带宽(Bandwidth)是计算和网络世界中的常用术语。事实上，它经常被使用，以至于很容易忘记有些人实际上并不理解它的含义。
在Google(Google)上快速搜索“什么是带宽”会从字典中找到两个不同的定义，但都不是正确的(neither of which is correct)。本文将解释什么是带宽，它是如何测量的，以及不同任务需要多少带宽。
什么是带宽？(What Is Bandwidth?)
带宽(Bandwidth)定义为在指定时间段内通过指定连接可以传输的最大数据量。
此定义最常用于指互联网服务提供商或ISP给出的下载和上传速度。但是，它可以指代任何类型的连接，包括以太网(Ethernet)、USB、HDMI等。
例如，以太网(Ethernet)分为不同类别的电缆：最常见的是 3、5、5e、6 和 6a。以下(Below)是电缆类别及其最大理论带宽的列表。
- Cat3：每秒 10 兆比特
- Cat5：每秒 100 兆比特
- Cat5e：每秒 1000 兆比特
- Cat6：每秒 10 Gb
- Cat6a：每秒 10 Gb
需要注意的重要一点是带宽不是指速度(does not refer to speed)。它指的是数据容量，特别是从网络中的一个点（或节点）到另一个点。如果您想测量数据传输的速度，您将需要检查网络的延迟（通常称为 ping）。
如何测量带宽？(How Is Bandwidth Measured?)
带宽(Bandwidth)是通过网络每秒传输多少比特来衡量的。但是，要理解这一点，您必须首先了解什么是位。
“位”是计算机中最基本的信息单位。该术语是二进制数字的缩写形式；换句话说，是 1 或 0。您可能还知道“字节”这个词。如果组合 8 位，则产生 1 个字节。
由于计算和网络技术的进步，通过网络传输的比特数量急剧增加。在网络的早期（以及最近的 90 年代末到 2000 年代初），带宽可以以每秒几千比特或千比特来衡量。
现在，带宽通常以每秒数百万比特或兆比特来衡量。如果您居住在连接速度更快的地区，您甚至可能会看到千兆连接，或每秒数十亿比特。
将连接想象成一根管道。在任何给定时间，只有这么多的水可以通过该管道，一旦达到最大水量，就不可能再将更多的水装入管道。您需要一根直径更大的管道。这与通过更好的连接方法（例如光纤线路）增加带宽的概念相同。
也就是说，光纤(fiber)（或光纤(fiber)）连接实际上并没有利用更大的直径，而是一种更好的数据传输方法。最初的铜线通过电脉冲传输数据。光纤(Fiber)连接通过光脉冲传输数据。
对于您的ISP，您可能会为 100 Mbps的连接付费，但只能获得 75 Mbps。您的计划所指的是您可用的最大带宽量，但这可能会因一天中的时间、温度、天气条件等而有所不同。
您可能会在下午 6 点看到比在凌晨 3 点大多数人都睡着的时候更多的人在家时看到的较低速度（因此整体互联网使用率较低）。
您需要多少带宽？(How Much Bandwidth Do You Need?)
带宽(Bandwidth)要求因人而异。与仅在下班后 浏览Facebook的人相比，流式传输游戏或教学视频等实时内容的人需要更多的带宽。
要确定您需要多少带宽，请分解您的互联网使用习惯。
- 你玩很多网络游戏吗？
- 您流式传输大量视频内容吗？
- 您是否定期传输大文件？
如果您对上述任何问题的回答为“是”，那么您的带宽要求略高于平均水平。值得庆幸的是，很容易发现您当前的带宽。Ookla是最重要的速度测试公司之一。快速访问他们的网站( site)将为您提供当前的延迟、下载和上传速度。
注意：Wi-Fi 上的速度可能低于以太网等硬连线连接，具体取决于笔记本电脑或 PC 中 Wi-Fi 卡的类型。上述结果来自通过 Wi-Fi 连接的笔记本电脑，其中以太网连接上的台式机的速度通常是这些速度的 5 倍。(Note: Speeds may be lower on Wi-Fi than on a hardwired connection like Ethernet, depending on the type of Wi-Fi card in your laptop or PC. The above results are from a laptop connected through Wi-Fi, where a desktop on an Ethernet connection regular sees 5x these speeds.)
根据NCTA 2018 年的一份报告( 2018 report from the NCTA)，美国的平均下载速度为 93.98 兆比特每秒，几乎是全球平均速度 46.25 兆比特每秒的两倍。
但是，由于地理位置的原因，您目前可能无法达到平均速度。在许多农村地区，唯一可用的ISP(ISPs)提供的最大下载速度为每秒 3 兆比特。
要流式传输Netflix，您需要下载速度介于 5 Mbps的高清视频和 25 Mbps的 4K 分辨率之间。如果您想在Twitch 上流(Twitch)式传输视频游戏，您需要至少 3 Mbps的上传速度，但您可以达到的速度越高，您的流传输质量就越好。
请记住(Remember)，上传速度 10 是下载速度的 1/10 左右，因此 3 Mbps的下载速度可能会达到 30 Mbps或更高。
如果您只想偶尔观看Facebook视频或听音乐，您的带宽要求要低得多。但是，更高的带宽会带来更好的浏览体验。
如果您发现自己在网上做某事时感到沮丧，这可能意味着您需要比目前更多的带宽。如果是这种情况，请研究您当地的ISP(ISPs)并找出可供您选择的选项。
HDG Explains : What Is Bandwidth?
