CS 6250 LESSON 8 EXAM QUESTIONS WITH VERIFIED SOLUTIONS
LATEST UPDATE 2026
As IP networks grew into adoption, what were some of the challenges? - Answers 1.
Handling the growing complexity/dynamic nature of networks
2. Tightly coupled architecture
Software defined networking (SDN) - Answers Control vs data plane. Network
switches perform task of forwarding and the logic is implemented in a centralized
controller
Computer networks have 3 planes of functionality - Answers Data plane, control
plane, and management plane
Data plane - Answers These are functions and processes that forward data in the form
of packets or frames.
Control plane - Answers These refer to functions and processes that determine which
path to use by using protocols to populate forwarding tables of data plane elements.
Management plane - Answers These are services that are used to monitor and
configure the control functionality
Advantage of SDN vs traditional approach - Answers 1. Shared abstraction 2.
Consistency of same network info 3. Locality of functional placement 4. Simpler
integration
Southbound interfaces - Answers Interfaces that are connecting bridges between
control and forwarding elements, they separate control and data plane functionality.
Network OS - Answers Provides abstractions, essentials services, and common APIs
to developers. It helps ease network management and solve networking problems. It is
a centralized controller.
Northbound interface - Answers Mostly a software ecosystem. It is one of the core
abstractions of an SDN ecosystem (along with Southbound)
Language based virtualization - Answers Expressing modularity and allowing
different levels of abstraction.
Network applications - Answers Functionalities that implement the control plane
logic and translate the commands in the data plane.
Difference b/w networks in the SDN infrastructure vs traditional approach - Answers
They are built on top of open/standard interfaces that ensure configuration and
communication compatibility and interoperability among control/data plane devices.
3 information sources for OpenFlow - Answers 1. Event based messages that are sent
by forwarding devices to controller when there's a link or port change
2. Flow statistics generated by forwarding devices and collected by the controller
3. Packet messages sent by forwarding devices to controller
Controller - Answers A controller is a critical element in an SDN architecture as it is
the key supporting piece for control logic (applications) to generate network
configuration based on the policies defined by the network operator.
Centralized controller - Answers Single entity manages all forwarding devices in the
network which is a single point of failure and may have scaling issues. Cannot really
scale in practice.
Distributed controller - Answers Can be scaled to meet requirements of environment.
IT can be a centralized cluster of nodes or physically distributed set of elements. The
properties include weak consistency semantics and fault tolerance.
LATEST UPDATE 2026
As IP networks grew into adoption, what were some of the challenges? - Answers 1.
Handling the growing complexity/dynamic nature of networks
2. Tightly coupled architecture
Software defined networking (SDN) - Answers Control vs data plane. Network
switches perform task of forwarding and the logic is implemented in a centralized
controller
Computer networks have 3 planes of functionality - Answers Data plane, control
plane, and management plane
Data plane - Answers These are functions and processes that forward data in the form
of packets or frames.
Control plane - Answers These refer to functions and processes that determine which
path to use by using protocols to populate forwarding tables of data plane elements.
Management plane - Answers These are services that are used to monitor and
configure the control functionality
Advantage of SDN vs traditional approach - Answers 1. Shared abstraction 2.
Consistency of same network info 3. Locality of functional placement 4. Simpler
integration
Southbound interfaces - Answers Interfaces that are connecting bridges between
control and forwarding elements, they separate control and data plane functionality.
Network OS - Answers Provides abstractions, essentials services, and common APIs
to developers. It helps ease network management and solve networking problems. It is
a centralized controller.
Northbound interface - Answers Mostly a software ecosystem. It is one of the core
abstractions of an SDN ecosystem (along with Southbound)
Language based virtualization - Answers Expressing modularity and allowing
different levels of abstraction.
Network applications - Answers Functionalities that implement the control plane
logic and translate the commands in the data plane.
Difference b/w networks in the SDN infrastructure vs traditional approach - Answers
They are built on top of open/standard interfaces that ensure configuration and
communication compatibility and interoperability among control/data plane devices.
3 information sources for OpenFlow - Answers 1. Event based messages that are sent
by forwarding devices to controller when there's a link or port change
2. Flow statistics generated by forwarding devices and collected by the controller
3. Packet messages sent by forwarding devices to controller
Controller - Answers A controller is a critical element in an SDN architecture as it is
the key supporting piece for control logic (applications) to generate network
configuration based on the policies defined by the network operator.
Centralized controller - Answers Single entity manages all forwarding devices in the
network which is a single point of failure and may have scaling issues. Cannot really
scale in practice.
Distributed controller - Answers Can be scaled to meet requirements of environment.
IT can be a centralized cluster of nodes or physically distributed set of elements. The
properties include weak consistency semantics and fault tolerance.
