When session manager attempts to put a packet to processor for further processing and the processor's queue is full, it returns an error: feature not implemented to the client. This error is misleading. We need to return a different error which better describes the error.

I think the best candidates are:

1. http://xmpp.org/rfcs/rfc6120.html#stanzas-error-conditions-resource-constraint

2. http://xmpp.org/rfcs/rfc6120.html#stanzas-error-conditions-service-unavailable

With a human readable description: "Server subsystem overloaded, service temporarily unavailable."