Megabytes and Gigabytes
Choosing a hosting plan can be difficult when the question of bandwidth arises, as choosing an option that falls short of what you need can be costly in a couple of ways. While some hosting providers will simply charge you an overage if you break through your bandwidth limitations, others will make your site inaccessible, which can end up costing sales and customers. Most Managed Hosting providers express their bandwidth limits in Gigabytes, or GB for short, whereas San Jose Colocation providers talk in terms of Megabits, or Mbps (Megabits-per-second). This can be more than a little confusing for most, with the main question being what the difference between Gigabytes and Megabits really is. The explanation is actually fairly simple and goes as follows: Megabits-per-second it a measurement of the rate of traffic across a certain point such as the uplink connection at your colocation facility, which means that the larger the number of bits across an interface, the more traffic there is at your site. If you do the math, 1 Megabit = one million bits, which in turn translates to 128 kilobytes (8 bits = 1 byte). So as an example, if you have a website that has an average webpage size of 50 kilobytes, with 2 or 3 webpages available around the clock, the site would be doing around 1Mbps of traffic.
The good news is that you don’t have to be a math wizard in order to figure out what your monthly data usage is. The switches and routers that connect you to the internet have built-in counters that accurately capture all the data required to calculate your usage. That task is usually performed by your colocation provider using a 95th percentile method that we will explain later. Mbps is usually charted on an X-Y graph, with the data rate on the vertical and time represented on the horizontal. Compare that to Gigabytes which are nothing more than a cumulative total of bytes that go in and out of a certain point. The monthly total is usually calculated by tallying every byte to see if it falls within the limits of your hosting plan. When you take into account that one Gigabyte is equal to a little over 1 million Kilobytes, you can an idea of how difficult it can be to get an accurate reading. Hosting companies generally use a number of different techniques such as converting rate data and scanning log files to get to the final number. It’s not an accurate science and the final number is considered by many to be nothing more than an approximation. Simply put, Mbps gives you a data rate, whereas GB provides a total. Neither method is considered better than the other, but it does require you to do a little bit of hard thinking when trying to compare the two. That is essential when you are trying to compare bandwidth pricing, so keep in mind that 1 Mbps in a 30 day period is roughly the same as 320GB. Traffic rates change all the time, so it’s important to understand that yield is usually a hypothetical number. That may all sound a little confusing, but we still have talk about 95th Percentile Monitoring.
95th Percentile Monitoring Explained
Just when you think you have Megabits-per-second down pat, along comes 95th Percentile Monitoring. That’s a technical term, often referred to as the 95% method, which pertains solely to colocation bandwidth. While many San Jose colocation data centers will simply use the X-Y graph method mentioned earlier to calculate Mbps usage for the month, there are those that choose to use the 95% method, and here is how they do that:
- A log of 30 days’ worth of traffic samples at the default sample frequency (every 5 minutes is typical) is accumulated;
- The log is sorted in descending order, which places the biggest traffic peaks at the top;
- The top 5% of the log data is discarded;
- The value of the largest remaining peak becomes the effective bandwidth usage value for the month.
The biggest advantage that the 95th Percentile Method provides is that in the span of a 30-day period, 36 hours of peak traffic will be completely thrown out when it comes to billing, no matter how high the peaks go during that time. For example, if you had a 36.3 Mbps number using the averages method, the actual billed amount would be 25.7 Mbps when the 95% method is used instead. That explains why businesses that are well versed in colocation bandwidth methods will go with 95th Percentile Monitoring.
If you have done any type of research on colocation, then you are probably aware that when you get IP addresses for your equipment, you will also be assigned as many subnets as you need. Basically, an IP subnet is nothing more than a group of smaller IP addresses taken from a larger group of IP’s, so that it can be treated separately from any that may come before or after. There is a far more complex, technical explanation, but it’s not really anything that you need to know. What is important is that by assigning subnets, you can be sure that instead of getting random IP’s from all over, the ones you receive will a uniform chunk of addresses assigned to you alone. Subnets come in a variety of sizes, from a single unit all the way up to millions, although you will normally be assigned chunks of 8, 16, or 32. Not every IP subnet that you receive can be used for hosting as some have to be put aside for internal networking tasks that make the subnetting possible in the first place. These are known as the network, or base, address (1st in the range), broadcast address (last in the range), and possibly a gateway address (2nd address in the range), with the remaining IP’s yours to use as you wish. That means that if you are assigned 16 subnet IP’s, only 13 of those will be available for hosting purposes. The subnet size, which is basically the number of IP’s included in the subnet, is found by applying a network mask, or netmask as it is commonly referred to. A netmask is a number string that follows the dotted notation used by IP addresses. If the netmask is longer it will essentially black out more of a range, which in turn will result in fewer usable IP’s, meaning that a shorter netmask will produce more usable IP’s. A unique subnet is denoted by its network address, followed by a '/', followed by the length of its subnet mask, i.e. 192.168.1.0/24.