Ospf Packet Formats - D-Link DES-6500 Manual

• Loading − The routers are finalizing the information exchange. Routers have link-state request list and a link-
state retransmission list. Any information that looks incomplete or outdated will be put on the request list. Any
update that is sent will be put on the retransmission list until it gets acknowledged.
• Full − The adjacency is now complete. The neighboring routers are fully adjacent. Adjacent routers will have the
same link-state database.
Adjacencies on Point-to-Point Interfaces
OSPF Routers that are linked using point-to-point interfaces (such as serial links) will always form adjacencies. The
concepts of DR and BDR are unnecessary.

OSPF Packet Formats

All OSPF packet types begin with a standard 24-byte header and there are five packet types. The header is described first,
and each packet type is described in a subsequent section.
All OSPF packets (except for Hello packets) forward link-state advertisements. Link-State Update packets, for example,
flood advertisements throughout the OSPF routing domain.
OSPF packet header
•
Hello packet
•
Database Description packet
•
Link-State Request packet
•
Link-State Update packet
•
Link-State Acknowledgment packet
•
OSPF Packet Header
Every OSPF packet is preceded by a common 24-byte header. This header contains the information necessary for a
receiving router to determine if the packet should be accepted for further processing.
The format of the OSPP packet header is shown below:
Field
Version No.
Type
Packet Length
DES-6500 Chassis-based Layer 3 Ethernet Switch Manual
OSPF Packet Header
Type
Version No.
Checksum
Figure 6- 117. OSPF Packet Header Format
Description
The OSPF version number
The OSPF packet type. The OSPF packet types are as follows: Type
Description Hello Database Description Link-State Request Link-State
Update Link-State Acknowledgment
The length of the packet in bytes. This length includes the 24-byte header.
Packet Length
Router ID
Area ID
Authentication Type
Authentication
Authentication
155