QUESTIONS WITH ANSWERS GRADED
A+
◍ an accompanying integer variable that holds the number of items that are
actually stored in the array.
Answer: A partially filled array is normally used with ________.
◍ Pages.
Answer: A three-dimensional array can be thought of as ________ of
two-dimensional arrays
◍ L7: What spurred the development of Software Defined Networking
(SDN)?.
Answer: > 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 plane2. data plane.
◍ L7: What are the three phases in the history of SDN?.
Answer: 1. Active networks2. Control and data plane separation3.
OpenFlow API and network operating systems
◍ Subscripts.
Answer: Access the individual elements in an array by using their
________.
◍ L7: Summarize each phase in the history of SD
N. .
Answer: 1. Active networks2. Control and data plane separation3.
,OpenFlow API and network operating systemsActive 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 networkDiffered 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
deviceAttempts 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 functionsVision of a network operating systemsDistributed state
management techniquesr
◍ subscript.
Answer: Every element in an array is assigned a unique number known as a
________.
◍ Expanded History.
Answer: Active networksIntroSlow and frustrating process to standardize
protocols fostered the push for active networks trying to open up network
controlActive networks with their network API went against the concept of
keeping the core simple2 types of programming models in active
, networking:Capsule model - carried in-band in data packetsProgrammable
router/switch model - established by out-of-band mechanismsTechnology
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.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
separationIntroThis 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