affect management traffic, disabling DBA removes efficient bandwidth sharing, and sharing an S-VLAN with residential traffic prevents differentiated treatment. Classification and scheduling provide the guarantee.

Question 20Fixed access

What is the role of the Nokia ISAM in relation to the BNG in a fixed access network?

  1. It aggregates access traffic and forwards it toward the BNG, which terminates subscriber sessions Correct answer.
  2. It acts as the DHCP relay only and carries no subscriber data
  3. It replaces the BNG by terminating all subscriber IP sessions
  4. It provides the core routing between data centers

Explanation

The ISAM aggregates traffic from ONTs and forwards it toward the BNG, which terminates subscriber IP sessions and applies subscriber-level policies. The access node does not replace the BNG, is not limited to DHCP relay, and does not provide data-center core routing. The two nodes have complementary roles.

Question 21Mobile access

In Nokia mobile access architecture, which logical element terminates the NR radio interface toward the UE and connects to the core through NG interfaces?

  1. gNB Correct answer.
  2. AMF
  3. UPF
  4. NSSF

Explanation

The gNB is the 5G base station that terminates the NR air interface and connects to the 5G core via the NG-RAN, using N2 toward the AMF and N3 toward the UPF. The other listed nodes are core network functions, not radio access elements.

Question 22Mobile access

Which interface carries control-plane signalling between a gNB and the AMF in a Nokia 5G access deployment?

  1. N3
  2. N2 Correct answer.
  3. N6
  4. Xn-U

Explanation

N2 is the reference point between the NG-RAN and the AMF, carrying NAS and NGAP control signalling. N3 is user-plane traffic to the UPF, Xn-U is inter-gNB user plane, and N6 connects the UPF to data networks.

Question 23Mobile access

A Nokia AirScale base station must support dual connectivity where the LTE anchor carries control plane while NR adds user-plane capacity. Which architecture does this describe?

  1. Carrier aggregation within LTE only
  2. EN-DC Correct answer.
  3. NR-DC
  4. Standalone NR

Explanation

EN-DC (E-UTRA-NR dual connectivity) uses the LTE eNB as master node for control plane while an NR gNB acts as secondary node for added user-plane throughput. Standalone NR uses NR as the sole anchor, and NR-DC pairs two NR nodes.

Question 24Mobile access

Which Nokia mobile access function performs radio resource management, scheduling and handover decisions inside a gNB?

  1. The RRC and MAC scheduling functions of the distributed/centralized unit Correct answer.
  2. The SMF session management function
  3. The UDM subscription repository
  4. The AMF mobility management function

Explanation

Radio resource control, scheduling and handover preparation are RAN functions executed within the gNB, split across centralized and distributed units. Core functions such as AMF, SMF and UDM handle mobility, sessions and subscriptions but do not schedule radio resources.

Question 25Mobile access

In a Nokia Cloud RAN split, which option correctly pairs a function with the unit that typically hosts it?

  1. RF in the centralized unit and PDCP in the distributed unit
  2. RRC in the distributed unit and PHY in the centralized unit
  3. MAC in the centralized unit and RRC in the distributed unit
  4. PDCP in the centralized unit and RLC in the distributed unit Correct answer.

Explanation

The standard split places PDCP in the centralized unit and RLC, MAC and PHY high layers in the distributed unit, with RF at the radio unit. This division lets the CU pool packet processing while the DU stays close to the antenna site.

Question 26Mobile access

Which statement describes the role of the Xn interface between two Nokia gNBs?

  1. It carries subscriber authentication credentials to the UDM.
  2. It provides the air-interface timing reference to the UE.
  3. It supports inter-gNB handover and coordination of dual connectivity. Correct answer.
  4. It transports charging records to the billing domain.

Explanation

Xn connects gNBs to each other so they can exchange handover preparation and context data and coordinate dual connectivity and mobility. It is a RAN-to-RAN interface, so authentication, charging and air-interface timing are handled elsewhere.

Question 27Mobile access

A planner needs to verify that a Nokia massive MIMO radio unit can be located far from the baseband unit using a functional split. Which split point is designed for this fronthaul use case?

  1. Split 8, carrying only management alarms
  2. Split 2, carrying RRC over the fronthaul
  3. Split 1, carrying only DC power
  4. Split 7.2, carrying frequency-domain IQ samples Correct answer.

