As part of research, we are designing physical network in Simulator environment. On of the way to do is writing .brite file as example Image 3. We are Writing nodes and them connectivity to file. It Describe the node, BW, Edges etc… such kind of system used by many simulator like cloudSim and NS2. In single Sentence I will say Physical network or topology in notepad. (E.I .brite File).
The specific details as per ref  regarding how a topology is generated depend on the specific generation model being used. We can think of the generation process as divided into a four-step process:
Placing the nodes in the plane
1. Interconnecting the nodes
2. Assigning attributes to topological components (delay and bandwidth for links, AS id for nodes, etc.)
3. Outputting the topology to a specific format.
The BRITE Output Format
We can generate .brite file using brite generating tool given here A BRITE-formatted output file contains three sections:
1. Model information:
information about the topology contained in the file. Includes number of nodes and edges, and information specific to the model used to generate the topology. We have Different topology model like RTWaxman, ASWaxman… Again it provides related data in same line.
for each node in the graph, a line is written into the output file with the following format :
Image 1: Format for node assignment in Image 3
|NodeId||Unique id for each node|
|xpos||x-axis coordinate in the plane|
|ypos||y-axis coordinate in the plane|
|indegree||Indegree of the node|
|outdegree||Outdegree of the node|
|ASid||id of the AS this node belongs to (if hierarchical)|
|type||Type assigned to the node (e.g. router, AS)|
Table 1: Nodes Detail in Brite File
For each edge in the graph, a line with the following format is written in the output file:
|EdgeId||Unique id for each edge|
|from||node id of source|
|to||node id of destination|
|bandwidth||bandwidth (assigned by AssignBW method)|
|ASfrom||if hierarchical topology, AS id of source node|
|ASto||if hierarchical topology, AS id of destination node|
|type||Type assigned to the edge by classification routine|
Table 2: Edge Details in Brite File.
Image 2: Edge details Given in Image 3
Image 3: Britefile Example 
Above image describe, Topology having 5 Nodes and 8 Edges
 http://www.cs.bu.edu/brite/user_manual/n (BriteFile) (BriteFile)ode8.html4