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CS 6250 > Exam 2: Lesson 8 > Flashcards

Exam 2: Lesson 8 Flashcards

1
Q

Lesson 8:

An OpenFlow switch can function as a router (T/F).

A

True

An OpenFlow switch can be instructed by the controller to behave like a firewall, switch, router, or even perform other roles like load balancer, traffic shaper, etc.

  • Target independence: The packet processing programs should be programmed independent of the underlying target devices. These generalized programs written in P4 should be converted into target-dependent programs by a compiler which are then used to configure the switch.
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2
Q

Lesson 8:
Determine which plane executes a network policy?

Data Plane
Control Plane
Management Plane
All planes

A

Data plane

In short, say if a network policy is defined in the management plane, the control plane enforces the policy and the data plane executes the policy by forwarding the data accordingly.

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3
Q

Lesson 8:
Determine which type of network can implement load balancing.

Conventional Networks
SDN
Neither
Both

A

Both conventional and SDN

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4
Q

Lesson 8:
Determine which type of network decouples the control and data planes?

Conventional Networks

Software-Defined Networks

Neither conventional nor software-defined networks

Both conventional and software defined networks

A

SDN is correct.

Conventional networks are tightly coupled

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5
Q

Lesson 8:

Middleboxes can only be used in conventional networks? (T/F)

A

False

Conventional Networks: Since these middleboxes are required to be carefully placed in the network topology, it is much harder to later change or reconfigure them.

SDN: Locality of functionality placement:Previously, the location of middleboxes was a strategic decision and big constraint. However, in this model, the middlebox applications can take actions from anywhere in the network.

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6
Q

Lesson 8:
Determine which of the following can be implemented as a network application in SDN. Select all that apply:

  Routing 
  Load balancing 
  Security enforcement 
  Quality of Service (QoS) enforcement 
  Power consumption reduction 
  Network virtualization 
  Mobility management 
  MAC Learning 
  Intrusion Detection
A

All of them:

  Routing 
  Load balancing 
  Security enforcement 
  Quality of Service (QoS) enforcement 
  Power consumption reduction 
  Network virtualization 
  Mobility management 
  MAC Learning 
  Intrusion Detection
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7
Q

Lesson 8:

The networking operation system (NOS) is a part of the data plane (T/F)?

A

False

4. Network operating systems:

  • The promise of SDN is to ease network management and solve networking problems by using a logically centralized controller by way of a network operating system (NOS).
  • The value of a NOS is in providing abstractions, essential services and common APIs to developers. For example, while programming a network policy, if a developer doesn’t need to worry about low-level details about data distribution among routing elements, that is an abstraction.
  • Propel more innovation by reducing inherent complexity of creating new network protocols and network applications.
  • Some popular NOSs are OpenDayLight, OpenContrail, Onix, Beacon and HP VAN SDN.
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8
Q

Lesson 8:
The physical devices in an SDN network have embedded intelligence and control required to perform forwarding tasks (T/F)?

A

False

The physical devices do not have embedded intelligence or control, as the network intelligence is now delegated to a logically centralized control system - the Network Operating System (NOS).

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9
Q

Lesson 8:
When a packet arrives in an OpenFlow device and it does not match any of the rules in one of the tables, that packet is always dropped (T/F)?

A

False

In an OpenFlow device, when a packet arrives, the lookup process starts in the first table and ends either with a match in one of the tables of the pipeline or with a miss (when no rule is found for that packet). Some possible actions for the packet include:

  1. Forward the packet to outgoing port
  2. Encapsulate the packet and forward it to controller
  3. Drop the packet
  4. Send the packet to normal processing pipeline
  5. Send the packet to next flow table
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10
Q

Lesson 8:
The Southbound interfaces are the separating medium between the Network-control Applications and the Control plane functionality (T/F).

A

False

The Southbound interfaces or APIs are the separating medium between the control plane and data plane functionality.

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11
Q

Lesson 8:
OpenFlow enables the communication between the control plane and data plane through event-based messages, flow statistics and packet messages that are sent from forwarding devices to controller (T/F).

