This is the size of the largest buffer the router is designed or configured to store, which should be at least as big as the maximum ciiSysLevelOrigLSPBuffSize supported by the system, and if resources allow the router will store and flood LSPs larger than this to help avoid problems with mismatched values elsewhere in the network. It sets the largest LSP fragment the router guarantees it can process without truncation, so a value left too low on a router in an area with larger LSPs elsewhere can silently mishandle oversized LSPs it receives. For example, an admin migrating to wide-metric TE with many sub-TLVs per LSP might need to raise this from the legacy 1492-byte default to something like 4096 bytes to accommodate the larger LSPs other routers are now originating.