How can a single ethernet cable running to a gigabit switch provide multiple connections with gigabit speeds?


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.