MMCS is a private Objective-C framework that provides networking support for connecting to cloud services. MMCS may stand for MobileMe Cloud Services or Connection Services. It is used by CloudKitDaemon.framework for a NSURLSession pool which allows a session to be used per-domain among other options. This allows a unique NSURLSession and operation queue to be used for each domain being connected to which allows apps to do multiple requests for different things simultaneously. This is achieved via the C2SessionPool classes, C2 might stand for Cloud v2.