Which of these protocols carries commands for reading from/writing to storage over a TCP/IP session?

iSCSI (Internet Small Computer System Interface) is a storage networking protocol designed to transport SCSI commands over TCP/IP networks. It operates at the session layer of the OSI model, encapsulating SCSI commands and data into TCP packets for transmission across standard Ethernet infrastructure. This allows for the creation of IP-based Storage Area Networks (SANs) using existing network hardware. The protocol establishes a reliable, connection-oriented session via TCP (typically on port 3260) to facilitate block-level read and write operations between an initiator (client) and a target (storage server).

A. RDMA: This is a transport mechanism for direct memory-to-memory data transfer, designed to bypass the OS kernel and TCP/IP stack, not a storage command protocol itself.
C. NVMeoF-RDMA: This protocol transports NVMe commands using RDMA as the fabric, which bypasses the traditional TCP/IP session stack for lower latency.
D. FCoE: This protocol encapsulates native Fibre Channel frames directly into Ethernet frames. It operates at Layer 2 and does not use the TCP/IP protocol suite.

1. IETF RFC 7143

"Internet Small Computer System Interface (iSCSI) Protocol (Consolidated)": Section 1

"Introduction"

Paragraph 1

states

"The iSCSI protocol is a mapping of the SCSI family of application protocols onto the TCP/IP protocol suite... iSCSI is a client-server protocol that can be used on an intranet or on the global Internet."

2. HPE SAN Design Reference Guide (a00001805enw.pdf): Page 14

Table 1

"SAN protocol comparison". The table explicitly lists the "Transport" for iSCSI as "TCP/IP". In contrast

it lists FCoE's transport as "Ethernet (non-routable)" and NVMe-oF's transport as "RDMA

Fibre Channel

TCP". This clearly distinguishes iSCSI as the protocol using a standard TCP/IP session for SCSI commands.

3. HPE Nimble Storage Networking Best Practices (a00017942enw.pdf): Page 6

"iSCSI Overview" section. The document states

"iSCSI is a block protocol that uses the TCP/IP protocol for transport. It allows SCSI commands to be sent over a LAN

WAN

or the internet."