I spend a lot of time architecting for scalability, availability and security during my daily work. Currently I've got a distributed system consisting of several windows services communicating across machines using WCF and authenticating through Active Directory. In such a situation, if the Active Directory Domain Controller (let's just call it DC from now on) dies, everything more or less dies as no clients/servers are able to authenticate incoming requests anymore. Security is paramount, so the services are not allowed to simply cache the domain logon, thus the logon has the occur at each service call - requiring a...