Airport Application

First note that the "schematic" is not 100% reliable and is known to "shift" what it displays.

However, by design, devices using a wired (Ethernet) connection will be shown with a solid line. Those with wireless connections are represented with a dashed line.

When devices are shown as "stacked" indicate that they are connected in series; whereas, those "branching off" are connected in parallel.

For example, in a simple extended network with an AirPort Extreme and an AirPort Express extending that Extreme will be shown as follows:

• Single solid line between the Internet and the Extreme.
• Single dotted line between the Extreme and the Express.

Another example of an extended network using two Express extenders would appear as:

• Single solid line between the Internet and the Extreme.
• Two dotted lines one each running to an AirPort Express.

Not sure if it matters at all as far as signal strength and connectivity for devices but was just curious as to why and if there's any benefit or drawback to Serial vs. Parallel.

As far as overall bandwidth, ideally you will want all connections between routers to be wired creating what is known as a roaming network. With this type of network you can then place base stations where you need wireless access. It really doesn't matter how they are represented (in series or parallel fashion) in the AirPort Utility display.