A very important criterion in choosing a host for your Website is bandwidth. Most of us will ask about it, right after they ask about "space". But do we really understand what bandwidth is, and why most hosts put a limit on it?

First, what is bandwidth?

Put simply, bandwidth is the amount of data allowed to occur between a certain computer and the rest of the Internet. As such, there are many types of bandwidths.

For example, I use DSL service to log onto the Internet. My DSL subscription has a bandwidth limit of 1024 KBit/second. This means that the maximum amount of data I'm allowed to recieve from my provider at any given second is 1024 KBit.

Now my DSL provider access the Internet through certain channels. The higher the number of these channels, the higher their bandwidth is. Let's assume that my DSL provider is also a Web host, and that it has a bandwidth limit of 1024 MegaBit/second.

This means that the maximum amount of data this server can handle at any given second is 1024 MBit. So if we assume that all other DSL users such as myself are accessing this server at 1024 KBit/sec, this means that the maximum number of users the server can handle is 1024 users (since 1 MBit = 1024 KBit .. you do the math ).

But wait a second! Web hosts offer bandwidths that are as high as 2GB and even 5GB a month. What's up with that? That's a good point, and it should be easy to explain...

When a host offers 2GB/month for a certain Website, that means that the maximum amount of data this Website is able to send in any given month will be only 2GB. Some sites have low traffic, small pages, and few graphics, so they won't use a lot of bandwidth. Others are huge sites with millions of visitors and thousands of images, which will probably consume the 2GB in 2 weeks or something.

But why do hosts put a limit on bandwidth?

Because, if you remember the 1024MBit/second example, hosts can only handle so much data per second. As the number of Websites they host increases, the 1024MBit/second is quickly approached. If too many visitors are at a certain Website, this site will take a lot of that bandwidth, decreasing the performance of other Websites. So how do hosts solve this problem?

Well, they can't put a secondly limit on Websites, so they make the limit a monthly one. If a certain Website consumes A LOT of bandwidth, it'll eat up all of the 2GB very quickly and get suspended afterwards, giving the other Websites their fair share of bandwidth.

Ok, another question, then? If this is the case, how come hosts charge more money for more bandwidth? That's because, in order for them to increase their own bandwidth, they have to buy access to more channels. This way, they increase their bandwidth, which enables them to increase their customers' bandwidth.



Now, to be perfectly honest, this is my own theory. The question of bandwidth has been plaguing my mind for so long, and after searching for informatino about it, that's all I could come up with. If any of you guys knows a truer, more precise theory, please let me know .



Warm regards,
Djetamun

seems to me like it's something like that. it's logical.

Unfortunately, you made the most common mistake techies make, the base two exuberance mistake. Because computers work in bytes, and base two, many things are based on the base two system. For example, Megabytes in storage and RAM measures. In these cases, the prefix relates to the base two value closest to the SI prefix meaning, like 1024 for Kilo. However, in two common cases, storage limits by computer manufacturers and network speeds, the prefixes are directly SI prefixes. 1 Kbps (Kilobit per second) is exactly 1000 bits per second, not 1024 (even though that makes fractions of bytes, and it doesn't seem to make sense). 1 Mbps (Megabit per second) is 1000 Kbps or 1000000 bits per second.

The other method of discussing network speeds is the kibibit, which is exactly like the standard Kbps but is in base two so 1 kibibit is 1024 bps.

For verification see:
Wikipedia for Kbps
Wikipedia for Kibibits
Conversion Site

Other than that mistake, that is the simplified explanation of the how and why. It gets to be more detailed (for example, overselling because some sites hardly use bandwidth, so the hoster charges for more bandwidth knowing many sites will never reach the 2GB per month so they have extra they can make a buck off of) but this is a decent summary.

~Viz

Excellent catch, Viz .

Truth to be told, whenever I tell anyone that sometimes 1MBit actually equals 1000KBits and not 1024, they tell me that I don't know squat and that I'm full of it. So much so that I stopped doing it altogether. But I'm honestly glad that there are people here who know better .

I'm also glad that, at last, someone confirmed this information for me. Thanks a lot Viz and finaldesign .

Hm, I didn't know that 1Mbit was 100Kbits. Hawever, this can be a bit wierd, I'll show you why.

1Mb = 1000Kb

When we divide by 8 to get bytes:

1000Kb = 125KB
1024KB = 1MB

125KB = 0.122MB

Now we return to bits again

0.122MB = 0.976Mb

So we get 0.976Mb = 1Mb? Now, Wikipedia says that for bits 1Mb = 1000Kb is the standard, whereas we know that for bytes 1MB = 1024KB is the standard. And how can we combine these two if the standards are different???

Anyway, back to the topic. An interesting thing to mention is NOT limiting the bandwidth. Out there you can find many hosts that offer unlimited bandwidth (somewhere unlimited space, too). Any beginner will be delighted, but experts know it isn't so.

We can compare it to GMail. If they said we had unlimited space, every one would believe them, because nobody would get to the 2.5GB limit that easy. However, if some freak shows up and starts sending massive emails to himself, he is bound to reach the limit. The same thing is with hosts. The bandwidth is not limited - and unfortunately, it's not even big. The host know beginners will come, with their unknown web sites, and therefore will not spend a lot of bandwidth. It can be quite a good deal, since these hosts usually cost quite a lot.

