Software Defined Networking (SDN) ?????

What is SDN?

The physical separation of the network control plane from the forwarding plane, and where a control plane controls several devices.

Software-Defined Networking (SDN) is an emerging architecture that is dynamic, manageable, cost-effective, and adaptable, making it ideal for the high-bandwidth, dynamic nature of today's applications. This architecture decouples the network control and forwarding functions enabling the network control to become directly programmable and the underlying infrastructure to be abstracted for applications and network services. The OpenFlow® protocol is a foundational element for building SDN solutions. The SDN architecture is:

• Directly programmable: Network control is directly programmable because it is decoupled from forwarding functions.
• Agile: Abstracting control from forwarding lets administrators dynamically adjust network-wide traffic flow to meet changing needs.
• Centrally managed: Network intelligence is (logically) centralized in software-based SDN controllers that maintain a global view of the network, which appears to applications and policy engines as a single, logical switch.
• Programmatically configured: SDN lets network managers configure, manage, secure, and optimize network resources very quickly via dynamic, automated SDN programs, which they can write themselves because the programs do not depend on proprietary software.
• Open standards-based and vendor-neutral: When implemented through open standards, SDN simplifies network design and operation because instructions are provided by SDN controllers instead of multiple, vendor-specific devices and protocols.

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Computing Trends are Driving Network Change

SDN addresses the fact that the static architecture of conventional networks is ill-suited to the dynamic computing and storage needs of today’s data centers, campuses, and carrier environments. The key computing trends driving the need for a new network paradigm include:

• Changing traffic patterns: Applications that commonly access geographically distributed databases and servers through public and private clouds require extremely flexible traffic management and access to bandwidth on demand.
• The “consumerization of IT”: The Bring Your Own Device (BYOD) trend requires networks that are both flexible and secure.
• The rise of cloud services: Users expect on-demand access to applications, infrastructure, and other IT resources.
• “Big data” means more bandwidth: Handling today’s mega datasets requires massive parallel processing that is fueling a constant demand for additional capacity and any-to-any connectivity.

In trying to meet the networking requirements posed by evolving computing trends, network designers find themselves constrained by the limitations of current networks:

• Complexity that leads to stasis: Adding or moving devices and implementing network-wide policies are complex, time-consuming, and primarily manual endeavors that risk service disruption, discouraging network changes.
• Inability to scale: The time-honored approach of link oversubscription to provision scalability is not effective with the dynamic traffic patterns in virtualized networks—a problem that is even more pronounced in service provider networks with large-scale parallel processing algorithms and associated datasets across an entire computing pool.
• Vendor dependence: Lengthy vendor equipment product cycles and a lack of standard, open interfaces limit the ability of network operators to tailor the network to their individual environments.

Software-Defined Networking is Not OpenFlow

Often people point to OpenFlow as being synonymous with software-defined networking, but it is only a single element in the overall SDN architecture. OpenFlow is an open standard for a communications protocol that enables the control plane to interact with the forwarding plane. It must be noted that OpenFlow is not the only protocol available or in development for SDN.

The Benefits of Software Defined Networking

Offering a centralized, programmable network that can dynamically provision so as to address the changing needs of businesses, software-define networking also provides the following benefits:

• Directly Programable:  Network directly programmable because the control functions are decoupled from forwarding functions.which enable the network to be programmatically configured by proprietary or open source automation tools, including OpenStack, Puppet, and Chef.
• Centralized Management:  Network intelligence is logically centralized in SDN controller software that maintains a global view of the network, which appears to applications and policy engines as a single, logical switch.
  Reduce CapEx: Software Defined Networking potentially limits the need to purchase purpose-built, ASIC-based networking hardware, and instead supports pay-as-you-grow models
• Reduce OpEX: SDN enables algorithmic control of the network of network elements (such as hardware or software switches / routers that are increasingly programmable, making it easier to design, deploy, manage, and scale networks. The ability to automate provisioning and orchestration optimizes service availability and reliability by reducing overall management time and the chance for human error.
• Deliver Agility and Flexibility: Software Defined Networking helps organizations rapidly deploy new applications, services, and infrastructure to quickly meet changing business goals and objectives.
• Enable Innovation: SDN enables organizations to create new types of applications, services, and business models that can offer new revenue streams and more value from the network.

Why Software Defined Networking Now?

Social media, mobile devices, and cloud computing are pushing traditional networks to their limits. Compute and storage have benefited from incredible innovations in virtualization and automation, but those benefits are constrained by limitations in the network. Administrators may spin up new compute and storage instances in minutes, only to be held up for weeks by rigid and oftentimes manual network operations.
Software-defined networking has the potential to revolutionize legacy data centers by providing a flexible way to control the network so it can function more like the virtualized versions of compute and storage today.

Software Defined Networking Use Cases

As detailed above, Software Defined Networking offers several benefits for businesses trying to move into a virtual environment. There are a multitude of use cases that SDN offers for different organizations, including carrier and service providers, cloud and data centers, as well as enterprise campuses.
For carrier and service providers, Software-Defined Networking offers bandwidth on demand, which gives controls on carrier links to request additional bandwidth when necessary, as well as WAN optimization and bandwidth calendaring. For cloud and data centers, network virtualization for multi-tenants is an important use case as it offers better utilization of resources and faster turnaround times for creating a segregated network. Enterprise campuses experience network access control and network monitoring when using Software-Defined Networking policies.

With SDN, the administrator can change any network switch's rules when necessary -- prioritizing, de-prioritizing or even blocking specific types of packets with a very granular level of control. This is especially helpful in a cloud computing multi-tenant architecture, because it allows the administrator to manage traffic loads in a flexible and more efficient manner. Essentially, this allows the administrator to use less expensive commodity switches and have more control over network traffic flow than ever before.