Questions to Ask Before Beginning Network Design
By Kerry Anders
Before you can even begin to design your network, you need to ask, and have answered,
several key questions:
• What do you want it to do?
• Where do you want to do it?
• How do you want to do it?
• What are your priorities?
1. What do you want it to do?
This is the basic question and is rather difficult to answer. There are a number of things
that most people want:
• Allow your PC(s) to access Internet services;
• Allow your telephone to access Voice over IP (VoIP - such as Skype) services
as well as its own (usually BT) comms network;
• Allow vital non-PC systems (such as games consoles, alarm systems, smart meters)
to access their necessary services.
Additionally, you might want to:
• Allow your laptop⁄work PC to access your home computer remotely across the Internet;
• Allow other users to access services that you provide from your private network;
• Make secure private connections between multiple sites using (e.g.) Virtual Private Network connections;
• Distribute entertainment services (such as audio or video) around your home
2. Where do you want to do it?
All the comments about networking are specifically addressed at users in the UK. Most of them
will be applicable to everywhere else in the world, but you should relate them to your local conditions.
Most of the issues addressed in this series of articles relate to Local Area Networks
(LANs). This is the network that covers a single building or group of buildings on a single
site. Generally, the site will be small with direct cable or wireless access available across
the whole site. It is possible to use a single LAN across multiple sites that are close to
one another (an extended LAN) even if a physical cable interconnection is not practicable but
this is not advisable except in special circumstances.
Where a site is very large (such as an airfield or a farm with widely-spaced buildings)
or there are multiple, widely separated sites, then a Wide Area Network (WAN) should be used.
What are the differences? Basically, within a LAN, there may be little or no filtering
of signals between computers. With a WAN, only specific types of data are transmitted across
the WAN, meaning that a slower (and cheaper) connection medium is practicable.
Location affects another key aspect of most networks: how they connect to external services
such as the Internet. In towns or high-density rural areas, most networks connect to the Internet,
for instance, using telephone lines (ADSL - Asymmetric Digital Subscriber Line) or cable services.
Outside these areas, if ADSL or cable are not available or practicable, then mobile telephone
or satellite links may be used. Another, rarer, alternative is point-to-point wireless links
(normally microwave).
3. How do you want to do it?
As with most technologies, there are a number of alternatives when implementing a solution:
• Simple and relatively cheap: using the minimum hardware and with no resilience to failure
• Moderately complex: with key systems duplicated to provide a moderate level of resilience to failure
• All singing, where every single point of failure is at least duplicated to provide maximum availability.
This is also the maximum cost solution.
Unless you are providing safety-critical services (such as fly-by-wire systems in aeroplanes)
or communications between military services, then option 3 is probably not necessary, and for
most home and SME users, option 1 or possibly a very simplified option 2 is all that's necessary.
However, this is a value judgement on the part of the user.
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