Dijkstras Algorithm - Avaya 8800 Configuration Manual

In large networks, OSPF offers the following benefits:
• Fast convergence
When network topology changes, OSPF recalculates routes quickly.
• Minimal routing protocol traffic
Unlike distance vector routing protocols, such as RIP, OSPF generates a minimum of
routing protocol traffic.
• Load sharing
OSPF provides support for equal-cost multipath routing. If several equal-cost routes to a
destination exist, traffic is distributed equally among them.
• Type of Service
Separate routes can be calculated for each IP Type of Service.

Dijkstras algorithm

A separate copy of the OSPF routing algorithm (Dijkstra's algorithm) runs in each area. Routers
that connect to multiple areas run multiple copies of the algorithm. The sequence of processes
governed by the routing algorithm is as follows:
1. When a router starts, it initializes the OSPF data structures and then waits for
2. A router then uses the Hello Protocol to discover neighbors. On point-to-point and
3. On all multiaccess networks (broadcast or nonbroadcast), the Hello Protocol elects
4. The router attempts to form adjacencies with some of its neighbors. On multiaccess
5. Adjacent neighbors synchronize their topological databases.
6. The router periodically advertises its link state, and also does so when its local state
Configuration — OSPF and RIP
indications from lower-level protocols that the router interfaces are functional.
broadcast networks the router dynamically detects neighbors by sending Hello
packets to the multicast address AllSPFRouters. On Non-Broadcast Multiple
Access networks, some configuration information is required to discover
neighbors.
a designated router (DR) for the network.
networks, the DR determines which routers become adjacent. This behavior does
not occur if a router is configured as a passive interface because passive interfaces
do not form adjacencies.
changes. LSAs include information about adjacencies, enabling quick detection of
dead routers on the network.
Open Shortest Path First
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