open shortest path first is a link state interior routing protocol used to
flood topology information within an mpls core. topology info consists of
loopback reachability and feaure parameters used within the domain.
routers send periodic hello packet in order to discover each other.
once a new router discovered, a master is elected and the database
descriptors are sent out. only the missing lsas are requested,
sent out and acknowldged. once the initial flood is over, just
the changed lsas are sent when arrive from an other router.
neighborships and internal prefixes are described in the
router lsas, redistributed routes are described in the external
lsas, and inter-area routes are described in the summary lsas.
once the lsa database changed, a router calculates shortest path first,
and fills it's routing table.
on broadcast networks they elect a designated router and a backup dr.
the elected dr lists it's peers on the lan in a network lsa, and peers
describe theirselves to this network lsa advertised by the dr, not to each other.
here are the captures for
look for the features within the area-opaque lsa in case of ospfv2
and e-router and e-prefix lsa in case of ospfv3.