CS 6250 Exam 2 Latest Exam 2026 | Computer
Networks Exam | All Questions and Correct
Answers | Verified Answers | Just Released
What is the relationship between forwarding and routing? ---------CORRECT
ANSWER-----------------· Forwarding is what a router does when it receives a packet
at its input link, it must determine which output link that packet should be sent
through
§ Forwarding is a function of the data plane and is implemented in the hardware
itself
· Routing involves determining the path form the sender to the receiver across the
network
§ Routing is a function of the control plane and is implemented in the software
What is the difference between a traditional and SDN approach in terms of
coupling of control and data plane? ---------CORRECT ANSWER-----------------·
Traditional approach - the routing algorithms (control plane) and forwarding
function (data plane) are closely coupled
§ The router runs and participates in the routing algorithms and thus able to
construct the forwarding table
· SDN approach - there is a remote controller that computes and distributes the
forwarding tables to be used for very router
§ The routers are solely responsible for forwarding, and the remote controllers
are solely responsible for computing and distributing the forwarding tables
,What are the main components of an SDN network and their responsibilities? -----
----CORRECT ANSWER-----------------· SDN-controlled network elements (switches) -
sometimes called the infrastructure layer, is responsible for the forwarding of
traffic in a network based on the rules computed by the SDN control plane
· SDN controller - a logically centralized entity that acts as an interface between
the network elements and the network-control applications
· Network-control applications - programs that manage the underlying network by
collecting information about the network elements with the help of the SDN
controller
What are the four defining features of an SDN architecture? ---------CORRECT
ANSWER-----------------· 1. Flow-based forwarding - the rules for forwarding packets
in the SDN-controlled switches can be computed based on any number of header
field values in various layers such as the transport layer, network layer, and data
link layer
· 2. Separation of data plane and control plane - the SDN-controlled switches
operate on the data plane, and they only execute the rules in the flow tables;
those rules are computed, installed, and managed by software that runs on
separate servers
· 3. Network control functions - the SDN control plane (running on multiple
servers for increased performance and availability), consists of two components:
the controller and the network applications
§ The controller maintains up-to-date network state information about the
network devices and elements and provides it to the network-control applications
· 4. A programmable network - the network-control applications act as the "brain"
of the SDN control plane by managing the network; for example, applications can
include network management, traffic engineering, security, automation, analytics,
etc.
,What are the three layers of SDN controllers? ---------CORRECT ANSWER--------------
---· Communication Layer - consists of a protocol through which the SDN
controller and the network controlled elements communicate; using this protocol
the devices send locally observed events to the SDN controller providing the
controller with a current view of the network state (communication between the
SDN controller and the controlled devices is known as the "southbound"
interface)
· Network-wide state-management layer - is about the network-state that is
maintained by the controller; the network-state includes any information about
the state of the hosts, links, switches, and other controlled elements in the
network; network-state information is needed by the SDN control plane to
configure the flow tables
· Interface to the network-control application layer - also known as the
controller's "northbound" interface which the SDN controller interacts with
network-control applications; network-control applications can read/write
network state and flow tables in controller's state-management layer; the SDN
controller can notify applications of changes in the network state, based on the
event notifications sent by the SDN-controlled devices
Describe the three perspectives of the SDN landscape. ---------CORRECT ANSWER--
---------------o (a) A plane-oriented view, (b) the SDN layers, and (c) a system design
perspective
What are the SDN layers, going from the data plane up to the management
plane? ---------CORRECT ANSWER-----------------o Network Infrastructure
o Southbound Interface
o Network Hypervisor/Virtualization
, o Network Operating System
o Northbound Interface
o Language-Based Virtualization
o Network Programming Languages
o Network Applications
Describe the responsibility of each layer in the SDN layer perspective -
Infrastructure ---------CORRECT ANSWER-----------------§ Consist of networking
equipment (routers, switches and other middlebox hardware); only forward
packets, any logic to operate them is directed from the centralized control system
§ Example, includes OpenFlow switches like SwitchLight, Pica8
Describe the responsibility of each layer in the SDN layer perspective -
Southbound Interface ---------CORRECT ANSWER-----------------§ Interfaces that act
as connecting bridges between control and forwarding elements, and since they
sit in between control and data plane, they play a crucial role in separating control
and data plane functionality
§ Most popular implementation is OpenFlow
Describe the responsibility of each layer in the SDN layer perspective - Network
Virtualization ---------CORRECT ANSWER-----------------§ For a complete
virtualization of the network, the network infrastructure needs to provide support
for arbitrary network topologies and addressing schemes, similar to the
computing layer
§ New advancements in SDN network virtualization include VxLAN, FlowVisor
