Dual network switches

KD0RC

I have occasionally been experiencing network drops at my home station. On a whim, I took all of my gigabit devices (computer, Flex 6400) and put them on one NetGear Gb/100 Mb switch. I put all of my 100 Mb gear (TeensyMaestro, TV, printer, etc) on another NetGear Gb/100 Mb switch. So far, no drop outs. Note that each switch is plugged directly into the ISP-provided router (one switch is not plugged into the other).

My question is - is this just coincidence, or is this truly a better setup?

reed

Hi Len,

I'm going to say it's a definite "maybe".

Network switches aren't all equal in terms of performance, even if they have the same port speed configuration. Internally, there is a crossbar of some kind doing the port-to-port routing, and it has some maximum bandwidth. Even if a single port-to-port transfer may support the full gigabit speed, the switch may not have internal bandwidth on this crossbar to support gigabit transfers on multiple ports simultaneously, resulting in lower speeds (for a given connection) when under additional load. In addition to the total bandwidth, the internal crossbar may also experience increased jitter or latency depending on the number of simultaneous data streams and routing "fairness" strategies employed internally.

With that in mind, consider what your new topology does:

• Any traffic from the radio to the computer stays on a single switch - no routing or extra hops needed
• The TeensyMaestro isn't very latency sensitive, so jumping between switches through the router isn't a big deal
• Any traffic from other devices going to the Internet (e.g. TV) doesn't affect the switch the radio traffic is on

If we assume that one of your networking devices was running into either of the internal networking limitations described above, then your new topology would likely help, not because you separated the speed classes into 100Mbps vs 1Gbps, but because it eliminated traffic patterns that would interfere with your radio-to-computer connection, and streamline the radio-to-computer connection for minimal hops.

Reed

John KB4DU

Are you able to select 1GB vs. 100Mb?

KD0RC

Hi John, No, the switches just follow the speed presented to them by whatever device is plugged in.

KD0RC

Thanks for the excellent explanation Reed, I appreciate it!