As we promised in our last blog, “Who is INCITS,” we are now going to take a look at INCITS (International Committee for Information Technology Standards) groups in greater detail, including answering the extremely common question: What is the difference between T10, T11, and T13? And what happened to T12?!

The three INCITS committees, T10, T11, and T13 generally work on block-based data, as compared to file or object based, to storage interfaces. These committees are also generally aligned with focus on T10 and SCSI, T11 and Fibre Channel, and T13 ATA.  These three committees are not siloes. They support each other and work jointly to embrace new technologies and advance current technologies.  For example, T10 and T11 have actively contributed to, and added support for, the NVM Express™ (NVMe™) specifications, even though this emerging NVMe™ technology comprised of ratified technical proposals from consortium members, is not an intended national standard developed under INCITs governance. A couple of examples are SCSI enclosure services and the Fibre Channel Control protocol for SCSI version 5 (FCP 5).

I should add the T13 committee’s focus is on Advanced Technology Attachment (ATA), also known as Integrated Drive Electronics (IDE), is no longer actively developing or evolving the standard, as the AT Attachment Command Set (ATA8-ACS) INCITS standard has moved to maintenance status. Hence the focus in this discussion is T10 and T11 because the committees are very active embracing and standardizing new technology. T10 and T11 committees have face-to-face meetings six times a year and are developing and maintaining standards with an eye to multi-generational compatibility and interoperability.  I must point out these published standards are maintained on a periodic review cycle, and may be amended by the people who developed them.  This is a major benefit to those who have materially invested in these technologies and standards and plan to continue those investments with standards based technology refreshes.  Participation in these INCITS committees is open to anyone materially and directly affected by the work of these Task Groups.  Contrary to some beliefs, standards are not defined in the back room by a select few company representatives.  Participation is open and encouraged. In fact, public review and comment is a required step in the process of becoming a published national standard under INCITs’ governance.

Before we move into Task Group charters, there is a question as to what happened to T12? Why start with T10 and skip T12, when naming an INCITS committee?  My investigation concludes that no participants in these interface and protocol focused committees wanted to confuse information technologies with standardizing fluorescent and incandescent lighting and fixtures.  This really was a matter of timing, and T12 got their name first.  The U.S. government standardized commercial fluorescent lighting in 1938, long before computer information technologies needed standardization. Fluorescent tubes come in a range of sizes and it was clever to name these fluorescent tube standards based on the diameters of the tubes.  T8 has a one inch (8/8 inch) diameter, a T5 has a 5/8 inch diameter, and a T12 is a 12/8 inch diameter.  If a T12 and a T8 use the same bi-pin base, you can use them interchangeably with the same lighting fixture.  Today one is able to upgrade T12 fixtures with compatible LED based T12 bulbs. This example highlights the advantages of standards and how the specifications can have multi-generational compatibility and enable interoperability with benefits to all those materially invested.  For the U.S. government, the scope of the T12 standard impacted every public building.  Standardization of computer information exchange interfaces came nearly 50 years later.  So it is fair to say the T12 standard was well known before T10, T11, and T13 committees needed names and there was no reason to create potential confusion with lighting fixture standards. It was also established that there would not be a tube standard beyond T12.

SCSI was standardized in 1986, Fibre Channel and ATA in 1994.  Even though T10, T11, and T13 have been around for a long time in modern technological time scales, they continue to be relevant, continue to evolve and provide material technology advantages.

T12 Fluorescent Bulb Standard!

Back to INCITS committees. Each INCITS committee has a charter which defines the scope of the standardization of information exchanged using their respective protocols and physical transports.  These Task Groups are not independent of one another, in fact because of interdependencies, T10 develops and maintains (with T11 contribution and review)  the common standardized specification called the Fibre Channel Protocol (FCP), which is the SCSI interface protocol utilizing an underlying Fibre Channel connection. The Fibre Channel standards define a high-speed data transfer mechanism that can be used to connect workstations, mainframes, supercomputers, storage devices and displays.  Working jointly, T10 and T11 committees posted the Fibre Channel Protocol for SCSI, Fifth Version (FCP-5) Draft revision for Public Review in December, 2019.

