NCS 20022252510 NCSS 2G 3G PaCo OaM 2 2 Practice
Exam
Question 1. **Which protocol is primarily used on the Gn interface between SGSN
and GGSN for signaling?**
A) SIP
B) GTP‑C
C) MAP
D) Diameter
Answer: B
Explanation: GTP‑C (GPRS Tunneling Protocol – Control) carries signaling messages
for PDP context management over the Gn interface.
Question 2. **What is the main function of the GGSN in a 2G/3G packet core
network?**
A) Authenticate the subscriber with the HLR/HSS
B) Route user plane traffic to external IP networks
C) Allocate radio resources on the RAN
D) Perform handover decisions between cells
Answer: B
Explanation: The GGSN terminates the GTP tunnel and forwards user data packets
to external IP networks such as the Internet.
Question 3. **In PDP context activation, which message is sent from the SGSN to
the GGSN to request a tunnel?**
, NCS 20022252510 NCSS 2G 3G PaCo OaM 2 2 Practice
Exam
A) Create PDP Context Request
B) Update PDP Context Response
C) Delete PDP Context Request
D) Activate Default EPS Bearer Context Request
Answer: A
Explanation: The SGSN sends a GTP‑C Create PDP Context Request to the GGSN to
establish a user plane tunnel.
Question 4. **Which database stores subscriber authentication keys for
GPRS/UMTS?**
A) VLR
B) BSC
C) HLR/HSS
D) EPC
Answer: C
Explanation: The Home Location Register (HLR) for 2G and Home Subscriber
Server (HSS) for 3G/4G store authentication credentials and subscriber profiles.
Question 5. **The Gi interface connects the GGSN to which type of network?**
A) Core network backbone
B) Public Land Mobile Network (PLMN)
, NCS 20022252510 NCSS 2G 3G PaCo OaM 2 2 Practice
Exam
C) Internet or external packet data network
D) Radio Access Network (RAN)
Answer: C
Explanation: Gi is the IP interface between the GGSN and external packet data
networks (e.g., the Internet).
Question 6. **Which KPI directly measures the success of PDP context
establishment?**
A) Packet loss rate
B) PDP Context Activation Success Rate
C) Handover latency
D) Voice MOS score
Answer: B
Explanation: PDP Context Activation Success Rate reflects the percentage of
successful PDP context setups.
Question 7. **What is the purpose of the APN (Access Point Name) in a PDP
context request?**
A) Identify the subscriber’s IMSI
B) Indicate the required QoS class
C) Define the external packet data network to be accessed
D) Specify the encryption algorithm
, NCS 20022252510 NCSS 2G 3G PaCo OaM 2 2 Practice
Exam
Answer: C
Explanation: The APN tells the GGSN which external IP network the subscriber
wishes to reach.
Question 8. **Which of the following is a typical cause of PDP context activation
failure with cause value “34 – PDP authentication failure”?**
A) Invalid APN syntax
B) Missing QoS profile
C) Incorrect password or CHAP failure
D) Overloaded GGSN CPU
Answer: C
Explanation: Cause 34 indicates that the authentication (e.g., CHAP) between
SGSN and HLR/HSS failed.
Question 9. **In a non‑disruptive upgrade of a SGSN, which technique is used to
keep traffic flowing?**
A) Immediate shutdown and reboot
B) Parallel active/standby configuration with traffic switchover
C) Disabling all GTP tunnels before upgrade
D) Resetting the OMC database
Answer: B
Exam
Question 1. **Which protocol is primarily used on the Gn interface between SGSN
and GGSN for signaling?**
A) SIP
B) GTP‑C
C) MAP
D) Diameter
Answer: B
Explanation: GTP‑C (GPRS Tunneling Protocol – Control) carries signaling messages
for PDP context management over the Gn interface.
Question 2. **What is the main function of the GGSN in a 2G/3G packet core
network?**
A) Authenticate the subscriber with the HLR/HSS
B) Route user plane traffic to external IP networks
C) Allocate radio resources on the RAN
D) Perform handover decisions between cells
Answer: B
Explanation: The GGSN terminates the GTP tunnel and forwards user data packets
to external IP networks such as the Internet.
Question 3. **In PDP context activation, which message is sent from the SGSN to
the GGSN to request a tunnel?**
, NCS 20022252510 NCSS 2G 3G PaCo OaM 2 2 Practice
Exam
A) Create PDP Context Request
B) Update PDP Context Response
C) Delete PDP Context Request
D) Activate Default EPS Bearer Context Request
Answer: A
Explanation: The SGSN sends a GTP‑C Create PDP Context Request to the GGSN to
establish a user plane tunnel.
Question 4. **Which database stores subscriber authentication keys for
GPRS/UMTS?**
A) VLR
B) BSC
C) HLR/HSS
D) EPC
Answer: C
Explanation: The Home Location Register (HLR) for 2G and Home Subscriber
Server (HSS) for 3G/4G store authentication credentials and subscriber profiles.
Question 5. **The Gi interface connects the GGSN to which type of network?**
A) Core network backbone
B) Public Land Mobile Network (PLMN)
, NCS 20022252510 NCSS 2G 3G PaCo OaM 2 2 Practice
Exam
C) Internet or external packet data network
D) Radio Access Network (RAN)
Answer: C
Explanation: Gi is the IP interface between the GGSN and external packet data
networks (e.g., the Internet).
Question 6. **Which KPI directly measures the success of PDP context
establishment?**
A) Packet loss rate
B) PDP Context Activation Success Rate
C) Handover latency
D) Voice MOS score
Answer: B
Explanation: PDP Context Activation Success Rate reflects the percentage of
successful PDP context setups.
Question 7. **What is the purpose of the APN (Access Point Name) in a PDP
context request?**
A) Identify the subscriber’s IMSI
B) Indicate the required QoS class
C) Define the external packet data network to be accessed
D) Specify the encryption algorithm
, NCS 20022252510 NCSS 2G 3G PaCo OaM 2 2 Practice
Exam
Answer: C
Explanation: The APN tells the GGSN which external IP network the subscriber
wishes to reach.
Question 8. **Which of the following is a typical cause of PDP context activation
failure with cause value “34 – PDP authentication failure”?**
A) Invalid APN syntax
B) Missing QoS profile
C) Incorrect password or CHAP failure
D) Overloaded GGSN CPU
Answer: C
Explanation: Cause 34 indicates that the authentication (e.g., CHAP) between
SGSN and HLR/HSS failed.
Question 9. **In a non‑disruptive upgrade of a SGSN, which technique is used to
keep traffic flowing?**
A) Immediate shutdown and reboot
B) Parallel active/standby configuration with traffic switchover
C) Disabling all GTP tunnels before upgrade
D) Resetting the OMC database
Answer: B
