**3.3. 'Changing infinity'—didactical experiment**

Because the metric chosen for implementation by the RIP protocol is the hop count metric, and because for representing infinity, the value chosen is 16, the following drawback appears: If there exists a route longer than 15 hops, the protocol will not consider it (RIP uses the numeric value of 16 to mark unreachable devices) [13].

In this next experiment, a network system with routes of length 16 or bigger will be imple‐ mented, with the goal of highlighting the drawback. Assume a network system composed of 20 chain-linked routers as shown in Figure 22.

Starting the simulation, the network will converge after 18 sec. To illustrate the drawback, in Table 3, the routing table of the R1 router is presented.

The absence of connections with routers R17, R18, R19 and R20 can be observed. This takes place because they are situated at the distances of 16, 17, 18 and 19 hops, respectively, from R1.

**Figure 22.** Network topology example in which the routing tables will be incomplete.


**Table 3.** R1's routing table, after the convergence of the network—table automatically generated by the application

Although the initial traffic generated peaked at 117600 bps, it will stabilize at around 14016 bps in the absence of network topology changes and in the absence of some eventual (although improbable) synchronizations of automatic RIP updates (see Figure 23).

An interesting fact about this example is the initial form of the network usage chart—for the situation in which all routers have become simultaneously online. The reason for which the

**Figure 23.** RIP network usage (first minute).

**Figure 22.** Network topology example in which the routing tables will be incomplete.

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**Table 3.** R1's routing table, after the convergence of the network—table automatically generated by the application

improbable) synchronizations of automatic RIP updates (see Figure 23).

Although the initial traffic generated peaked at 117600 bps, it will stabilize at around 14016 bps in the absence of network topology changes and in the absence of some eventual (although

An interesting fact about this example is the initial form of the network usage chart—for the situation in which all routers have become simultaneously online. The reason for which the

RIP Table - R1: 192.168.0.0/30 (Update in 6 sec.)

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The HypeRSimRIP application allows, for experimental purposes, to change infinity's numerical value. If, for example, it changed from 16 to 20, then all the routers could commu‐ nicate between each other (Figure 24), but if it decreased to 5, a drastic decrease in the sizes of the routing tables can be observed (Table 4).

**Figure 24.** The route from R1 to R20 (infinity is represented through 20).


**Table 4.** The routing tables of R1 and R2, after the convergence of the network (infinity is represented through 5)
