The Open SPF Protocol

The Open SPF Protocol

It is a interior gateway protocol that use the link state algorithm

Open standard

• Anyone can implement without paging license fee.
  AS name implies specification is avalable in published literature

Type of Service Routing

• Manger can install multiple routes to given destination,one for each priority or type of service

Load balancing

• OSPF distributs traffic over all routes equally
• If a manger specifies multiple routes to a given destination at same cost  then also traffic distributed equally over all routes

Heirarchical subdivision into areas

• It allows large intranet or site to partition its network and routers into subset called areas and limit routing overhead
• Each area is self-contained, knowledge of an area topology remain hidden from other areas
• multiple group with in a site can cooperate even when Each group retain the ability to change its internal network topology independently.

Support for authentication

• Support variety of authentication schema and allows one area to choose a different scheme than another one

Arbitrary granularity

• OSPF includes support for host specific subnet specific network specific  and default routes

Support for Multi Access Network

• If k router present in an Ethernet they broadcast K^2 status messages , each node represent either a network or router and only  A designated gateway sends link status messages on behalf of all routers attached to the network

Multicast Delivery

• To reduce load on non participating system OSPF uses hardware multicast capabilities
• two IPV4 multicast address are pre assigned to OSPF 
• 224.0.0.5 for all routers
• 224.0.0.6 for all nodes

Virtual topology

•  A manger can create a virtual network topology, A manger can create virtul link between two roters even if physical connection between them require multiple transit networks

Route Importation

• OSPF can import and spread routing information based from external site(i.e from routes that do not use OSPF)

Direct use of IP

• OSPF message are encapsulated directly in IP datagaram