CPU utilization plays a major role in network throughput. More CPU resources are needed for processing higher throughput levels. Insufficient CPU resources limit maximum throughput so monitoring CPU is imperative.

Network performance issues are typically caused by the saturation of a network link between the clients and servers. vSphere 6 supports 1 Gigabit, 10 Gigabit Ethernet, and also 40 Gigabit Ethernet. These higher bandwidth networks reduce the chance of having network bottlenecks but it is always a possibility. The network performance will be dependent on application workload as well as the network configurations. Network-intensive applications can result in oversubscribed network links, which may lead to network contention.

Physical NICs (vmnics) are commonly used by multiple consumers (virtual machines and/or VMkernel ports). It's possible that each consumer could impact the performance of another. Consider placing consumers with heavy networking I/O on separate physical NICs than consumers with latency-sensitive workloads.

Ultimately, ensure that the infrastructure bandwidth is sufficient for all traffic types. Network I/O Control, discussed previously in Chapter 5, vSphere Storage Concepts and Management, can be configured to prioritize network access for the different traffic types.