Typical Layer 2 and Layer 3 Architecture Considerations

When we look at the performance and functionality of Layer 2 switches, we immediately need to understand what the throughput is, how many MAC addresses are supported, is STP support included, is it nonblocking, and so forth. Anything less than wire speed throughput is typically deemed not acceptable in a Layer 2 device. Likewise, the lack of STP support or the inability to auto detect and negotiate link speed would be seen as insufficient.

In a Layer 3 environment, we see the basic Layer 2 functionality as a given and the ability to support multiple routing and routed protocols as an absolute must. With routing now being performed in the switching plane, the ability to forward infinitely more data has become a reality. While there will always be a place for the router, the days of collapsed backbones in the LAN environment are long gone. Layer 3 switching is seen as the norm, and as technology progresses, this too will become dated.

During the evolutionary process our requirements and acceptance of minimum functionality change with it. Just as it is currently the norm for most people to have a mobile phone, this was not the case 10 years ago. Mobile phones were seen as expensive luxury items that very few had or could afford. Today, Layer 2 and Layer 3 switches are the norm, and we expect nothing less from our network manufacturers. All switches need to have a comprehensive feature set that will typically run at very fast speeds. In addition, management of these devices must be simple and cost effective. With the maturity of the technology allowing for large-scale deployment, we are now able to move further up the OSI reference model without worrying whether the basics will function or be available.