Validating node self description database riverbed

A Direct Link Network with Media Access Control

Objective

This lab is designed to demonstrate the operation of the Ethernet network. The simulation

in this lab will help you examine the performance of the Ethernet network under different

scenarios.

Overview

The Ethernet is a working example of the more general Carrier Sense, Multiple Access

with Collision Detect (CSMA/CD) local area network technology. The Ethernet is a

multiple-access network, meaning that a set of nodes sends and receives frames over a

shared link. The “carrier sense” in CSMA/CD means that all the nodes can distinguish

between an idle and a busy link. The “collision detect” means that a node listens as it

transmits and can therefore detect when a frame it is transmitting has interfered (collided)

with a frame transmitted by another node. The Ethernet is said to be a 1-persistent

protocol because an adaptor with a frame to send transmits with probability 1 whenever a

busy line goes idle.

In this lab you will set up an Ethernet with 14 nodes connected via a coaxial link in a bus

topology. The coaxial link is operating at a data rate of 10 Mbps. You will study how the

throughput of the network is affected by the network load as well as the size of the

packets.

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Procedure

Create a New Project

To create a new project for the Ethernet network:

1. Start Riverbed Modeler Academic Edition ⇒ Choose New from the File menu.

2. Select Project ⇒ Click OK ⇒ Name the project _Ethernet, and the scenario Coax_2 ⇒ Make sure that the Use Startup Wizard is checked ⇒ Click OK.

Local area networks (LANs) are designed to span distances of up to a few thousand meters.

3. In the Startup Wizard: Initial Topology dialog box, make sure that Create Empty

Scenario is selected ⇒ Click Next ⇒ Choose Office from the Network Scale list

⇒ Click Next ⇒ Assign 200 to X Span and keep Y Span as 100 ⇒ Click Next

twice ⇒ Click Finish.

4. Close the Object Tree dialog box.

Create the Network

To create our coaxial Ethernet network:

1. To create the network configuration, select Topology ⇒ Rapid Configuration.

From the drop-down menu choose Bus and click Next.

2. Click the Select Models button in the Rapid Configuration dialog box. From the

Model List drop-down menu choose ethcoax and click OK. 3. In the Rapid Configuration dialog box, set the following eight values and click OK.

The eth_tap is an Ethernet bus tap that connects a node with the bus.

The eth_coax is an Ethernet bus that can connect nodes with bus receivers and transmitters via taps.

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A higher delay is used here as an alternative to generating higher traffic which would require much longer simulation time.

Thickness specifies the thickness of the line used to “draw” the bus link.

4. To configure the coaxial bus, right-click on the horizontal link ⇒ Select Edit Attributes (Advanced) from the menu:

a. Click on the value of the model attribute ⇒ Select Edit from the drop-

down menu ⇒ Choose the eth_coax_adv model. b. Assign the value 0.05 to the delay attribute (propagation delay in sec/m).

c. Assign 5 to the thickness attribute.

d. Click OK.

5. Now you have created the network. It should look like the illustration below.

6. Make sure to save your project.

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Configure the Network Nodes

To configure the traffic generated by the nodes:

1. Right-click on any of the 30 nodes ⇒ Select Similar Nodes. Now all nodes in the

network are selected.

2. Right-click on any of the 30 nodes ⇒ Edit Attributes.

3. Check the Apply Changes to Selected Objects check box. This is important to

avoid reconfiguring each node individually.

The argument of the exponential distribution is the mean of the interval