What is Routing?

Introduction to Routing

The whole world is digitalized and connected over the network. Packets, the atomic unit of information in packet-switched communication networks, are exchanged between the nodes (a node might be an end device, a router, a data generating device, etc.).Transferring these packets of information from their source node to the destination node with one or more hops along the most optimum path is called ‘Routing.’ Routers and switches are the devices used for the purpose of working on the routing protocols and algorithms they are configured with. These packets are taken care of by the L3 layer of the OSI Reference Model’s network layer.

How does it take place?

When a packet is introduced into the network and received by one of the routers, it reads the packet’s headers to understand the destination. It checks its routing table marked with its metrics to see what would be the next best hope for the packet to reach the destination optimally. Then, it pushes the packet to the next node, and the above process also repeats at the new node until the packet reaches the destination node.

Routing metrics

These tables have information on which packet switching takes place in the most optimal path. And this information is different metrics or variables the routing algorithms look for and then decide their path. The standard metrics include –

1. Path Length: The administrator will assign costs to each path (between two nodes). The path length will be the sum of all the path costs. The path with the less path length will be chosen as the most optimal one.
2. Delay: This is the measure of time it takes for the packet to route from source to destination. This depends on many factors like network bandwidth, the number of intermediate nodes, congestion at nodes, etc. Sooner the transfer, the better the Quality of Service (QoS).
3. Bandwidth: This refers to the amount of data a link can transfer through it. Usually, the enterprise lease the network line to achieve a higher link and bandwidth.
4. Load: Load refers to the traffic a router or a link handles. The unbalanced or unhandled load might cause congestion and a lower rate of transmission packet losses.
5. Communication Cost: This is the operational expense that the company incurs by sending the packets on the leased line between the nodes.
6. Resilience and Reliability: This refers to the error handling capacity of the router and the routing algorithms. If some nodes in the network fail, then the resilience and reliability measure will show us how well the other nodes can handle the traffic.

Types of Routing

There are two types:

1. Static Routing

This type is the optimal path between all possible pairs of sources & destinations in the given network, is pre-defined, and fed into the routing table of the network’s routers.

Advantages

• There is no CPU overhead for the routers to decide the next hop for the packet as the paths are predefined.
• This offers higher security as the administrator has autonomy over packet flow permissions along a defined path.
• Between the routers, no bandwidth would be used (for tasks like updating its table, etc.)

Disadvantages

• It will be difficult for the administrator to identify and pre-define an optimal path from all possible combinations of source & destination nodes for larger network topology.
• The administrator would be expected to be thorough in the concepts of networks and topology. Transitioning to a new administrator would consume time understanding the topology and defined policies.

2. Dynamic Routing

This type gives the router the ability to discover the network by protocols like OSPF (Open Shortest Path First) and RIP (Routing Information Protocol), updates the routing table by itself, and effectively decides upon the path that the incoming packet must follow to reach its destination.

Advantages

• This is easy to configure.
• It would be efficient to discover some remote networks and execute routing there.

Disadvantages

• When one of the routers in the network implementing dynamic routings discovers change or generates an update, it broadcasts it to all the nodes. Thus, consuming a higher amount of bandwidth.
• It is relatively less secure than static.

Types of Routing Algorithms

There are two types of algorithms:

1. Adaptive

The routes are decided dynamically based on the changes in the network topology.

• Distance Vector Routing: In this algorithm, each router maintains an entry for each router in the network. This is called the Bellman-Ford Algorithm. Initially, this was the ARPANET algorithm.
• Link State Routing: LSR discovers the neighbors, measures the cost to each neighbor, then constructs the packets and sends them along the computed shortest path.

2. Non-Adaptive

The routes are decided in a static fashion by the routers.

• Flooding: In this, you send the packets to every other neighboring router & they turn to the same, and by some path, the packet reaches its destination. This duplicates the packets, but the reliability is very high in a type of routing. This is mainly used in defense networks, distributed databases, wireless networks, and populating the routing tables.

How will this help in your career growth?

The network architecture in data centers, telephonic lines, cloud clusters, etc., is crucial for businesses to run. Telecommunication companies, Computer Network companies work day in and day out to come up with better network routing algorithms and routing protocols, to have the network virtualized, enhance the network security by designing secure network protocols and encryption techniques, achieve higher resilience, and provide better & faster quality of service. With such an overwhelming scope in the domain, it is great to pursue one’s career in Computer Networks.

Conclusion

It is the primary action in a computer network that transfers data from source to destination. It is also manipulated to do stuff like congestion control and load balancing. The performance and efficiency of the router are determined by the types in which it is employed, by the routing algorithm being used, and also by its other metrics.

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