Layered Architecture

This pattern refers to the practice of layering services on top of each other, with the prime example being the OSI network layers.


My main exposure to this pattern has been in network stacks, having written some of the layers for one. This approach makes it less cumbersome to add layers, such as ICMP when IP is already separate. They also recommend in the paper decoupling the layers, through callbacks if necessary. I can say from personal experience that this works quite well until someone new doesn't follow the architecture. From there it is a downward slope toward becoming unmaintainable.

With the evolution of mobile technologies more people expect to be able to access software from more devices, where do you see this expectation having the biggest impact on the architectural layers (ranging from close to the client to close to the hardware or anywhere in between)?

I believe the impact is in two places, the hardware layer and the presentation to the user layer. The hardware is different, often with substantially less memory and resources, thus requiring changes. Also, the way a person interacts with mobile devices is substantially different from a PC, and this presentation layer needs to be changed accordingly.