A network node within a network includes a first receive buffer, first buffer management, a second receive buffer and second buffer management. A computer system comprising a directed acyclic graph data structure representing a platform hierarchy; and a control arrangement for traversing the directed acyclic graph to determining paths therein affected by removal of a device. The active regions of the third and fourth transistors have a longer length in the channel length direction than that of the active regions of the first and second transistors. Sealing relationships are formed between the coupler and the insert, and between the insert and the received second container.