WMS or Web Mapping Service is a popular way of distributing geospatial data.
However, something that has been showing up more recently is that people may overlook the performance gains they get with simply using client-side asychronous access. Instead, they make one of their server components work really hard and subsequently slow down their entire application.
Cascading Services through a single server.
In the diagram you can see one WMS Server requesting information from another WMS Server, then sending the combined information onto the client application. Whilst this may seem "convenient" to a system administrator, the solution is also likely to underperform. One service is going to be dependent on the other service, and do some unnecessary extra work. On top of this, often the requesting server doesn't just pass through the information, it saves the information to its own system, then passes on the data. This doubles up the work needed to be done to present the information.
A better way to get the data to people faster, is to make "asynchronous" requests to the different services, from the client.
Asynchronous delivery of geospatial data 
In this instance, neither service is dependent upon each other, and neither service has to do more work than it needs to. By saving your system resources, you get to save time, with faster responses. And, by conserving your system resources, you can do more with your existing hardware.
This is typically how we setup our web based applications. The web-browser becomes the client that makes independent requests for information from what services it wants. The end result is a fast, responsive application that makes the best use of available resources.