Networks Exam | All Questions and Correct
Answers | Verified Answers | Just Released
What is the relationship between forwarding and routing? ---------CORRECT
ANSWER-----------------· Forwarding is what a router does when it receives a packet
at its input link, it must determine which output link that packet should be sent
through
§ Forwarding is a function of the data plane and is implemented in the hardware
itself
· Routing involves determining the path form the sender to the receiver across the
network
§ Routing is a function of the control plane and is implemented in the software
What is the difference between a traditional and SDN approach in terms of
coupling of control and data plane? ---------CORRECT ANSWER-----------------·
Traditional approach - the routing algorithms (control plane) and forwarding
function (data plane) are closely coupled
§ The router runs and participates in the routing algorithms and thus able to
construct the forwarding table
· SDN approach - there is a remote controller that computes and distributes the
forwarding tables to be used for very router
§ The routers are solely responsible for forwarding, and the remote controllers
are solely responsible for computing and distributing the forwarding tables
,What are the main components of an SDN network and their responsibilities? -----
----CORRECT ANSWER-----------------· SDN-controlled network elements (switches) -
sometimes called the infrastructure layer, is responsible for the forwarding of
traffic in a network based on the rules computed by the SDN control plane
· SDN controller - a logically centralized entity that acts as an interface between
the network elements and the network-control applications
· Network-control applications - programs that manage the underlying network by
collecting information about the network elements with the help of the SDN
controller
What are the four defining features of an SDN architecture? ---------CORRECT
ANSWER-----------------· 1. Flow-based forwarding - the rules for forwarding packets
in the SDN-controlled switches can be computed based on any number of header
field values in various layers such as the transport layer, network layer, and data
link layer
· 2. Separation of data plane and control plane - the SDN-controlled switches
operate on the data plane, and they only execute the rules in the flow tables;
those rules are computed, installed, and managed by software that runs on
separate servers
· 3. Network control functions - the SDN control plane (running on multiple
servers for increased performance and availability), consists of two components:
the controller and the network applications
§ The controller maintains up-to-date network state information about the
network devices and elements and provides it to the network-control applications
· 4. A programmable network - the network-control applications act as the "brain"
of the SDN control plane by managing the network; for example, applications can
include network management, traffic engineering, security, automation, analytics,
etc.
,What are the three layers of SDN controllers? ---------CORRECT ANSWER--------------
---· Communication Layer - consists of a protocol through which the SDN
controller and the network controlled elements communicate; using this protocol
the devices send locally observed events to the SDN controller providing the
controller with a current view of the network state (communication between the
SDN controller and the controlled devices is known as the "southbound"
interface)
· Network-wide state-management layer - is about the network-state that is
maintained by the controller; the network-state includes any information about
the state of the hosts, links, switches, and other controlled elements in the
network; network-state information is needed by the SDN control plane to
configure the flow tables
· Interface to the network-control application layer - also known as the
controller's "northbound" interface which the SDN controller interacts with
network-control applications; network-control applications can read/write
network state and flow tables in controller's state-management layer; the SDN
controller can notify applications of changes in the network state, based on the
event notifications sent by the SDN-controlled devices
Describe the three perspectives of the SDN landscape. ---------CORRECT ANSWER--
---------------o (a) A plane-oriented view, (b) the SDN layers, and (c) a system design
perspective
What are the SDN layers, going from the data plane up to the management
plane? ---------CORRECT ANSWER-----------------o Network Infrastructure
o Southbound Interface
o Network Hypervisor/Virtualization
, o Network Operating System
o Northbound Interface
o Language-Based Virtualization
o Network Programming Languages
o Network Applications
Describe the responsibility of each layer in the SDN layer perspective -
Infrastructure ---------CORRECT ANSWER-----------------§ Consist of networking
equipment (routers, switches and other middlebox hardware); only forward
packets, any logic to operate them is directed from the centralized control system
§ Example, includes OpenFlow switches like SwitchLight, Pica8
Describe the responsibility of each layer in the SDN layer perspective -
Southbound Interface ---------CORRECT ANSWER-----------------§ Interfaces that act
as connecting bridges between control and forwarding elements, and since they
sit in between control and data plane, they play a crucial role in separating control
and data plane functionality
§ Most popular implementation is OpenFlow
Describe the responsibility of each layer in the SDN layer perspective - Network
Virtualization ---------CORRECT ANSWER-----------------§ For a complete
virtualization of the network, the network infrastructure needs to provide support
for arbitrary network topologies and addressing schemes, similar to the
computing layer
§ New advancements in SDN network virtualization include VxLAN, FlowVisor