There are several information technology standardization committees and the diagram below highlights the varied areas of focus.  Not all of these organizations publish formal standards.  There are Technical Proposals (TPs), Requests for Comments (RFCs), technical reports and tutorials, and other forms of standard documents.  The objective is to have documentation which has a defined format and describes what it means to be conformant, which is a reference for the validation that underpins interoperability and interchangeability.

T10 is responsible for all SCSI projects, except IEEE is responsible for IEEE1394.  IEEE1394 is also known as FireWire, and is an interface standard adopted by Apple and others for a high-speed serial bus for communications utilizing SCSI capabilities. T11 is responsible for Fibre Channel; Internet Engineering Task Force (IETF) is responsible for iSCSI and the Internet; the InfiniBand Trade Association is responsible for InfiniBand; and the USB Implementers Forum, Inc. is responsible for the Universal Serial Bus (USB). Standards based, consortium based, work group based, task force based, or just one company can promote use of technologies but there are higher degrees of risk with incompatibilities and interoperability without standardization.

SCSI Storage Interfaces (T10) develops standards and technical reports on I/O interfaces, particularly the series of SCSI (Small Computer System Interface) standards. Since its standardization in 1986, SCSI has been commonly used as the I/O interface by most computer systems.  T10 as an INCITS Technical Committee is responsible for SCSI Storage Interfaces. Its principal work is the Small Computer System Interface (SCSI), including the family of SCSI-3 projects. T10 is responsible for SCSI architecture standards (SAM-n), which are used by parallel SCSI, SAS, iSCSI, SCSI Express, USB Attached SCSI, Fibre Channel, SSA, ADI, and IEEE 1394 (FireWire). T10 is also responsible for at least 9 SCSI command set standards, for example Direct Access Block commands (SPC-5, SBC-4). These standards are used by almost all modern computer I/O interfaces. An example of how a technology can be derived from a standard is iSCSI, or SCSI over TCP/IP Ethernet connections.  An RFC 3720 defined iSCSI logical connections and preserves the basic SCSI paradigm, especially the command set, almost unchanged, through embedding of SCSI-3 over TCP/IP.  This RFC 3720 is not a T10 standard and although used widely, may have vendor specific interoperability problems because of the language used which allows for varied interpretations and implementations. This is one reason why standards use specific terms like shall, should, and may and serve as a guideline for conformance and interoperability validations.

The ancestral SCSI standard, X3.131-1986, generally referred to as SCSI-1, was published by the X3T9 technical committee of the American National Standards Institute (ANSI) in 1986. SCSI-2 was published in August 1990 as X3.T9.2/86-109, with further revisions in 1994 and subsequent adoption of a multitude of interfaces. Further refinements have resulted in improvements in performance and support for ever-increasing storage data capacity. The SCSI protocol has been mapped over various transports, including Parallel SCSI, IPI, IEEE-1394 (FireWire) and Fibre Channel.

The third-generation SCSI standards used the name SCSI-3 to distinguish them from SCSI-2. Subsequent SCSI standards have dropped the ‘-3’ from their names. When the SCSI-3 Architecture Model (SAM) was revised, it became the SCSI Architecture Model – 2 (SAM-2). Hence SCSI-3 is the sum of quite a few independent standards developed by independent special interest groups. For example, magnetic tape storage. While the individual components of the SCSI family continue to evolve, there is no SCSI-4 project envisioned, however there is SAS-4, which operates at 22.5 Gb/s. The quest for high and higher speeds is a dominant area of development for standards based technologies.

Currently the SCSI Architecture Model – 6 (SAM-6) is in T10 committee review and open for comment.  Like T12, T10 continues to provide a foundation for the evolution of this information exchange interconnect technology.

The Information Technology Industry Council (ITI) is the Secretariat for INCITS. ITI charges a fee for membership in T10 to cover the INCITS Secretariat’s operating costs. T10 Voting membership includes one principal member and unlimited alternate members. Certain attendance rules apply to obtain and maintain voting membership.  The key to development of National standards is face-to-face meeting, because the conversations about what is written and has been written in standards language matters to conformance. Remember that standards conformance precedes interoperability.

