http://www.rfc-editor.org/rfc/rfc5311.txt
RFC 5311: Simplified Extension of Link State PDU (LSP) Space for IS-IS, D. McPherson, L. Ginsberg, S. Previdi, M. Shand2009-02-01T23:00:00-00:00This document describes a simplified method for extending the Link State PDU (LSP) space beyond the 256 LSP limit. This method is intended as a preferred replacement for the method defined in RFC 3786. [STANDARDS-TRACK]