OVS Kernel Datapath Offload

Open Virtual Switch (OVS)

Open vSwitch is a production quality, multilayer virtual switch licensed under the open source Apache 2.0 license. It is designed to enable massive network automation through programmatic extension, while still supporting standard management interfaces and protocols.

Figure 1 – OVS

Chelsio OVS Kernel Datapath Offload Solution

The Terminator 5 (T5) and Terminator 6 (T6) ASICs from Chelsio Communications, Inc., are highly integrated, hyper-virtualized 1/10/25/40/50/100Gb Ethernet controllers with full offload support for a complete Unified Wire solution. Chelsio T5 and T6 adapters enable a Unified Wire for LAN, SAN and cluster applications, built upon a high bandwidth and low latency architecture, along with a complete set of storage and cluster protocols operating over Ethernet (iSCSI, SMBD, iWARP, NVMe over Fabrics, Crypto, and FCoE). Unified Wire means having the ability to utilize all offload or non-offload protocols at the same time, over the same link, using the exact same firmware, host software and adapter.

Chelsio solution scales to a true 100 Gigabit line rate operation, from a single TCP connection to thousands of connections. It also offloads OVS datapath flow match entries and action processing onto Chelsio adapter for hardware acceleration of OVS datapath flow processing. This is achieved by adding, removing and synchronizing the OVS flow table entries on adapter with following capabilities:

Figure 2 – Chelsio OVS offload solution
  • Offloaded kernel data path, Acceleration via Match, Action, Tunnels and lookups Offload to NIC. OVS flow tables offloaded to adapter
    • Match / Action supported at the Port
    • L2 learning for new flows (hit/miss)
  • NVGRE/VXLAN tunnel encap/decap: Offloads for tunnels – Header caching / Hardware offloading
  • OVS monitoring and statistics: Retrieving flow statistics (viz. flow-hit count, etc.) from adapter as and when requested by OVS & the management plane
  • WDP (wildcard datapath) abstraction/offload

Chelsio 1/10/25/40/50/100Gb Ethernet controllers and adapters are capable of offloading OpenFlow and non-OpenFlow network traffic simultaneously, including DPDK interfaces using OVS for packet processing, tunnel handling (e.g. VXLAN / IPsec), NAT, IP stack (ARP, route lookup, frag tracking, fragment / defragment) and other kernel networking functionalities. A high performance, scalable network I/O is delivered by leveraging built in 264 ports eSwitch and Traffic Management capabilities and features like traffic classifier, load balancer, and Firewall which are supported at port level by all Chelsio adapters.

Following is the OVS performance summary, comparing Chelsio T5 based 40GbE adapter with OVS offload capabilities and a traditional NIC using software based switching:

The Chelsio Adapter:

  • Switching rate is about 3X higher than standard NIC.
  • Returns ½ CPU per node for use by applications.
  • Has superior scaling for large number of flow entries.

Supported Adapters and Operating Systems

Chelsio OVS Kernel Datapath Offload and other related capabilities are supported by all T5 and T6 adapters and available for standard Linux Platforms.

To download latest Chelsio drivers/software, visit
To know more about Chelsio Unified Ethernet Adapters, visit