Software-defined networking (SDN)
SDN
technology is a network management technique that uses for dynamic,
programmatically efficient network setup to increase network performance and
monitoring.
·
Controls traffic from a centralized control
console without having individual switches in the network.
·
SDN controller directs the switches to
deliver network services.
·
To make networks agile and flexible.
Needs of
SDN
·
Increased control with better speed and flexibility.
·
Customizable network infrastructure.
·
Robust security.
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SDN architecture
·
Three layers: the application layer, the
control layer, and the infrastructure layer.
·
These layers Separate using northbound and
southbound application programming interfaces (APIs).
Application layer
·
Contains the typical network applications or
functions.
·
Include interruption detection systems, load
balancing or firewalls.
·
Use a specialized application, such as a
firewall or load balancer.
·
Replaces the application with a controller application
to manage data plane behavior.
Data plane:
end-user sends data packets by this plane. It includes:
·
packets Forwarding
·
Segmentation and
reassembly of data
·
packets Replication
for multicasting
Control layer
·
Acts as the brain of SDN, which Represents the
centralized SDN controller.
·
This controller exists on a server and manages
policies and traffic flows throughout the network.
·
Perform data plane activities but not involve
end-user data packets.
·
Making routing tables.
· Setting packet handling
policies.
· Each packet has a flow table that
consists of match fields (like input port number and packet header) and
instructions.
·
The packet is
first matched against the match fields of the flow table entries.
·
Then the
instructions of the corresponding flow entry are executed.
·
The instructions
can be forwarding the packet via one or multiple ports, dropping the packet, or
adding headers to the packet.
·
If a packet
doesn’t find a corresponding match in the flow table, the switch queries the
controller which sends a new flow entry to the switch.
·
The switch
forwards or drops the packet based on this flow entry.
Infrastructure layer
·
Made up the physical switches in the network.
·
These switches forward the network traffic to
their destinations.
APIs
·
Communicate using respective northbound
and southbound APIS.
·
Applications communicate to the controller
through its northbound interface.
·
The controller and switches communicate using
southbound interfaces, such as OpenFlow.
Southbound Interface:
·
Interface between controller and networking
devices lies to the south of controller.
·
An interface between a program on the controller
and a program on a networking device.
Northbound Interface:
·
Interfaces between controller and software in the north direction,
·
These interfaces enable the programmability of the network.
·
Interface of two programs for exchanging data
between them.
SDN working
·
SDN encompasses several types of
technologies, including functional separation, network
virtualization, and automation through programmability.
·
Focused only on the separation of the network control
plane from the data plane.
·
Control plane makes decisions about how
packets should flow through the network, and the data plane moves packets from
place to place.
·
Rules built into the switch's proprietary
firmware tell the switch where to forward the packet.
·
These packet-handling rules are sent to the
switch from the centralized controller.
·
The switch -- also known as a data plane device -- queries
the controller for guidance as needed and provides the controller with
information about the traffic it handles.
·
The switch sends every packet going to the
same destination along the same path and treats all the packets the same way.
·
SDN uses an operation mode that is sometimes
called adaptive or dynamic, in which a
switch issues a route request to a controller for a packet that does not have a
specific route.
·
This process is separate from adaptive
routing, which issues route requests through routers and
algorithms based on the network topology, not through a controller.
·
The virtualization aspect of SDN comes into
play through a virtual overlay, which is a logically separate network on top of
the physical network.
·
Users can implement end-to-end overlays to
abstract the underlying network and segment network traffic.
·
This micro-segmentation is especially useful
for service providers and operators with multi-tenant cloud
environments and cloud services, as they can provide a separate virtual
network with specific policies for each tenant.
Benefits of SDN
SDN benefits are:-
Simplified policy changes
·
An administrator can change any network
switch's rules when necessary -- prioritizing, deprioritizing, or even blocking
specific types of packets with a granular level of control and security.
·
Enables the administrator to manage traffic
loads in a flexible and efficient manner.
Network management and visibility
·
Deal with only one centralized controller to
distribute policies to the connected switches.
·
Controller can monitor traffic and deploy
security policies, if traffic is suspicious then it can reroute or drop the
packets.
Reduced hardware footprint and lower
operational costs.
Networking innovations
·
Software-defined wide area network (SD-WAN)
technology.
·
SD-WAN employs the virtual overlay aspect of
SDN technology.
Provides better
security
·
Controller can
monitor traffic and deploy security policies. For example, if the controller
detects suspicious activity in network traffic, it can reroute or drop the
packets.
Disadvantages of
SDN:
Security
The centralized SDN controller presents a
single point of failure and, if targeted by an attacker, can prove detrimental
to the network.
Unclear definition
Different vendors offer various approaches to
SDN, ranging from hardware-centric models and virtualization platforms to
hyper-converged networking designs and controller methods.
Market confusion
SDN, including white box networking, network
disaggregation, network automation, and programmable networking.
Slow adoption and costs
Adoption has been relatively slow, especially in smaller networks and fewer resource enterprises.
SDN use (Application area)
Some use cases for SDN include the following:
·
DevOps.
·
Campus networks.
·
Service
provider networks.
·
Data center
security.
Models
of SDN
different
models of SDN are:-
·
Open SDN:
use a protocol like OpenFlow to control the behaviour of virtual and physical
switches at the data plane level.
·
SDN by APIs: using
an open protocol, application programming interfaces control how data moves
through the network on each device.
·
SDN Overlay Model:
runs a virtual network on top of an existing hardware infrastructure, creating
dynamic tunnels to different on-premise and remote data centres.
·
Hybrid SDN: Combines
software-defined networking with traditional networking protocols in one
environment to support different functions on a network. ============================================================
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