However, the achievable throughput can be increased by performing network coding either within each layer, referred to as intra-layer network coding, or across different layers, referred to as inter-layer network coding. Figs. 5(c)-(e) show intra-layer network coding being applied to our example, where the network given in Fig. 5(a) is split into subgraphs and each subgraph transmits a layer of the data stream with capacity equal to one. In this way, network coding allows both the sink nodes t1 and t2 to achieve the total aggregate throughput of seven. Fig. 5(f) shows inter-layer network coding being applied to our example. In this method, the intermediate node 3 linearly encodes layers L1, L2, L4, and L5 into L1+L4, and L2+L5 to achieve a maximum throughput of