Lesson 7 - SDN (part 1)

Question 1

Why are computer networks are very complex and especially difficult to manage?

Answer 1

1. Diversity of equipment on the network

2. Proprietary technologies for the equipment

Question 2

The history of SDN can be divided into three phases. What are these phases?

Answer 2

1. Active networks
2. Control and data plane separation
3. OpenFlow API and network operating systems

Question 3

Why separate the control from the data plane?

Answer 3

1. Independent evolution and development

2. Control from high-level software program

Question 4

What is the difference between a traditional and SDN approach in terms of coupling of control and data plane?

Answer 4

Traditional approach, routers are responsible for both routing and forwarding functionalities. The routing algorithms (control plane) and forwarding function (data plane) are closely coupled. The router runs and participates in the routing algorithms. From there it is able to construct the forwarding table which consults it for the forwarding function.

SDN, routers only focus on forwarding. There is a remote controller that computes and distributes the forwarding tables to be used by every router. This controller is physically separate from the router.

Question 5

What are the main components of SDN network?

Answer 5

1. SDN-controlled network elements
2. SDN controller
3. Network-control applications

Question 6

What are the four defining features in an SDN architecture?

Answer 6

1. Flow-based forwarding
2. Separation of data plane and control plane
3. Network control functions
4. A programmable network

Question 7

What are the three layers of SDN controller?

L7-The SDN Controller Architecture

Answer 7

1. Communication layer
2. Network-wide state-management layer
3. Interface to application layer

Question 8

define SDN

Answer 8

Software-defined networking (SDN) technology is an approach to network management that enables dynamic, programmatically efficient network configuration in order to improve network performance and monitoring making it more like cloud computing than traditional network management. This architecture decouples the network control and forwarding functions.

Question 9

What are SDN-controlled network elements responsible for?

Answer 9

SDN-controlled network elements - (or infrastructure layer), is responsible for the forwarding of traffic in a network based on the rules computed by the SDN control plane.

Question 10

What is a SDN controller?

Answer 10

SDN Controller - A logically centralized entity that acts as an interface between the network elements and the network-control applications.

Question 11

What are Network-control applications?

Answer 11

programs that manage the underlying network by collecting information about the network elements with the help of SDN controller.