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Hi, guys, and welcome to the first lecture of the namespace section in this module, we will go over
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the anatomy of a typical domain name and break it down into its individual components.
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This is by far one of the most important lectures in this course, as it sets the foundational knowledge
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required to follow the rest of the material.
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If you are completely new to most of the information we're going to cover, I would highly recommend
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that you go over this video list twice, taking as many notes along the way as possible.
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We will start examining the domain four months from right to left, because that is the direction that
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a domain name is interpreted.
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What I mean by that is contrary to the way we type a domain name into a browser from left to right.
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For instance, w WW dot example dot com domain names are interpreted by DNS the other way around, from
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right to left.
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I know that this probably doesn't make much sense to you right now, but it will do later on the course.
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The first component for domainname starting from right to left is the route represented by a dot.
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This is a very special dot and not to be confused with any other dots, this dot is in fact so dominant
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that nothing else can take its place, meaning that the rightmost component of a domain name can only
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be the route represented by this dot and nothing else to the end.
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Think of the route as a component in the domain name, just so you don't confuse the special dot with
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other dots being present.
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After the route comes, the top level domain abbreviated as till date, we will not go into depth until
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dates at this stage, since there's going to be an entire module dedicated to two days further down
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the line.
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But it should be pointed out that comm is just one of a plethora of TLDs that you can come across.
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The reason why I have chosen this particular field for this demonstration is because it's one of the
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most popular ones, and so chances are you can recognize it even if you do not have any previous experience
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with DNS.
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Other well-known fields, I could have very easily taken up this spot, net org, Io and many others.
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What follows a top-level domain is the second level domain, which in this case is example for simplicity
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sake.
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The second level domain, along with a top level domain, make the zone apex otherwise known as naked
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domain or apex domain.
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Finally, the third level domain is usually something like W W W, which is more of a naming convention
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rather than a necessity, as you could very easily replace it with BBB, CCC or any other arbitrary
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string of characters.
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If it came down to creating a domain name for, say, your website.
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The components of a domain name are known as labels, with a route being said to have a label of no.
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Each label is a subdomain of its parent domain.
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For instance, W WW is a subdomain of examiner.com, while example is a subdomain of the com top-level
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domain.
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The entire domain name stretching all the way from the route down to the third level domain is known
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as the fully qualified domain name abbreviated as F and which is the absolute reference to a domain
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name.
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Important to note that the student is not the same thing as a euro, as a euro contains the domain name
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of a site, as well as other information, including the transfer protocol and the path, for example,
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in the Euro Europe's column forward slash forward slash w WW dot example dot com forward slash learning
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forward slash w WW dot example dot com is the domain name, while hedge DPS is the protocol and forward
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slash learning.
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Forward Slash is the path to a specific page on the website.
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A portion of a domain name, such as the House portion of the WWE W Dot Examiner.com domain is known
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as a partially qualified domain name abbreviated as PCDI, and a partially qualified domain name starts
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with a hostname, but it may not reach up to the root.
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Finally, it is important to note that the reason why the dots representing the route is colored differently
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to the other dots is because the first is a special dot, while the other dots serve as the limiters
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separating the labels of a domain.
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Before finishing off this lecture here, a few more things to keep in mind in relation to the syntax
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of a domain name.
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The first one is that each label can be up to 63 characters long.
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The characters allowed and labels can be a through z uppercase a lowercase digits from zero all the
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way to nine and hyphen.
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This rule is known as the LDH rule letters.
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Digits hyphen labels may not start or end with a hyphen.
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An additional rule requires a top level domain.
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Names should not be old numeric.
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Last but not least, there is no maximum limit on the number of subdomains.
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In our example, we only went up to third level domain, but it could just as easily have a 4th level
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domain, 5th level domain, etc..
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However, a domain name in society can be up to 255 characters in total, including the dots.
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That's everything for this lecture, everybody.
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Thank you for watching, and I'll see you in the next one.
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