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Routing information protocol is vital to computer networking. Routing information protocol, known as RIP, is a protocol that enables information about routes between networks and hosts to be transmitted, allows hosts and gateways to trade information enabling routers to learn new routes for data to take, and metrically control the hop count from one router to another.
RIP was intended to work with small to moderate sized networks, which pretty much all used the same hardware. It was not intended to work complex network systems. RIP is generally used for steering traffic the right direction in the Internet and is an interior gateway protocol (also known as IGP for short) which means it performs routing within a single self-directed system. On the Internet, an autonomous system is either a group of networks regulated by a network administrator, or a single network. An autonomous system is every now and then referred to as a routing domain. There are several algorithms to determine routes between networks. One categorization is on the type of information that is needed to be exchanged between the networks. Distance vector algorithms exchange only a small amount of data. Each participating gateway keeps information about all destinations within the network.
RIP is a "distance vector algorithm". The basic distance vector algorithm attempts to find the shortest number of "hops" possible to reach the destination. A hop is when data passes through a node. When the network has many interconnected nodes, the shortest distance is harder to find. Distance vector algorithms use tables that contain the "best" routes to every destination in the system. Metrics is used to determine the "best" routes. In small networks, a common metric would be to count how many gateways a message would need to traverse to reach the destination. More complex networks would choose a metric that represents the time delay, cost of sending, or some other quantity. The main point is that the metric represents the "cost" for individual hops. So in the following example you can see that the distance from A to C is only two hops:
A ----- B ----- C
In the diagram just to the right, you can see that the shortest path from A to M could be A-B-C-E-M, A-B-D-H-M, or A-G-J-L-M. There are two algorithms that try to find the shortest path, the Bellman-Ford algorithm and the Dijkstra algorithm. Once one of these algorithms is enabled, each node in the network will identify the most direct path from itself to every node in the network. Each algorithm uses some sort of fixed metrics for the route comparisons. The fixed metrics can be a time delay, cost, or any other type of value used to compare routes.
Algorithms work based on some assumptions, and that is that the nodes never fail, the cost of "hopping" never changes, you have the space to store all of the data, and that you also have the ability to collect the data. However, in practice, these assumptions are not valid. Nodes can/do crash, cost change, and there is a specified limit on how much information can be kept, so this is whenever protocols come in. They do not only do they need to acknowledge a changing topology or arrangement of a network but they also have to implement the algorithm in code.
The Internet is a collection of networks connected by gateways and RIP is intended for use within the Internet. Gateways are hardware and software that link two different types of networks. They use routes to determine where to send the datagrams. If the endpoint is on one of the networks that it is directly linked to the gateway or host, it can send the datagram right to it; otherwise it will try to deliver the datagram to a gateway that is closer its destination. Routing is the method of discovering a path from a transmitter to the anticipated destination, but on the Internet, this would be finding gateways between networks. If the networks are not together, the data must pass through gateways. Once the message gets to the gateway that the destination network is on, the local network router will send the message to its destination.
Each gateway maintains a database, which contains entries of where datagrams should be sent. This database contains a metric attribute that measures the "total distance" to the next gateway. The "total distance" may be the time delay in getting the message to the next gateway, the cost of the sending the message, or a different measurable factor. Each entity or gateway keeps a routing database. There will be access for every thinkable endpoint in the system. Each destination requires information including an IP address, a gateway, the interface, Metric and a timer. As time goes by, the database will be modified with information about the connections are directly linked to the system, as well as information from other systems on different networks. However, Split horizons derive from the indication that it is on no occasion beneficial to direct data about a route back in the route from which it came. For the following example keep in mind R1 and R2 represent routers, and N1 and N2 represent networks. The following model demonstrates the split-horizon rule:
N1 ---- R1 ---- N2 ---- R2
Router 1 initially broadcasts that it has a route to network 1 so there is no purpose for router 2 to this route in its update back to R1 since R1 is closer to N1. Split-horizons are implemented because they provide extra stability. The split-horizon rule says that R2 ought to eliminate this route from any updates it sends to R1. The split-horizon rule avoids routing loops. For example, if R1's connection to N1 were to go down, R2 would continue to notify R1 that it can still get to N1 through R1. If R1 does not have enough knowledge, it may pick up R2's route as a substitute to its failed connection, thus causing a routing loop.
There are a number of limitations of the protocol. It is limited to networks with no more than 15 hops as its longest path; this is to limit the use to moderate sized networks, most RIP networks are flat; meaning in RIP networks, there is no idea of areas or limits and subnet masks are not supported by RIP version 1. Gateways and lines can fail and come back up and to handle this we are required to update the routes and distribute it throughout the network. The process of establishing routes is called convergence. Transmission of the route through the network takes time, so convergence doesn't happen instantaneously. "Counting to infinity" is a method to help speed-up the convergence of the network. This comes into play when the network system consists of several hundred networks, in which a routing table would involve all of them. The concern is that it would take too much bandwidth and time to build the routing table. This is really only a concern for slower lines. Although modern enhancement have been made to RIP known as RIP version 2. RIP version 2 permits more information to be added to RIP packets and offers a modest authentication mechanism. It expands the quantity of valuable information passed in RIP datagrams and adds security provisions.
RIP is an efficient routing protocol used in small to moderate sized networks. Its basic algorithm structure is a distance vector algorithm using hop count and other metrics to navigate through the network. RIP has been around since the days of ARPANET and I predict it will be here for quite some time.