A program is a passive entity that has a set of codes and instructions required to accomplish a task. A process, on the other hand, is an active entity of a program that is started with the execution of the program. Thus, the process is started by the program, once it is executed. The instructions of the program are then executed by the process. Read through this article to find out more about programs and processes and how they are different from each other. What is a Program? A program is a set of instruction codes that has been designed ... Read More

DefinitionIn computer science and mathematics, a directed acyclic graph (DAG) refers to a directed graph which has no directed cycles.ExplanationIn graph theory, a graph refers to a set of vertices which are connected by lines called edges. In a directed graph or a digraph, each edge is associated with a direction from a start vertex to an end vertex. If we traverse along the direction of the edges and we find that no closed loops are formed along any path, we say that there are no directed cycles. The graph formed is a directed acyclic graph.A DAG is always topologically ... Read More

In computer networks, the shortest path algorithms aim to find the optimal paths between the network nodes so that routing cost is minimized. They are direct applications of the shortest path algorithms proposed in graph theory.ExplanationConsider that a network comprises of N vertices (nodes or network devices) that are connected by M edges (transmission lines). Each edge is associated with a weight, representing the physical distance or the transmission delay of the transmission line. The target of shortest path algorithms is to find a route between any pair of vertices along the edges, so the sum of weights of edges ... Read More

Flooding is a non-adaptive routing technique following this simple method: when a data packet arrives at a router, it is sent to all the outgoing links except the one it has arrived on.For example, let us consider the network in the figure, having six routers that are connected through transmission lines.Using flooding technique −An incoming packet to A, will be sent to B, C and D.B will send the packet to C and E.C will send the packet to B, D and F.D will send the packet to C and F.E will send the packet to F.F will send the ... Read More

Flooding and fixed routing are methods to transmit data packets from the source to the destination through a number of intermediate routers connected by transmission lines.Flooding is a non-adaptive routing technique following this simple method − when a data packet arrives at a router, it is sent to all the outgoing links except the one it has arrived on.Fixed routing algorithm is a procedure that lays down a fixed route or path to transfer data packets from source to the destination. The route is a mathematically computed best path, i.e. “least–cost path” that the packet can be routed through. The ... Read More

Routing Algorithms − A routing algorithm is a procedure that lays down the route or path to transfer data packets from source to the destination. There can be many paths from the source to the destination; routing algorithm mathematically computes the best path, i.e. “least – cost path”. Routing algorithms are broadly classified into adaptive and non-adaptive routing algorithms.Adaptive Routing Algorithms − Also known as dynamic routing algorithms, they makes routing decisions dynamically depending on the network conditions. It constructs the routing table depending upon the network traffic and topology.Non-Adaptive Routing Algorithms − Also known as static routing algorithms, they ... Read More

DefinitionSink trees of a given node in a computer network is a tree formed by connecting the node with all the other nodes of in the network with the optimal path, or more precisely the shortest path. Or, in other words, a sink tree is a minimal cost tree formed with the given node as the destination and all other nodes as sources. A popular measure for the path or the cost is the number of hops.ExplanationThe sink tree follows from the optimality principle. According to it, in a network of routers for data transmission, if a router ‘J’ lies ... Read More

The optimality principle in computer networks is stated as follows −ExplanationThe purpose of a routing algorithm at a router is to decide which output line an incoming packet should go. The optimal path from a particular router to another may be the least cost path, the least distance path, the least time path, the least hops path or a combination of any of the above.The optimality principle can be logically proved as follows −If a better route could be found between router J and router K, the path from router I to router K via J would be updated via ... Read More

Adaptive routing algorithms, also known as dynamic routing algorithms, makes routing decisions dynamically while transferring data packets from the source to the destination. These algorithms constructs routing tables depending on the network conditions like network traffic and topology. They try to compute computes the best path, i.e. “least – cost path”, depending upon the hop count, transit time and distance.Types of Adaptive Routing AlgorithmsThe three popular types of adaptive routing algorithms are shown in the following diagram −Centralized algorithm − In centralized routing, one centralized node has the total network information and takes the routing decisions. It finds the least-cost ... Read More

Non-adaptive routing algorithms, also known as static routing algorithms, do not change the selected routing decisions for transferring data packets from the source to the destination. They construct a static routing table in advance to determine the path through which packets are to be sent.The static routing table is constructed based upon the routing information stored in the routers when the network is booted up. Once the static paths are available to all the routers, they transmit the data packets along these paths. The changing network topology and traffic conditions do not affect the routing decisions.Types of Non − adaptive ... Read More