Tech Primer

Infiniband

What is Infiniband?

It is a channel-based serial-switched fabric Input/ Output technology designed to meet the requirements of a high-speed standard interconnect in large servers. It handles the data flow between processors and I/O devices ensuring greater bandwidth and expandability. The high-speed serial computer bus is used for both internal and external connections. Infiniband’s goal is to connect the CPU (Central Processing Unit) and high-speed device into a cluster for running ‘back office applications.’ Infiniband was called System I/O for some time. It is a full-fledged network that uses Internet Protocol Version 6 with 128-bit addresses, allowing almost limitless device expansion.

What are the advantages in using Infiniband?

Infiniband uses a low-cost bi-directional serial bus with low latency. It uses a switched fabric topology, ensuring that several devices can share the network at the same time. The Infiniband specification creates three performance classes of 1x, 4x, and 12x, each link transmitting 2.5 Gbps in both directions. At its slowest, InfiniBand is on par with the fastest PCI bus, SCSI, Gigabit Ethernet, and Fibre Channel technology. Infiniband is expected to replace the ubiquitous Peripheral Components Interconnect (PCI). Its architecture ensures increased reliability and provides better sharing of data between clustered processors and built-in security of any size.

Which are the companies working on Infiniband?

Infiniband is the result of two competing designs being merged—Future I/O from IBM, HP (Hewlett Packard) and Compaq along with Next Generation I/O (NGIO) developed by Intel, Microsoft and Sun Microsystems. Intel has played the lead role in developing Infiniband.

What are the features of Infiniband?

Some of the features of Infiniband are a layered protocol, multiple layer connectivity, packet-based communications, multicast capable packet, end node fault tolerance, subnet management, varied link speeds of 1x, 4x, 12x, 2.5 to 30 Gigabit per second transfers, PCB, copper, and fibre links and support for remote DMA.

What are its architectural details?

InfiniBand architecture allows for multiple connect paths scaling up to 30 Gigabit per second in performance. Since the full duplex serial communications nature of IBA specifies a requirement of only four wires, a high-speed 12x implementation requires a moderate 48 wires (or pathways). This spec is quite impressive, especially as compared to the 90-pin design of the PCI-X architecture when utilised for back plane connectivity. Other specifications of the IBA physical layer include provisions for custom back plane I/O connectors and hot swapping capabilities. For cost efficiency, IBA at the network interconnect level will rely on current off-the-shelf copper-twisted pair and fibre optic cabling technologies.

—For more information visit www.catc.com/conntech/infiniband.html

—Garima Grover

grover_garima@hotmail.com