JTO Advanced — 5G Core & NFV/SDN

NFV & SDN — The Network Transformation

SDN (Software Defined Networking)

•Separates control plane (routing decisions) from data plane (packet forwarding)

•Centralized SDN Controller (e.g. OpenDaylight, ONOS)

•Southbound interface: OpenFlow protocol (controller → switches)

•Northbound interface: REST APIs (applications → controller)

•Benefits: Programmable, centrally managed, vendor-agnostic

NFV (Network Functions Virtualisation) — ETSI NFV Framework

•Replaces dedicated hardware with software running on COTS servers

•VNF (Virtual Network Function): Software implementation of a network function (vFirewall, vRouter, vEPC)

•NFVI (NFV Infrastructure): Compute + Storage + Network resources

•MANO (Management and Orchestration):

- VIM (Virtual Infrastructure Manager) — OpenStack, VMware vSphere

- VNFM (VNF Manager) — lifecycle management of VNFs

- NFVO (NFV Orchestrator) — end-to-end service orchestration

Telecom use cases:

•vEPC (virtualised EPC): Full 4G core as VNFs

•vIMS (virtualised IP Multimedia Subsystem): Voice over LTE

•vCPE (virtual Customer Premises Equipment): Replace hardware at customer site

•vRAN (virtual RAN): Baseband units in data center

5G Network Slicing

A 5G network can be divided into multiple isolated virtual networks (slices) on the same physical infrastructure:

Slice Type	3GPP Name	Latency	Speed	Use Case

|------------|-----------|---------|-------|----------|

Broadband	eMBB	< 10ms	> 1 Gbps	Video streaming, AR/VR
Mission Critical	URLLC	< 1ms	Moderate	Autonomous vehicles, surgery
IoT	mMTC	Tolerant	Low	Smart meters, sensors

Each slice has dedicated AMF, SMF, UPF (or shared depending on design). Network Slice Selection Assistance Information (NSSAI) identifies the slice.

BSNL JTO Previous Year Questions (Pattern)

Electronics:

Q1: In a series resonant circuit, at resonance, the impedance is:

Answer: Equal to resistance R only (L and C reactances cancel)

Q2: The noise figure of a cascaded system (Friis formula):

NF_total = NF1 + (NF2-1)/G1 + (NF3-1)/(G1×G2) + ...

Answer: First stage noise figure is most critical

Communication:

Q3: OFDM is used in LTE because:

Answer: Resilience to multipath fading; efficient spectrum use; allows flexible subcarrier allocation

Q4: For a bandwidth of 1 MHz and SNR of 30 dB, Shannon capacity is:

C = B × log2(1 + SNR) = 1 × 10⁶ × log2(1001) ≈ 10 Mbps

Networking:

Q5: Which layer of OSI model is responsible for routing?

Answer: Network Layer (Layer 3) — IP protocol

Q6: The maximum segment size in TCP is negotiated during:

Answer: Three-way handshake (SYN exchange) — MSS option