CS 6250 EXAM 2 STUDY QUESTIONS UPDATED ACTUAL
QUESTIONS AND CORRECT ANSWERS
Question:
1. L7 - What spurred the development of Software Defined Networking?
Answer:
Computer Networks are difficult to manage due to diversity of equipment and proprietary technology
Question:
2. L7 - What are the three phases in the history of SDN?
Answer:
1. Active Networks
2. Control and Data Plane Separation OpenFlow API and Network Operating Systems
Question:
3. L7 - Summarize each phase in the history of SDN.
Answer:
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
Question:
4. L7 - What is the function of the control and data planes?
, Answer:
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.
Question:
5. L7 - Why separate the control from the data plane?
Answer:
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.
Question:
6. L7 - Why did the SDN lead to opportunities in various areas such as data centers, routing, enterprise
networks, and research network?
Answer:
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.
The interdomain routing protocol used today, BGP, constrains routes. There are lim■ ited controls over
inbound and outbound traffic. There is a set procedure that needs to be fol■ lowed for route selection.
Additionally, it is hard to make routing decisions using multiple cri■ teria. With SDN, it is easier to update
the router's state, and SDN can provide more control over path selection.
3. Enterprise networks.
SDN can improve the security applications for enterprise networks. For example, using SDN it is easier to
protect a network from volumetric attacks such as DDoS, if we drop the attack traffic at strategic locations
of the network.
4. Research networks. SDN allows research networks to coexist with production networks.
Question:
7. L7 - What is the relationship between forwarding and routing?
QUESTIONS AND CORRECT ANSWERS
Question:
1. L7 - What spurred the development of Software Defined Networking?
Answer:
Computer Networks are difficult to manage due to diversity of equipment and proprietary technology
Question:
2. L7 - What are the three phases in the history of SDN?
Answer:
1. Active Networks
2. Control and Data Plane Separation OpenFlow API and Network Operating Systems
Question:
3. L7 - Summarize each phase in the history of SDN.
Answer:
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
Question:
4. L7 - What is the function of the control and data planes?
, Answer:
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.
Question:
5. L7 - Why separate the control from the data plane?
Answer:
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.
Question:
6. L7 - Why did the SDN lead to opportunities in various areas such as data centers, routing, enterprise
networks, and research network?
Answer:
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.
The interdomain routing protocol used today, BGP, constrains routes. There are lim■ ited controls over
inbound and outbound traffic. There is a set procedure that needs to be fol■ lowed for route selection.
Additionally, it is hard to make routing decisions using multiple cri■ teria. With SDN, it is easier to update
the router's state, and SDN can provide more control over path selection.
3. Enterprise networks.
SDN can improve the security applications for enterprise networks. For example, using SDN it is easier to
protect a network from volumetric attacks such as DDoS, if we drop the attack traffic at strategic locations
of the network.
4. Research networks. SDN allows research networks to coexist with production networks.
Question:
7. L7 - What is the relationship between forwarding and routing?
