Hello! The ICMP (ping) response typically measures the network latency, regardless of the operating system, or the consumption of the same. However, ICMP has a low traffic priority, so if your server has a lot of access, the ICMP response time will increase due to the prioritization of other packages (web services, ftp, etc).
What I suggest is to install an external server monitoring tool (I use serverdensity.com, which is great but paid for). With it you will be able to monitor all the parameters of the server like load, ram, disk, network, etc. In addition, this tool allows you to monitor services externally (such as http access to your application).
In this way, with this data, you can see if the problem is on the server or if it is your hosting that is having problems.
Things you should consider:
1) Since you already said that your IIS was increasing the load of the server, I can tell you that the problem is in the high traffic of your application. Time to upgrade the server or optimize the application.
2) It may be that you have some bug in the application that is generating high load. Sometimes a database query without indexes can cause this problem.
3) You may be experiencing some DDOS attack. Talk to your datacenter to rate.
4) Have you checked that there is no virus on your server? When it comes to Windows server it is indispensable to see this.
I'm sure if you follow these checks, the problem will appear.
Good luck! Thanks.
