NCS 20022303010 NCSS LTE EPC OaM 2 2 Practice Exam
Question 1. **What is the primary function of the Mobility Management Entity
(MME) in the LTE EPC?**
A) User‑plane data forwarding between eNodeB and PDN
B) Authentication, mobility management, and signaling control for LTE users
C) Allocation of IP addresses to subscriber equipment
D) Policy enforcement for QoS
Answer: B
Explanation: The MME is a control‑plane element responsible for NAS signalling,
authentication, bearer management and mobility handling; user‑plane traffic is
carried by the S‑GW and P‑GW.
Question 2. **Which interface connects the eNodeB to the Serving Gateway
(S‑GW) for user‑plane traffic?**
A) S1‑MME
B) S1‑U
C) S5/U
D) S11
Answer: B
Explanation: S1‑U is the user‑plane interface between the eNodeB and the S‑GW,
carrying GTP‑U tunneled user data.
,NCS 20022303010 NCSS LTE EPC OaM 2 2 Practice Exam
Question 3. **The Diameter protocol is used on which of the following EPC
interfaces?**
A) S1‑U
B) S5/S8 (Control)
C) S6a
D) GTP‑U
Answer: C
Explanation: Diameter is employed on the S6a interface for authentication,
authorization and accounting between the MME and the HSS.
Question 4. **In LTE, which component is responsible for allocating the
subscriber’s IP address?**
A) MME
B) S‑GW
C) P‑GW
D) HSS
Answer: C
Explanation: The Packet Data Network Gateway (P‑GW) assigns IP addresses to
UEs and acts as the anchor point toward external IP networks.
,NCS 20022303010 NCSS LTE EPC OaM 2 2 Practice Exam
Question 5. **Which protocol provides reliable transport for SCTP‑based
signalling between eNodeB and MME?**
A) UDP
B) TCP
C) SCTP
D) IPsec
Answer: C
Explanation: SCTP (Stream Control Transmission Protocol) offers reliable, ordered
delivery with multi‑streaming, used for S1‑MME signalling.
Question 6. **The Policy and Charging Rules Function (PCRF) interacts directly
with which EPC element to enforce QoS?**
A) MME
B) S‑GW
C) P‑GW
D) HSS
Answer: C
Explanation: PCRF sends policy and QoS rules to the P‑GW via the Gx interface,
which then applies them to user traffic.
Question 7. **Which of the following best describes the S11 interface?**
, NCS 20022303010 NCSS LTE EPC OaM 2 2 Practice Exam
A) MME ↔ S‑GW control signalling (GTP‑C)
B) eNodeB ↔ MME signalling (SCTP)
C) S‑GW ↔ P‑GW user‑plane (GTP‑U)
D) MME ↔ HSS authentication (Diameter)
Answer: A
Explanation: S11 carries GTP‑C control messages between the MME and S‑GW for
session management and bearer creation.
Question 8. **During a handover from LTE to 3G, which EPC element is primarily
involved in transferring the user plane tunnel?**
A) MME
B) S‑GW
C) P‑GW
D) PCRF
Answer: B
Explanation: The S‑GW anchors the user‑plane and is responsible for
re‑establishing the GTP‑U tunnel towards the 3G SGSN during inter‑system
handover.
Question 9. **What is the role of the Home Subscriber Server (HSS) in LTE?**
A) Routing user‑plane packets to the Internet
Question 1. **What is the primary function of the Mobility Management Entity
(MME) in the LTE EPC?**
A) User‑plane data forwarding between eNodeB and PDN
B) Authentication, mobility management, and signaling control for LTE users
C) Allocation of IP addresses to subscriber equipment
D) Policy enforcement for QoS
Answer: B
Explanation: The MME is a control‑plane element responsible for NAS signalling,
authentication, bearer management and mobility handling; user‑plane traffic is
carried by the S‑GW and P‑GW.
Question 2. **Which interface connects the eNodeB to the Serving Gateway
(S‑GW) for user‑plane traffic?**
A) S1‑MME
B) S1‑U
C) S5/U
D) S11
Answer: B
Explanation: S1‑U is the user‑plane interface between the eNodeB and the S‑GW,
carrying GTP‑U tunneled user data.
,NCS 20022303010 NCSS LTE EPC OaM 2 2 Practice Exam
Question 3. **The Diameter protocol is used on which of the following EPC
interfaces?**
A) S1‑U
B) S5/S8 (Control)
C) S6a
D) GTP‑U
Answer: C
Explanation: Diameter is employed on the S6a interface for authentication,
authorization and accounting between the MME and the HSS.
Question 4. **In LTE, which component is responsible for allocating the
subscriber’s IP address?**
A) MME
B) S‑GW
C) P‑GW
D) HSS
Answer: C
Explanation: The Packet Data Network Gateway (P‑GW) assigns IP addresses to
UEs and acts as the anchor point toward external IP networks.
,NCS 20022303010 NCSS LTE EPC OaM 2 2 Practice Exam
Question 5. **Which protocol provides reliable transport for SCTP‑based
signalling between eNodeB and MME?**
A) UDP
B) TCP
C) SCTP
D) IPsec
Answer: C
Explanation: SCTP (Stream Control Transmission Protocol) offers reliable, ordered
delivery with multi‑streaming, used for S1‑MME signalling.
Question 6. **The Policy and Charging Rules Function (PCRF) interacts directly
with which EPC element to enforce QoS?**
A) MME
B) S‑GW
C) P‑GW
D) HSS
Answer: C
Explanation: PCRF sends policy and QoS rules to the P‑GW via the Gx interface,
which then applies them to user traffic.
Question 7. **Which of the following best describes the S11 interface?**
, NCS 20022303010 NCSS LTE EPC OaM 2 2 Practice Exam
A) MME ↔ S‑GW control signalling (GTP‑C)
B) eNodeB ↔ MME signalling (SCTP)
C) S‑GW ↔ P‑GW user‑plane (GTP‑U)
D) MME ↔ HSS authentication (Diameter)
Answer: A
Explanation: S11 carries GTP‑C control messages between the MME and S‑GW for
session management and bearer creation.
Question 8. **During a handover from LTE to 3G, which EPC element is primarily
involved in transferring the user plane tunnel?**
A) MME
B) S‑GW
C) P‑GW
D) PCRF
Answer: B
Explanation: The S‑GW anchors the user‑plane and is responsible for
re‑establishing the GTP‑U tunnel towards the 3G SGSN during inter‑system
handover.
Question 9. **What is the role of the Home Subscriber Server (HSS) in LTE?**
A) Routing user‑plane packets to the Internet
