Routing Protocols Simulation over a 8

Routing Protocols
Simulation over a 8-node
network with OPNET
OPNET
Routing Protocols Simulation
ROUTING PROTOCOLS SIMULATION IN A 8-NODE
NETWORK WITH OPNET
The aim of this project is to simulate the behavior of some routing protocols in a
network with 8 nodes with OPNET simulator. The following figure shows the scenario that is
going to concern us in our study:
Figure 1:
8-node network
Nowadays, with the development of new technologies and specially those related to
Internet, routing protocols have been, and are, constantly revised and improved. Although there
exist lots of them, there are some ones that have spread more than others and have taken a great
part of the market, such as RIP (Routing Information Protocol), OSPF (Open Shortest Path
First), IS-IS (Intermediate System to Intermediate System) and BGP (Border Gateway
Protocol). However, not all of them are always useful as they have been designed in order to
run in different kinds of networks.
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OPNET
Routing Protocols Simulation
On the one hand, despite BGP is a very important protocol, it is not going to be simulated
in our network since it works between different Autonomous Systems and is usually
implemented among the networks of Internet Service Providers (ISPs), situation that has
nothing to do with the 8-node network.
On the other hand, protocols such as RIP, OSPF and IS-IS, which are Internal Gateway
Protocols (IGPs) are going to be simulated under the same initial conditions. At the end, we
will be able to take conclusions about the network convergence time, the metrics used, the
selected paths and many more issues that depend directly on the routing protocol implemented.
When examining the results we should take account of the main features of each protocol
in order to evaluate whether the outcome has been satisfactory or not.
In the first place, RIP is a distance vector protocol that uses hop count as the metric to
choose the best path to a destination. Since a packet is discarded by default if hop count is
greater than 15 hops, this protocol is only useful in small networks.
Secondly, OSPF is a link state protocol and uses a more complex metric than RIP. It only
sends updates when there are changes in the network topology and distributes the routers in
areas. It doesn’t have distance limitations in sending packets and is therefore useful in medium
to large networks.
Finally, IS-IS is the most complex of these three protocols and is the one that differs more
from the others in the way of implementation. It is an OSI protocol (Open System
Interconnection) by the ISO (International Organization for Standardization), useful for large
networks. Some of its peculiarities are the two-level hierarchy and the different way of
addressing.
In order to prove that the protocol is running properly, the first step we should take is to
examine the routing tables and verify that each router has the knowledge to reach all possible
destinations. For instance, in a network where IS-IS is running, we should see something
similar to the following routing table:
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OPNET
Routing Protocols Simulation
Figure 2:
Routing table in a network running IS-IS
Once total connectivity is reached, we will be able to study the different parameters
mentioned before. The easiest way to compare the outcomes of the different routing protocols
is to make some graphs. One of the features that can lead us to choose one protocol before than
another is the time it spends to make the network converge. This parameter relies in the
complexity of the protocol, fact that is easily reflected in the following pictures, which show
the convergence time in a scenario implemented with the different protocols:
Figure 3:
Convergence Time Graphs
To sum up, at the end of this project we will be able to know which is the best routing
protocol for the network. Furthermore, we should know which parameters to adjust in order to
make the network as efficient as possible.
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