Session is a bidirectional pipe of datagrams between transport and dstConn Destination can be a connection with origin or with eyeball When the destination is origin: - Manager receives datagrams from receiveChan and calls the transportToDst method of the Session to send to origin - Datagrams from origin are read from conn and Send to transport using the transportSender callback.

ErrVithVariableSeverity are errors that have variable severity.

Manager defines the APIs to manage sessions from the same transport.