Explanation

Split 7.2 divides PHY into high and low parts, sending frequency-domain IQ over the fronthaul between the DU and the radio unit, which suits centralized baseband with remote radios. Split 2 is an intra-gNB higher-layer split and splits 1 and 8 are not functional data splits of this kind.

Question 28Mobile access

Which Nokia mobile access capability allows a single gNB to serve multiple network slices with different service requirements?

  1. Assigning each slice its own dedicated radio spectrum by default
  2. Disabling handover for sliced subscribers
  3. Forcing all slices to share one fixed QoS profile
  4. Per-slice selection of AMF and UPF resources during UE registration and session setup Correct answer.

Explanation

The RAN supports slicing by routing UEs to slice-appropriate core instances, selecting AMF during registration and UPF during PDU session establishment based on requested S-NSSAI. Slices normally share spectrum with differentiated QoS rather than receiving dedicated spectrum by default.

Question 29Mobile access

What is the primary purpose of the NG-RAN's N3 interface in a Nokia deployment?

  1. Providing time synchronization to the radio unit
  2. Exchanging handover signalling between gNBs
  3. Transporting user-plane packets between the gNB and the UPF Correct answer.
  4. Carrying NAS registration messages to the AMF

Explanation

N3 is the user-plane tunnel between the NG-RAN and the UPF, typically using GTP-U to carry UE packets toward data networks. NAS signalling uses N2, inter-gNB signalling uses Xn, and synchronization uses dedicated timing mechanisms.

Question 30Mobile access

An operator wants to reduce latency by placing a Nokia edge UPF near the gNB while keeping the AMF centralized. Which design principle does this illustrate?

  1. Combining AMF and gNB into one node
  2. Control and user plane separation with distributed user plane Correct answer.
  3. Replacing GTP-U with NAS transport
  4. Removing the N3 interface entirely

Explanation

CUPS lets the control plane stay centralized for efficiency while the user plane is distributed to the edge for low latency. The AMF and gNB remain distinct nodes, and N3 and GTP-U remain in use for user traffic.

Question 31Mobile access

Which mechanism lets a Nokia gNB reduce energy use during low traffic while preserving coverage?

  1. Disabling synchronization to save power
  2. Symbol and carrier shutdown with cell sleep modes coordinated across layers Correct answer.
  3. Permanent shutdown of all radio units at night
  4. Removing the Xn interface during idle periods

Explanation

Energy-saving features such as symbol shutdown, carrier shutdown and cell sleep reduce transmission during low load, often coordinated with neighbour cells so coverage is maintained. Permanently switching off radios, losing synchronization or removing Xn would harm service and mobility.

Question 32Mobile access

What does the term 'beam management' refer to in Nokia 5G massive MIMO access?

  1. Balancing DC power across radio units
  2. Selecting and refining NR beams for transmission and reception between gNB and UE Correct answer.
  3. Managing the billing of beamformed traffic
  4. Allocating beam identifiers to core network slices

Explanation

Beam management covers the procedures that establish, refine and switch beams used for NR transmission and reception, including beam sweeping and reporting. It is a physical-layer and RRC concern, not billing, slicing or power distribution.

Question 33Mobile access

A UE moves from a cell served by gNB-A to a cell served by gNB-B, both connected to the same AMF. Which procedure sequence best matches a successful Xn-based handover?

  1. Handover request over Xn, admission control at target, path switch toward the AMF, release of source resources Correct answer.
  2. PDU session release, then re-registration with the UDM, then radio reconfiguration
  3. Beam failure recovery without any target cell preparation
  4. N2 release before any target preparation, then blind redirection

Explanation

Xn handover prepares the target cell with a handover request, performs admission control, switches the user-plane path toward the core, and then releases source resources. Releasing sessions or the N2 connection before target preparation would cause unnecessary interruption.

Question 34Mobile access

Which Nokia element provides the timing and synchronization reference needed by TDD radio units in a mobile access network?

  1. The NSSF slice selector
  2. The synchronization distribution using PTP or GNSS at the radio site Correct answer.
  3. The charging gateway
  4. The SMF session anchor

Explanation

TDD radios need a common phase and frequency reference, delivered through PTP (IEEE 1588) or GNSS and distributed to radio units. Core functions such as SMF, NSSF and charging do not supply radio timing.

Question 35Mobile access

In Nokia mobile access, what distinguishes a centralized unit (CU) from a distributed unit (DU)?

