Sistema Stykovki i Vnutrennego Perekhoda, SSVP (Russian: Система стыковки и внутреннего перехода, System for docking and internal transfer) is a docking standard used by Soviet and Russian spacecraft,[1] sometimes called RDS for Russian Docking System. It has been used on all variants of Soyuz other than the Soyuz 7K-L3 and early flights of the Soyuz 7K-OK, as well as Progress, TKS, ATV, and on all Soviet and Russian space stations.