Updated June 9, 2023
Introduction To Routing Protocol
The two main essential components in computer networks are the source and destination. The information should be communicated from source to destination from time to time. There are many paths in which the data can be transferred. Routing refers to the selection process of choosing the best path over other paths; protocols, which are software-programmed devices, can perform this task. Standard protocols help to find the best route to ensure good data transfer. The system also provides the data packets that need sending with information to identify the best routing protocol.
The main purpose of routing protocols is to know about all the existing networking routes and make correct decisions. Some examples of common routing protocols are RIP, EIGRP, IGRP, BGP, IS-IS, etc.,
How does Routing Protocol work?
Let us understand the concept with a simple example. Let us consider two directly connected networks that are initially configured. The routing table consists of only these networks, and other networks other than these two cannot enter into this. So how can the router recognize other networks? This can be done in the following ways. Routers use remote network administrators to learn about routing, such as
1. Static Routing
static routing can have a pre-defined and installed router with a single path to the destination. This routing takes priority over routes chosen by dynamic routing protocols, and destination within routing tables is also forced. This protocol is particularly suitable for medium to large-sized networks, as they require a large workload to run. Stub networks mostly use static routing protocols.
2. Default Routing
You can define the default routing protocol as the path the route manually takes when there is no specific route to the destination. The gateway of last resort is the router that receives the routing information. Mostly, small networks use default routing.
3. Dynamic Routing
Dynamic routing protocols have pre-defined algorithms that can analyze and choose the optimal path to the destination. People mainly use this because it adapts well to network topology.
You can also call it one of the most frequently used routing methods. To better understand how it works, there is a need to have prior knowledge of certain terms such as convergence and accuracy.
- Convergence
In this type of routing, the routing table must have exact, accurate, and up-to-date information about the network topology. Convergence time refers to how long the router takes to update the routing table with a new change in value during routing. Routing protocol with fast convergence time is preferable because disturbance can occur during the router to calculate networks for the optimal path. It can also be called an act of approach to a state where all routing tables have detailed information and are steady.
- Accuracy
The convergence time, updated by the router, should reflect the exact details about the values, known as accuracy.
Routing Mechanism
The routing update mechanism is a process of information transfer between the neighboring routers. You can explain this as a router advertising its data information via broadcast or multicast at a specific time duration while routing. Various routing protocols have different time intervals. These routing updates contain information on routing protocols such as AS, AD, matrix values, and interface details.
1. Autonomous system: AS can be defined as a collection of routers with similar routing table information, simply defined as the boundary line for the routing protocol. It can be one-to-one or one-to-many and can be defined by a numeric value. As numbers define it, an internet-assigned numbers authority provided a range from 1-65535
This is of two types.
- The internal network uses a private autonomous system.
- Internet backbones use the public autonomous system.
2. Interior gateway protocols: These are used in data transfer to share routing information between routers in the same autonomous system. Some examples of interior gateway protocols are RIPv1, RIPv2, IGRP, and OSPF.
3. Exterior gateway protocols: These are used in data transfer to share routing information between routers in the different autonomous systems. An example of an exterior gateway protocol is the Border gateway protocol.
4. Administrative distance: AD can be defined as the reliability of routing updates received from the neighboring router. For instance, if a router receives two updates for the same path from two different routing protocols, it checks the best AD value to select the most optimistic path. The system gives more preference to the AD that has the lowest value.
5. Metric: If two routing updates have the same Ad value, then the metric will come in to picture to calculate the best path. Similar to AD, different routing protocols use different metric values. The system will select the routing protocol that has the lowest value. For example, EIGRP uses bandwidth, MTU, and load, while RIP uses only hop count as a metric value.
Types OF Routing Protocols
The routing protocols can be mainly classified into three types. Each of these has its importance in data transfer. Let us now discuss in detail each of these protocols.
1. Distance Vector
This mainly uses distance as the metric value and direction as a vector to select the optimal path to the destination network. The router receives the routing information from neighboring routers, which get it from their neighboring router until the destination network. The term “hop” refers to every neighboring router that the path to a destination network includes. Every time a data packet goes through a router, the hop value increases and the route with the least hop value will be chosen.
For example, RIP directly shares an entire routing table with directly connected neighbors.
2. Link State Routing Protocols
The link-state routing protocol uses a complex metric table to choose the best path for the destination network. As the name itself indicates that it works in a linked format. It uses three tables.
- The first table contains information about directly connected neighbors.
- The second table handles the entire network topology.
- The third table keeps data on the actual path.
An example is OSPF. This shares its link to routers.
3. Hybrid Routing Protocols
Hybrid routing protocols are a mix of distance vector and link-state protocols. A hybrid routing protocol uses distance vector and link-state protocol aspects to locate a more accurate path.
An example of a hybrid routing protocol is EIGRP.
Conclusion
The routing protocol’s primary purpose is to find a better and more accurate path for transferring the data packet from source to destination. Using various parameters such as the Autonomous system and metric locates a better path; all protocols have pros and cons. They take different approaches to share routing updates and locate the best path.
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