Distributoris responsible for assigning new calls to Create Session to a
Node. It's possible that the first attempt to create a session fails for any number of reasons, and so a well-behaved implementation will continue trying additional nodes until either a session starts or nothing is successful.
To complicate matters, local ends may send a session request that is one of two different dialects (presumably in the future there may be more. *sigh*) and care must be taken to ensure that dialects match, or that a converter of some sort is added. The Node may be the part of the system responsible for adding this converter.