Software Defining Network Flashcards

1
Q

Examples of Network management tasks

A

balancing traffic load
achieving security goals
satisfying business relationships

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2
Q

Examples of Network Configuration Errors

A
  1. Persistent oscillations can occur when routers can’t agree on a route to a destination.
  2. Loops
  3. Partitions occur when the network is split into two or more segments that are not connected.
  4. Black holes (router will just drop the packet)
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3
Q

The main goal of SDN

A

Change device-level configuration - centralize the network configuration to a logically centralized controller.

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4
Q

Three things that SDN provide operators

A
  1. Provides operators with network-wide views of both topology and traffic
  2. the ability to satisfy network-level objectives, such as load balancing and security
  3. allows an operator to write a control program that directly affects the data plane.
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5
Q

Two functions of today’s routers

A

Data Plane: forward traffic

Control Plane: compute routing tables (state) to make decisions for data plane

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6
Q

Defining features of SDN

A
  1. Control plane (software program written in high-level language) runs in a logically centralized controller
  2. Provide network view - control all of the routers in the network
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7
Q

Advantages of SDN

A
  1. easier debug and reason
  2. easier coordination of behavior across network devices
  3. easier evolution of network behavior
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8
Q

Reasons for separating data and control plane

A
  1. Independent evolution of data plane (network hardware) & control plane (software control)
  2. Easier debug and reason
  3. Separate vendor hardware from the control logic
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9
Q

How does control/data separation make managing data center easier?

A
  1. Monitor/control of routers from a central point

2. Migrating VMs without renumbering host address

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10
Q

Challenges of SDN

A

Scalability: hundreds to thousands of switches
Consistency: ensure different replicas see the same view
Security/robustness: cope with failers

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11
Q

Ways to cope with scalability challenges

A
  1. eliminate redundant data structures
  2. only perform control-plane operations for a limited number of operations
  3. cache forwarding decisions in switches
  4. run multiple controllers
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