The individual transport specifications allow NVM Express to isolate and independently evolve transports for evolving memory and fabric transports. The NVM Express® (NVMe®) 2.0 specifications define the theory of operations for transports in the NVMe Base specification and the mapping of specific transports to individual specifications.

What is the NVMe over PCIe Transport specification?

The NVMe Base specification was initially created to help define how host software communicates with non-volatile memory across a PCI Express® (PCIe®) bus. The NVMe specifications have grown to include multiple types of transports. The PCIe transport specific information for NVMe technology is now defined in this specification

NVMe architecture works with PCIe technology to transfer data to and from SSDs. NVMe enables rapid storage in computer SSDs and improves over older Hard Disk Drive (HDD) related interfaces such as SATA and SAS.

What is the RDMA Transport specification?

The RDMA Transport specification uses Remote Direct Memory Access (RDMA) and enables data and memory to be transferred between computer and storage devices across a fabric network. RDMA is a way of exchanging information between two computers’ main memory in a network without involving the processor, cache, or OS of either computer. Because RDMA avoids the OS, it is a fast and low-overhead mechanism for transmitting data across a network.

What is the TCP Transport specification?

NVMe/TCP defines the mapping of NVMe queues, NVMe-oF capsules and data delivery over the IETF Transport Control Protocol (TCP). The NVMe/TCP transport offers optional enhancements such as inline data integrity (DIGEST) and online Transport Layer Security (TLS).

NVMe/TCP enables efficient end-to-end NVMe operations between NVMe-oF host(s) and NVMe-oF controller devices interconnected by any standard IP network with excellent performance and latency characteristics. This allows large-scale data centers to utilize their existing ubiquitous Ethernet infrastructure with multi-layered switch topologies and traditional Ethernet network adapters. NVMe/TCP is designed to layer over existing software-based TCP transport implementations and future hardware accelerated implementations.