There's nothing like a fast switch that appeals to network administrators. Gnodal's new switch, the GS0072, supports 10 Gb and 40 Gb, and will certainly appeal. Aimed at data centers and situations requiring high capacity, low latency and high density, the GS0072 packs 6 Tbytes of capacity with 285-nanosecond port-to-port latency across 72 40-Gbit ports, 288 10-Gbit ports or any combination in between. Granted, not every organization needs that much capacity, but it's there if you need it.
"Gnodal has several key features," explains network architect and Network Computing contributor Greg Ferro. "The number of 40 GbE Ethernet ports is far ahead of other switch vendors, and the choice to use each QSFP port. With 72 by 40 GbE Ethernet ports using QSFP, you have a lot of design choices for a Layer 2 network. For example, you can allocate 12 x 40 GbE for uplinks, and the remaining ports can be 60 x 40 GbE or 240 x 10GbE ports with a 5-to-1 oversubscription. Change the mix according to your needs. And combined with the Gnodal fabric capability, you can scale vertically and horizontally to a large size. Combined with low latency, it's a strong L2 switching product that has no other competitor."
Gnodal switches operate only at Layer 2. There aren't any Layer 3 switch/router functions, except for switch management. Fast is great, but there are fast switches on the market. When Gnodal switches are interconnected, the connected media access controllers (MACs) take advantage of built-in logic to ensure lossless Ethernet, multipath Ethernet, live load balancing and frame ordering end to end. The Gnodal MACs set up a reverse path from port to port, forming a feedback loop that can signal the ingress port of congestion along the path, as well as set up multiple paths automatically. Flows are balanced along the available paths among two or more interconnected Gnodal switches.
In the event of congestion, for example, the egress port signals back along the reverse path the ingress port to pause transmitting and determine a new path. As soon as the last frame starts to exit the egress port, new frames are sent along the new, uncongested path. While there are Ethernet standards for link aggregation (LAG), which bonds multiple uplinks into a single, logical interswitch link, and many vendors have proprietary methods to interconnect one downstream switch to two or more upstream switches, link aggregation has a fundamental problem. Once a flow is assigned to a LAG member, it remains on the member until the link fails. This is called polarization, and in worst-case scenarios it can result in one member being congested while another member is idle.
The live load balancing when going Gnodal to Gnodal makes more efficient use of all available LAG members and can respond to failure more quickly and without loss. The Gnodal switches track frames using a special tag prepended to each frame so no frames are lost and to ensure in-order delivery--two critical features of lossless Ethernet.
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