Plexxi Flattens Networks Using Optical Links

Uncloaking from stealth mode, startup Plexxi has revealed technology that attempts to “flatten” the network through a mix of traditional high-speed Ethernet and dedicated optical links.

Plexxi’s Switch 1 starts at $64,000, including all inter-switch optics and cabling; the associated Plexxi Control software starts at $5,000 per switch. Monthly pricing options are available. The company refers to its approach as “affinity networking,” reasoning that, since most networks don’t evenly distribute data, assigning networking resources evenly across the network makes no sense.

“Big data, mobile and XaaS are bringing on new application connectivity requirements and more intense workloads at an accelerating pace. Legacy network switching architectures cannot respond to application needs,” David Husak, chief executive of Plexxi, wrote in a statement.

Plexxi, he added, “is on a mission to replace this mess with a complete SDN system for the data center—designed from the ground up—that makes networking simple, efficient and transparent.”

Instead of sending data up from an endpoint to a central switch and back down, Plexxi tech connects those endpoints using what it calls LightRail: two full-duplex optical interfaces that connect each switch and deliver 240 Gbits/s each—as far as LightRail is concerned, there’s only two connections per switch. The LightRail technology creates a Layer 1 optical mesh network (or ring topology) between the switches, controllable by the related Plexxi Control software. Plexxi Control dynamically and continuously plots the connectivity solutions needed to optimize the network.

Plexxi’s data sheet claims that each LightRail connection delivers 240 Gbits/s each, full duplex, but a related blog post claims 400 Gbits/s in aggregate. That’s accommodated by the other ports on the switch, according to Mat Mathews, the vice president of product management at Plexxi. Each 1RU switch contains 32 10GbE and 2 40GbE connections in addition to LightRail.

“The press release mentioned 400 Gbps of ‘dynamically assignable core bandwidth,’ that is because there are always at least 2×10 GbE’s to neighbor switches to the east and to the west that we don’t allow to be re-assigned,” Mathews wrote in an email. “So that is 80 Gbps [full duplex]. The remaining 20 10-GbE channels are dynamically assignable to either adjacent switches or non-adjacent switches. There are some finer details in how the assignments work, but that is the general gist.”

Plexxi offers two versions of its switch, with just a difference in fan direction (front-to-back versus back-to-front) for different hot- and cold-aisle setups. Typical power draw is 120 watts, according to the company.

How It Works

So how does Plexxi’s LightRail interact with the more traditional Ethernet interfaces?

Each switch features an electrical domain (with a standard merchant silicon L2/L3 chip) as well as an optical domain. “The servers connect to the switch over Ethernet and into the electrical domain, which connects to the optical domain (also over Ethernet),” Mathews explained. “The optical domain multiplexes 24 x 10 GbE Ethernet interfaces coming out of the optical domain over 2 “LightRail” optical interfaces, one heading east (12 channels) to a neighboring switch and one heading west (12 channels) to a neighboring switch.”

Each switch includes an optical mux/demux and an optical crossbar, and Plexxi was able to “logically connect non-adjacent switches in the optical domain (without any electrical processing required),” according to Mathews. That allows the platform to create arbitrary, software-defined topologies that align with actual application characteristics.

The Plexxi Control software tool collects information about the resources deployed as part of various application groupings, as well as where those resources are physically located within the network. “By collecting some very basic policy information (i.e. this application workload is sensitive to bandwidth, or latency, etc) we can calculate the best possible topology and reconfigure the physical topology dynamically,” Mathews continued, “as well as manipulate flow forwarding (like traditional SDN aims to do).”

He went on to claim that optical interconnect is a “very simple, yet dynamic” method of creating larger-scale topologies. Whereas a typical setup might demand a whole separate aggregation tier of switches in order to connect access switches, with the topology between that aggregation tier and access tier hardwired over discreet cables. “In our system you don’t need that tier, instead you have great degrees of flexibility of what the logical wiring looks like.”

In some of the company’s installations, “customers use standard Ethernet access to servers and standard Ethernet ‘uplinks’ to go to their traditional aggregation tier, but then use the optical LightRail as sort of a very high-bandwidth ‘east-west’ highway for server to server and server-to-storage traffic,” he concluded. “In other cases, customers get rid of the aggregation tier altogether (in this case this is because they predominately have only “east-west” traffic and connect our Plexxi ring directly to their core for outbound traffic).”

Editor’s Note: The platform’s technical details have been updated.

 

Image: Plexxi

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