CS6250 COMPUTER NETWORK EXAM 2
QUESTIONS WITH VERIFIED ANSWERS
2026 | Practice Test | A+
• L7 - What spurred the development of Software Defined Networking? -✓✓Computer
Networks are difficult to manage due to diversity of equipment and proprietary
technology
• L7 - What are the three phases in the history of SDN? -✓✓1. Active Networks
2. Control and Data Plane Separation
OpenFlow API and Network Operating Systems
• L7 - Summarize each phase in the history of SDN. -✓✓1. Active Networks - Opened
up network control and allowed for customization of functionality of packets passing
through nodes
There were two types of programming models in active networking. These models differ
based on where the code to execute at the nodes was carried.
1. Capsule model - carried in-band in data packets
2. Programmable router/switch model - established by out-of-band mechanisms.
Although the capsule model was most closely related to active networking, both models
have some effect on the current state of SDNs. By carrying the code in data packets,
capsules brought a new data- plane functionality across networks. They also used
caching to make code distribution more efficient. Programmable routers made decision
making a job for the network operator.
1. Programmable functions in the network to lower the barrier to innovation.
2. Network virtualization, and the ability to demultiplex to software programs based on
packet headers.
3. The vision of a unified architecture for middlebox orchestration.
2. Control and Data Plane Separation
Inspired two main innovations:
• Open interface between control and data planes
• Logically centralized control of the network
This phase was different from active networking in several ways:
• It focused on spurring innovation by and for network administrators rather than end
users and researchers.
• It emphasized programmability in the control domain rather than the data domain.
, • It worked towards network-wide visibility and control rather than device-level
configurations.
3. OpenFlow API and network operating systems
OpenFlow was born out of the interest in the idea of network experimentation at a scale
(by researchers and funding agencies). It was able to balance the vision of fully
programmable networks and the practicality of ensuring real world dep
• L7 - What is the function of the control and data planes? -✓✓The control plane
contains the logic that controls the forwarding behavior of routers such as routing
protocols and network middlebox configurations.
The data plane performs the actual forwarding as dictated by the control plane. For
example, IP forwarding and Layer 2 switching are functions of the data plane.
• L7 - Why separate the control from the data plane? -✓✓1. Independent evolution and
development
In the traditional approach, routers are responsible for both routing and forwarding
functional- ities. This meant that a change to either of the functions would require an
upgrade of hardware. In this new approach, routers only focus on forwarding. Thus,
innovation in this design can proceed independently of other routing considerations.
Similarly, improvement in routing algorithms can take place without affecting any of the
existing routers. By limiting the interplay between these two functions, we can develop
them more easily.
2. Control from high-level software program
In SDN, we use software to compute the forwarding tables. Thus, we can easily use
higher-order programs to control the routers' behavior. The decoupling of functions
makes debugging and checking the behavior of the network easier.
Separation of the control and data planes supports the independent evolution and
development of both. Thus, the software aspect of the network can evolve independent
of the hardware aspect. Since both control and forwarding behavior are separate, this
enables us to use higher-level software pro- grams for control. This makes it easier to
debug and check the network's behavior.
• L7 - Why did the SDN lead to opportunities in various areas such as data centers,
routing, enterprise networks, and research network? -✓✓1. Data centers.
Consider large data centers with thousands of servers and VMs. Management of such
large network is not easy. SDN helps to make network management easier.
2. Routing.
QUESTIONS WITH VERIFIED ANSWERS
2026 | Practice Test | A+
• L7 - What spurred the development of Software Defined Networking? -✓✓Computer
Networks are difficult to manage due to diversity of equipment and proprietary
technology
• L7 - What are the three phases in the history of SDN? -✓✓1. Active Networks
2. Control and Data Plane Separation
OpenFlow API and Network Operating Systems
• L7 - Summarize each phase in the history of SDN. -✓✓1. Active Networks - Opened
up network control and allowed for customization of functionality of packets passing
through nodes
There were two types of programming models in active networking. These models differ
based on where the code to execute at the nodes was carried.
1. Capsule model - carried in-band in data packets
2. Programmable router/switch model - established by out-of-band mechanisms.
Although the capsule model was most closely related to active networking, both models
have some effect on the current state of SDNs. By carrying the code in data packets,
capsules brought a new data- plane functionality across networks. They also used
caching to make code distribution more efficient. Programmable routers made decision
making a job for the network operator.
1. Programmable functions in the network to lower the barrier to innovation.
2. Network virtualization, and the ability to demultiplex to software programs based on
packet headers.
3. The vision of a unified architecture for middlebox orchestration.
2. Control and Data Plane Separation
Inspired two main innovations:
• Open interface between control and data planes
• Logically centralized control of the network
This phase was different from active networking in several ways:
• It focused on spurring innovation by and for network administrators rather than end
users and researchers.
• It emphasized programmability in the control domain rather than the data domain.
, • It worked towards network-wide visibility and control rather than device-level
configurations.
3. OpenFlow API and network operating systems
OpenFlow was born out of the interest in the idea of network experimentation at a scale
(by researchers and funding agencies). It was able to balance the vision of fully
programmable networks and the practicality of ensuring real world dep
• L7 - What is the function of the control and data planes? -✓✓The control plane
contains the logic that controls the forwarding behavior of routers such as routing
protocols and network middlebox configurations.
The data plane performs the actual forwarding as dictated by the control plane. For
example, IP forwarding and Layer 2 switching are functions of the data plane.
• L7 - Why separate the control from the data plane? -✓✓1. Independent evolution and
development
In the traditional approach, routers are responsible for both routing and forwarding
functional- ities. This meant that a change to either of the functions would require an
upgrade of hardware. In this new approach, routers only focus on forwarding. Thus,
innovation in this design can proceed independently of other routing considerations.
Similarly, improvement in routing algorithms can take place without affecting any of the
existing routers. By limiting the interplay between these two functions, we can develop
them more easily.
2. Control from high-level software program
In SDN, we use software to compute the forwarding tables. Thus, we can easily use
higher-order programs to control the routers' behavior. The decoupling of functions
makes debugging and checking the behavior of the network easier.
Separation of the control and data planes supports the independent evolution and
development of both. Thus, the software aspect of the network can evolve independent
of the hardware aspect. Since both control and forwarding behavior are separate, this
enables us to use higher-level software pro- grams for control. This makes it easier to
debug and check the network's behavior.
• L7 - Why did the SDN lead to opportunities in various areas such as data centers,
routing, enterprise networks, and research network? -✓✓1. Data centers.
Consider large data centers with thousands of servers and VMs. Management of such
large network is not easy. SDN helps to make network management easier.
2. Routing.
