NDR

This glossary covers a set of acronyms that define the evolution of high-speed data transmission, primarily within the InfiniBand interconnect standard, which is vital for High-Performance Computing (HPC) and AI. The terms SDR, DDR, and QDR describe fundamental signaling techniques that transfer data one, two, or four times per clock cycle. Succeeding generations—including FDR, EDR, HDR, NDR, and future standards like GDR—are named data rates that mark significant, sequential increases in aggregated bandwidth. Collectively, these terms map the constant industry effort to achieve maximum throughput and minimum latency in modern data centers.

SDR (Single Data Rate) is an InfiniBand standard introduced in 2001, utilizing 8b/10b encoding with a per-lane rate of 2.5 Gbit/s. A 4x link delivers a theoretical throughput of 10 Gbit/s, with an actual rate of approximately 8 Gbit/s. SDR uses CX4 connectors.

DDR (Double Data Rate) is an InfiniBand standard introduced in 2005, also employing 8b/10b encoding but doubling the per-lane rate to 5 Gbit/s. A 4x link achieves a theoretical throughput of 20 Gbit/s, with an actual rate of around 16 Gbit/s. It similarly relies on CX4 connectors.

QDR (Quadruple Data Rate) is an InfiniBand standard introduced in 2007, retaining 8b/10b encoding while increasing the per-lane rate to 10 Gbit/s. A 4x link offers a theoretical throughput of 40 Gbit/s, with an actual rate of roughly 32 Gbit/s. QDR marked the transition to QSFP+ connectors.

FDR (Fourteen Data Rate) is an InfiniBand standard introduced in 2011, adopting the more efficient 64b/66b encoding with a per-lane rate of 14.0625 Gbit/s. A 4x link provides a theoretical throughput of 56 Gbit/s, with an actual rate of approximately 54.54 Gbit/s.

FDR also uses QSFP+ connectors; however, note that QSFP+ is a standard 40G Ethernet connector. When FDR devices require QSFP+ cables, ensure they are labeled as FDR-compatible to avoid compatibility issues.

FDR10, introduced in 2011, is a non-standard InfiniBand data rate. Its 4x ports operate at 10.3125 Gbit/s per lane with 64b/66b encoding, achieving an effective bandwidth of 40 Gbit/s. Due to the higher encoding efficiency (64b/66b), FDR10 supports greater bandwidth than QDR.

EDR (Enhanced Data Rate) is an InfiniBand standard introduced in 2014, utilizing 64b/66b encoding with a per-lane rate of 25.78125 Gbit/s. A 4x link delivers a theoretical throughput of 103.125 Gbit/s, with an actual rate of approximately 100 Gbit/s.

EDR adopts QSFP28 connectors. Due to its speed alignment with 100GE Ethernet, ensure QSFP28 connectors are explicitly labeled as InfiniBand EDR-compatible to avoid compatibility issues.

Note: The ConnectX-5 EDR NIC uses a PCIe 3.0 x16 interface. Due to bandwidth limitations, dual-port EDR QSFP28 NIC operation at 100 Gb/s per port cannot achieve an aggregate 200 Gb/s throughput.

HDR (High Data Rate) is an InfiniBand standard introduced in 2018, employing 256b/257b encoding with a per-lane rate of 53.125 Gbit/s. A 4x link provides a theoretical throughput of 212.5 Gbit/s, with an actual rate of around 200 Gbit/s.

HDR uses QSFP56 connectors. Similarly, as its speed matches 200GE Ethernet, verify QSFP56 connectors are marked for InfiniBand HDR support.

Note: ConnectX-6 HDR NICs utilize a PCIe 4.0 x16 interface. Due to performance limitations of this interface, when both network ports of a dual-port HDR QSFP56 NIC operate at 200 Gb/s, the combined total bandwidth cannot exceed 400 Gb/s.

HDR100, also introduced in 2018, differs from HDR by using a 2x link configuration with 53.125 Gbit/s per lane, yielding a total rate of 100 Gbit/s. It similarly employs QSFP56 connectors.

While HDR100 and EDR both offer 100G speeds, HDR100 leverages 50G PAM4 modulation, whereas EDR uses 25G NRZ. Consequently, HDR100 products cannot be used with EDR network interface cards.

NDR (Next Data Rate) is an InfiniBand standard introduced in 2022, employing 256b/257b encoding with a per-lane rate of 106.25 Gbit/s. A 4x link achieves a theoretical throughput of 425 Gbit/s, with an actual rate of approximately 400 Gbit/s.

OSFP connectors come in two hardware variants: finned top (used in NVIDIA Quantum™-2 NDR Switches) and flat top (used in NVIDIA DGX systems or ConnectX-7 NICs). QSFP112 connectors are exclusive to NVIDIA ConnectX-7 NICs. Due to their compact size, they are typically found on dual-port QSFP112 CX7 NICs.

NDR200, also introduced in 2022, adopts a 2x link configuration with 106.25 Gbit/s per lane, delivering a total rate of 200 Gbit/s.

NDR200 uses the same connectors as NDR. Although NDR connectors are designed for 400G speeds, they can auto-detect NDR200 devices and throttle down to 200G (by disabling two of the four lanes).

Although NDR200 and HDR share the same data rate, NDR200 employs 100G PAM4 modulation while HDR uses 50G PAM4 modulation. Consequently, they are not interoperable.

XDR (eXtreme Data Rate) is an InfiniBand standard introduced in 2024, utilizing 256b/257b encoding with a per-lane rate of 212.5 Gbit/s. A 4x link delivers a theoretical throughput of 850 Gbit/s, with an actual rate of approximately 800 Gbit/s.

XDR employs OSFP connectors, identical to NDR, with two variants: OSFP (finned top) for switches and OSFP (flat top) for NICs.

As the latest InfiniBand technology, XDR entered commercial deployment in 2025 with NVIDIA's release of the NVIDIA Quantum-X800 switch and NVIDIA ConnectX-8 XDR NIC.

Note: Both models include an additional OSFP port for UFM management, a feature absent in NDR switches.

The Mellanox ConnectX-8 NIC is currently available only in a single-port XDR OSFP (flat top) configuration, with backward compatibility for NDR OSFP (flat top).

GDR (Gxx Data Rate) is the next-generation InfiniBand standard, targeting double the speed of XDR. With XDR products commercially launched in 2025, GDR is expected to finalize its specification in 2026 and achieve commercial availability by 2028.