1. A method performed by a network access device for network traffic analysis of a plurality of client devices in a local area network (LAN) associated with the network access device, the method comprising: maintaining, by the network access device, a hierarchical key combination traffic analysis (HKCTA) table for each of the plurality of client devices of the LAN (LAN devices) to store network traffic statistics of each LAN device, wherein the HKCTA includes a plurality of entries identified by a plurality of keys, each key being formed based on a combination of zero or more packet attributes of packets or flow attributes of a network flow associated with the packets (packet/flow attributes) exchanged by the LAN device, wherein each key is formed based on a unique combination of zero or more packet/flow attributes having at least one non-overlapped packet/flow attribute compared to a remainder of the plurality of keys, wherein each key represents one of a plurality of hierarchical levels of a hierarchy of the plurality of entries, wherein each level of the hierarchy includes all packet/flow attributes of its parent hierarchical level plus at least one additional packet/flow attribute that is not present in its parent hierarchical level, and wherein each hierarchical level excludes at least one packet/flow attribute of its child hierarchical level if there is any child hierarchical level; in response to a first packet exchanged by a first of the plurality of LAN devices, inspecting, by a packet inspector of the network traffic device, a plurality of packet/flow attributes associated with the first packet; identifying a plurality of entries of a first HKCTA table associated with the first LAN device, wherein the entries of the first HKCTA table are identified based on a plurality of first keys representing combinations of the packet/flow attributes associated with the first packet; populating, by a traffic analysis (TA) module of the network access device, the identified entries of the first HKCTA table based on network traffic data obtained from the identified packet/flow attributes, the network traffic data including an amount of traffic carried by the first packet transmitted or received by the first LAN device; and periodically transmitting network traffic statistics represented by the first HKCTA table to a remote management server over the Internet, wherein the network access device is one of a plurality of network access devices managed by the management server over the Internet, and wherein the remote management server is to incorporate the network traffic statistics into an aggregated TA table maintained by the management server.