Software-Defined Networking(SDN):A New Approach to Networking
A New Approach to Networking
Anju Ann Joseph
Semester: VII Batch: C
B-Tech Seminar Sept 2013
Why we need new approach?
Why not traditional networks?
Virtual Network Overlay Approach
Challenges & Future Expectation
Software Defined Networking (SDN) is an evolutionary
approach to network design and functionality based on
the ability to programmatically modify the behavior of
SDN uses user-customizable and configurable software
that’s independent of hardware to expand data flow
It will make networks more flexible, dynamic, and cost-
efficient, while greatly simplifying operational
The Need for a New Network Architecture
Changing Traffic Pattern
The Rise of Cloud Services
Consumerization of IT
“Big data” means more bandwidth
Configure basic activities
Data Forwarding plane:
Traditional Computer Networks
Data flow is controlled by switches and routers and contains
the following basic elements:
Traditional Networks worked well…
Hardware based networks have historically shown that
they were stable and reliable.
Operational capacities were quickly regained after a
power loss, without significant external interventions.
Operated consistently in varying environments.
Limitations of Current Networking
Complexity that leads to Static Nature
Inability to Scale
Introducing Software-Defined Networking
Software Defined Networking (SDN) is an emerging network
architecture where network control plane is decoupled from
forwarding plane and is directly programmable.
Lead by Open Networking Foundation(ONF)
SDN-enabled control plane allows the underlying
infrastructure to be abstracted
Network appears to the applications as a
single, logical switch entity
SDN Control Software
Business Appl Business Appl Business Appl
Southbound API(eg. OpenFlow)
Specifies how software components should interact each
API’s makes it possible to implement basic network functions
like path computation, loop avoidance, routing, security and
many other tasks.
Allows controller to define the behaviour
of switches at the bottom of the
Provides a network abstraction interface to
the applications and management systems
at the top of the architecture
The controller is the core of an SDN network.
By running the control plane as software, the controller
facilitates automated network management and makes it
easier to integrate and administer applications.
SDN controllers uses protocols such as OpenFlow to
configure network devices
It manages flow control to enable intelligent networking.
OpenFlow is a protocol that is used to define the
communication interface between the control and forwarding
It provides direct access to and manipulation of the forwarding
plane of network devices.
Uses the concept of flows to identify network traffic.
Flow table & Group table
Perform packet lookups and forwarding
Interface that connects a switch to a
Pipeline process: Maintains sending of packets between flow
tables by matching flow entries.
Logically connects each OpenFlow switch
Types of ports: standard logical reserved
OpenFlow Packet header
Version Type Length of Msg Transaction id
0 7 15 31 63
Packet arrives at switch
Header fields compared
to flow table entries
DroppedOREncapsulates packets and
sends to controller
Drops Make new entry in
Match FoundMatch Not Found
Benefits of OpenFlow Approach
Reduced Complexity through Automation
Higher rate of Innovation
Increased Network Reliability and Security
Use Case: Network Slicing among
large Data Centers
Large Data centers have to accommodate many access requests,
each seeking a unique policy and security requirements.
SDN helps to overcome this by creating logical isolated networks
and allow them to be partitioned using slicing technique.
Involves abstraction of control plane management, out of each
network device into a centralized controller via OpenFlow protocol,
helps isolated networks to grow within themselves and also
communicate with other networks.
Few vendors who have produced OpenFlow
enabled network switches
Few OpenFlow based SDN Controllers
C++/Python on Linux
Java based controller
Focuses on achieving
MX series IBM Rack Switch
Virtual Network Overlays(VNO)
It creates a virtual network infrastructure for the underlying
Using VNO concept, the physical network is partitioned into
multiple logical networks that can be individually
programmed and managed.
VNOs are based on a ‘map-and-encap’ approach:
1. Mapping performed to find the destination address of the
2. Overlay device encapsulates the packet within an overlay
3. Encapsulated packet is forwarded to destination where it is
Scheme followed by VNO- Tunneling Scheme
VXLAN(Virtual Extensible LAN)
VXLAN(Virtual Extensible LAN)
It is a tunneling scheme to overlay Layer2 networks on Layer3.
Virtual LANs (VLAN) have similar functioning, but its specifications only
allow for up to 4,096 network IDs to be assigned at any given time.
Extends the VLAN address space by adding a 24-bit segment ID (VNI)and
increasing the number of available IDs to 16 million.
VNI can differentiate individual logical networks so millions of isolated
Layer 2 networks can co-exist on a common Layer 3 infrastructure.
With VLANs, only virtual machines (VMs) within the same logical network
can communicate with each other. VXLAN can potentially allow network
engineers to migrate VMs across long distances.
Use Case: Multi-tenancy in Cloud
In a cloud environment, abstraction of the
management layer becomes important to
enable more interaction of applications with
the networking elements.
The virtual network overlay abstracts the
underlying physical network, which allows
the overlay to move to other physical
Virtual Network Overlay
stack for Cloud
Virtual Network Switch
Tenant 1 Tenant 2 Tenant 3
To support co-existence with existing devices the existing
technologies must have additional enhancement.
For ex, the existing standard path computation elements
in routers are not sufficient, they need to be enhanced.
To find a unique SDN approach.
Some Frequently Raised Questions..
Why is SDN taking so long to adopt?
• Enterprises confused about how SDN will specifically
save them on network costs
• No compelling use-cases
Is SDN and network virtualization same?
• similar goals
• overlapping sets of technologies
SDN promises to transform today’s static networks into
flexible ,scalable, programmable platforms with the
intelligence to allocate resources dynamically.
With its many advantages and astonishing industry
momentum, SDN is on the way to become- the new
approach for networking.
:Kapil Bakshi,“Considerations for Software Defined
Networking(SDN):Approaches and Use Cases,” IEEE Aerospace
Conference, March 2013.
:“Software-Defined Networking: The New Norm for Networks,”
Open Networking Foundation(ONF) White Paper, April 2012.
:“Software Defined Networking: A new paradigm for
virtual, dynamic, flexible networking,” IBM Systems and Technology
Thought Leadership White Paper, October 2012.
: Hyojoon Kim and Nick Feamster, “Improving network
management using SDN,” IEEE Communications
Magazine, February 2013, pp.114-119.