Question

12.Consider a 10Mbps Ethernet network consisting of 20 nodes interconnected by a bus topology with a single bridge placed in the approximate centre of the network resulting in an equal number of nodes on each side of the bridge.

a) Briefly explain why collisions can/cannot occur.

b) If two pairs of nodes attempted to communicate at the same time, discuss the throughput they can achieve.

Answer 1

let us suppose the 20 nodes are labelled as 1, 2, 3 uptil 20.

Since nodes are eually placed on each side of the bridge connected by bus topology, so on each side of the bus we have 10 nodes as shown in the following figure drawn in in MS Word

a) The collisions will occur because when any node on one side of bus topology wants to communicate to another node on the other side of the bus or on the side of the bus as any other pair of nodes may be commnunicating with each other at given time and hence both messages from both the pairs of nodes may intefere with each other.

b) The throughput achieved will be 10 times less than the given bandwidth as we have a total of 10 pairs of nodes communicating at a given time since 20 nodes are there in the newtork

So net throughput = 10 Mbps / 10 = 1 Mbps