We kickstarted the SDN series with the first post on the underlying motivations. Moving on, the next question in anyone's mind would be about the use cases. In this blog post, we look at the broader SDN use cases from the perspective of network deployment.
The Tectonic Shifts in Networking World
Every new technology innovation goes through a phase of adoption challenges. Shifts in user/market dynamics drive adoption. In the realm of the networking world, two shifts are working in favor of SDN.
The Rise of CSPs
One of the biggest trends in the past few years is the gradual emergence of CSP(Communication Service Provider). CSPs offer end to end communication services under the SaaS model. Enterprises are keener to leverage these services from CSPs instead of building them in house. Therefore the power has gradually shifted to CSPs.
In their frantic effort to reduce the cost of network administration, CSPs have considered SDN as a panacea to all of their cost and deployment concerns. So there lie the challenges in adoption, with a high benchmark for the new technology to upheaval the entire industry.
Move Away from Blackbox Approach
The networking technologies have traditionally embraced a black-box approach. This is because enterprises are worried about security. Many of these enterprises belong to the BFSI (Banking, Financial, Securities, and Insurance) verticals. Due to the ramifications around data theft and pilferages that cause enormous damage, these companies have historically favored black-box solutions for their in-house network deployment. These solutions are built on proprietary hardware & software to achieve high reliability and security. In such cases, the "elasticity" we have been talking about since the beginning is desperately missed.
The shift is now towards elasticity. It is quite evident that the black-box approach cannot keep the OPEX of an expanding network under check. The SDN, as a standalone entity, does not provide a complete solution to this problem. The NFV is also needed to realize the true potential. NFV solves the problem by virtualizing the network components on COTS hardware. In contrast, SDN offers software to orchestrate the service instantiation centrally and manage network functions to bring much needed "elasticity."
The virtualization provides the much-needed abstraction for higher layers to work on it for the desired action. At the same time, SDN governed central control does the rest of magical work at the administrators' software layer. With SDN and NFV combo, the whole philosophy transcends from black-box to white-box or universal CPE.
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The SDN Use Cases for Network Deployment
We can split the SDN use cases into two main network deployment scenarios, greenfield, and brownfield.
The choice of SDN for a greenfield network deployment is a no brainer. Brownfield deployment is the real challenge. However, every network goes through a series of changes that result in upgrades, migrations, expansions. These change events offer a window of opportunity for incorporating SDN in many different ways.
Depending upon the network deployment or change scenario, we can have the following use cases for SDN.
Use Case #1: Greenfield Deployment
If you are going to set up a corporate WAN, or service provider network, catering to multiple end-user applications, requiring different traffic, QoS, VPN routing requirements (through VRF), or seasonal variations, SDN is the way forward. The only reason you would choose legacy routing over SDN is for those cases where the requirement is for an isolated, fairly static network.
Use Case #2: Tech Refresh
An SDN based infrastructure can be planned and deployed as part of a tech refresh to upgrade an existing network deployment. All networking equipment and systems eventually reach their end of life when the network hardware inventory undergoes disbandment. This event may be an internal decision to replace obsolete technology or may be enforced by the vendor by declaring an end of support. It is an appropriate case for a company to upgrade their networking hardware and software suite to support SDN.
Tech refresh should not only restrict to hardware lock ins, performance throughputs and number of ports but also include software capabilities to operate on x86 based COTS hardware and licensing portability. In effect, it should pull away from blackbox approach towards whitebox approach.
Use Case #3: Network Migration
The physical infrastructure of networks undergoes continual transitions to support business expansions, realignments, and other changes. One of the most frequent activities is the migration of a network segment from one physical location to another location. This provides an ideal opportunity to deploy the migrated segment with SDN. Using an SDN gateway that supports both the SDN controlled routing and legacy routing, independent islands of network segments can be established.
Apart from extension in physical infrastructure, there are other forms of migration as well. Migration also applies to scenarios where the network segments are sliced further to support dedicated applications or provide a new service. All these change scenarios can be leveraged to plug in the SDN capability via a gateway. As SDN roll out extends to multiple segments, it becomes more accessible for the network administration team to manage the enterprise-wide policies and ACLs homogeneously.
Use Case #4: Merger and Divestiture
This scenario is applicable for combining the networks of two separate companies due to mergers or acquisitions. In many ways, this is similar to network migration. However, in this case, you are dealing with two different networks having different policies. If both the sides are SDN enabled, then it is a matter of unifying the policies and deploying them centrally through SDN. If either party is not SDN compatible, then this again becomes a case of extending the network reach by gradually building islands of SDN enabled network segments.
However, this case has its limitations when there are two different vendor proprietary SDN solution deployed on both sides. The alternate solution is to offer a forwarding path to two disparate vendor solutions via gateway or HUB routing function while the other island comes for license renewal.
Use Case #5: Hybrid Cloud
It is no secret that enterprises want to adopt a hybrid cloud approach. This strategy offers better control over confidential data and exhibits the elasticity of a cloud-hosted application. With SDN, the traffic breakout between on-prem and cloud can be planned centrally and managed more efficiently.
One more interesting concept of SDN around the cloud is the virtual SDN controller. While running applications on the cloud, there is a lack of fine-grained control over the traffic, QoS, and other routing functions between the cloud computing instances. Using a virtual SDN controller, coupled with the data center SDN controller, network administrators can devise application-specific traffic and routing flows that can stitch together on-prem data center applications with cloud-hosted hosted applications. This scenario opens up some compelling use cases that we will cover in the future.
The hybrid cloud deployment architecture also gives flexibility for network and IT administrators to enable the remote users to access the applications hosted in corporate data centers as well as in public cloud service providers.
The above use cases are very broad, and they mostly act as gating criteria for considering SDN in a network deployment. However, there are more granular, application-level use cases where SDN shines, compared to the traditional approaches. And then, there are also some unique use cases that SDN enables, which were unthinkable earlier.
One example is about giving controls at the users' hands to choose their network configuration, instead of the network administrator provisioning it. Think of this as the Uber model of on-demand communication service for a specific application. It is akin to calling for an Uber cab for a particular destination. We will discuss more on this use case in a subsequent post.
Stay tuned while we unravel more such interesting use cases of SDN.