Orhan Ergun No Comments

You always wonder how fast is your network, right? How long does it take the information travel over the network?

I will share with you this special article, which you can use to find the speed of your network and define it with a numerical number.

I will use ring, partial mesh and full-mesh physical topologies to explain the concept.

Note : I assume bandwidth of all the links in the examples are the same for simplicity.

Terminology in the article :

Cd : Connection degree of a node. It is found by using the neighbors of the node. Fraction of pairs of neighbors which are connected to one another.

In figure-1, Router A’ Cd is 0. Because Router A has two neighbors; Router B and Router C. They are not connected to each other. This is same for all the nodes in the figure – 1. Connection degrees of all the nodes is 0.

Ncd : Network connection degree. Sum of the Cds is divided to the number of nodes. In Figure 1, since all the nodes have Cd is 0, Ncd is calculated as 0 as well.

 

Ncd is used to understand the how long an information takes to travel on the network between any given node as well as how badly network fall apart if any node fails in the network. This is the subject of this article, that’s why understanding the calculation and meaning of “Ncd” is very important.

 

ring topology

Figure -1 Ring Topology Connection Degree

 

Let’s look at Figure – 2.

Figure -2 is a full mesh topology. All the nodes in the network is connected to each other. That’s why; Cd of each node is 1 thus Ncd is 1 as well.

full mesh topology

Figure -2 Full Mesh Topology Connection Degree

Understanding partial meshed topology might be little hard but if you understand it, you will get the whole idea.

Router A has three neighbors; Router B, Router C and Router F.

Between Router B, C, F we could have 3 connected pairs. Router B/Router C, Router B/Router F and Router C/Router F.

But in figure-3 only Router B/Router C pair is connected.

If we divide number of connected pairs of router to total possible pairs of router we find the Connection Degree (Cd) of any given node.

Since Router A has only one connected pair of router which is Router B and Router C but totally three possible pairs of routers, Cd of a Router A is 1/3.

Let’s look at Router D in the figure -3.

Router D has two neighbors. Router B and Router F. Total possible pairs of routers is 1 ; Router B/Router F. Since they are not connected to each other Cd of Router D is 0. At least one of its neighbor should be connected for the nodes to have higher Cd than 0.

partial mesh topology

Figure -3 Partial Mesh Topology Connection Degree

 

In figure -4, I just added the link between Router D and Router E in addition to figure-3 and the Network Connection Degree (Ncd) of a network increased significantly which mean the overall speed of a network increased two times.

I think in this point calculation for the Cd and Ncd is clear. If you have any question or any thought please share in the comment box below.

partial mesh topology

Figure -4 Partial Mesh Topology Connection Degree

Conclusion : The speed of entire network is related with the topology. Ring topologies are the slowest and full mesh topologies are the fastest. Management of ring is much easier, cost is much cheaper compare to full mesh topologies though. In this article I show how you can calculate overall network speed, but don’t forget that speed is only one attribute for the network designer to deal with.

Ncd; Network Connection degree is a good indicator to understand ‘ How fast is your network ‘.

Information in this article is solely  my thoughts, never tested on the large scale networks so please just use it as an informational purpose.

So How fast is your network ?

 
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