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Setting up a business network means calculating what you
need and why, so you can distribute hardware to meet those needs. While these
calculations are relatively complex, chances are, you can get a ballpark idea
of what you need before you go to an installer, so you’ll have a better idea of
what to ask for and why.
Importantly, you have to know which devices will be on your
system, when, and why. While you don’t need exact figures, you should have a
rough idea of what your maximum bandwidth needs will be at any given time.
Understanding “Peak” Usage
Peak usage is maximum usage, such as during the busiest
period of the day, when the most devices are used concurrently. Your network
must meet or exceed peak needs.
In some cases, peak needs won’t be based on data use
throughout the day but rather on data use at a specific time of the month (such
as end-of-month accounting or when large files are sent in from outsourcing).
You have to be able to meet maximum load, or your network
won’t function.
Calculating Devices
Most devices can be organized based on general speed and
bandwidth requirements.
Light – Devices categorized as needing 100 Kbps
or less and typically comprise devices such as VoIP phones, low volume
printers, and simple streaming and emailing devices.
Medium – Medium devices utilize between 100-500
kbps, typically including printers, most laptops, most client hosts, most
general computers, etc. This is your standard device.
Heavy – Heavy use devices typically include
enterprise-level software and servers such as cloud and application hosts,
servers, video conferencing, point of sale, etc. Video conferencing platforms
can well-exceed 2 Mbps but most devices will range between 500 Kbps and 2 Mbps.
You can also choose to look at individual devices on your
network and their actual usage. For example, most printers need 1-2 kb per
print job, which remains the same whether it’s client-to-server or
server-to-server.
Here, you can simply tally the total number of devices of
each type on your network. For example, if you have 120 VoIP phones you could
calculate they will need 100 Kbps each at peak use, or a total of about 12 Mbps
if all of them are at peak use at the same time across your network (this is
unlikely, but possible).
You should calculate multiple expected bandwidth usage
points:
Here, it’s also important to consider room for growth and if
your network will shortly need to handle more data transfer than it currently
does.
Network Throughput
Network throughput calculates the volume of data you can
successfully move in a given time period, measured in bps, Mbps, or Gbps. Your
desired network throughput will affect your network in that you have to
consider latency, network capabilities, and machines.
Network throughput = TCP Window ÷ Latency
Transmission Control Protocol – A standard host running a
Windows OS uses a 64KB transmission control protocol window. This may vary
depending on device. To convert this window size to bits, simply multiply by 8.
TCP Window = 64KB x 8 = 524,288 bits
Network latency measures the responsiveness of your network.
In plain terms, it’s the length of time it takes data to reach its destination,
usually measured as a round trip of “there and back again”. (most businesses
have 60 ms-10ms of latency)
TCP Window ÷ Latency
524,288 ÷ .020 = 262,144,00 bits
Convert Network Throughput to Mbps by dividing the result by
1,000,000:
524,288 b ÷ .020 = 262,144,00 ÷ 1,000,000 = 26.21 Mbps
26.21 Mbps is your network throughput, or the maximum amount
of data that particular device and another on the network. Of course, this calculation
will vary depending on whether you’re utilizing TCP or IP and what device
you’re using, but this is the standard calculation.
There are also bandwidth calculators you
can use to automate some of these calculations.
Subnetting
Subnetting is the process of breaking networks down into
smaller networks to reduce the load on primary servers. This means that most
data transfer is handled between a smaller group of hosts that have more reason
to talk to each other more often. These hosts can then be directly connected to
reduce demand on the rest of the network, while freeing up more bandwidth for
those hosts, without adding to total network capacity.
Here, you typically create different classes of network,
divide them with nodes, and then connect those hosts to their own server, data
storage, and possibly printers and print servers (although this latter is
unlikely). Subnet servers are then linked to a larger server, which may be a
subnet of its own, and eventually branched into the main server.
This structure eventually creates something of an inverted
tree, with “branches” extending out from the main server and splitting and
splitting again. Depending on the size of your organization, you could have
anywhere from a few to several dozen branches.
However, these branches mean something important for your
organization, only the channels at the top of the tree have to handle full
network load. This greatly reduces the total cost of network implementation and
ownership, because it’s significantly easier to install subnets each capable of
handling a lower amount of data. The top of your network must be able to handle
(and hopefully exceed) peak demand from all subnets.
If you have a good idea of how many devices you will have on
a network, what those devices will likely be doing, and what their average data
usage should be, you can relatively easily calculate a ballpark estimate for
network needs. This will help you and your network installer to better create
network topology and better supply hardware in the form of switches, subnets,
servers, and access points.