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There are two data path models that are in use today.
Figure 2. Single root-IO Virtualization
1.Single Root-IO Virtualization (SR-IOV) is a performance-oriented data path model. SR-IOV allows physical NICs (PF) to be used as multiple virtual NIC (VF) through virtualization. SR-IOV uses physical functions (PFs) and virtual functions (VFs) to manage global functions for the SR-IOV devices. PFs are full PCIe functions that are capable of configuring and managing the SR-IOV functionality. It is possible to configure or control PCIe devices using PFs, and the PF has full ability to move data in and out of the device. VFs are lightweight PCIe functions that support data flowing but have a restricted set of configuration resources. In this model, the application is aware of the underlying physical hardware and is a complete pass-through model, bypassing the NSX and the ESXi hypervisor. Though this model ensures low latency and high bandwidth, many salient virtualization features, such as HA, DRS, vMotion, and network security features cannot be leveraged.
Figure 2. Enhanced Data Path
2.Enhanced Data-path (EDP) is a networking stack mode, which when configured provides superior network performance. It is primarily targeted for NFV workloads, which offers performance benefits leveraging DPDK capability. In EDP, when a packet arrives on the port through a physical NIC, it continuously forwards packets to the shared memory space using the dedicated CPU cores assigned to it. When a specific packet is identified in the shared memory space, it is first looked at by the software-based Fast Path. If a similar flow is identified in Fast Path, it is determined which VM the packet will be forwarded to. However, if it cannot be found, that is, if a cache miss occurs, it goes to the slow path. Slow Path decides what to do from a network and security perspective based on the settings it receives from the NSX manager.
The biggest advantage of Enhanced Data Path is the use of VMXNET3 paravirtualization driver that is, the application is not aware of the underlying physical hardware. The EDP model requires host CPU cycles for packet processing, networking, and security policies thereby providing superior network performance. This model also leverages many salient virtualization features, such as HA, DRS, vMotion, and network security features.