Computer Networks -CS6250 Exam 2025
Questions and Answers
In terms of SDN, describe the network-control application layer - ✔✔This is how the
SDN controller interacts with network-control applications
What is another name for this layer? - ✔✔Northbound interface
What is the different between conventional and SDN? - ✔✔Conventional networks have
tightly coupled data and control plane
Software defined networks decouple the control plane from physical networking
What things should all SDN core controllers provide? - ✔✔Topology, statistics,
notifications, device management, shortest path forwarding, security mechanisms
What is a centralized controller? - ✔✔Typically has a single entity that manages
all forwarding devices in the network (a single point of failure)
What is a distributed controller? - ✔✔An entity that runs across multiple data
centers interconnected by a WAN
What is Open Networking Operating System (ONOS)? - ✔✔A distributed SDN
control platform
What is the goal of ONOS? - ✔✔Provide a global view of the network to the applications,
scale out performance and fault tolerance
, How is the propagation of state change handled in ONOS? - ✔✔State changes between
a switch and the network is handled solely by the master instance of that switch
What happens if an instance fails in ONOS? - ✔✔A master is selected from the
remaining instances of instances with which they already had a connection
What is used to maintain the mastership between switch and controller? - ✔✔Zookeeper
What is P4? - ✔✔A high-level language used to configure switches which works
in conjunction with SDN control protocols
What is P4 used for? - ✔✔Configure the switch programmatically and act as an interface
between the switches and the controller with the main aim of allowing the controller to
define how the switches operate
What are the goals of P4? - ✔✔Reconfigurability, protocol independence,
target independence
How can you access the match action tables in P4? - ✔✔In multiple stages in a series
or parallel
What are the main operations of the P4 forwarding model? - ✔✔Configure - Operations
used to program the parser; specify the header fields to be processed in each match action
stage and define the order of the stages
Populate - Entries in the match action tables may be altered using the populate
operations which allow addition and deletion of entries in tables
What is the goal of DNS abuse? - ✔✔Remain undetectable for as long as possible
Questions and Answers
In terms of SDN, describe the network-control application layer - ✔✔This is how the
SDN controller interacts with network-control applications
What is another name for this layer? - ✔✔Northbound interface
What is the different between conventional and SDN? - ✔✔Conventional networks have
tightly coupled data and control plane
Software defined networks decouple the control plane from physical networking
What things should all SDN core controllers provide? - ✔✔Topology, statistics,
notifications, device management, shortest path forwarding, security mechanisms
What is a centralized controller? - ✔✔Typically has a single entity that manages
all forwarding devices in the network (a single point of failure)
What is a distributed controller? - ✔✔An entity that runs across multiple data
centers interconnected by a WAN
What is Open Networking Operating System (ONOS)? - ✔✔A distributed SDN
control platform
What is the goal of ONOS? - ✔✔Provide a global view of the network to the applications,
scale out performance and fault tolerance
, How is the propagation of state change handled in ONOS? - ✔✔State changes between
a switch and the network is handled solely by the master instance of that switch
What happens if an instance fails in ONOS? - ✔✔A master is selected from the
remaining instances of instances with which they already had a connection
What is used to maintain the mastership between switch and controller? - ✔✔Zookeeper
What is P4? - ✔✔A high-level language used to configure switches which works
in conjunction with SDN control protocols
What is P4 used for? - ✔✔Configure the switch programmatically and act as an interface
between the switches and the controller with the main aim of allowing the controller to
define how the switches operate
What are the goals of P4? - ✔✔Reconfigurability, protocol independence,
target independence
How can you access the match action tables in P4? - ✔✔In multiple stages in a series
or parallel
What are the main operations of the P4 forwarding model? - ✔✔Configure - Operations
used to program the parser; specify the header fields to be processed in each match action
stage and define the order of the stages
Populate - Entries in the match action tables may be altered using the populate
operations which allow addition and deletion of entries in tables
What is the goal of DNS abuse? - ✔✔Remain undetectable for as long as possible
