There are 5 types of OSPF packets. Beginning of all OSPF packets is specified by
standard header of 24 bytes. A list of link state advertisements is used in
dealing with all OSPF packet types.
Types of OSPF packets:
1. The Hello Packet :
The hello packets are sent over a period of time on all interfaces for
the purpose of establishing and maintaining neighbor relationships. Hello
packets are multicast on the networks having multicast capability, which
enables discovery of neighboring routers dynamically. The inhabitance of
differences among hello packets can form neighbor relationships by agreeing
certain parameters.
2. The Database Description Packet :
At the time of adjacency is being initialized, these packets are
exchanged. These packets describe topological database contents. The database
may be described by using multiple packets. A poll-response procedure is used
for the description of multiple packets usage. Among the routers, one is
designated to be master, and the other a slave. The Database Description
packets are sent by the slave after sending the Database Description packets by
the master.
3. The Link State Request packet :
A router may find the parts of its topological database are out of date, after
database description package exchange with a neighboring router. The Link State
Request packet is utilized for requesting the pieces of the neighbor’s database
which are more up to date. There may be a need to utilize multiple Link State
Request packets.
4. The Link State Update packets:
The flooding of link state advertisements is implemented by these
packets. A collection of link state advertisements are carried by each Link
Statement Update packet, one hop further from its origin. A packed may be
included by several link state advertisements.
5. The Link State Acknowledge packets:
The reliability of flooding link state advertisement is made by explicitly
acknowledging flooded advertisements. The accomplishment of this
acknowledgement is done through the sending and receiving of Link Sate
Acknowledgement packets. A single Link State Acknowledgement packet is used to
acknowledge the multiple link state advertisements.
