The simplest currency swap structure is to exchange only the principal with the
counterparty at a specified point in the future at a rate agreed now. Such an agreement performs a function equivalent to a
forward contract or
futures. The cost of finding a counterparty (either directly or through an intermediary), and drawing up an agreement with them, makes swaps more expensive than alternative derivatives (and thus rarely used) as a method to fix shorter term forward exchange rates. However for the longer term future, commonly up to 10 years, where
spreads are wider for alternative derivatives, principal-only currency swaps are often used as a cost-effective way to fix forward rates. This type of currency swap is also known as an FX-swap