Final answer:
The OSPF Type 1 packet is known as the hello packet. It is used to establish and maintain adjacency between OSPF routers and contains important parameters such as the router's ID and list of known neighbors.
Step-by-step explanation:
The OSPF Type 1 packet is the hello packet. OSPF (Open Shortest Path First) is a routing protocol used in Internet Protocol (IP) networks to find the most efficient path for data packets. The hello packet is fundamental to OSPF as it is used to establish and maintain adjacency between OSPF routers. When OSPF routers start up, they send hello packets to multicast addresses to discover other OSPF routers on their local link or network. This process allows routers to elect a designated router (DR) and backup designated router (BDR) on multi-access networks, ensures that routers know about their neighbors, and maintains information about which routers are alive.
Each hello packet contains important parameters, such as the router's ID, the hello and dead intervals, and the list of known neighbors. The hello and dead intervals must match between routers for them to become neighbors. If there is a mismatch in these intervals, the routers will not form an adjacency. Routers regularly exchange hello packets to verify that a neighbor is still reachable. If a router stops receiving hello packets from a neighbor for a period of time, marked by the dead interval, it assumes the neighbor is down and adjusts its routing table accordingly.