In network transmission, the unit of Mbps is often used, and GbE or 1 GigE network cards are now very popular, and this thing is called "Gigabit network cards".
In network transmission, the unit of Mbps is often used, and GbE or 1 GigE network cards are now very popular, and this thing is called "Gigabit network cards".
At the same time, it is very common to use GB or MB to describe the size of a disk. This is called Gigabyte or Megabyte.
But when describing file size (or disk space), we usually use GiB or MiB to describe it.
The comparison between GB and GiB is actually the relationship between the above labels, KB, MB, GB, TB comes from the decimal three-digit notation, that is, every three digits are added to a comma, which corresponds to the calculation method in Europe and the United States, which comes from the "short scale system", which originally refers to 1000 previous numbers, such as 1 billion = 1000 million, that is, 1 billion = 1000 million. But this method of counting itself can be confusing. If a more sensitive reader sees the "short scale system", they will definitely think of the "long scale", which is based on millions (10 to the 6th power) as the next level, and in the long scale difference system, 1 billion represents "trillion", representing 1 million million, that is, 10 to the 12th power.
Whether it is the short grade difference system or the short grade difference system is used in Europe, this matter will cause confusion, so the International Organization for Standardization has defined a set of standardized prefix counting methods according to the short grade difference short method, with 10 to the third power as the grade, which is our current kilolo, trillion, auspicious, Tai, beat, Ai, Ze...... The counting method too.
In the same way, in binary, we will calculate the size of the number by the n*10 power of 2, so there is a binary prefix, which is written in a similar way to the prefix of the national standard, but in English, the last two digits are replaced with bi according to the pronunciation convention, for example, Giga is changed to Gibi, Tera is changed to Tebi, and the MB (megabyte) we say has also been changed to mebibyte, which is the abbreviated MiB.
Back to the question of the message: 1000Mbps network, converted to MB is how much, first of all, let's figure out what 1000Mbps is, as mentioned earlier, it is GbE, this thing is called "Gigabit Ethernet (Gigabit Ethernet)" Note that Giga is used here, which means that it is calculated in 10 decimal system, that is, 1,000,000,000 bits can be transmitted in one second.
What we all know is that a byte is made up of 8 bits. Theoretically, 1000Mbps of network transmission bandwidth can deliver 125Megabytes of data in one second.
However, we have to know that the data you need is not optically transmitted during network transmission, and the data needs to be changed into network data packets in the process of transmission.
This information doesn't make much sense for the transfer of the file itself, just to be able to complete the network transfer. At this time, the speed you see when transferring files in the file manager is no longer the speed of the network card, but the speed of the net file stream data acquisition after the transfer is packaged layer by layer.
Therefore, some people are asking, why is it that the transfer speed does not reach 125MB/s even though it is a gigabit network card? Part of the speed lost here is the transmission traffic occupied by the packaged data packets.
Therefore, the speed of not reaching 125MB/s is not a problem of the network, but a normal phenomenon.
So is it possible to increase the transfer speed even further, as close as possible to the limit of 125MB/s? We have to start with the Ethernet frames at the data link layer.
I talked about Ethernet frames before, and there is an MTU setting called the Maximum Transmission Unit, and each Ethernet frame can be defined as a transmission unit. The size of a frame defined by Ethernet is 1538
When the transmission starts on the network device, the device will first send out a 7-byte pilot code, and then transfer the subsequent data in a fixed format and sections. This process is called a transmission unit, and the final frame ends with a four-byte checksum. The maximum number of bytes of data in the Data section is 1500 bytes.
If we think of a frame as a truck, it looks like this:
The front of the locomotive, the frame, and the wheels are all encapsulated structures of the data packet, and the carriage is the data in the data packet.
Even if there is little data, the front of the car, the frame, and the wheels cannot be streamlined.
But we can try to increase the size of the carriage so that we can carry as much cargo as possible in one trip. This is to reduce the rate of loss per transmission packet.
Therefore, we can calculate the transmission rate that we can know, roughly efficiency = real transmission data content/frame size, so we can calculate the efficiency calculation on an Ethernet with an MTU of 1500 is 1500/(1500+38)=97.53%, this is still a clean Ethernet frame, if we attach Vlan and other settings on the switch, we need to add the number of packets of VLan. And that's what it feels like to take a truck as an example:
One truck is loaded into another truck as cargo.
In this case, the four-byte mark of the VLAN must also be added, and it becomes 1500/(1500+38+4)=97.28%.
Therefore, in terms of network transmission efficiency, the real transmission efficiency of 975.3Mbps can be achieved with Gigabit Ethernet, and 972.8Mbps transmission efficiency can be achieved if VLan is added. Of course, this is the highest value in theory.
Isn't this number divided by 8 even if it is the number of bytes that can be transferred to a file on the network? Not yet!
Generally, we use SMB for file sharing and transmission, which is a protocol in the TCP protocol set:
Look—there's also a bunch, control, basic data, and a host of other extras. Therefore, 975.3Mbps divided by 8 to 121.9MB/s is not a true value for a file transfer, and it has to be discounted.
It's still a truck, this SMB is just the cargo in the truck compartment, but it's not your document.
For example, this truck is loaded with an Apple laptop, and you want an Apple laptop, but as long as you are not buying a second-hand computer, most computers still have a box when they are shipped, and a package of this box is the data package transmitted by SMB.
In your purchase behavior, it is just a computer that is packaged layer by layer. Excess stuff is actually shipping loss.
Knowing this background information, you will see that with the same bandwidth of 1000Mbps, you need to reduce the loss of these protocol packets that come with it. What to do?
It would be nice to change to a larger compartment with more data at once. This brings us to jumbo frames on the switch, which refers to frames with an MTU greater than 1500. As a specification, jumbo frames can be set to 9000 bytes. This size far exceeds the limitations of the IEEE 802.3 Ethernet protocol. It can transmit up to 9000 bytes of data in a packaged Ethernet frame, which is MTU=9000.
If we calculate according to the previous efficiency algorithm, we can know that efficiency = 9000 / (9000 + 38) = 99.58%, which is more than the 97.53 of the default Ethernet.
However, it is important to know that the network not only exchanges the contents of file transfer packets back and forth, but also transmits some small packet instructions non-stop.
At this point, it is possible for a huge frame to transmit only a small amount of load. For example, a large container truck has only one small cargo in it:
As with truck drivers, Ethernet actually takes up the same Ethernet frame size to transmit small packets of data. As a result, more than a dozen bytes of data have to occupy hundreds of times the transmission bandwidth on the jumbo frame switch. As a result, the performance of the network will decrease instead of increasing.
The general practice is to separate the two types of switches, and use a switch with a jumbo frame set for large data transmission, while the transmission of small instructions and small data packets will be transmitted by using an ordinary Ethernet switch with an MTU set to 1500.
This separates the storage network from the common service network. In order to meet the storage requirements, storage protocols such as iSCSI have emerged that run exclusively on Ethernet. Of course, there are also some Fibre Channel switches that specialize in storage services. This is a bit out of the realm of Ethernet, which is often used.
Author丨iN in
Source丨 post.smzdm.com/p/azoqenzp/
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