Bandwіdth is a common term in the computing and networking world. It’s used so often, in fact, that it’s еasy to forget that some peoрle don’t actually understand what it means.
A quick Google search for “what is bandwidth” will turn up two different definitions from the dictionary, neither of which is correct. This article will explain what bandwidth is, how it is measured, and how much you need for different tasks.
What Is Bandwidth?
Bandwidth is defined as the maximum amount of data that can be transmitted through a specified connection within a specified period of time.
This definition is most often used to refer to download and upload speeds given by an internet service provider, or ISP. However, it can refer to any type of connection, including Ethernet, USB, HDMI, and more.
For example, Ethernet is broken down into different categories of cable: 3, 5, 5e, 6, and 6a most commonly. Below is a list of the category of cable and its maximum theoretical bandwidth.
- Cat3: 10 megabits per second
- Cat5: 100 megabits per second
- Cat5e: 1000 megabits per second
- Cat6: 10 gigabits per second
- Cat6a: 10 gigabits per second
Something important to note is that bandwidth does not refer to speed. It refers to data capacity, specifically from one point (or node) in the network to another. If you want to measure the speed of the data transfer, you will want to check the network’s latency (often called ping).
How Is Bandwidth Measured?
Bandwidth is measured by how many bits per second transfer over the network. However, to understand this, you must first understand what a bit is.
A “bit” is the most basic unit of information in a computer. The term is a shortened form of binary digit; in other words, a 1 or 0. You might also know the word “byte.” If you combine eight bits, you make one byte.
Due to advancements in computing and network technology, the number of bits transferred over a network has increased dramatically. In the early days of networking (and as recently as the late 90s to early 2000s), bandwidth could be measured in how many thousands of bits per second, or kilobits.
Now bandwidth is most often measured in millions of bits per second, or megabits. If you live in an area with better connection speeds, you might even see gigabit connections, or billions of bits per second.
Think of a connection like a piece of pipe. Only so much water can travel through that pipe at any given time, and once you reach the maximum amount of water, it’s impossible to fit any more into the pipe. You need a pipe with a larger diameter. That’s the same concept as increasing bandwidth through better connection methods, such as fiber optic lines.
That said, fiber optic (or fiber) connections do not actually utilize a larger diameter, but a better method of transferring data. The original copper wires transferred data through electrical pulses. Fiber optic connections transfer data through pulses of light.
With regard to your ISP, you might pay for a 100 Mbps connection but receive only 75 Mbps. What your plan refers to is the maximum amount of bandwidth available to you, but this can vary depending on time of day, temperature, weather conditions, and more.
You are likely to see lower speeds at 6 PM when more people are home than you might at 3 AM when most people are asleep (and thus overall internet usage is lower).
How Much Bandwidth Do You Need?
Bandwidth requirements differ wildly from person to person. Someone who streams live content such as gameplay or instructional videos will require far more bandwidth than someone that only browses Facebook after work.
To determine how much bandwidth you need, break down your internet usage habits.
- Do you play a lot of online games?
- Do you stream a lot of video content?
- Do you transfer large files on a regular basis?
If you answered “yes” to any of the above questions, then your bandwidth requirements are a bit above average. Thankfully, it’s easy to discover your current bandwidth. Ookla is one of the foremost speed testing companies out there. A quick visit to their site will give you your current latency, download, and upload speed.
Note: Speeds may be lower on Wi-Fi than on a hardwired connection like Ethernet, depending on the type of Wi-Fi card in your laptop or PC. The above results are from a laptop connected through Wi-Fi, where a desktop on an Ethernet connection regular sees 5x these speeds.
According to a 2018 report from the NCTA, the average US download speed is 93.98 megabits per second, nearly double the global average speed of 46.25 megabits per second.
However, the average speed might not be something you can currently reach due to geographic location. In many rural areas, the only available ISPs provide a maximum download speed of 3 megabits per second.
To stream Netflix, you will want download speeds somewhere between 5 Mbps for high-definition video and 25 Mbps for 4K resolution. If you want to stream video games on Twitch, you will want an upload speed of at least 3 Mbps, but the higher you can achieve, the better quality your stream will be.
Remember that upload speeds ten to be somewhere around 1/10 the download speed, so 3 Mbps will likely have a download speed of 30 Mbps or more.
If you only want to watch the occasional Facebook video or listen to music, your bandwidth requirements are much lower. However, higher bandwidth results in a better browsing experience all around.
If you find yourself frustrated at the time it takes to do something online, it might mean you need more bandwidth than you currently have. If this is the case, research your local ISPs and find out what options are available to you.
