When clients and services authenticate, Windows Communication Foundation (WCF) supports a mode where the service credential is negotiated as part of authentication. In such scenarios, a potentially multi-leg exchange occurs between the client and the service to propagate the service credential to the client. The NegotiationTimeout property controls how long the multi-leg exchange can take to complete. However, this timeout only applies if the exchange actually takes more that a single request-response. In cases where the negotiation completes in a single round trip, the timeout does not apply.