Every router in an OSPF network advertises a Type 1 LSA.
The Type 1 LSA is a essential part within the link state database.
An entry exists as a Type 1 LSA for every OSPF enabled link including its interface, and attached networks.
Type 1 LSAs are not advertised outside of an area.
The packet fields on a Type 1 LSA give an indication of the Router ID for the advertising router, LSA age, LSA sequence number, link count and link ID.