INCITS T11 is responsible for standards development in the areas of Intelligent Peripheral Interface (IPI), High-Performance Parallel Interface (HIPPI) and Fibre Channel (FC).  Fibre Channel (FC) is a high-speed network transport technology that interconnects network elements and allows them to communicate with one another, most often utilizing the SCSI command sets. Fibre Channel is primarily used in storage area networks (SANs) because it provides reliable, lossless, in-order data block (frame) transport delivery, achieved utilizing a per link level credit mechanism between initiators, switches, and targets.  These basic properties of Fibre Channel make for a stable platform for many varied computer workloads which heavily depend on the computer to storage I/O behavior.  When the technology was originally devised, it ran over optical fiber cables only and, as such, was called “Fiber Channel”.  In order to avoid confusion and to create a unique name, the committee decided to use the British English fibre for the name of the standard.

INCITS T11 is the parent committee of Task Groups T11.2 and T11.3.  INCITS/T11 is the U.S. TAG to ISO/IEC JTC 1.  INCITS T11 coordinates the work of the Task Groups and retains overall responsibility for work area. INCITS T11 assumed the program of work of the predecessor Task Group X3T9.3 following a reorganization of TC X3T9. INCITS T11 held its first meeting in February, 1994.

The physical variants Task Group is T11.2 is the Task Group within Technical Committee T11 responsible for all projects and parts of projects dealing with physical variants i.e. media, connector, transmitter, and receiver requirements. T11.2 held its first meeting on August 5, 1997 and today has standardized FC-PI-7 which includes 64GFC single link and parallel links 256GFC, and continues to develop the next generation of transport speedup.

T11.3 is the Task Group within Technical Committee T11 responsible for all FC projects which define Fibre Channel Interconnection Schemes. T11.3 held its first meeting on April 23, 1998. The primary focus of T11 activities has been directed towards the Fibre Channel (FC) family of transport standards. It should be noted, that included in the FC family are mappings which allow protocols from the IP, HIPPI, and NVMe standards families to be transported across Fibre Channel. This provides a straightforward migration path among all of the T11 standards.

The Fibre Channel Industry Association (FCIA) is not responsible for the technical standards concerning the Fibre Channel specifications. The FCIA is a mutual benefit non-profit international organization of manufacturers, system integrators, developers, vendors, industry professionals and end users and provides market direction to the INCITS T11 Task Groups. FCIA members contribute to the marketing of Fibre Channel solutions.  This blog is written in cooperation with the FCIA Education Committee.

INCITS T13 is a Task Group and operates under rules approved by the American National Standards Institute (ANSI). These rules are designed to ensure that voluntary standards are developed by the consensus of directly and materially affected interests. The T13 Technical Committee was formally established in December 1995 to develop standards and technical reports on I/O interfaces, specifically ATA, also known as IDE (Integrated Drive Electronics).   Apple started using the less-expensive parallel ATA (PATA, also known as IDE) for its low-end computers in1994. The charter of T13 is to provide a public forum for the development and enhancement of storage interface standards for high volume personal computers.

The interface used by these drives was standardized in 1994 as ANSI standard X3.221-1994, AT Attachment Interface for Disk Drives. After later versions of the standard were developed, this became known as “ATA-1”.  As mentioned, T13 has evolved to become a national standard in maintenance.

Want to learn more about standards development? Check out the other four blogs in this series.

Next Time…

Part V: What’s With the Funky Acronyms?

With the above background, and T12 perspectives in mind, we turn our focus on INCITS T11.  We will highlight the structure of T11 standards which are logically and loosely organized into a five functional layered model, FC0 to FC4. The layers of the Fibre Channel model are referred to as levels in ANSI documentation. The Fibre Channel architecture is defined by a large series of specifications published by T11 Task Groups for ANSI management.

The Fibre Channel architecture operates at the physical, data-link, and application layers.  Fibre Channel model layers build upon each other starting with FC-0 as the foundation.  One notable exception is the FC-3 layer.  FC-3 builds upon the node-addressing functionality within FC-2.  However, link services defined by FC-3 are required for FC-2 operation.  Hence, FC-3 resides above and below FC-2.  Perhaps it is better to represent FC-2 and FC-3 as peers.