Sets the size, in bytes, of the largest LSP the router is configured to receive and store, defaulting to 1492 and ranging 1492-16000; it should be at least as large as the biggest isisSysLevelOrigLSPBuffSize used anywhere in the network, and the router will still try to store and flood larger LSPs than this if resources allow, to avoid breaking networks with mismatched buffer-size configurations. An admin raises this when the network's LSPs are expected to exceed the 1492-byte default, for example on an area with many redistributed routes inflating LSP size.