SDN control of hybrid packet / optical leaf and spine network

9/19 DemoFriday: CALIENT, Cumulus Networks and InMon Demo SDN Optimization of Hybrid Packet / Optical Data Center Fabric demonstrated how network analytics can be used to optimize traffic flows across a network composed of bare metal packet switches running Cumulus Linux and Calient Optical Circuit switches.

The short video above shows how the Calient optical circuit switch (OCS) uses two grids of micro-mirrors to create optical paths. The optical switching technology has a number of interesting properties:

• Pure optical cut-through, the speed of the link is limited only by the top of rack transceiver speeds (i.e. scales to 100G, 400G and beyond without having to upgrade the OCS)
• Ultra low latency - less than 50ns
• Lower cost than an equivalent packet switch
• Ultra low power (50W vs. 6KW for comparable packet switch)

The challenge is integrating the OCS into a hybrid data center network design to leverage the strengths of both packet switching and optical switching technologies.

The diagram shows the hybrid network that was demonstrated. The top of rack switches are bare metal switches running Cumulus Linux. The spine layer consists of a Cumulus Linux bare metal switch and a Calient Technologies optical circuit switch. The bare metal switches implement hardware support for the sFlow measurement standard, and a stream of sFlow measurements is directed to an InMon's sFlow-RT real-time analytics engine, which detects and tracks large "Elephant" flows. The OCS controller combines the real-time traffic analytics with accurate topology information from Cumulus Networks' Prescriptive Topology Manager (PTM) and re-configures the packet and optical switches optimize the handling of the large flows - diverting them from the packet switch path (shown in green) to the optical circuit switch path (shown in blue).

The chart shows live data from the first use case demonstrated. A single traffic flow is established between servers. Initially the flow rate is small and the controller leaves it on the packet switch path. When the flow rate is increased, the increase is rapidly detected by the analytics software and the controller is notified. The controller then immediately sets up a dedicated optical circuit and diverts the flow to the newly created circuit.

The demonstration ties together a number of unique technologies from the participating companies:

• Calient Technologies
  • Optical Circuit Switch provides low cost, low latency bandwidth on demand
  • OCS controller configures optimal paths for Elephant flow
• Cumulus Networks
  • Cumulus Linux is the 1st true Linux Networking Operating System for low cost industry standard Open Networking switches
  • Prescriptive topology manager (PTM) provides accurate topology required for flow steering
  • Open Linux platform makes it easy to deploy visibility and control software to integrate the switches with the OCS controller.
• InMon Corp.
  • Leverage sFlow measurement capabilities of bare metal switches
  • sFlow-RT analytics engine detects Elephant flows in real-time

To find out more and see the rest of the demo, look out for the full presentation recording and Q&A when it is posted on SDN Central in a couple of weeks.

Update November 6, 2014: The recording is now available, Q&A + Video: SDN Helps Detect and Offload Elephant Flows in Hybrid Packet/Optical Fabric. 

Other related articles include:

• Helios: A Hybrid Electrical/Optical Switch Architecture for Modular Data Centers, describes early work in building hybrid networks that integrate packet and optical switches - original research paper describing advantages of hybrid architecture.
• RESTful control of Cumulus Linux ACLs - demonstrates how priority marking can be used to improve network latency. This complementary technology can be combined with optical circuit switching to further improve network performance.
• SDN fabric controller for commodity data center switches - overall architecture for building self tuning networks from commodity switches.