Introduction To Routing Protocol
In computer networks, the two main important components 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. The process of selection of best path over other paths is known are routing this can be done by software programmed devices known as protocols. Standard protocols help to find the best route to ensure good data transfer. The data packets which have to be sent will also be provided with some information to help in finding the best routing protocol.
Understanding
The main purpose of routing protocols is to know about all the networking routes that are existing 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 by following ways. Routers use remote network administrator to learn about routing such as
1. Static Routing
static routing can be said to have a pre-defined and installed router which has a single path given to the destination. This routing takes the priority over routes chosen by dynamic routing protocols and destination within routing tables is also forced. This is mainly suitable for medium to large sized network because the workload needed to run the network is really large. Stub networks mainly use static routing protocols.
2. Default Routing
The default routing protocol can be defined as the manually defined path to take by the route when no specific route to the destination is known. The router to which the routing information is sent is known as the gateway of last resort. Default routing is mainly used for small networks.
3. Dynamic Routing
Dynamic routing protocols have predefined algorithms that can analyze and choose the optimal path to the destination. This is mainly used because of its adaptability to any kind of network topology.
It can also be called as one of the most commonly used methods of routing. For a better understanding of how it works there is a need to have prior knowledge of certain terms such as convergence and accuracy.
- Convergence
In this routing, the routing table used should reflect the exact accurate and up to date information about the network topology and the time taken by the router to reflect a new change in the value while routing in the routing table is known as convergence time. Routing protocol with fast convergence time is preferable because disturbance can occur during the router spends time in calculating networks for the optimal path. It can also be called an act of approach to a state where all routing tables have detailed information are in steady-state.
- Accuracy
The convergence time which is updated by the router should reflect the exact details about the values is known as accuracy.
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Routing Mechanism
The routing update mechanism is a process of information transfer between the neighboring routers. This can be explained as follows while routing at a particular time duration router to advertise its data information through broadcast or multicast. Various routing protocols have various time intervals. These routing updates contain information of routing protocols such as AS, AD, matrix values and interface details.
1. Autonomous system: AS can be defined as a collection of routers that have similar routing table information simple defined as the boundary line for routing protocol. It can be one-to-one or one-to-many and can also be defined by a numeric value. As it is defined by numbers internet assigned numbers authority provided a range from 1-65535
This is of two types
- The private autonomous system is used for the internal network.
- The public autonomous system is used as an internet backbone.
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 exterior gateway protocols is the Border gateway protocol.
4. Administrative distance: AD can be defined as the reliability of routing updates received from the neighboring router. For example, if two updates are received for the same path from two different routing protocols then the router will check the best AD value to choose the optimistic path. The AD with the lowest value will be given more preference.
5. Metric: If there are two routing updates that have the same Ad value then metric will come in to picture to calculate the best path. Similar to AD different routing protocols use different metric values. The routing protocol with the lowest value will be selected. Example EIGRP uses bandwidth, MTU, 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 own importance in data transfer. Let us now discuss in detail each of these protocols in detail.
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. Basically, the router receives the routing information from neighboring routers which in-turn receives this information from their neighboring router until the destination network. Each neighboring router in the path of a destination network is called hop. Every time a data packet goes through a router the hop value increases and the route with the least hop value will be chosen.
Example RIP directly shares an entire routing table to 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 linked format. It uses three tables.
- The first table contains information about directly connected neighbors.
- Second table handles the entire network topology
- Third table keeps data of the actual path
Example is OSPF. This shares their own link to routers.
3. Hybrid Routing Protocols
Hybrid routing protocols can be defined as the mix of distance vector and link state protocol. To locate a more accurate path hybrid routing protocol uses aspects from both distance vector and link state protocol.
An example of the hybrid routing protocol is EIGRP.
Conclusion
The main purpose of the routing protocol is to find a better and accurate path for the data packet to transfer from source to destination. By using various parameters such as the Autonomous system and metric it locates a better path and all types of protocols have their own pros and cons. They take different approaches to share routing updates and locating the best path.
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