How can a single ethernet cable running to a gigabit switch provide multiple connections with gigabit speeds?
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A Gigabit switch with 10 Gigabits cable and 10 ports could give each port 1 Gigabit per second, even with 1 cable.
Each nano second can be divided into 10 “slots”, 0.1 nano second long each. The ports would split each frame to pieces, and take turns using the ethernet cable, sending in a small piece of the frame at a time. This way, each port would get 1 gigabit transfered per second, while sharing the cables with others.
It can’t. It can give any of the computers connected to the switch 1 Gbit/s speeds, but not at the same time.
If computers A and B tried to send to computer C, A and B would be sending at half a gigabit each.
If you wanted to transfer at more than 1 Gbit to computer C, the switch would need at least one port with more than 1 Gbit speeds, and C would have to be connected to that port.
If you’re asking how computer A can talk to B, and D can talk to E at 1 Gbit at the same time, that’s because they’re not going through C at all.
The switch directs the data from A directly to B and D to E without it first sending anywhere else.
Switches typically have higher speed uplink ports, so that you might have 24 or 48 downstream ports capable of operating at 1G each, then you have a pair of higher speed uplinks ports, which might be 10, 25, or 40G uplinks.
Outside of a certain datacenter environments, it’s very unusual for clients to consistently maintain high utilization levels. So 2 10G uplinks (20G total) are almost certainly going to be able to handle the traffic of 48 1G connections.
If not, you chose your hardware wrong and likely should be using high throughput fiber switches that link to the servers via fiber, and use bundled 40G / 100G uplinks.
Source: Me. Network engineer currently slacking off at work.
It can’t but in many cases, that is not the point of a switch.
Imagine that you have 5 computers connected to a switch. Computers 1 and 2 are transfering a large file between each other and are not doing anything else network related. They would be able to transfer the file at 1Gbps.
Let’s say that computers 3 and 4 are downloading a file from computer 5. Since computer 5 only has a 1Gbps port, the total amount of bandwidth computers 3 and 4 can get their files at could not exceed that 1Gbps, total.
But both scenarios could happen at the same time. Each of those transfers would be a total of 2Gbps of bandwidth.
Switches often have a rating called their Backplane bandwidth. This describes how much total throughput the switch is capable of transferring between all of its ports. For example, there are some 48 port switches that might only have 24Gbps of backplane, which means all of the ports total through put can not exceed 24Gbps. There are some switches where ports are in groups, like ports 1-24 have full bandwidth between each other and 25-48 and ful bandwidth between each other, but transfers between the first group and second group might be limited to 10Gbps or something.
Oops, I guess my dream of all devices being connected at the same time with lightning speeds is just a dream.
The short answer is: It can’t.
The longer answer is: Using some very clever software and hardware, it splits up a single data stream to more than one over ‘time’ and also tags some data as ‘special’ to have higher priority so it can pause less important data.
Slightly longer answer: Using that ‘time’ analogy, it also uses the packet number and retransmit functions, as well as some clever software that guesses what the content of each packet is, that are baked into the protocol so that it knows that other data streams are ‘more important’ than others can just wait. The router is operating at speeds many thousands of times per second, but not all data needs to operate at those critical speeds.
Streaming video needs lots of data, but you buffer it in seconds. You can ‘slow down’ the data stream of network files (which are not as time sensitive) to give the video a couple of extra milliseconds seconds to download 2-3 seconds of video buffer, and then the file can resume after that. And that is because you are going to notice when your video buffer runs out, rather than your network file transfer taking a few seconds extra. (network transfer is mostly bound by CPU speed most of the tim, but that is off topic.)
However, audio and video calls have lots of data AND they are crucial to being on time. So you need to have all other stuff stop, and let that time sensitive and probably more importantly in the proper order show up. The human brain is kind of amazing, and it can automatically correct for quite a bit of weird audio stuff, but video is REALLY noticeable. So, even within that one stream, the video is more important than the audio.
Really makes you look at the router which does that for XX devices, and also authenticating wireless clients and switching channels, and encryption for that wireless to be renewed, etc. etc.
Kind of amazing, eh?
A network switch is like a traffic junction with stop lights. You can have a 4 way or 6 way or 100 way junction, but at any one time only the roads that don’t crash into each other can go.
no car needs to change lanes (no need to squeeze two lanes into one) while going through the junction, so technically the bandwidth of the junction is no different than the roads going in and out of it. if the light is green you can coast through with no loss (maybe you will slow down a little, known as “overhead”) but on a total time basis, the junction does cause traffic to slow down because due to the shared nature of a junction, eventually somebody needs to wait for somebody else.
a network switch is exactly like a traffic junction, but a very fast and efficient one that can switch the lights many times a second to let a few cars go at a time. to go into more detail, some more advanced switches are like traffic cops who can decide to let some special cars go earlier and make other cars wait longer(prioritzation) or even designate certain lanes to be carpool lanes so all vehicles on it get priority.
tldr; when you’re allowed to go, you can go at your usual speed. when you are not allowed to go, your speed is zero for that entire time waiting. because electronics, this stop and go can happen thousands of times a second. but real people only care about average, and on average, if all lanes are busy, you will obviously not be getting your usual speed.
If one road leads to a roundabout and then out to five other roads, but the speed is 55mph to all the roads, you’ll get that speed to each branch, but you’ll get a traffic jam if they all try and take the same road out.
Very few internet connections are gigabit. It’s usually the choking point, where data on a network can usually move around the network at gigabit speeds.
Not everyone is going to use a full gigabit 100% of the time unless they’re running a big website or torrent host or something like that. At home, you’re not going to run into any problems unless five or ten people are streaming 4K netflix at once.
It doesn’t, not really. Think of it like water pipes, where the speed rating is just the diameter of the pipe. You can split a single 1 inch pipe into multiple 1 inch pipes, but you can still only get so much water from that one source pipe. Now, the water isn’t going to be flowing all the time though. If only one of the pipes has an open valve, then you get the same amount of water flowing through it as the source pipe. But if two are open, the pressure drops and you only get half as much out of each.
Similarly, you can get gigabit speeds to any one given device, as long as nothing else is actively sending or recieving data at the moment, but if multiple devices are “talking” at the same time, the speed will slow down for each individual device. The gigabit rating on each port is just the maximum speed that the port itself can handle over that one connection.
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