2018
SDN
for
CCNA Students
By
Eng. Abeer Hosni
SDN(Software-Defined Networking):
- All network traffic is classified to control plane, data plane and management plane.
- SDN moves the intelligence of the network (control plane) from individual devices to
a central device (controller).
- The controller will be responsible of network monitor, configuration,
troubleshooting, resolution and software updates.
- The GUI application is a layer above the controller which shows the admin every thing
running in the network. For example, a red line indicates a congested path, and a
yellow icons of routers and switches indicates a failure whith in the last week.
SDN Components:
- The controller (Ex: APIC-EM).
- The API (Application Program Interface): Used to help communication
between the controller and the network devices. The API usually is a
proprietary.
- The interface protocol, which is the communication channel between the
controller and upper layer application or between the controller and the
network devices.
Interface types:
SBI (Southbound Interface)
- It is the communication to/from the controller and
infrastructure equipment like routers, switches and firewalls.
- Examples on SBI are OpenFlow, NetConf, PCEP, BGP-LS, OVSDB.
NBI (Northbound Interface)
- It is the communication to/from the controller and upstream SDN-
aware applications.
Hint:
Open flow is an open standard API protocol.
NetConf is an open standard protocol created by IETF, used to push
configuration to devices.
OPFlex is an open standard protocol which assumes that the
device has a little control plane.
SDN Architecture:
Application layer: business application.
Control layer: SDN controller.
Infrastructure layer: network devices.
SDN Models:
Complete centralization of the control plane
(Open SDN solution)
- It is a theory till now. A lot of companies with the Open
Networking Foundation work together to build that controller.
- That model will use the open flow protocol which deals only with switches,
not routers. The switch will be a white box switch which is a generic switch
only builds MAC address table and all other switching features like STP,
DTP will the responsibility of the controller.
- The “Open Day Light Controller” is the controller to use when dealing with
this model. It is an open source code application. It supports Open flow,
NetConf, PCEP, BGP-LS and OVSDB protocols.
- The Cisco implementation of the “Open Day Light Controller” is “Cisco
open SDN controller (OSC)” which supports ASR9000 routers, Nexus 3000
switches, Catalyst 4500X switches and Catalyst 4500 switches. It uses Open
flow as the SBI protocol.
- The “Cisco open SDN controller” controller supports fewer features
than the “Open Day Light Controller”.
Partial centralization of the control
plane (Cisco ACI model)
- The Cisco implementation of the partial control plane is the “Application
Centric Infrastructure” controller, which is suitable for data centers.
- The network devices have some control plane. The servers in the data
center are classified to groups according to their BW and QOS needs.
The controller applies a policy to each group of applications
- The ACI controller uses the OPFlex protocol.
- Designed for Nexus switches only.
Distributed control plane
(Cisco APIC-EM)
- Suitable for already configured enterprises.
- Doesn’t require special plate forms.
- Uses the management plane to communicate with devices like telnet,
SSH and SNMP protocols
- The controller pushes commands to the devices and collects statistics about
the devices then uses NBI protocol tells the upper application about the
network which then can modify the devices configuration.
- Cisco implementation of that model is “Application Policy Infrastructure
Controller-Enterprise Model”.
Best wishes:
Abeer
