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Converged network fuses Ethernet, Infiniband

Posted: 21 Apr 2010 ?? ?Print Version ?Bookmark and Share

Keywords:Infiniband? Ethernet? converged network? Fibre Channel?

Taking a step forward in the race towards converged networks, a trade group announced a capability for layering Infiniband's low latency features on top of Ethernet. The so-called Remote Direct Memory Access (RDMA) over Converged Ethernet (RoCE, pronounced Rocky) is geared for high-performance computing applications, typically running on large clusters.

Infiniband and Ethernet chip and card vendors could announce 10Gbit/s RoCE products before the end of April, according to the Infiniband Trade Association, which developed the technology.

The RoCE products could offer lower latency, price and power consumption that competing cards and chips based on advanced versions of Ethernet. However, it will not support Internet Protocol, making them unsuitable for use in majority of computer networks that require IP routing.

For several years, engineers have been consolidating features from multiple networks as a way to simplify the management and lower the costs of business networking. In 2008, they paved the way for merged storage and networking by creating the Fibre Channel over Ethernet specification. RoCE extends the consolidation to include interprocessor communications used in large computer clusters for a range of database, financial, simulation and scientific uses.

Specifically RoCE layers Infiniband data and transport features (layers three and four respectively of the OSI stack) on top of the physical and media access control layers (layers 1 and 2) of Ethernet. Infiniband was one of the first networks to implement RDMA techniques and as such its upper layers are relatively simple and mature compared to Ethernet which uses a set of relatively newer overlapping protocols.

Mellanox, one of the primary producers of Infiniband chips, will implement the Infiniband layers in hardware to deliver latencies as low as 1.3?s. Many Ethernet chip and card makers are expected to implement the Infiniband features in software running on a host processor and thus deliver latencies closer to those of today's advanced Ethernet products with latencies of seven to 10?s.

The lower latencies can deliver up to ten-fold performance boost in Oracle databases optimized for Infiniband. The low latencies are required for data-intensive applications such as simulations running in a computer cluster.

Other apps, such as the batch rendering of a large animated movie, can be handled using systems with the higher latency figures. Ethernet vendors who may adopt software versions of RoCE include Broadcom, Emulex, Intel and QLogic.

"Think of [RoCE] as a way to bring Infiniband applications which are predominantly based on clusters on to a common Ethernet converged fabric," said Michael Krause, an I/O specialist at Hewlett-Packard who co-wrote a 2009 paper on RoCE. "Nearly all of the [existing networking] software should come across without modification with the exception of the Infiniband management code which is not applicable to an Ethernet infrastructure," he added.

The software compatibility is due in part to the broad use of so-called Open Fabrics middleware, open source code that supports RoCE in its version 1.2.1. HP is taking an agnostic stance on the variety of merged Ethernet, Infiniband and Fibre Chanel network technologies emerging, supporting whatever flavors users request.

"While RoCE may be seen by some as a threat, others will see it as validating an Ethernet-centric interconnect strategy as well as reinforcing the merits of RDMA technology which has been seen as the main strength of Infiniband and [advanced Ethernet] to date," Krause said.

Flow-control support
RoCE also depends in part on a version of Ethernet that supports so-called priority flow control, a technique for maintaining quality of service that is also used for Fibre Channel over Ethernet. Cisco Systems Nexus switch already supports the flow-control capability and several other vendors will begin supporting it over the next six months, said Sujal Das, a senior director of product management at Mellanox.

Work is still going on in a handful of IEEE committees to hammer out standards that add more robustness to Ethernet networks.

Meanwhile, Teranetics announced the TN8000, a new family of 40nm transceivers for 10Gbit/s Ethernet over copper. The 10GBase-T parts include a four-port device that dissipates less than 4W per port while carrying data 100m.

Last year, competitor Aquantia announced it will ship in late 2010 10GBase-T transceivers consuming as little as 3.5 W. Another pioneer in the field, Solarflare Communications, announced in August a single-chip 10GBase-T controller that consumes 8W.

"We believe that low-power 40nm designs like [the TN8000] will lead to broader adoption of 10-Gigabit Ethernet over copper in the data center," said Jag Bolaria, senior analyst at The Linley Group in a prepared statement.

- Rick Merritt
EE Times

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