This appendix describes the format of OSPF protocol packets and OSPF link state advertisements. The OSPF protocol runs directly over the IP network layer. Before any data formats are described, the details of the OSPF encapsulation are explained.
Next the OSPF Options field is described. This field describes various capabilities that may or may not be supported by pieces of the OSPF routing domain. The OSPF Options field is contained in OSPF Hello packets, Database Description packets and in OSPF link state advertisements.
OSPF packet formats are detailed in Section A.3. A description of OSPF link state advertisements appears in Section A.4.