Software-based techniques are transforming networking. Commercial off-the-shelf hardware is finding a place in several networking use cases. However, high-performance hardware is also an important part of a successful software-defined networking (SDN). As you optimize your networks using SDN tools and complementary technologies such as network function virtualization (NFV), an important step is to strategically assess your hardware needs based on the functions and performance requirements. These need to be aligned with your intended business outcome for individual applications and services.

Two Categories of High Performance Hardware

• Network hardware that utilizes purpose-built designs. These often involve specialized Application-Specific Integrated Circuit (ASIC)s to achieve significantly higher performance than what is possible or economically feasible using commercial off-the-shelf servers that are based on state of the art, x86-based, general purpose processors.
• Network hardware that uses standard x86 servers that is enhanced to provide high performance and predictable operation for example, via special software techniques that bypass hypervisors, virtualization environments, and operating systems.

Where to Deploy Network Functions
Can virtualized network functions be deployed like cloud-based applications? No. There is a big difference between deploying network functions as software modules on x86 general purpose servers and using a common cloud computing model to implement network virtualization. Simply migrating existing network functions to general purpose servers without due regard to all the network requirements leads to dramatically uneven and unpredictable performance. This unpredictability is mainly due to data plane workloads being often I/O bound and/or memory bound and software layers containing important configuration details that may impact performance.
These issues are not specifically about hardware but how the software handles the whole environment. Operating systems, hypervisors, and other infrastructure that is not integrated into best practices for data plane applications will continue to contribute to unpredictable performance.

Bandwidth and CPU Needs

A good way to begin to assess hardware requirements is to examine network functions in two dimensions: I/O bandwidth or throughput needs, and computational power needs. In considering which network function to virtualize and where to virtualize it, CPU load required and bandwidth load required throughout different layers of the network can help determine that some but not all network functions are suitable for virtualization.

Applications with lower I/O bandwidth and low-to-high CPU requirements may be most appropriate for virtualized deployment on optimized x86 servers. Applications with higher I/O bandwidth and low-to-high CPU requirements may be best deployed on specialized high-performance hardware with specialized silicon. Many other factors may play a role in determining what hardware to use for which applications, including cost, user experience, latency, networking performance, network predictability, and architectural preferences.
Service-Network Abstraction is Key
Additionally, you might not need high performance hardware for certain functions initially. But as such a particular function scales, it might require a high performance platform to meet its performance specifications, or it might be more economical on a purpose-built platform. So you might start out with commercial off-the-shelf hardware and then transfer the workload to the high performance hardware later. If you have focused on establishing a clean abstraction of the services from the underlying hardware infrastructure using SDN principles, the network deployment can be more easily changed or evolved independently of the upper services and applications. This is the true promise of SDN.
Read more about how to assess hardware performance requirements in your SDN in the Cisco? white paper "High-Performance Hardware: Enhance Its Use in Software-Defined Networking." You can find it here: "Do You Know your Hardware Needs?" along with other useful information.

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