Hello Ninjas! As we know, in computer networking and distributed systems communication between nodes is critical for proper communication. But sometimes, the most reliable protocols can fail and cause issues. One such problem is the count to infinity problem.

In this article, we will be discussing the count to infinity problem. This problem occurs when nodes in the network use the Distance Vector Routing(DVR) Protocol. Let’s dive deeper into the problem and understand it with examples and solutions to the problem.

The Count of Infinity Problem

The “Count to Infinity Problem” is a challenging problem that arises in Computer Networks and distributed systems. This problem occurs when nodes in the network use the Distance Vector Protocol(DVP). Routing loops are fundamental issues with the Distance Vector algorithm because the Bellman-Ford Algorithm, which is commonly used in distance vector routing is unable to prevent these loops.

This happens when a node sends information to a neighbor, thinking it has discovered a shorter route to a destination node through that neighbor. The node then updates its distance based on this information and acknowledges the updated estimate to its neighboring. As soon as the neighbor updates its own routing database, it broadcasts the new data to all of its neighbors, including the original node. This procedure can go on forever, creating a loop and possibly clogging the network.

The Distance Vector Routing Algorithm employs a number of methods to avoid this issue, such as setting a limit hop count or enforcing a "split horizon" rule that forbids a node from announcing a route back to the node from which it was learned, which we will discuss later.

Example of Count to Infinity Problem

Let's understand the Count to Infinity Problem with an example:

In the above example, node A act as the source, whereas node D act as the destination. Suppose node A want to send a packet to node D using the shortest path. Node A sends the distance estimate to its neighboring node. The updated distance at B=1 and C=3.

Now, node A receives the updated distance from B and updates its own estimates using the shortest path as A=1.Node A then broadcasts its new estimate to C and updates its estimate C= 2. Node C then sends its new estimate to neighboring node and node B updates its new estimates as B= 3.

Now node B believes that the shortest path to node D is through node C with a new distance of 2 + 1 = 3. And node C thinks that the shortest distance is through B at a distance of 2. This difference leads to an infinite loop of the distance between B and C, and its keeps on incrementing 1 unit at every iteration.

So, the above example demonstrates the count to infinity problem. Additionally, if the distance between nodes A and C is made 2 units, the count to infinity problem can be avoided and the network remains stable.

Solution for the Count to Infinity Problem

The count to infinity problem generates inconsistency between the nodes in the network. The problem makes the network unstable. This problem must be prevented from happing and making the network stable. Let's look at the solution to the problem of count to infinity:

Split Horizon

Split Horizon is a method to avoid the count to infinity problem. The basic approach in this method is to prevent the nodes from broadcasting the routing information back to the node from which they had received it. It excludes the routes that it learned from the neighbor to it was advertised. It helps in preventing the routing loop and avoids the problem.

In the diagram, router A broadcasts the route to network A, and router B updates its routing table. router B does not include network A in the routing table.

However, split horizon is not a perfect solution to the count to infinity problem. It is important to consider the limitations of the method and use it with other routing protocols to ensure optimal performance.

Route Poisoning

Route Poisoning is a technique that prevents the router from sending packets through a route that has become unreachable. It broadcasts an update to all its neighbors with the neighbor’s distance set to infinity. This technique of poisoning the route that is unreachable is called Route Poisoning. The node ensures that other nodes in the network will not continue to use that particular route which could create a loop and make the network unstable.

In the diagram, the interface to network 4 fails. All the routers knew about network 4 from router C. The router C will tell this failure to B and router B will stop routing to network 4 through C.

The disadvantage of the route poisoning method is that it increases the size of the routing advertisements significantly in many common network topologies.

What causes the Count to Infinity Problem in DVR protocols?

The count to infinity problem is caused by the slow transmission of routing information throughout the network. This results in making the node incorrect assumptions about the distance to the destination, which could create routing loops and make the network unstable.

What is the poised reverse count to infinity problem?

The poised reverse technique is used to prevent the count to infinity problem. The basic idea is to make sure that a path does not turn back to the same node if a cost has changed within that network.

How does the Bellman-Ford algorithm contribute to the Count to Infinity Problem?

The Bellman-Ford algorithm can contribute to the count to infinity problem by allowing nodes to broadcast information about the distance to a destination leading to routing loops and other issues. This occurs because the updates transmit slowly through the network.

What happen when we face count to infinity issue in routing?

When facing the "count to infinity" issue in routing, it creates a problem where network routers repeatedly update each other with incorrect information about the best path to reach a destination. This can result in never-ending loops of updates and cause the network to become unstable and unusable.

What is a remedy for avoiding the count to infinity problem in the distance vector routing algorithm?

A remedy for avoiding the count-to-infinity problem in the distance vector routing algorithm is the split horizon technique. It prevents a router from advertising a route back to the neighbor from which it learned the route, thereby breaking the loop and stopping the infinite counting of distances.

Conclusion

This article briefly discussed the count to infinity problem. We have discussed the example and solutions to the problem in detail. You can check out our other blogs to enhance your knowledge: