Recently i caught up with Lady Lara Croft Angelina Jolie .This Tomb Raider star is truly amazing , not only she is known as the most sexiest women on this earth even she has one of the best brains..she knows in and out of the Networking Technology...Woaho!!!
Here, She explains about OSPF technology developed by John T. Moy and the Internet Engineering Task Force in 1988 which reverse engineered from an alien spacecraft now widely used in routers across the world which is very intelligent and very dangerous too. It is a social creature that can recognize neighboring OSPF enabled routers and it will initiate a dialog with it’s neighbors.
Me : Hey ,Angelina, wassup...thanks for coming here ...i heard that you are a networking geek ... could you please give us little bit gyaan about OSPF ??
Angelina: Hey, Ranjan ...well, lemme share some knowledge about OSPF with you...here we go!..
In the first phase,Once OSPF routers have communicated with their neighbors by saying Hello to each other , they begin to organize themselves into a Social hierarchy with other routers occupying roles as President, Vice-president and others. This is called “forming adjacencies”.
In the next phase the OSPF routers will send broadcast message to all other OSPF enabled routers. we call it as “Flooding Link State Advertisements”. Once this occurs, every router knows what the entire Social Hirearchy looks like. each and every router will known other routers designation and the place where they situated, each one of this will have a map of the entire hierarchy of the society known as “link state database”. Now they have knowledge of each other, soon they will each run their Shortest Path First algorithm and they will posses enough intelligence to rule the world of networks !!....kinda a powerful community from the future ready to dominate the entire world...isn't it ??
Once they have ran the SPF algorithm...they will find the shortest path to each other no matter what part of the world other router resides in .They will connect each other within the fraction of second!!!
These OSPF routers act as a true team. Each is aware of the entire network. These OSPF routers are bit broad minded and they don't limit themselves to Metrics like hop counts or bandwidth and delay. As a collective force, any router can route any IP packet to any corner on your planet. And they depend on metric known as “cost” for routing.
OSPF behaves differently on different types of networks. Networks can be classified as Broadcast Multi Access such as Ethernet, Non Broadcast Multi Access such as ATM and finally Point to Point such as a frame relay circuit between two sites.
Me : Wow...you know so much about Networking..well , i heard that OSPF is a Link state protocol could you please let me know what is this all about Link state protocol.
Angelina :Ha ha..sure Ranjan, All the routing protocols are divided in to two categories , One is Distance Vector and other one is Link State. and Combined of these two types called Hybrid ,like EIGRP.
Distance vector protocols periodically exchange their routing tables with their neighbor routers. This is known as “routing by rumor” because routers are advertising routes to networks that they are not directly connected to. Distance vector protocols are very easy on a routers CPU but as more routers are added to a network, the exchanging of entire routing tables can use up valuable bandwidth...that is why we have the second one..Link State protocol :-)
Link state protocols monitor the links they have with adjacent routers by using a “hello protocol” to test the status of their links to their neighbors. Link state protocols only advertise their directly connected networks and their active links. Every link state router captures these link state advertisements and pieces these together and create a topology of the entire network or area..then it will run a specified algorithms to decide what will be the best way to route the packets to the remote networsk .Link state protocols are very quite as they only transmit small hello packets and only transmit link state advertisements when an actual change in the network topology has occured. Link state protocols are more CPU intensive, especially when a router is performing the complex “Shortest Path First” calculation based on Dijkstra alogoritm . is the way our OSPF works !...
Me: ohhh!!...that's cool ....i have heard about Areas in OSPF...is that related to Area 51, the place where most alien ships were sighted ??.
Angelina: Heh..he..he ..Ranjan, you are funny...Well,its not about Area 51 ..There OSPF networks divided in to small segments called Areas.In a given area all OSPF routers are aware of each other and all the links between each router in their territory or area. Every OSPF network must have an area known as zero.
for Other OSPF areas are you can number them as “area 2" or “area 3" but all areas must be directly connected to area 0. Area 0 is the backbone area which connects other areas together and carries only inter-area traffic between areas. All the areas under a common administration known as an Autonomous System. OSPF is an Interior Gateway Protocol and is used to route between areas in a common autonomous system but routing between autonomous systems must be handled by an Exterior Gateway Protocol such as BGP.
Me:Angelina, i am really impressed with your knowledge ..in a nutshell, OSPF is just like a Evolution of super artificial intelligent community...isn't it ??.Angelina :Exactly!!...As an process of evolution it has to go through five stages ;
- Form Adjacencies With Neighbors.
- Elect a Leader and a Vice Leader.
- Discovering Routes.
- Determine Which Routes to Use.
- Maintain Routing Information.
Thats it !!.
Me : Cool..Thanks Angelina...for providing all the information would like to know advanced OSPF in detail from you on some other time ..its pleasure speaking with you .
Angelina:Sure Ranjan, we will discuss in detail about the Hello Packet and The way OSPF Election will be held ...its really interesting ...But, for now i am in hurry ...Brad is waiting for me... need to go ..Will meet you again in some nice restaurant for candle light dinner ...Take care, bbye.
Me:Oh!!!!! really!!!!!!!!!!!!!!!!!!!!
***********************To be continued*********************************