A

True

There are three information sources provided by OpenFlow protocol:

  1. Event-based messages that are sent by forwarding devices to controller when there is a link or port change
  2. Flow statistics are generated by forwarding devices and collected by controller
  3. Packet messages are sent by forwarding devices to controller when they do not know what to do with a new incoming flow
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12
Q

Lesson 8:
One of the disadvantages of an SDN centralized controller architecture is that it can introduce a single point of failure and also scaling issues (T/F)?

A

True

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13
Q

Lesson 8:
Select advantages that apply to a distributed controller architecture:

Distribution can be a centralized cluster of nodes or physically distributed set of elements.

Fault tolerance

Its network operating system can be scaled easily.

A

Distribution can be a centralized cluster of nodes physically distributed set of elements.

Fault tolerance

Its network operating system can be scaled easily.

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14
Q

Lesson 8:

ONOS is an example of a centralized controller platform (T/F)?

A

False

It is a Distributed SDN Controller

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15
Q

Lesson 8:
In order to make forwarding and policy decisions in ONOs, applications get information from the view and then update these decisions back to the view (T/F)?

A

True

To make forwarding and policy decisions, the applications consume information from the view and then update these decisions back to the view. The corresponding OpenFlow managers receive the changes the applications make to the view, and the appropriate switches are programmed.

https://gatech.instructure.com/courses/216318/pages/an-example-controller-onos?module_item_id=1331076

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16
Q

Lesson 8:
In order to achieve fault tolerance, whenever there is a failure of an ONOS instance, a master is chosen randomly for each of the switches that were controller by the failed instance (T/F)?

A

False

The distributed architecture of ONOS offers scale-out performance and fault tolerance. Each ONOS instance serves as the master OpenFlow controller for a group of switches. The propagation of state changes between a switch and the network view is handled solely by the master instance of that switch. The workload can be distributed by adding more instances to the ONOS cluster in case the data plane increases in capacity or the demand in the control plane goes up.

To achieve fault tolerance, ONOS redistributes the work of a failed instance to other remaining instances. Each switch in the network connects to multiple ONOS instances with only one instance acting as its master. Each ONOS instance acts as a master for a subset of switches. Upon failure of an ONOS instance, an election is held on a consensus basis to choose a master for each of the switches that were controlled by the failed instance. For each switch, a master is selected among the remaining instances with which the switch had established connection. At the end of election for all switches, each switch would have at most one new master instance.

Zoopkeeper is used to maintain the mastership between the switch and the controller.

17
Q

Lesson 8:

The purpose of the creation of the P4 language was to offer programmability on the control plane?

A

False

In this topic, we are talking about the need to offer programmability on the data plane and we are introducing P4 which is a language that was developed for this purpose.

18
Q

Lesson 8:
P4 acts as an interface between the switches and the controller, and its main goal is to allow the controller to define how the switches operate (T/F)?

A

True

P4 is used to configure the switch programmatically and acts as a general interface between the switches and the controller with its main aim of allowing the controller to define how the switches operate.

19
Q

Lesson 8:
The P4 model allows the design of a common language to write packet processing programs that are independent of the underlying devices (T/F).

A

True

The P4 model allows generalization of packet processing across various forwarding devices such as routers, load balancers, etc., using multiple technologies such as fixed function switches, NPUs, etc.. This generalization allows the design of a common language to write packet processing programs that are independent of the underlying devices. A compiler then maps these programs to different forwarding devices.

20
Q

Lesson 8:
In an SDX architecture, each AS can define forwarding policies as if it is the only participant at the SDX, as well as having its own SDN applications for dropping, modifying or forwarding their traffic.

A

True

  • Each AS the illusion of its own virtual SDN switch that connects its border router to every other participant AS. For example, AS A has a virtual switch connecting to the virtual switches of ASes B and C.
  • Each AS can define forwarding policies as if it is the only participant at the SDX, without influencing how other participants forward packets on their own virtual switches.
  • Each AS can have its own SDN applications for dropping, modifying, or forwarding their traffic.
21
Q

Lesson 8:
Select all the SDX applications in the domain of wide area traffic delivery:

Group of answer choices

Application specific peering

Traffic engineering

Wide-area server load balancing

Redirection through middle boxes

A

Application specific peering

Traffic engineering

Wide-area server load balancing

Redirection through middle boxes

CS 6250 (6 decks)

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