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SDN Questions

March 16th, 2020 Go to comments
SDN Quick Summary
Everything that networking devices do can be categorized into three planes: Data Plane, Control Plane and Management Plane.
+ Data Plane: responsible for the switching of packets through the router. In short, it includes any action after receiving data (processing, encapsulating/decapsulating, matching destination MAC & IP addresses, forwarding, QoS, filtering with access-list)
+ Control Plane: responsible for maintaining sessions and exchanging protocol information with other network devices. It consists of dynamic IP routing protocols (OSPF, EIGRP, BGP…), the RIB, routing updates, in addition to other protocols such as STP, ARP, ICMP, PIM, IGMP, LACP…
+ Management Plane: is used to manage a device through its connection to the network. Examples of protocols processed in the management plane include Simple Network Management Protocol (SNMP), Telnet, File Transfer Protocol (FTP), Secure FTP, and Secure Shell (SSH). These management protocols are used for monitoring and for command-line interface (CLI) access

Most traditional devices use a distributed architecture, in which each control plane is resided in a networking device. Therefore they need to communicate with each other via messages to work correctly.

In constrast to distributed architecture, centralized (or controller-based) architectures centralizes the control of networking devices into one device, called SDN controller.
As we took the control planes off networking devices but not data planes so we need a way to communicate with them. So we put a southbound interface (SBI) at the bottom of SDN controller for this task. An SBI communicates with the devices via an application programming interface (API).

SDN_controller_based_architecture.jpg

Now, in turn, the networking administrators and SDN applications want to control the controller! So the controller need a northbound interface (NBI) to communicate with us. The NBI applications included various network services, including network virtualization, dynamic virtual network provisioning, firewall monitoring, user identity management and access policy control.

Southbound_Northbound_APIs.jpg

REST (Representational State Transfer) describes a type of API that allows applications to sit on different hosts, using HTTP messages to transfer data over the API.
Three SDN controllers which are mentioned in CCNA:
+ OpenDaylight Controller: an OpenFlow-based SDN
+ Cisco Application Centric Infrastructure (ACI)
+ Cisco APIC Enterprise Module (APIC-EM)

Question 1

Question 2

Explanation

The Southbound API is used to communicate with network devices.

Southbound_Northbound_APIs.jpg

Question 3

Question 4

Explanation

OpenFlow is a well-known southbound API. OpenFlow defines the way the SDN Controller should interact with the forwarding plane to make adjustments to the network, so it can better adapt to changing business requirements.

The Network Configuration Protocol (NetConf) uses Extensible Markup Language (XML) to install, manipulate and delete configuration to network devices.

Other southbound APIs are:
+ onePK: a Cisco proprietary SBI to inspect or modify the network element configuration without hardware upgrades.
+ OpFlex: an open-standard, distributed control system. It send “summary policy” to network elements.

Question 5

Explanation

Most traditional devices use a distributed architecture, in which each control plane is resided in a networking device. Therefore they need to communicate with each other via messages to work correctly.

In contrast to distributed architecture, centralized (or controller-based) architectures centralizes the control of networking devices into one device, called SDN controller -> Answer D is correct.

SDN_controller_based_architecture.jpg

Comments (1) Comments
  1. Sandeep Singh
    June 23rd, 2020

    Good to see about SDN .. Can you put some stuff on SDWAN as well

    https://www.thenetworkdna.com/search/label/Viptela%20SDWAN?&max-results=7

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