A.3 OSPF Packet Formats
There are five distinct OSPF packet types. All OSPF packet types
begin with a standard 24 byte header. This header is described
first. Each packet type is then described in a succeeding section.
In these sections each packet's division into fields is displayed,
and then the field definitions are enumerated.
All OSPF packet types (other than the OSPF Hello packets) deal with
lists of link state advertisements. For example, Link State Update
packets implement the flooding of advertisements throughout the OSPF
routing domain. Because of this, OSPF protocol packets cannot be
parsed unless the format of link state advertisements is also
understood. The format of Link state advertisements is described in
The receive processing of OSPF packets is detailed in Section 8.2.
The sending of OSPF packets is explained in Section 8.1.