Flow Control in RDMA Networks
The Intel® Ethernet 800 Series supports both iWARP and RoCEv2 RDMA transports. Flow control is strongly recommended for RoCEv2, it can also improve iWARP performance.
| Base Transport | Flow Control Requirements |
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| iWARP TCP | - iWARP runs over TCP, a reliable protocol that implements its own flow control.
- TCP's flow control might be relatively slow to respond in a high-performance, low-latency RDMA environment, especially under bursty traffic patterns.
- Ethernet flow control is optional, can improve performance.
- iWARP mode requires VLAN to be configured fully to enable PFC.
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| RoCEv2 UDP | - RoCEv2 runs over UDP, an unreliable protocol with no built-in flow control.
- RoCEv2 therefore requires a lossless Ethernet network to ensure packet delivery.
- If the irdma driver is in RoCEv2 mode and detects no flow control, it automatically de-tunes, causing lower performance.
- Flow control is always recommended for RoCEv2.
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