  1. The CU hosts RF amplifiers, while the DU hosts the core network
  2. The CU is always the AMF, while the DU is always the UPF
  3. The CU terminates NG interfaces only, while the DU terminates N6
  4. The CU hosts higher-layer protocols such as PDCP and RRC, while the DU hosts lower layers such as RLC, MAC and PHY Correct answer.

Explanation

The CU carries higher-layer protocols including PDCP, SDAP and RRC, while the DU handles RLC, MAC and physical layer functions close to the radio. Core functions such as AMF and UPF are separate from this RAN split.

Question 36Mobile access

Which parameter set is most relevant when a Nokia planner tunes the NR air interface for a low-latency service?

  1. Disabling beamforming to simplify scheduling
  2. A longer cyclic prefix with reduced subcarrier spacing
  3. Numerology with a larger subcarrier spacing and shorter slot duration Correct answer.
  4. Using only the LTE frame structure for NR traffic

Explanation

Larger subcarrier spacing in NR shortens symbol and slot duration, which reduces transmission time intervals and supports low-latency services. Longer symbols or disabling beamforming would increase latency or reduce capacity, and LTE framing does not apply to NR.

Question 37Mobile access

What role does the SDAP layer play in a Nokia gNB?

  1. It allocates IP addresses to UEs
  2. It performs ciphering of NAS messages
  3. It maps QoS flows to data radio bearers and marks reflective QoS Correct answer.
  4. It selects the AMF during registration

Explanation

SDAP sits above PDCP and maps QoS flows from the core to data radio bearers, adding reflective QoS indications. NAS ciphering, IP allocation and AMF selection are handled by core and RRC procedures, not SDAP.

Question 38Mobile access

A Nokia gNB receives a UE registration request indicating a slice the local cells cannot support. What is the most appropriate RAN behaviour?

  1. Convert the request into a handover to LTE unconditionally
  2. Select an AMF that supports the requested slice if available, otherwise reject or redirect per policy Correct answer.
  3. Silently map the UE to any AMF regardless of slice support
  4. Drop the UE context without notifying the core

Explanation

The RAN uses the requested S-NSSAI to choose a suitable AMF and, if no supporting AMF is reachable, applies rejection or redirection policy. Ignoring slice support or dropping the UE silently would break service and hide the failure from the core.

Question 39Mobile access

Which statement best describes carrier aggregation in Nokia mobile access?

  1. A UE registers simultaneously with two different AMFs
  2. Multiple component carriers are combined so a UE can transmit and receive on several carriers at once Correct answer.
  3. The core duplicates all packets to every cell
  4. The gNB uses one carrier and alternates between UEs

Explanation

Carrier aggregation combines component carriers, possibly in different bands, so a UE gains wider effective bandwidth and higher throughput. It is a radio-level feature and does not involve dual AMF registration or core packet duplication.

Question 40Mobile access

An operator observes that NR user-plane throughput is limited while N2 signalling is healthy and radio conditions are good. Which area should be investigated first in a Nokia access deployment?

  1. Slice selection policy at the NSSF
  2. UE registration timers on the UDM
  3. NAS ciphering algorithms on the AMF
  4. N3 transport capacity and UPF placement relative to the gNB Correct answer.

Explanation

With good radio conditions and healthy control signalling, a user-plane bottleneck likely lies in N3 transport capacity or the distance and capacity of the serving UPF. AMF ciphering, NSSF policy and UDM timers affect control procedures rather than raw throughput.

Question 41Core networks

In Nokia core network architecture, which functional element is responsible for terminating NAS signalling and acting as the mobility management anchor for 4G subscribers?

  1. HSS
  2. PCRF
  3. SGSN
  4. MME Correct answer.

Explanation

The Mobility Management Entity terminates NAS signalling, handles bearer and connection management, and anchors subscriber mobility for E-UTRAN access. The SGSN performs the comparable role for 2G/3G access, while the PCRF handles policy and the HSS holds subscription data.

Question 42Core networks

Which interface carries control-plane signalling between the MME and the Serving Gateway in a Nokia EPC deployment?

  1. S1-MME
  2. S5/S8
  3. S11 Correct answer.
  4. S6a

Explanation

S11 is the reference point between the MME and the Serving Gateway, carrying GTP-C signalling for bearer and session management. S1-MME connects the eNodeB to the MME, S5/S8 connects the Serving Gateway to the PDN Gateway, and S6a carries Diameter signalling between the MME and the HSS.

