Security Negotiation and Timeouts
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 multileg exchange occurs between the client and the service in order to propagate the service credential to the client. The NegotiationTimeout property controls how long the multileg 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.