LAN Design Best Practice
From Best Practices
Contents |
Introduction
Best practice for LAN Design is comming for the experience acquired by manufacturer, consultant, network engineer over the time. They are continuously evolving, following the evolution of technologies. Sharing best practice for LAN design on a wiki is one of the best solution to make sure they are upt to date.
In order to simplify reading and clarify visibility, this best practice document has been split into several chapters, which will be refered to later on. For those interested in this subsections, they are:
Before jumping into details, we will study what are the actual overall LAN design concept.
Design principle
Today's LAN, and more generally networks, are based on the three layer architecture theoretical model:
- Core
- Distribution
- Access
This architecture allow to split the different functionalities, which simplify design, sizing and troubleshooting.
Access
The access layer is where the end users devices, personal computer, IP phone, printer, etc. are connected. It is also where the Quality of Service (QoS) is controlled and validated. This laye is also, usually, the demarcation point of the Trusted Boundary.
Distribution
The distribution layer aggregates the traffic comming from the access layer and forward it to the core devices. It is also where departmental servers or printers could be connected.
Core
The core layer is responsible for the high layer three routing (IP). This is also where WAN access is connected, as well as bandwidth demanding servers. The core layer will very often be used in large campus made of several building. Each building will have an access and distribution layer, ad the core layer will be common to the campus. This is often the situation of a MAN.
Comment
It is not always cost effective to install three physical layer of devices, especially on a site where there are only a few users. Therefore the three layer is called theoretical. It means that some functions could be located in the same device.
For example, in a small location with 15 users, we might use a 24 port layer two switch as access layer, and regroup core and distribution layer in the access router. In some other medium size location, the core and distribution layer could be merged together in a medium size switch.
