Argthtjtr

The following picture describes the network setup of an institution:

So one side of the building, closest to the server and main switch, has 6 classrooms, each one with 25 computers that connect to a switch that is connected directly to the main switch. Then, on the other side of the building there are another 3 classrooms with 25 computers each. Each classroom has its own switch and they connect to another switch that is connected to the main switch through a CAT7 cable that runs a distance of less than 300ft. The institution has been experiencing a lot of network congestion on the second part (C_7, C_8, C_9), mainly slow internet download speed, and also they wants to add 3 more classrooms on the second part of the building (C_10, C_11, C_12).

My questions are:

1. Is it obvious that the congestion is because of the network's physical configuration, meaning that since C_7, C_8 and C_9 all connect through the same CAT7 the bandwidth is not enough? Would the problem most likely be solved if, lets say, each classroom was connected directly to the main switch through its own CAT7 cable? This was my first thought, without digging in too deep, because of the simple fact that nodes C_1 to C_6 are not experiencing connection problems.


2. 
   

   Even if the answer to the question is no, should they change the physical configuration when they add the 3 new classrooms?
   If so, what would you recommend:

   
   
   
   
   
   • replacing the existing CAT7 cable with fiber optics and have the 6 classrooms(c_7 to c_12) connect to it through the same switch
   
   
   • OR connect each one of the 6 classrooms directly to the main switch with its own CAT7 cable.
   
   
   
   

Please justify your choice so that I can learn.

Based on network topology, there's a obvious bandwidth problem. Lets me explain:

• You have 75 comps connected to a switch, each computer with a gigabit ethernet link, and then, only one gigabit link to the main switch. If, for example, two computers are trying to communicate with the server (LAN request), there's not bandwidth for serving these requests simultaneously.


• Also, you have a "main switch" with another 150 comps, and the server with only one link. Here, you have another bottleneck.

At last, you have this scenario:

• One server, with 1gbps connection.


• 150 comps, with 1gbps each one.


• 75 comps, with shared 1gbps for all of them.

Maybe, a good topology for this deployment are:

• One switch for each classroom. We're talking about 25 1gbps link on each switch.


• One uplink from each switch to the core, working at 2gbps (teaming with two physical links).


• Server connected to the core, also with a greater connection (Maybe 4 teamed links at 1gbps, or a 10gbps link).

Think the main problem aren't on the second building itself, the problem are who all computers on the building are sharing a unique link.

Note: That's my personal opinion based on my past work time and experience. Maybe isn't the best solution for your problem, but I think there's great better topology compared with the actual one.