CS6250 COMPUTER NETWORKS EXAM 2 ACTUAL EXAM NEWEST COMPLETE QUESTIONS AND
CORRECT DETAILED ANSWERS| ALREADY GRADED A+
L7: What spurred the development of Software Defined Networking (SDN)?
> SDN arose to make CN more programmable
> 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
, Page 2
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
, Page 3
> 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
Expanded History
Active networks
Intro
Slow and frustrating process to standardize protocols fostered the push for active networks trying
to open up network control
Active networks with their network API went against the concept of keeping the core simple
2 types of programming models in active networking:
Capsule model - carried in-band in data packets
Programmable router/switch model - established by out-of-band mechanisms
Technology push - The pushes that encouraged active networking were:
Reduction in computation cost (more processing into the network).
Advancement in programming languages. (Java: platform portability, code execution safety, and
VM (virtual machine) technology to protect the active node in case of misbehaving programs).
Advances in rapid code compilation and formal methods.
, Page 4
Funding from agencies such as DARPA (U.S. Defense Advanced Research Projects Agency) for
a collection promoted interoperability among projects. There were no short-term use cases.
Use pull - The use pulls for active networking were:
Network service provider frustration concerning the long timeline to develop and deploy new
network services.
Third party interests to add value by implementing control at a more individualistic nature. This
meant dynamically meeting the needs of specific applications or network conditions.
Researchers’ interest in having a network that would support large-scale experimentation.
Unified control over middleboxes. Active networking envisioned unified control that could
replace individually managing these boxes.
Active networks contributions related to SDN:
Programmable functions in the network to lower the barrier to innovation.
While many early visions for SDN concentrated on increasing programmability of the control-
plane, active networks focused on the programmability of the data-plane.
The concept of isolating experimental traffic from normal traffic has emerged from active
networking and is heavily used in OpenFlow and other SDN technologies.
Network virtualization, and the ability to demultiplex to software programs based on packet
headers.
The vision of a unified architecture for middlebox orchestration.
Conclusion:
Did not see widespread deployment because it didn't solve a specific short-term problem and was
too ambitious. It also did not focus on performance and security.
Control and data plane separation
Intro
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.
CORRECT DETAILED ANSWERS| ALREADY GRADED A+
L7: What spurred the development of Software Defined Networking (SDN)?
> SDN arose to make CN more programmable
> 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
, Page 2
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
, Page 3
> 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
Expanded History
Active networks
Intro
Slow and frustrating process to standardize protocols fostered the push for active networks trying
to open up network control
Active networks with their network API went against the concept of keeping the core simple
2 types of programming models in active networking:
Capsule model - carried in-band in data packets
Programmable router/switch model - established by out-of-band mechanisms
Technology push - The pushes that encouraged active networking were:
Reduction in computation cost (more processing into the network).
Advancement in programming languages. (Java: platform portability, code execution safety, and
VM (virtual machine) technology to protect the active node in case of misbehaving programs).
Advances in rapid code compilation and formal methods.
, Page 4
Funding from agencies such as DARPA (U.S. Defense Advanced Research Projects Agency) for
a collection promoted interoperability among projects. There were no short-term use cases.
Use pull - The use pulls for active networking were:
Network service provider frustration concerning the long timeline to develop and deploy new
network services.
Third party interests to add value by implementing control at a more individualistic nature. This
meant dynamically meeting the needs of specific applications or network conditions.
Researchers’ interest in having a network that would support large-scale experimentation.
Unified control over middleboxes. Active networking envisioned unified control that could
replace individually managing these boxes.
Active networks contributions related to SDN:
Programmable functions in the network to lower the barrier to innovation.
While many early visions for SDN concentrated on increasing programmability of the control-
plane, active networks focused on the programmability of the data-plane.
The concept of isolating experimental traffic from normal traffic has emerged from active
networking and is heavily used in OpenFlow and other SDN technologies.
Network virtualization, and the ability to demultiplex to software programs based on packet
headers.
The vision of a unified architecture for middlebox orchestration.
Conclusion:
Did not see widespread deployment because it didn't solve a specific short-term problem and was
too ambitious. It also did not focus on performance and security.
Control and data plane separation
Intro
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.