Question 43Core networks

What is the primary role of the PCRF within a Nokia policy and charging architecture?

  1. Anchoring user-plane traffic for roaming subscribers
  2. Making policy decisions and providing charging rules to the PCEF Correct answer.
  3. Storing subscriber authentication vectors
  4. Managing IP address allocation for UEs

Explanation

The PCRF is the policy decision point that evaluates subscriber and service policies and delivers PCC rules to the PCEF, typically embedded in the PDN Gateway. It does not store authentication vectors, allocate IP addresses, or anchor user-plane traffic.

Question 44Core networks

In Nokia's cloud-native core, which network function corresponds to the SMF in a 5G standalone deployment?

  1. UPF
  2. AMF
  3. SMF Correct answer.
  4. AUSF

Explanation

The Session Management Function is the 5G core element that manages PDU session establishment, modification and release, and controls the UPF. The AMF handles access and mobility, the UPF forwards user traffic, and the AUSF performs authentication.

Question 45Core networks

Which Nokia element acts as the user-plane anchor that forwards subscriber packets between the access network and external data networks in a 5G core?

  1. NSSF
  2. NRF
  3. UPF Correct answer.
  4. AMF

Explanation

The User Plane Function handles packet routing and forwarding, acting as the anchor between the RAN and data networks under SMF control. The AMF is control-plane only, the NRF is the service registry, and the NSSF selects network slices.

Question 46Core networks

In a Nokia EPC, which node provides the Diameter-based interface toward the HSS for retrieving subscriber profiles during attach?

  1. eNodeB
  2. PDN Gateway
  3. Serving Gateway
  4. MME Correct answer.

Explanation

The MME uses the S6a Diameter interface to query the HSS for subscription data and authentication information during attach. The gateways and eNodeB do not directly query the HSS for subscriber profiles.

Question 47Core networks

A Nokia core deployment uses network slicing to isolate an industrial customer's traffic. Which 5G function is responsible for selecting the appropriate network slice instance for a UE?

  1. PCF
  2. NRF
  3. UDM
  4. NSSF Correct answer.

Explanation

The Network Slice Selection Function determines which slice instances serve a UE, using subscribed S-NSSAI information and operator policy. The NRF handles NF discovery, the UDM stores subscription data, and the PCF provides policy rules.

Question 48Core networks

During an EPS attach, a UE requests a PDN connection to a new APN. Which sequence correctly reflects the control-plane interaction in a Nokia EPC?

  1. MME allocates the UE IP address and pushes it to the PDN Gateway over S1-U
  2. eNodeB sends NAS to Serving Gateway, which selects the MME and PDN Gateway
  3. eNodeB sends NAS to MME, MME selects Serving Gateway and PDN Gateway, and S11/S5 signalling establishes the bearer Correct answer.
  4. PDN Gateway queries the HSS directly and then informs the eNodeB to establish the bearer

Explanation

The eNodeB forwards NAS messages to the MME, which performs gateway selection and uses S11 and S5/S8 GTP-C signalling to establish the session with the Serving and PDN Gateways. IP address allocation is performed by the PDN Gateway, not the MME.

Question 49Core networks

An operator wants policy rules enforced on a per-subscriber basis for sponsored data in a Nokia core. Which pairing correctly identifies the decision and enforcement points?

  1. OCS decides and SGSN enforces
  2. HSS decides and MME enforces
  3. PCRF decides and PCEF enforces Correct answer.
  4. PCEF decides and PCRF enforces

Explanation

The PCRF is the policy decision point that generates PCC rules, and the PCEF, typically located in the PDN Gateway, enforces them. Reversing these roles or assigning policy to the HSS or OCS misplaces the functions.

Question 50Core networks

A Nokia 5G core uses service-based architecture. How does an SMF discover and select an available UPF during PDU session establishment?

  1. It asks the AUSF to allocate a UPF for the session
  2. It queries the NRF for registered UPF instances and selects one based on the requested parameters Correct answer.
  3. It reads the UPF address from the UE's SIM card
  4. It broadcasts a GTP-C request to all UPFs and uses the first reply

Explanation

In the SBA, network functions register with the NRF, and the SMF performs discovery to obtain candidate UPF instances before selecting one based on slice, DNN, and load criteria. There is no broadcast mechanism, and the SIM does not contain UPF addresses.