I've always wondered whether network interfaces that have these flashing lights flash as a gimmick or do they actually indicate the flow of traffic? Perhaps one flash per packet in or out? I wish I could remember what my call up modem looked like to make a historical comparison too.
TL-SG105E
It's an activity indicator, it doesn't necessarily correlate to anything other than transmission or receiving is occurring. I would also not assume that they work the same between brands. Some devices may have a separate link light, others may not. Some will have a combined tx/rx light, others separate. Some vendors they're configurable. Some vendors use them to indicate things like device boot state. Etc
It's not a gimmick though, they're still useful for that purpose.
They flash a lot longer then it takes to recieve one packet, but it's a useful indicator that tells you that there is some activity.
In 10MB ethernet days, they might have been directly driven by the signal on the wire. After that, they’re pretty much just “a flashing mechanism turned on when activity is present”
I went down some kind of a rabbit hole. I looked up my motherboard's NIC's data sheet and... Dam it! Why is tech so interesting!?
Source: https://datasheet4u.com/pdf-down/R/T/L/RTL8125BG-CG-Realtek.pdf
I'm going off what I remember from a decade ago when working on embedded CPUs that have an Ethernet interface. IIRC, the activity LED -- whether a separate LED than the link LED, or combined as a single LED -- is typically wired to the PHY (the chip which converts analog signals on the wire/fibre into logical bits), as part of its transceiver functions. But some transceivers use a mechanism separate from the typical interface (eg SGMII) to the MAC (the chip which understands Ethernet frames; may be integrated into the PHY, or integrated into the CPU SoC). That auxiliary interface would allow the MAC to dictate what the LED should indicate.
In either case, there isn't really a prescribed algorithm for what level of activity should warrant faster blinking, and certainly not any de facto standard between switch and NIC manufacturers. But generally, there will be something like 4 different "speeds" of blinking, based on whatever criteria the designers chose to use
It depends on the hardware
https://www.tp-link.com/us/business-networking/soho-switch-easy-smart/tl-sg105e/#specifications
Says your switch handles 7.4 million packets per second. How fast is your light flashing?
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