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RFC 1583 http://tools.ietf.org/html/rfc1583
RFC 2328 http://tools.ietf.org/html/rfc2328

IETF RFC1583 defines the OSPF (Open Shortest Path First) protocol as a link-state routing protocol used for routing IP.

OSPF is an interior gateway protocol which is used for routing within a group of routers. It uses link-state technology in which routers send each other information about the direct connections and links which they have to other routers.

The OSPF header structure is shown in the illustration below.

8
16
32 bits

Version No.

Packet Type

Packet length

Router ID

Area ID

Checksum

AU type

Authentication

OSPF header structure

Version number
Protocol version number (currently 1).

Packet type
Valid types are as follows:

1 Hello
2 Database Description
3 Link State Request
4 Link State Update
5 Link State Acknowledgment.

Packet length
The length of the protocol packet in bytes. This length includes the standard OSPF header.

Router ID
The router ID of the packetís source. In OSPF, the source and destination of a routing protocol packet are the two ends of an (potential) adjacency.

Area ID
A 32-bit number identifying the area that this packet belongs to. All OSPF packets are associated with a single area. Most travel a single hop only. Packets traveling over a virtual link are labeled with the back bone area ID of 0.0.0.0.

Checksum
The standard IP checksum of the entire contents of the packet, starting with the OSPF packet header but excluding the 64-bit authentication field. This checksum is calculated as the 16-bit oneís complement of the oneís complement sum of all the 16-bit words in the packet, except for the authentication field. If the packet length is not an integral number of 16-bit words, the packet is padded with a byte of zero before checksumming.

AU type
Identifies the authentication scheme to be used for the packet.

Authentication
A 64-bit field for use by the authentication scheme

Vulnerabilities for this protocol (from CVE)

CVE ID Protocol Source Port Targetport

TCP/IP Protocols:

AHARP/RARPATMPBGP-4COPSDCAPDHCPDNS
DVMRPEGPEIGRPESPFANPFingerFTPHSRP
HTTPICMPICMPv6IGMPIGRPIMAP4IPIPDC
IPv6ISAKMPL2FL2TPLDAPMARSMobile IPNARP
NetBIOS/IPNHRPNTPOSPFPIMPOP3PPTPRadius
RIP2RIPng for IPv6RLOGINRSVPRTSPRUDPS-HTTPSCTP
SLPSMTPSNMPSOCKS V5TACACSTALITCPTELNET
TFTPUDPVan JacobsonVRRPWCCPX-WindowXOT