InfiniBand


InfiniBand is a computer networking communications standard used in high-performance computing that features very high throughput and very low latency. It is used for data interconnect both among and within computers. InfiniBand is also used as either a direct or switched interconnect between servers and storage systems, as well as an interconnect between storage systems. It is designed to be scalable and uses a switched fabric network topology.
, it was the most commonly used interconnect in supercomputers. Mellanox and Intel manufacture InfiniBand host bus adapters and network switches, and, in February 2016, it was reported that Oracle Corporation had engineered its own InfiniBand switch units and server adapter chips for use in its own product lines and by third parties. Mellanox IB cards are available for Solaris, FreeBSD, RHEL, SLES, Windows, HP-UX, VMware ESX, and AIX.
As an interconnect, IB competes with Ethernet, Fibre Channel, and Intel Omni-Path.
The technology is promoted by the InfiniBand Trade Association.

Specification

Performance

Links can be aggregated: most systems use a 4× aggregate. 8× and 12× links are typically used for cluster and supercomputer interconnects and for inter-switch connections.
InfiniBand also provides RDMA capabilities for low CPU overhead.

Topology

InfiniBand uses a switched fabric topology, as opposed to early shared medium Ethernet. All transmissions begin or end at a channel adapter. Each processor contains a host channel adapter and each peripheral has a target channel adapter. These adapters can also exchange information for security or quality of service.

Messages

InfiniBand transmits data in packets of up to 4 KB that are taken together to form a message. A message can be:
In addition to a board form factor connection, it can use both active and passive copper and optical fiber cable.
QSFP connectors are used.
The InfiniBand Association also specified the CXP connector system for speeds up to 120 Gbit/s over copper, active optical cables, and optical transceivers using parallel multi-mode fiber cables with 24-fiber MPO connectors.

API

InfiniBand has no standard API. The standard only lists a set of verbs such as ibv_open_device or ibv_post_send, which are abstract representations of functions or methods that must exist. The syntax of these functions is left to the vendors. Sometimes for reference this is called the verbs API. The de facto standard software stack is developed by OpenFabrics Alliance. It is released under two licenses GPL2 or BSD license for GNU/Linux and FreeBSD, and as Mellanox OFED for Windows under a choice of BSD license for Windows. It has been adopted by most of the InfiniBand vendors, for GNU/Linux, FreeBSD, and Windows. IBM states this at their knowledge center on verbs API:
A presentation from Mellanox Technologies, dated 2014, with title "Verbs programming tutorial" states on page 31:
InfiniBand originated in 1999 from the merger of two competing designs: Future I/O and Next Generation I/O. This led to the formation of the InfiniBand Trade Association, which included Compaq, Dell, Hewlett-Packard, IBM, Intel, Microsoft, and Sun. At the time it was thought some of the more powerful computers were approaching the interconnect bottleneck of the PCI bus, in spite of upgrades like PCI-X. Version 1.0 of the InfiniBand Architecture Specification was released in 2000. Initially the IBTA vision for IB was simultaneously a replacement for PCI in I/O, Ethernet in the machine room, cluster interconnect and Fibre Channel. IBTA also envisaged decomposing server hardware on an IB fabric. Following the burst of the dot-com bubble there was hesitation in the industry to invest in such a far-reaching technology jump.

Timeline

Ethernet over InfiniBand, abbreviated to EoIB, is an Ethernet implementation over the InfiniBand protocol and connector technology.
EoIB enables multiple Ethernet bandwidths varying on the InfiniBand version.
Ethernet's implementation of The Internet Protocol Suite, usually referred to as TCP/IP, is different to some of the implementations used on top of the InfiniBand protocol in IP over IB.
TypeLanesBandwidth Compatible Ethernet TypeCompatible Ethernet Quantity
SDR12.5GbE to 2.5 GbE2 x GbE to 1 x 2.5 GbE
SDR410GbE to 10 GbE10 x GbE to 1 x 10 GbE
SDR820GbE to 10 GbE20 x GbE to 2 x 10 GbE
SDR1230GbE to 25 GbE30 x GbE to 1 x 25 GbE + 1 x 5 GbE
DDR15GbE to 5 GbE5 x GbE to 1 x 5 GbE
DDR420GbE to 10 GbE20 x GbE to 2 x 10 GbE
DDR840GbE to 40 GbE40 x GbE to 1 x 40 GbE
DDR1260GbE to 50 GbE60 x GbE to 1 x 50 GbE + 1 x 10 GbE
QDR110GbE to 10 GbE10 x GbE to 1 x 10 GbE
QDR440GbE to 40 GbE40 x GbE to 1 x 40 GbE