OSPF

Why
OSPF is important because it allows us to route packets within autonomous systems

What
OSPF is an intra-AS routing process that is typically deployed in upper tier ISPs

Specifications

 * OSPF is a link state algorithm that has each router hold complete information about the network and run a local dijkstra's algorithm setting the root to be itself
 * There is no standard way to set link weights in OSPF so the network administrator can choose anything that is convenient for him
 * Each router broadcasts messages to every other router in the autonomous system whenever there is a change and according to some regular interval such as 30 minutes even if the link state has not changed

Security
Exchanges between OSPF routers can be authenticated and only trusted routers can participate in the AS, preventing malicious intruders

Multiple Same Cost Paths
When there exist multiple same cost paths, OSPF can split the traffic up across all of those paths

Support for Hierarchy Within a Single Routing Domain
With OSPF, we can split up our AS itself into hierarchical sub structures

Support for Hierarchy With a Single Routing Domain
We can split up an OSPF routing domain into multiple areas, each running its own routing process. Moreover, exactly one of these areas is called the backbone area and is responsible for driving traffic between the other areas