What is Routing?

Introduction to Routing

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

How does it take place?

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

Routing metrics –

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

1. Path Length – In this, 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, 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 which a router or a link is handling. The unbalanced or unhandled load might cause congestion and a lower rate of transmission packet losses.
5. Communication Cost – This is the operational expense which 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–

• Static Routing – This is the type of routing in which 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 routers of the network.

Advantages –

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

Disadvantages

1. For a larger network topology, it will be difficult for the administrator to identify and pre-define an optimal path from all possible combinations of source & destination nodes.
2. The administrator would be expected to be thorough in the concepts of networks and topology. Transition to a new administrator would consume time so as understand the topology and policies that are defined.

• 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

1. This is easy to configure.
2. It would be efficient in order to discover some remote network and execute routing there.

Disadvantages –

1. 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.
2. It is relatively less secure than static.

Types of Routing Algorithms

There are two types of algorithms –

• Adaptive – The routes are decided dynamically based on the changes in the network topology.
  1. Distance Vector Routing – In this algorithm, each router maintains a routing table containing an entry for each router in the network. These entries are updated periodically. This is also called as the Bellman-Ford Algorithm. Originally, this was the ARPANET algorithm.
  2. Link State Routing – LSR discovers the neighbors, measures the cost to each neighbor, then constructs the packets and sends it along the computed shortest path.
• Non-Adaptive– The routes are decided in a static fashion by the routers.
  1. Flooding – In this you send the packets to every other neighboring router & they in-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 mostly used in defense networks, distributed databases, wireless networks and to populate the routing tables.

How this will help in your career growth?

The network architecture in data centers, telephonic lines, cloud clusters, etc. is all so crucial for businesses to run. Telecommunication companies, Computer Network companies work day-in and day-out to come up with better network routing algorithms, routing protocols, to have the network virtualized, to enhance the network security by designing secure network protocols and encryption techniques, to 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 the field of Computer Networks & routing.

Conclusion

Basically, routing is the primary action that happens 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 & efficiency of the router is determined by the type of routing it is employing, by the routing algorithm being used and also by other routing metrics.

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