CS6250 Exam 2 UPDATED ACTUAL QUESTIONS AND CORRECT ANSWERS
L7: What spurred the development of Software Defined > SDN arose to make CN more programmable
Networking (SDN)? > Networks are complex/difficult to manage due to the diversity of equipment on
the network and proprietary technologies for the equipment
> These made them highly complex, slow to innovate, and drove up the costs of
running a network.
SDN divides the network into two planes (separation of tasks):
1. control plane
2. data plane.
L7: What are the three phases in the history of SDN? 1. Active networks
2. Control and data plane separation
3. OpenFlow API and network operating systems
,L7: Summarize each phase in the history of SDN. 1. Active networks
2. Control and data plane separation
3. OpenFlow API and network operating systems
Active networks
> Researchers wanted to test new ideas to improve network services. This required
standardization of new protocols by the IETF which was a slow/frustrating
process.
> More active networks which wanted to open up network control.
> Community belief: simplicity of the network core was vital to internet success.
The pushes that encouraged active networking:
> Reduction in computation cost
> PL Advancement (like java)
> Advances in rapid code compilation and formal methods.
Active networking envisioned unified control that could replace individually
managing these boxes.
Active networks made three major contributions related to SDN:
> Programmable functions in the network to lower the barrier of innovation
> Introduced the idea of using programmable networks to overcome the slow
speed of innovation in networking.
Active networking produced a framework that described a platform that would
support experimentation with different programming models. This led to network
visualization.
Active networking was more involved in redesigning the architecture of networks,
so not as much emphasis was given to performance and security. Since there
were no specific short-term problems that active networks solved, it was harder
to see widespread deployment.
The next efforts had a more focused scope and distinguished between control
and data planes. This difference made it easier to focus on innovation in a specific
plane and inflict widespread change.
Control and data plane separation
> Network operators were looking for better network-management functions such
as control over paths to deliver traffic.
> Identified that the challenge in network management depended on the way
existing routers and switches tightly integrated the control and data planes.
> Efforts the separate the two began:
>> Higher link speeds in backbone networks led vendors to implement packet
forwarding directly in the hardware
>> ISPs found it hard to meet the increasing demands for greater reliability and
new services.
Two main innovations: Open interface between control and data planes AND
logically centralized control of the network
Differed from active networking, it:
> Focused on spurring innovation by/for network administrators rather than end
users/researchers.
> Emphasized programmability in the control domain rather than the data domain.
> Worked to network-wide visibility rather than device
, Attempts to separate control and data planes resulted in two concepts used in
further SDN design:
> Logically centralized control using an open interface to the data plane.
> Distributed state management - There was skepticism to moving away from a
simple network where all have a common view of the network state to one where
the router only had a local view of the outcome of route-selection. This concept
of separation of planes helped researchers think clearly about distributed state
management.
OpenFlow API and network operating systems
> OpenFlow was born out of interest in the idea of network experimentation at
scale, by researchers and funding agencies.
> OpenFlow built on the existing hardware and enabled more functions than
earlier route controllers. Enabled immediate deployment.
The basic working of an OpenFlow switch: Each switch contains a table of packet-
handling rules. Each rule has a pattern, list of actions, set of counters and a
priority. When an OpenFlow switch receives a packet, it determines the highest
priority matching rule, performs the associated action and increments the counter.
OpenFlow was adopted in the industry, unlike its predecessors.
Companies started investing more in programmers to write control programs, and
less in proprietary switches that could not support new features easily. This
allowed many smaller players to become competitive in the market by supporting
capabilities like OpenFlow.
Key effects that OpenFlow had were:
Generalizing network devices and functions
Vision of a network operating systems
Distributed state management techniquesr
L7: What spurred the development of Software Defined > SDN arose to make CN more programmable
Networking (SDN)? > Networks are complex/difficult to manage due to the diversity of equipment on
the network and proprietary technologies for the equipment
> These made them highly complex, slow to innovate, and drove up the costs of
running a network.
SDN divides the network into two planes (separation of tasks):
1. control plane
2. data plane.
L7: What are the three phases in the history of SDN? 1. Active networks
2. Control and data plane separation
3. OpenFlow API and network operating systems
,L7: Summarize each phase in the history of SDN. 1. Active networks
2. Control and data plane separation
3. OpenFlow API and network operating systems
Active networks
> Researchers wanted to test new ideas to improve network services. This required
standardization of new protocols by the IETF which was a slow/frustrating
process.
> More active networks which wanted to open up network control.
> Community belief: simplicity of the network core was vital to internet success.
The pushes that encouraged active networking:
> Reduction in computation cost
> PL Advancement (like java)
> Advances in rapid code compilation and formal methods.
Active networking envisioned unified control that could replace individually
managing these boxes.
Active networks made three major contributions related to SDN:
> Programmable functions in the network to lower the barrier of innovation
> Introduced the idea of using programmable networks to overcome the slow
speed of innovation in networking.
Active networking produced a framework that described a platform that would
support experimentation with different programming models. This led to network
visualization.
Active networking was more involved in redesigning the architecture of networks,
so not as much emphasis was given to performance and security. Since there
were no specific short-term problems that active networks solved, it was harder
to see widespread deployment.
The next efforts had a more focused scope and distinguished between control
and data planes. This difference made it easier to focus on innovation in a specific
plane and inflict widespread change.
Control and data plane separation
> Network operators were looking for better network-management functions such
as control over paths to deliver traffic.
> Identified that the challenge in network management depended on the way
existing routers and switches tightly integrated the control and data planes.
> Efforts the separate the two began:
>> Higher link speeds in backbone networks led vendors to implement packet
forwarding directly in the hardware
>> ISPs found it hard to meet the increasing demands for greater reliability and
new services.
Two main innovations: Open interface between control and data planes AND
logically centralized control of the network
Differed from active networking, it:
> Focused on spurring innovation by/for network administrators rather than end
users/researchers.
> Emphasized programmability in the control domain rather than the data domain.
> Worked to network-wide visibility rather than device
, Attempts to separate control and data planes resulted in two concepts used in
further SDN design:
> Logically centralized control using an open interface to the data plane.
> Distributed state management - There was skepticism to moving away from a
simple network where all have a common view of the network state to one where
the router only had a local view of the outcome of route-selection. This concept
of separation of planes helped researchers think clearly about distributed state
management.
OpenFlow API and network operating systems
> OpenFlow was born out of interest in the idea of network experimentation at
scale, by researchers and funding agencies.
> OpenFlow built on the existing hardware and enabled more functions than
earlier route controllers. Enabled immediate deployment.
The basic working of an OpenFlow switch: Each switch contains a table of packet-
handling rules. Each rule has a pattern, list of actions, set of counters and a
priority. When an OpenFlow switch receives a packet, it determines the highest
priority matching rule, performs the associated action and increments the counter.
OpenFlow was adopted in the industry, unlike its predecessors.
Companies started investing more in programmers to write control programs, and
less in proprietary switches that could not support new features easily. This
allowed many smaller players to become competitive in the market by supporting
capabilities like OpenFlow.
Key effects that OpenFlow had were:
Generalizing network devices and functions
Vision of a network operating systems
Distributed state management techniquesr
