The Complete IS-IS Routing Protocol - Hannes Gredler, Walter Goralski - Google Books

http://books.google.de/books?id=NxIadsCKZxMC&pg=PA178&dq=%22generation+interval%22&lr=&as_drrb_is=q&as_minm_is=0&as_miny_is=&as_

IS-IS has always been my favourite Interior Gateway Protocol. Its elegant simplicity, its well-structured data formats, its ?exibility and easy extensibility are all appealing – IS-IS epitomizes link-state routing. Whether for this reason or others, IS-IS…