Poor WAN Performance Issues

One of the things I occasionally come across is poor performance to the ISP.  Usually I find that there are two potential issues that cause this.
1.  Bandwidth utilization - Caused by traffic of some sort.  It can be traffic that is ok, malicious traffic, or that other malicious work traffic called youtube or facebook, etc.  Either way, bandwidth utilization is usually the number one reason I find for poor performance across a WAN.
2.  Port configuration issues - This usually comes in the form of port speed/duplex issues.  I have seen many times in the past where the ISP configures their port they way they want to without consulting the customer (me as their vendor) as to what needs to be configured on the customer end.

In explaining this to another engineer earlier, I thought I would post my diagram to show where these are to be looked at to make sure the speed/duplex match.  It will take a call to the ISP to verify their settings so that you can match yours, but I have overcome many performance issues my making sure they match.  Your ISP probably wont care enough to let you know on their own.