In 
Most agree to the popular belief that Software Defined Networking is all about controlling/automating many diverse elements within the network stack from a control plane rather than at the component level. The main concept in SDN is the separation of a network device’s control-plane from its data-plane.
SDN’s Modus Operandi
In simple terms, Vijay Sethi, VP-IT & CIO of HeroMoto Corp says that SDN provides a new network architecture in which the part of network system that makes decisions about where traffic is sent (the control plane) is separated from the systems that forwards traffic to the selected destination (the data plane). This ensures that intelligence of a network system can be controlled centrally by software. “With this the amount of automation and scalability in networks can increase tremendously. This also helps increase the flexibility of network utilization and thus making the entire system much more cost-effective,” informs Sethi.
According Nilesh Goradia, Head - Pre-Sales – India Subcontinent, Citrix in the SDN concept, the network simplification is brought about by making changes in the basic architecture where the user switch is replaced by a controller to create a virtual network.
Kamal Matta, Head-IT& Telecom, Sonic Biochem finds IT managers’ task will be made easy as their control over network will drastically increase due to network optimisation, their purchasing power will increase due to cost reduction in networking components. Management of large data center's network will become easier if implemented perfectly.
“Using SDN, a network administrator will be able to plan the traffic from a centralized control console without having to touch individual switches. They can change any network switch's rules as and when needed -- prioritizing, de-prioritizing or even blocking specific types of packets with a very granular level of control,” says Matta. He further adds, “This is especially helpful in a cloud computing architecture because it allows the administrator to manage traffic loads in a flexible and more efficient manner.” Essentially, this enables the administrator to use less expensive, normal switches and have more control over network traffic flow than ever before.
Ashish Khanna, AVP-IT, EIH Ltd, argues that in case of SDN, unlike traditional networks the logical control plane is decoupled with the hardware which is used only for data forwarding. This decoupling allows the control plane to be implemented using a different distribution model than the data plane.
“The Network administrators who used to take days to perform a particular change across the network i.e shaping the traffic for a new application, defining a new VLAN scheme etc. will be able to perform the same task in few hours,” he says.
Khanna further informs that organizations or service providers who already use cloud or mobile technologies in their data centres will get hugely benefitted by adopting SDN based network and this will certainly help IT to get closer to business goals.
The primary reason for adopting software defined network solution by most IT managers as Anand, Business Development Manager, Allied Telsis observes are for optimal utilization of network resources and achieving better scalability of data centres.
Anand says that the proponents of SDN are aiming to solve three problems: a) Simplify network management b) Optimize network performance through centralized flow management and c) Overlay virtual networks over a shared physical infrastructure
SDN solution, which is a controller aims to simplify the network management process.
Treating the network as a single unified entity, configured and maintained from one central location, can greatly reduce the cost of network management. Central management can also reduce disruption when major upgrades or policy changes are being implemented.
To ensure centralized flow management to optimize network performance, a set of switches are configured with rules that map out a network structure—which ports belong to which VLANs; which subnets are attached to which VLANs; a loop-protection mechanism to block redundant links; a routing protocol to distribute subnet information; possibly even dynamic VLAN allocation rules at the edge. “The switches are connected together; each applies its rules independently, and shares appropriate information with its neighbors and a system that can reliably transport data between thousands of individual end-points comes to life.,” says Anand.
Information; possibly even dynamic VLAN allocation rules at the edge. The switches are connected together; each applies its rules independently, and shares appropriate information with its neighbors and a system that can reliably transport data between thousands of individual end-points comes to life.
Such networks are resilient to failures of links and switching nodes—the loop protection and routing protocols re-converge onto a new forwarding topology, and data continues to flow.
Anand further says, the networks share a common set of hardware, and they are provisioned and updated frequently. Manually configuring dozens of switches to implement these regularly changing virtual networks is unfeasible.” Software Defined Networking solutions are being developed that implement the virtual networks. Such solutions use a centralized controller to directly update switch forwarding tables,” he adds.
Amandeep Singh Dang, Country Manager, Networking, Dell India points that from a monolithic system as the networks are today with each element having its own control and data plane; communication has been more of a democratic setup with 5000 + RFC standards of command and control for devices to collaborate, interconnect, inter-operate and form networks.
SDN decouples the control plane into a centralized control leaving the dataplane on commoditized switch hardware. “Centrality of control plane will complete eliminate inter device convergence protocols and associated issues, will enable network splicing, will bring around capabilities to port network services overlay as well as open the framework to build any kind of custom or stand network orchestration build-outs to deploy, manage, control, provision or analyze networks,” says Dang.
Joe Green, CTO, Systems Engineering, APAC, Juniper clearly articulates that inside every networking and security device – every switch, router, and firewall - you can separate the software into four layers or planes. As we move to SDN, these planes need to be clearly understood and cleanly separated. This is absolutely essential in order to build the next generation, highly scalable network.
“Centralization is powerful; it is a key principle for SDN and it’s very appropriate to apply centralization to networking software. Centralization only makes sense within a highly-connected, contained geographic area – for example, within a data center, throughout a campus, or in the case of a service provider, across a city,” says Green. Even with this centralization, network devices themselves will remain distributed and they must have local intelligence.
When you add the concept of centralization to networking software, the four planes move around a bit. Regardless of the number of distributed devices, you’d like to manage the network as a system and Centralized Management does that job. When you centralize management, it becomes the configuration master; all of the devices keep just a copy. Services have historically been implemented within each networking and security device but with SDN, Services can move to the center and are performed on behalf of all devices and there are four steps.
Step 1: Management is the best place to start as this provides the biggest bang for the buck. The key is to centralize network management, analytics, and configuration functionality to provide a single master that configures all networking devices. This lowers operating cost and allows customers to gain business insight from their networks.
Step 2: Extracting Services from network and security devices by creating service VM’s is a great next step because Services are an area that is terribly underserved by networking. This enables network and security services to independently scale using industry-standard, x86 hardware based on the needs of the solution.
Step 3: Creating a Centralized Controller is a big step forward. The Centralized Controller enables multiple network and security services to connect in series across devices within the network. This is called “SDN Service Chaining” – using software to virtually insert services into the flow of network traffic. Service chaining functionality is physically accomplished today using separate network and security devices. Today’s physical approach to service chaining is quite crude; separate devices are physically connected by Ethernet cables; each device must be individually configured to establish the service chain. With SDN Service Chaining, networks can be reconfigured on the fly, allowing them to dynamically respond to the needs of the business. SDN Service Chaining will dramatically reduce the time, cost and risk for customers to design, test and deliver new network and security services.
Step 4: The final step of optimizing network and security hardware can proceed in parallel with the other three. As services are disaggregated from devices and SDN Service Chains are established, network and security hardware can be used to optimize performance based on the needs of the solution. Network and security hardware will continue to deliver 10x or better Forwarding performance then can be accomplished in software alone. The combination of optimized hardware together with SDN Service Chaining allows customers to build the best possible
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