In WCF, whats the difference between the binding setting maxConnections and the ServiceBehaviors serviceThrottling settings (maxConcurrentCalls,maxConcurrentInstances,maxConcurrentSessions)?
I'm trying to get my WCF service setup and I'm not exactly sure how those work with each other to limit connections.
Two things are important to consider:
the serviceThrottling behavior is a service-/server-side setting that determines how many concurrent calls, instances and sessions are supported by the server. This is independent of any binding or service endpoint - it's a service-wide setting. This allows you to tweak how many concurrent requests (and/or sessions) a specific service can handle - that depends on things like server "power", RAM, CPU and a lot more factors. Those values are kept fairly low by default, to avoid servers from being "overloaded" and thus rendered unresponsive by large floods of requests (erroneously or maliciously)
the maxConnections setting on the binding is specific to the netTcpBinding (and it's "cousins", like the netNamedPipe and various Azure-oriented net***Relay bindings) and has to do with connection pooling. Much like ADO.NET database connections are pooled, TCP/IP connections to the server can be pooled and reused to reduce the overhead of having to destroy and re-create them. This is mostly a client-side setting (although it also has effects on the server-side), and again: it's specific to the netTcpBinding (and cousins; all based on TCP/IP) and doesn't exist for any of the other bindings.
See: More details on MaxConnections for more, great in-depth insights into the ins and outs of this setting.
