Samsung Ubigate iBG2016 Configuration Manual page 141

Ubigate iBG2016 Configuration Guide
CHAPTER 5. OSPF
The Open Shortest Path First(OSPF) protocol is an interior gateway
protocol(IGP) that routes packets within a single autonomous system(AS).
OSPF uses link-state information to make routing decisions, making route
calculations using the shortest path first(SPF) algorithm(also referred to as the
Dijkstra algorithm). Each router running OSPF floods link-state advertisements
throughout the AS that contain information about that router's attached interfaces
and routing metrics. Each router takes the information in these link-state
advertisements and creates a complete routing table for the network.
OSPF was designed for the TCP/IP environment and as a result explicitly
supports IP sub netting and the tagging of externally derived routing
information. OSPF also provides for the authentication of routing updates.
OSPF routes IP packets based solely on the destination IP address contained in
the IP packet header. OSPF quickly detects topological changes, such as when
router interfaces become unavailable, and calculates new loop-free routes
quickly and with a minimum of routing overhead traffic.
Each interface running OSPF is assigned a cost, which is a unitless number
based on factors such as throughput, round-trip time, and reliability, which are
used to determine how easy or difficult it is to reach a destination. If two or
more routes to a destination have the same cost, OSPF distributes traffic
equally among the routes, a process that is called load balancing.
Each router maintains a database that describes the topology of the AS.
Each OSPF router has an identical topological database so that all routers in
the area have a consistent view of the network. All routers maintain
summarized topologies of other areas within an AS. Each router distributes
information about its local state by flooding link-state advertisements
throughout the AS. When the AS topology changes, OSPF ensures that the
contents of all routers' topological databases converge quickly.
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