A network apparatus cluster for transferring multiple packets of a communication session to a network node includes a primary unit and a subordinate unit coupled together. The primary unit is operable for receiving the packets comprising a first packet and multiple subsequent packets, for generating a session data set indicating the communication session and a balance data set based on the first packet, and for determining that the subsequent packets belong to the communication session according to the session data set. The balance data set indicates whether the first packet is distributed to the primary unit or the subordinate unit. The subsequent packets are transferred from the primary unit to the network node according to the balance data set.