DOI: http://dx.doi.org/10.26483/ijarcs.v8i9.5101 Volume 8, No. 9, November-December 2017 International Journal of Advanced Research in Computer Science RESEARCH PAPER Available Online at www.ijarcs.info © 2015-19, IJARCS All Rights Reserved 425 ISSN No. 0976-5697 EXTENSIVE REVIEWS OF OSPF FOR REDUCING THE CONVERGENCE TIME Pertik Garg Department of Computer Science Engineering I.K.Gujral Punjab Technical University Jalandhar, India Anuj Kumar Gupta Department of Computer Science Engineering CGC, Landran Punjab, India Abstract: Link state routing protocols for example, OSPF synchronize the topology databases by flooding link state update messages occasionally or at whatever point there is an availability change. Topology changes trigger routing protocol to experience convergence procedure which gets ready new shortest routes required for packet delivery. Real-time applications these days need routing protocol to have a fast convergence time. This problem may be resolved by proposing an algorithm that can quickly respond to the topology change and reduce the convergence time by providing back up path which is already stored in routing table before the failover happens. EIGRP routing protocol gives a prevalent execution than OSPF routing protocol for real time applications. In this paper we reviewed the various papers on OSPF and EIGRP for the convergence time. Keywords: OSPF, Link State Routing Protocol, IP, Packet loss, Convergence time. I. INTRODUCTION A. Routing Protocol A routing protocol indicates how routers [1] communicate with every other, scattering data that empowers them to choose routes between any two nodes on a computer network. Routing algorithms decide the particular selection of route. Every router has from the earlier learning just of systems appended to it straightforwardly. A routing protocol shares this data first among quick neighbors, and after that all through the network. Routing is the prime factor in this advanced period of internet communication. Several routing protocols are in presence in nowadays. The routing of packets between IP networks is completed by two distinct ways i.e. static routing & dynamic routing. In static routing “static routes are generally physically designed by network administrator by including entries into routing table however this may not generally be the case [2]. Dynamic routing is broadly utilized for enormous IP networks. There are three classes of Routing Protocols  Interior gateway routing by link state routing protocols  Interior gateway routing by distance vector protocols  Exterior gateway routing B. Link State Routing Protocol The essential idea of link-state routing [1] is that each node builds a guide of the availability to the network, in the form of a graph, indicating which nodes are related with which different nodes. Every node at that point freely figures the following best sensible way from it to each conceivable goal in the network. The gathering of best ways will then shape the node's routing table. Through link state routing protocol  Routers broadcast and get link state packets to and from different routers via the network. Link state packets contain the status of a router's links or network interfaces.  The router builds a topology database of the network.  The router runs the Shortest Path First (SPF) algorithm against the database and generates a SPF tree of the network with itself as the base of the tree.  The router populates it route table with ideal ways and ports to transmit information through to achieve every network. Examples of link state routing protocols are:  Open Shortest Path First (OSPF) for IP  The ISO's Intermediate System to Intermediate System (IS-IS) for CLNS and IP  DEC's DNA Phase V  Novell's NetWare Link Services Protocol (NLSP) C. Open Shortest Path First (OSPF) OSPF [3] is classified as an Interior Gateway Protocol (IGP), it bases on link-state routing algorithm. OSPF always choose the shortest path to forward IP packets. At the point when a few equivalent cost routes to a goal exist, traffic is conveyed similarly among them. The cost of a route is depicted by a solitary dimensionless metric. When the utilization ratio of the current shortest path is not high, to choose the shortest path to forward IP packets is the best selection. However, if the current shortest path is congested, and there are other paths whose costs are larger and utilization ratio are lower, to choose other paths to forward packets maybe better. Open Shortest Path First (OSPF) [4] is a link state routing protocol (LSRP) that uses the Shortest Path First (SPF) network communication algorithm (Dijkstra's algorithm) to compute the shortest connection path between known devices. The OSPF routing approaches to build a route table are administered by link cost elements (external metrics) related with every routing interface. Cost elements might be the separation of a router (round-trip time), network throughput of a link, or link accessibility and unwavering quality, communicated as simple unit less numbers. This gives a dynamic procedure of traffic load adjusting between routes of equivalent cost.