QSFP-DD stands for Quad Small Form Factor Pluggable Double Density. The double density aspect of this form factor refers to the doubling of the number of high-speed electrical interfaces supported, in comparison with standard QSFP28 modules. Unlike the current QSFP system, QSFP-DD modules feature an additional row of contacts providing for an eight-lane electrical interface. QSFP-DD can support 36 ports of 400GbE in a single Rack Unit (RU) providing over 14Tb/s of bandwidth.