PC networking

This is going to sound like a dumb question but I am just curious.

How does Windows know it is connected to a device (through ethernet) and how does know to display the "connected pcs" emblem? Tthe reason why I ask this is right now I am on a computer with 3 nics, 2 of them are not showing up as connected. Now the reason why is the 2950 switch I had them connected to is currently powered off. My question is there some type of layer 1 keepalive/ack system to interact with the physical nics on devices it is it some sort of layer 2 system (I know it cannot be any higher than that in the OSI stack because then every machine connected via ethernet would need a router/layer 3 or higher device involved, right??)

I know that power can be provided over Ethernet so are electrical signals used as a keepalive/ack on the nics or is it something else? If it were electricity then all ports would need to be POE ports so I am not sure about this one either. I think there is some layer 2 system set up because if I actually shut down the ports on my devices, windows acts as if they are not connected, unless of course when you shutdown a port it actually kills the flow of power to that port, not just frames/packets.

That seems likely to me because all of the frames/packets are simply 1-2 layers away from being electrical signals anyway, so stopping traffic flow and stopping the electrical signal would be the same (?). If someone can point me in the right direction that would be great.

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Comments

stuh84

Would it not be the ARP protocol per chance?

Bl8ckr0uter

stuh84 wrote: »

Would it not be the ARP protocol per chance?

I don't thing so because this has nothing to do with resolving an an address, at least I don't think.

tiersten

It can tell there is a link because of the Ethernet physical layer i.e. layer 1. You'll have to dig around in the 802.11 standard docs for more details about what specific voltages and conditions it needs before recognising that there is a link.

Use paragraphs in your posts. A massive block of text is hard to read and understand.

Bl8ckr0uter

tiersten wrote: »

It can tell there is a link because of the Ethernet physical layer i.e. layer 1. You'll have to dig around in the 802.11 standard docs for more details about what specific voltages and conditions it needs before recognising that there is a link.

Use paragraphs in your posts. A massive block of text is hard to read and understand.

Sorry. It was late and I was very tired. I just wanted to be sure that it was in fact at layer 1. So when you go into the ios of a router/switch and say shutdown, what you are actually doing is stopping power from flowing. I thought so but I wanted to be sure.

RobertKaucher

Just to make a minor correction of Tiersten: 802.3 is Ethernet, 802.11 is for the wireless standards.

knwminus, here is a question for you:

How many pins are there on an RJ-45 connector and what are they used for?

If you can answer that then you know how two devices know they are connected to each other.

tiersten

RobertKaucher wrote: »

Just to make a minor correction of Tiersten: 802.3 is Ethernet, 802.11 is for the wireless standards.

Oops. Yeah. 802.3 not 802.11. My bad.