CS6250 COMPUTER NETWORKS EXAM 2
COMPREHENSIVE TEST PAPER WITH
SOLVED QUESTIONS
◉ What is the southbound interface?
Answer: communication protocol between controller and
controlled devices
(7)
◉ What in SDN is openflow an example of?
Answer: the southbound interface/communication layer of the
controller
(7)
◉ What is the network-wide state-management layer?
Answer: - stores network state that is maintained by controller
- info about state of hosts, and other controlled devices/elements
- includes copies of flow tables
- this info is needed to configure flow tables
(7)
,◉ Why does network state info need to be strored by controller?
Answer: In order to configure flow tables
(7)
◉ What is the interface to the network control application layer?
How do apps interact with it?
Answer: - Northbound interface
- How SDN controller interacts with network-control applications
- apps read/write network state and flow tables in controller's
state management layer
- controller notifies apps of changes in network state based on
notifications from the devices
- apps take actions based on events
(7)
◉ What is the northbound interface?
Answer: - controller to applications protocol
(7)
◉ Is the SDN controller implemented centralized or distributed?
Answer: DISTRIBUTED SERVERS - highly scalable services
,(7)
◉ Is SDN controller have fault tolerance? Efficiency? Availability?
Synchronization? Why??
Answer: Yes to all EXCEPT synchronization b/c of distributed
servers
(7)
◉ What are 2 challenges that became more pronounced as IP
networks grew in adoption worldwide?
Answer: 1. handling growing complexity and dynamic nature of
networks
- a policy requires changes t EVERY device
2. tightly coupled architecture
- traditionally control/data plane were together, which is not
flexible
(8)
◉ What is software defined networking?
Answer: - attempt to overcome limits of legacy IP networking
- separate control logic from data plane
, - data plane switches do forwarding, control logic is in logically
centralized controller
(8)
◉ What is the physical and logical location of control plane?
Answer: PHYSICALLY DISTRIBUTED and LOGICALLY
CENTRALIZED
(8)
◉ Do SDNs have logically distributed controller?
Answer: No, logically CENTRALIZED
(8)
◉ Do SDNS have a physically centralized control plane?
Answer: No, physically DISTRIBUTED
(8)
◉ How is separation between control plane and data plane
achieved?
Answer: Programming interface/API between controller apps and
switches/devices, like OpenFlow API
(8)
COMPREHENSIVE TEST PAPER WITH
SOLVED QUESTIONS
◉ What is the southbound interface?
Answer: communication protocol between controller and
controlled devices
(7)
◉ What in SDN is openflow an example of?
Answer: the southbound interface/communication layer of the
controller
(7)
◉ What is the network-wide state-management layer?
Answer: - stores network state that is maintained by controller
- info about state of hosts, and other controlled devices/elements
- includes copies of flow tables
- this info is needed to configure flow tables
(7)
,◉ Why does network state info need to be strored by controller?
Answer: In order to configure flow tables
(7)
◉ What is the interface to the network control application layer?
How do apps interact with it?
Answer: - Northbound interface
- How SDN controller interacts with network-control applications
- apps read/write network state and flow tables in controller's
state management layer
- controller notifies apps of changes in network state based on
notifications from the devices
- apps take actions based on events
(7)
◉ What is the northbound interface?
Answer: - controller to applications protocol
(7)
◉ Is the SDN controller implemented centralized or distributed?
Answer: DISTRIBUTED SERVERS - highly scalable services
,(7)
◉ Is SDN controller have fault tolerance? Efficiency? Availability?
Synchronization? Why??
Answer: Yes to all EXCEPT synchronization b/c of distributed
servers
(7)
◉ What are 2 challenges that became more pronounced as IP
networks grew in adoption worldwide?
Answer: 1. handling growing complexity and dynamic nature of
networks
- a policy requires changes t EVERY device
2. tightly coupled architecture
- traditionally control/data plane were together, which is not
flexible
(8)
◉ What is software defined networking?
Answer: - attempt to overcome limits of legacy IP networking
- separate control logic from data plane
, - data plane switches do forwarding, control logic is in logically
centralized controller
(8)
◉ What is the physical and logical location of control plane?
Answer: PHYSICALLY DISTRIBUTED and LOGICALLY
CENTRALIZED
(8)
◉ Do SDNs have logically distributed controller?
Answer: No, logically CENTRALIZED
(8)
◉ Do SDNS have a physically centralized control plane?
Answer: No, physically DISTRIBUTED
(8)
◉ How is separation between control plane and data plane
achieved?
Answer: Programming interface/API between controller apps and
switches/devices, like OpenFlow API
(8)
