Seminar on IP Routing protocols with simulations using Cisco Packet Tracer.

1. ROUTING PROTOCOLS
Narendran Thangarajan,
@naren_live
SSN College of Engineering,
Chennai.

2. RECAP..
 MAIN CLASSIFICATION
 STATIC ROUTING
 DYNAMIC ROUTING
 Concept of Autonomous System (AS)
 What is dynamic in Dynamic Routing
Protocols?

3. RECAP – Dynamic Routing Protocols
 Dynamic Routing Classification
 IntraDomain
 Distance Vector
 Link State
 InterDomain
 Path Vector

4. RECAP – Distance Vector Routing
 Distance Vectors shared
 Initialization – directly connected routers
 Sharing – Share the first two columns of the
routing table
 Updating – Better cost replaces old entry
 When to share? – Periodic and triggered
 Problems
 Eg: RIP

5. LINK STATE ROUTING
 Goal : To find the shortest path to the
destination.
 Difference from DV : In DV each router knows
only the next hop. But in LS each router has the
entire topology of the domain.

6. Steps:
 Initial State : All routers know their own link
state.
 Creation of LSPs
 Reliable Flooding of LSPs
 Formation of Shortest Path Tree
 Routing Table Calculation

7. Creating LSP
 Link State Packets (LSP) carry large amount
of information. Also called Hello Packets.
 Important Fields : Router ID, Link state of the
router, Sequence number, Time to Live.
 Created on two occasions:
 When there is change in the topology.
 Periodic basis.

8. Reliable Flooding
 ALL nodes broadcast their LSPs to their
adjacent nodes.
 Depending upon the sequence number and
the link state values, the receiving node
decides whether to discard or store the LSP.

9. Formation of Shortest Path tree
 After the LSP are shared among all nodes, each and
every node has the entire topology of the domain.
 Then Dijkstra’s algorithm is run over this information
to create a shortest path tree from the graph
obtained.
 Permanent List and Tentative list – An eg. Problem
 Demo -
http://www.ifors.ms.unimelb.edu.au/tutorial/dijkstra
/island.html

10. Creation of routing table
 From the generated shortest paths, the
routing table is generated.
 In both DV and LS, the final routing table is
the same. The difference lies only in the way
the routing table is prepared.

11. OSPF – Open Shortest Path First
 The Autonomous System is divided into
Areas.
 LS routing protocol runs inside an Area.
 The summary of the routing information is
given to the Backbone area through ABR.

12. Simulations

13. Thank you 