Ethernet 802.3 MAC Protocol Lab
Lab Purpose:
The goal of this lab is to analyze the Ethernet network topology. In this lab we will see how changing transmission rates and the number of hosts on a network affects the interactions between different hosts and total network stability.
figure 1. This is a graphical representation of an ethernet LAN with 8 nodes. Here, we see node 6 is sending a packet.
figure 2. Each node is connected to the LAN via a duplex link,
for transmitting and receiving.
When one node transmits, we can see above that all the nodes hear it (as seen
in figure 2) even if only one node is the proper destination.
Link to more pictures showing step-by-step packet transmission
Changing the number of nodes on the network, and the rate at which they can tramsmit affects the total traffic. If we make the transmission rate too high, packets are discarded as the buffers at each node begin to overflow. So, by limiting the rate at which nodes (hosts) may transmit, we may in fact be improving the network stabiliy and throughput.
Looking at the pictures:
You can see that as one node sends data, all other nodes then receive it. This
does not prevent the other nodes from continuing to send data, increasing the
network utilization. When too many packets are sent, you'll begin to see lost
packets falling.
Hint: Each source node has its own destination sink (Hence, multiple graphs). Refer to this link for the graphs: graph.png
For the following questions below, refer to ethernet_bc_es.tcl
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> In the current network topology all nodes are sending data to the last node of the LAN.
1) What is the Network Utilization of the current network topology?
>Run the ns simulation with different values for the transmission rate. >For the following questions you will analyze a graph similar to graph.png
3) From the data generated by the simulation, plot the number of bytes received
at the destination node.
4) From the data generated by the simulation, plot the data rate at which the destination node receives packets.
5) Discuss and compare the transmission rates of each node. (Hint: Why doesn't the destination node receive packets from each source in equal amounts?)
site created by: Brian Cassell & Edwin Soebijono
