Home > Storage > PowerMax and VMAX > Storage Admin > iSCSI Implementation Guide for Dell EMC Storage Arrays Running PowerMaxOS > Key iSCSI concepts and terminology
This white paper consistently uses or makes reference to specific concepts and terminology. The following table provides a detailed list of these terms and their definitions:
Terminology |
Equivalent term |
Definition |
Open Systems Interconnection Model |
OSI model |
A seven-layer conceptual model that characterizes and standardizes the communication functions of a telecommunication or computer network system without regard to its underlying internal structure and technology. The primary layers are the application (Layer 7), Presentation (Layer 6), Session (Layer 5), Transport (Layer 4), Network (Layer 3), Datalink (Layer 2), Physical (Layer 1) |
Ethernet |
Ethernet |
A family of computer networking technologies operating at the OSI physical layer (Layer 1) also providing services to the OSI datalink layer (Layer 2). Ethernet is comm*only used in local area networks (LAN) and wide area networks (WAN). Systems communicating over Ethernet based networks divide a stream of data into frames. Each frame contains source and destination addresses, and error-checking data so that damaged frames can be detected, discarded, and retransmitted when needed. Ethernet can use physical mediums of twisted pair and fiber optic links that can reach speeds of 10 Gbps (10 GbE), 25 Gbps, 40 Gbps, 50 Gbps, and now 100 Gbps. |
Virtual Local Area Network (VLAN) |
VLAN |
Any broadcast domain that is partitioned and isolated in computer network at the datalink layer (Layer 2). VLANs work by applying tags to network packets and handling these tags in networking systems – creating the appearance and functionality of network traffic that is physically on a single network but acts as if it is split between separate networks. |
Transmission Control Protocol/Internet Protocol |
TCP/IP |
A suite of communication protocols used to interconnect devices on communication networks. TCP/IP specifies how data can be exchanged over networks. TCP defines how applications can create channels of communication across a network. It manages how data is assembled into smaller packets before it is transmitted over the network and how it is to be reassembled at the destination address. In the OSI model, TCP provides services to the transport layer (Layer 4) and some services to the session layer (Layer 5). IP specifically defines how to address and route each packet to ensure it reaches the correct destination on the network. In the OSI model, IP provides services to the network layer (Layer 3). |
Small Computer System Interface (SCSI) |
SCSI |
A set of standards for physically connecting and transferring data between computers and peripheral devices such as disk storage. The SCSI standards define commands, protocols, and electrical and optical interfaces. |
Storage Area Network |
SAN |
A specialized, high-speed network that provides block-level network access to storage. A SAN consists of two types of equipment: initiator and target nodes. Initiators, such as hosts, are data consumers. Targets, such as disk arrays or tape libraries, are data providers. A SAN presents storage devices to a host such that the storage appears locally attached. SAN initiators and targets can be interconnected using various technologies, topologies, and transport layer protocols. |
Internet Small Computer Serial Interface (iSCSI) |
iSCSI |
A transport layer protocol that uses TCP/IP to transport SCSI commands enabling Ethernet based networks to function as a storage area network (SAN). iSCSI uses TCP/IP to move block data between iSCSI initiators nodes and iSCSI target nodes |
iSCSI Initiator Node |
Initiator |
Host-based hardware (virtual or physical) or software that sends data to and from iSCSI target nodes (storage arrays). The initiator makes requests for the data to be read from or written to the storage. In case of read operations, the initiator sends a SCSI READ command to the peer who acts as a target and in return the target sends the requested data back to the initiator. In the case of a write operation, initiator sends a SCSI WRITE command followed by the data packets to the target. The initiator always initiates the transactions. |
iSCSI Target Node |
Target |
Storage arrays, tape drives, storage servers on a SAN. In iSCSI, targets can be associated with either virtual or physical entities. A storage array target exposes one or more SCSI LUNs to specific initiators. A target is the entity that processes the SCSI commands from the initiator. Upon receiving the command from the initiator, the target runs the command and then sends the requested data and response back to the initiator. A target cannot initiate any transaction. |
iSCSI IP Interface (Network Portal) |
IP Interface |
Primary gateway for access to iSCSI nodes. IP Interfaces contain key network configuration information such as: IP Address, Network ID, VLAN information, and TCP Port Number. An IP Interface can only provide access to a single iSCSI target; however, an iSCSI target can be accessed through multiple IP Interfaces. |
PowerMaxOS 5978 (microcode) |
PowerMaxOS |
The PowerMaxOS 5978 release supports PowerMax NVMe arrays, dedupe, and other software enhancements and is offered with VMAX All Flash arrays. |
PowerMaxOS Network Identity |
Network ID/NetID |
A PowerMaxOS construct that is used internally by the system to associate an array IP interface with an array iSCSI target. The PowerMaxOS Network ID is specific to a single director on the array and is not visible to external switches or hosts. |
iSCSI Qualified Names |
IQN |
Primary mechanism to identify iSCSI nodes on a network. These names are a human-readable ASCII string that can be either user or algorithmically generated; however, the iSCSI Name must be unique on a per network basis in order to avoid duplication. |
iSCSI Protocol Data Unit (PDU) |
PDU |
SCSI commands encapsulated and placed into packets by the iSCSI Protocol at the session layer (Layer 5). |
iSCSI Connection |
Connection |
A TCP/IP connection that ties the session components together. The IP addresses and TCP port numbers in the IP Interfaces define the end points of a connection. |
iSCSI Session |
Session |
Primary communication linkage between iSCSI initiator and target nodes. The session is the vehicle for the transport of the iSCSI PDUs between the initiators and target nodes. |
Challenge Handshake Authentication Protocol (CHAP)
|
CHAP |
The most commonly used iSCSI authentication method. CHAP verifies identity using a hashed transmission of a secret key between initiator and target. |