600-212 Implementing Cisco Service Provider Mobility Lte Networks Practice Questions

This statement is false. The APN-AMBR, which limits the total bitrate for all non-GBR bearers of a specific APN, is enforced by the PGW for downlink traffic and by both the UE and the PGW for uplink traffic. The eNodeB is responsible for enforcing the UE-AMBR, which is the aggregate limit across all APNs for a single UE, not the APN-specific limit.

This describes a common MVNO model. The MVNO subscribers attach to the host operator's MME and SGW. The MME, based on the APN or subscriber information, selects the PGW belonging to the MVNO. The interface between the host operator's SGW and the MVNO's PGW is the S8 interface, which is the roaming variant of the S5 interface used for inter-PLMN connections. This allows the MVNO to maintain control over its core IP services.

In an offline charging system using the Gz interface and GTPP, the PGW buffers CDRs locally before sending them to the CGF. The transmission is triggered based on configurable parameters, such as the number of buffered CDRs or a time interval. If these values are set too high (e.g., flush only after 10,000 records or every 30 minutes), it will introduce a significant delay between when a session closes and when its CDR is sent to the billing system.

The 'relative MME capacity' is a value from 0 to 255 that the MME provides to the eNodeB. The eNodeB uses this information, along with the capacity values from other MMEs in the same pool, to distribute new UEs proportionally. An MME under heavy load can reduce its advertised capacity value, causing the eNodeBs to direct fewer new attach requests to it, thus achieving effective load balancing across the MME pool.

In the S8 Home Routed model, the UE attaches to the visited network's MME and SGW. The V-MME uses the S6a interface to contact the subscriber's H-HSS for authentication and subscription data. The key aspect of S8HR is that all user data is tunneled back to the home network. This is achieved by the V-SGW creating an S8 GTP tunnel to the H-PGW. The H-PGW then assigns the IP address and provides the connection to services like the home IMS core, ensuring a consistent user experience.

In many VoLTE implementations that use SIP preconditions (RFC 3312), the network waits for a Provisional Response Acknowledgement (PRACK) message from the UE before committing to the establishment of the dedicated bearer. The PRACK confirms that the UE has received the 183 Session Progress message with the SDP answer. If the PRACK is not received by the P-CSCF/PGW, the resource allocation for the QCI 1 bearer will not proceed, even if the PCC rule has been received from the PCRF.

DPI is required to identify traffic at the application layer, such as distinguishing video streams from a specific partner from other general internet traffic. This identification is the first step in applying a special charging policy.

Once the traffic is identified by DPI, a Policy and Charging Control (PCC) rule must be applied. This rule maps the sponsored traffic to a unique Service-Identifier or Rating-Group, which the OCS/OFCS can then use to apply the correct charging logic (i.e., charge the partner instead of the subscriber).

The state maintenance command within a service configuration (like mme-service) is the correct procedure for gracefully taking a service out of operation for maintenance. This command prevents the service from accepting new sessions and allows existing sessions to terminate normally or be handed over, ensuring a hitless transition in a redundant setup. The shutdown command is more abrupt, and chassis switchover forces a hardware state change which may not be as graceful.

Layer 2 Tunneling Protocol (L2TP) is a standard feature on the PGW (acting as an L2TP Access Concentrator, or LAC) designed for this exact purpose. It extends the UE's Layer 2 session to the customer's L2TP Network Server (LNS) located at the corporate site. This allows the corporate network to control authentication (often via RADIUS) and assign a trusted IP address directly to the UE, effectively placing the UE on the corporate network.

This statement is true. The Sv interface is the control plane interface between the MME and the MSC Server, used to facilitate the handover of the voice session from the packet-switched (PS) domain in LTE to the circuit-switched (CS) domain in UMTS/GERAN. The MSC Server is enhanced for SRVCC to manage the session transfer and control the media path switch.