For technicians who have regular contact with optical transceiver modules, the transceiver types such as SFP, QSFP28, QSFP-DD, etc. are all familiar words. Who defines these modules and how do the specifications become standards? It’s reasonable to talk about the MSA standard.
If you search for the specifications of an optical transceiver, you may find “MSA compliant” is written on the protocol section. MSA, short for multi-source agreement, is an agreement between multiple manufacturers to make products that have the same basic functionality and operability across different vendors.
Though MSA has become a recognized standard organization in optical communication industry, it is not an official one. It is known that IEEE (Institute of Electrical and Electronics Engineers) is the world’s largest technical professional organization and IEEE communities set up standards for transceivers. However, at one time, the interface types of optical transceivers from different equipment manufacturers were diversified. To solve the insufficiency of interoperability, multiple manufacturers established an organization to standardize the form, fit and function of transceiver modules, therefore MSA came into being and supplement with IEEE standards.
Products that adhere to MSAs include optical transceivers, fiber optic cables, and other networking devices. As for optical transceivers, MSA standards define not only the form factors, but also its electrical interface and optical interface, therefore forming a complete optical transceiver standard. Consider SFP MSA for example, the SFP transceiver is not standardized by any official standards body, but by SFP MSA.
As MSA defines the form factors and interfaces of an optical transceiver, transceiver vendors rely on MSAs when designing their systems, ensuring interoperability and interchangeability between interface modules. For users, there are three main reasons why MSA matters to optical transceivers.
First of all, MSA standard enables multiple choices for end users. The MSA compliant transceivers are equipped with the same form factor, thus many third-party transceivers provide the same functionality as the name-brand products, offering users more selections. In simple terms, customers can choose whatever optical transceivers from any third-party vendors as they like, as long as these modules meet the MSA standards and have good compatibility.
The second thing that matters is the cost. MSA standards prevent the optical transceiver market from being monopolized by some major manufacturers. A plenty of vendors using MSAs must compete with each other so as to gain their share of the transceiver market. Such a situation helps reduce the cost for the end users.
In addition, MSA compliant transceivers guarantee the identical form factor and functionality to the transceivers of other brands that follow the MSA standards, making it possible to normally use the third-party transceivers in the networking equipment such as switches and routers of other brands, enabling both interoperability and security.
Tracing the development of MSA organization since GBIC MSA specifications were defined, MSA process has helped accelerate the acceptance of modules such as SFP+, CFP and QSFP-DD transceivers over the past two decades, allowing optical transceivers to support greater bandwidth of 400G. Some approved fiber optic transceiver multi-source agreements are listed in the table below.
|GBIC||Gigabit Interface Converter||
Designed for Gigabit Ethernet, SDH/SONET (2.5Gb/s) and Fibre Channel (4Gb/s); Superseded by SFP
|SFP||Small Form-factor Pluggable||Designed for Gigabit Ethernet, SDH/SONET (2.5Gb/s) and Fibre Channel (4Gb/s)|
|XENPAK||Fiber Optic Transceiver for 10Gb Ethernet||Superseded by X2 and SFP+|
|X2||Fiber Optic Transceiver for 10Gb Ethernet||Superseded by SFP+|
|XFP||10 Gigabit Small Form Factor Pluggable||Designed for 10G. Supports 8Gb/s Fibre Channel, 10Gb/s Ethernet and Optical Transport Network|
|CSFP||Compact small form-factor pluggable||A version of SFP supporting 1.25G Ethernet/SDH/SONET/Fiber Channel|
|SFP+||Small Form-factor Pluggable Plus||Designed for 10 Gb/s. Supports 8Gb/s Fibre Channel, 10Gb/s Ethernet and Optical Transport Network standard OTU2|
|QSFP/QSFP+||Quad Small Form-factor Pluggable 40G||Supports Ethernet, Fibre Channel, InfiniBand and SONET/SDH standards up to 40GB/s and 100Gb/s|
|CDFP||400 Form-Factor Pluggable||Supports 400Gb/s (16 × 25G)|
|Micro QSFP||Micro Quad Small Form-Factor Pluggable||Designed for 100G Ethernet, expected for 200G applications|
|CFP||C Form-Factor Pluggable (100G)||
Optical transceiver form factors supporting 40Gb/s and 100Gb/s; Define CFP, CFP2 for 10G, 40G, 100G and 400G CFP4 for 40G and 100G, and CFP8 for 400G
|SFP28||Small Form-Factor Pluggable 28||The third generation of SFP interconnect systems, designed for 25G applications|
|QSFP28||Quad Small Form-Factor Pluggable 28||Designed for 100G|
|QSFP-DD||Quad Small Form-factor Pluggable Double Density||Supports 400Gb/s (8 × 50G)|
|OSFP||Octal Small Form Factor Pluggable||Support 400Gb/s (8 × 50G)|