In addition, I read somewhere that a lot of hosts make mistakes with the words Bandwidth and Traffic ... Bandwidth is the maximum size per second and etc. You can read about it on the wikipedia site. So what I want to say that I read that Traffic is the "better" word to say the limit of megabytes you can transfer monthly and say bandwidth should be named how much megabytes your server can transfer in one second ? Is this true ? Because I am quite lost, due to different sites write this issue differently.. Furthermore, if this was a real problem, wouldn't many hosts already change the names ? I saw some hosts who write "Bandwidth/Traffic" and if I understand good, you can offer "unmetered" Traffic, but not Bandwidth and Space.. ? :S

http://en.wikipedia.org/wiki/Bandwidth

(" There is nothing about Traffic on wikipedia, except for highway Traffic.. ")

Hey Djetamun, really appreciate for the thinking you did to solve the question brewing up in ur mind, but see, to answer any question completely, you need to understand the base technology. I will point out the mistake you made:


Firstly, there can be different types of webhosts. Let's say I become a webhost with a Linux Server and a Broadband connection of say 512Kbps.
Now as per your theory, suppose i have 4 customers, they will all get to offer a minimum 128Kbps share at any given moment even in the worst case, to their website visitors. So suppose there are 4 visitors concurrently on his site, the b/w of 128Kbps further gets divided into 32Kbps. So the problem is, how do I convert this secondly limit into monthly one? it doesn't make sense you see... Rather no secondly limit can be converted to monthly one.
To answer your question you need to know the underlying architecture of B-ISDN (ATM) for instance. Like my ISP provides me a DSL connection with the underlying architecture being that of ATM (Asynchronous Transfer Mode). So these modern digital networks have started using a technology called 'Packet Switching'.
Being short and sweet, when you make a land line phone call to your friend, using your static connection, you get a dedicated channel to your friend's phone, and whether you speak or not, that whole channel is reserved to you. So whether you speak or not, you get billed. It's logical and its called Circuit Switching. But with Packet Switching, which is applicable only to digital networks, data is sent in form of digital packets. In ATM, we have cells of 53 Bytes each. So what happens now is, these cells pass through networks AS THEY COME. That means you don't get a reserved channel or bandwidth. Unlike Dial up connections, now my DSL connection offers me to be online 24 hours and puts a limit of 1GB transfer per month. That's because now the whole deal is with data packets, I get billed as per the network resources I occupy. When I contact a webserver, I send ATM cells to my ISP network, which occupies its routers and gateways. So the management over there figures out the least amount of money that can be charged for each 1KB (1024 Bytes) of data transfer, and as per that they come out with a data transfer plan, which in my case is 1GB per month for around $10 per month. The same would apply for a webhost (after all webhosts are individual computers on network via an ISP).
Now the ISP sees that during offpeak hour, i.e. night time, their primary transfer channel (say Satellite network) usually goes unused. So they offer me an unlimited bandwidth plan from time 2 am to 8 am (which i utilize to download movies ).
So the bottom line is, now the basic billing criteria is Data instead of Time.

@Quatrux

Wikipedia says:



Furthermore, every CPanel you can find shows bandwidth not as the speed, but the available amount of, let's say, traffic.

Quatrux, initially the term Bandwidth came from Analog networks where the capacity of a channel was determined by the amplitude of the signal, which in turn determined different frequency signals that could be carried, hence the amount of information that could be carried.
Now, applying the same thing to digital networks, it figures out to the amount of data that can be carried per second or per unit time. If a connection can carry 512Kb in one second, then its called a bandwidth of 512Kbps.
Now converting the unit 's' into 'month', with 30 days would come out to 2592000 seconds in one month, and hence, 512Kb * 2592000 = 1327104000 Kb/month. Now this would be the monthly transfer that I can get IF i download 24x7.
Now to eliminate the confusion, ISP's never mention the per second bandwidth they have. Everyone of us must have encountered that some hosting providers provide slow service, and its because their per second bandwidth is low or there are a lot of visitors on its clients websites. Most webspace providers bypass mentioning how much speed per second they can allot because they pressume that the visitors of the website will have a connection way slower than their own, and there will never be many concurrent users.
So for that reason, if I were to start a website that would recieve more than 50 concurrent visitors, I would be very careful with buying a webspace that provides me 2+Mbps dedicated bandwidth. Similarly, for starting something of the stature of ebay.com, there is not much option other than starting your own server for it.

For the conclusion, bandwidth can be rightly used by webspace providers to indicate monthly traffic. Bandwidth is the information transfered per unit time.

That time unit can be seconds or months or years... whatever you deem fit. ISPs mention both the limits, webspaces usually mention just one, whereas logically they should be mentioning both. Instead, they rite in some of the section that they have say 4 dedicated servers with say 2Mbps connection each, which gives a rough figure to us about their speed.

This post has been edited by CaptainRon: May 30 2006, 09:32 AM

I would like to respond to pyost's confusion on the whole 1Mb = 0.976Mb:

(Using b for bit and B for byte)

1Mb = 1000000b
1000000b = 125000B

This is where you made your mistake
125000B is not 125KB, since you must divide the number of bytes by 1024 not 1000, which yields
125000B = 122.07...KB

Now, 1024 KB is 1MB
122.07...KB = 0.119209...MB

So that number was off, your next step seems to be a logical one, multiply by 8 to return to bits
The problem is that the M in MB stands for 1024 and the M in Mb stands for 1000
Let us now let M stand for the M in Mb and N stand for the M in MB
so after multiplying by 8 we have
1Mb = 0.95367...Nb
1(1000)^2b = 0.95367...(1024)^2b
1000000b = 1000000b
1Mb = 1Mb

So you see, it all comes down to forgetting to convert M standing for 1000 into M standing for 1024
It's similar to in physics trying to use cubic meters in a formula that requires liters, first you must convert, and the proper method to convert is to first convert cubic meters to cubic centimeters (which are the same volume as milliliters, so we have that conversion which is 1 to 1) then to liters.

~Viz