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Routing Information Protocol (RIP)

Hop count serves as the main statistic in the distance vector protocol known as Routing Information Protocol (RIP). RIP specifies how routers should exchange information when transferring traffic between a collection of connected local area networks (LANs).

In this article, we will look more into the RIP according to the GATE Syllabus for (Computer Science Engineering) CSE. We will read ahead to find out more about it.

Table of Contents

What is the Routing Information Protocol (RIP)?

Routing Information Protocol is referred to as RIP. Within an autonomous system, the intra-domain routing protocol RIP is utilised. Intra-domain in this context refers to packet routing within a specified domain, such as web browsing inside a corporate setting. Knowing the packet’s structure, the number of fields it includes, and how these fields affect the routing table is crucial in understanding the RIP.

Before delving into the packet’s structure, let’s first take a closer look at the following:

  • Since RIP is built on a distance vector-based approach, we can think of the entire structure in the form of a graph, where nodes represent routers and links represent networks.
  • The destination, or network address, is listed in the first column of a routing table.
  • The number of networks needed to get to the destination is the hop count. The cost of a network would depend on how many hops are accessible.
  • Since infinite in RIP is specified as 16, it can be applied to smaller networks or autonomous systems. As 16 is infinity, the greatest number of hops that RIP may have is 15; hence, it should not contain more than 15 hops.

How is Hop Count Determined?

A single hop occurs whenever the router sends a packet to a network segment.

Whenever the packet is forwarded from router 1 to router 2, it counts as one hop. The number of hops will increase as the packet is forwarded from router 2 to router 3 and decrease when it is forwarded from router 3 to router 4. Similar to this, RIP can accommodate a maximum of 15 hops so that 16 routers can be set in a RIP.

RIP Message Format

We now examine the RIP message format’s structure. Messages are used to exchange information across various routers. The RIP message has the following fields:

  • Command: For requests or responses, an 8-bit field is used. The request has a value of 1, while the response has a value of 2.
  • Version: Version in this context refers to the protocol version that we are using. When we are using version 1 of the protocol, we enter 1 in this field.
  • Reserved: Since this is a restricted field, it is entirely filled with zeros.
  • Family: It is a 16-bit field. We enter the value 2 in this section because we are using the TCP/IP family.
  • Network Address: It has a 14-byte field definition. When using IPv4, only 4 bytes are used; the remaining 10 bytes are all zeros.
  • Distance: The hop count, or the number of hops required to reach the destination, is specified in the distance field.

How Does the RIP work?

Example 1

If a network has 8 routers and Router 1 wishes to deliver data to Router 3, Router 3 cannot accept the request. If RIP is enabled on the network, it will select the route with the fewest hops. The network mentioned above has three routes: Routes 1, 2, and 3. RIP will select Route 2 because it has the fewest hops, just 2, compared to Routes 1 and 3, which both have 3 and 4.

Example 2

What if R1 wishes to relay the information to R4? Data transmission from r1 to r2 can take one of two paths. Since both routes have exactly three hops each, RIP will deliver the data to both routes at the same time. In this method, load balancing is managed, and data arrive at their destination a little quicker.

Advantages of RIP

The benefits of a RIP are as follows:

  • It is simple to set up.
  • It is less intricate.
  • Less of the CPU is being used.

Disadvantages of RIP

The drawbacks of RIP are as follows:

  • The hop count measure is used in RIP to select the route. This route would not be picked if a better bandwidth option was available. Let’s use an example to better grasp this situation.
  • The VLSM is not at all supported by the classful routing protocol RIP. The subnet mask information is not included in the routing updates of the classful routing protocol.
  • It generates a lot of traffic by broadcasting the routing modifications across the whole network. The routing database in RIP is updated every 30 seconds. Every time an update happens, it sends a copy to every neighbour but the one who initiated the update. There is a lot of traffic created by sending updates to every neighbour. This is called the split-horizon rule.
  • It has a slow convergence issue. It frequently takes minutes for the system to stabilise or choose an alternate route when a router or link dies; this issue is referred to as slow convergence.
  • A RIP can be designed to accommodate a maximum of 15 hops or a maximum of 16 hops.
  • The RIP is less dependable than the other routing protocols since it has the largest Ad value. The Administrative Disturbance value (Ad value) of RIP is 120. The protocol is more dependable than a protocol with a higher Ad value if the Ad value is lower.

How Does RIP Update Its Routing Table?

The routing table is updated using the following timers:

RIP update timer of 30 sec

Every 30 seconds, the RIP-configured routers broadcast their updates to all of their nearby counterparts.

RIP invalid timer of 180 sec

The RIP invalid timer is usually 180 seconds,and thus, if the router loses network connectivity or a link breaks, the neighbouring router must wait 180 seconds before accepting the update. It will label a specific route as impassable if it does not get the update in 180 seconds.

RIP flush timer of 240 sec

If the router doesn’t receive the update in 240 seconds, which is approximately equal to 4 minutes, the neighbour route will remove that specific route from the routing table. This is an extremely sluggish procedure because 4 mins is a long time to wait.

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