The video provides an informative session about DNS, zones, and records, serving as a guide for those responsible for setting up DNS for applications. It begins with a brief overview of the DNS protocol, explaining how it translates human-friendly web addresses into machine-readable IP addresses to facilitate web navigation.

Essential concepts such as DNS zones and various types of DNS records are discussed. A zone refers to an area of administrative control within the DNS namespace, which contains records like A records that map domain names to IP addresses. The video also details resource record sets, nameserver records, and specialized records for delegation purposes.

Main takeaways from the video:

Please remember to turn on the CC button to view the subtitles.

Key Vocabularies and Common Phrases:

1. resolver [rɪˈzɔlvər] - (noun) - Software component in DNS that translates domain names into IP addresses by querying authoritative DNS servers. - Synonyms: (resolver, name server, DNS resolver)

their PC talks to the local resolver which then goes out to the DNS

2. authoritative [ɔːˈθɒrɪtətɪv] - (adjective) - Having or showing authority; in DNS, referring to a name server that has the definitive data about a domain. - Synonyms: (official, definitive, conclusive)

authoritative DNS name server who looks up that name www.IBM.com

3. namespace [ˈneɪmspeɪs] - (noun) - A set of symbols that are used to organize objects of various kinds, such as addresses in DNS. - Synonyms: (domain, category, scope)

a DNS zone is an area of administrative control of a portion of the DNS namespace.

4. subzone [ˈsʌbˌzoʊn] - (noun) - A subdivision of a DNS zone, which can have its own records and be managed independently. - Synonyms: (subdivision, subsection, partition)

So in that case you'll set up a special record type called subzone

5. record set [ˈrɛkərd sɛt] - (noun) - A collection of DNS records with the same name and type but different data. - Synonyms: (collection, group, batch)

there's two records of with the same label with the same name and that's called a resource record set.

6. priority [praɪˈɒrɪti] - (noun) - A parameter used in DNS records like MX that determines the order in which servers are tried for connection. - Synonyms: (precedence, importance, ranking)

the mail server address, which is an MX record that has two portions to the value. It's got a priority and the mail server name.

7. redundancy [rɪˈdʌndənsi] - (noun) - The inclusion of extra components not strictly necessary, to ensure system functionality in case of failure. - Synonyms: (backup, duplicate, surplus)

there's kind of built in redundancy enabled through the DNS.

8. canonical [kəˈnɒnɪkəl] - (adjective) - In DNS, refers to the authoritative or standard version of a domain name. - Synonyms: (authoritative, accepted, standard)

this one stands for canonical name. It's essentially a redirection.

9. delegating [ˈdɛləˌɡeɪtɪŋ] - (verb) - Assigning authority or responsibility to another entity or group. - Synonyms: (assigning, entrusting, authorizing)

the ns record, just for completeness, we'll add it in and we'll have subzone ns dot IBM.com and again that's for delegating your zone to a different entity

10. administrative control [ədˈmɪnɪˌstreɪtɪv kənˈtrəʊl] - (noun) - Authority to manage settings, configurations, or infrastructure within an organization or system. - Synonyms: (management authority, governance, oversight)

So a DNS zone is an area of administrative control of a portion of the DNS namespace.

What are DNS Zones And Records?

Today we're here to learn about DNS, zones and records. First let's start with a quick review of the DNS. As you may remember, DNS is the protocol that's used to convert the name that someone types in their browser into a name into a number that the computer can understand. So for example, the user types www.IBM.com. their PC talks to the local resolver which then goes out to the DNS to an authoritative DNS name server who looks up that name www.IBM.com, and returns the IP address for www.IBM.com. and then the user is able to get to the web page for IBM and go view all of our products.

Now this all works great, but you may be now responsible for DNS and need to set it up for your particular application. So you're wondering what are these things that I'm hearing about zones, records, rr sets, all this different terminology, what does it all mean and how do I use it? So let's start at the beginning with what is a zone? So a DNS zone is an area of administrative control of a portion of the DNS namespace. So for example we might have a zone for IBM.com. and inside the zone we're going to have a number of records. And records are things like um, www would be the record the type is in. I'll go over all this in more detail in a minute. It's an a record type and the IP address is 9991.

Now I might have another record also. Dub dub dub. Actually we'll do four dubs in a and it's 9992. What this means is that there's two records of with the same label with the same name and that's called a resource record set. You'll often hear that in the DNS terminology all it means is that there's multiple records with the same name but different values, different answers. I want to also mention here a special record type called a nameserver record and that's used to do what we call delegate the zone to another group. The use case for this is for example maybe the central CIO team is managing IBM.com but there's another group for which you want to give access to a portion of the DNS and you want to give them their own zone on their own server.

So in that case you'll set up a special record type called subzone. This is the name. It'll point to a name server record ns and we'll just say it's going to subzone nameserver dot IBM.com. now what that does is it creates this redirection to another zone called subzone, subzone dot IBM.com. and in here we can also set up records. So say maybe that team wants to set up an API. So they create a record API, also an A record and it points to 9910. So this would, when someone does a lookup over there for API sz IBM.com comma, it will first go to this zone which will then redirect it via this NS record to a subzone where it will find the answer API subzone dot IBM.com and return nine dot nine dot nine dot 10 dot 10.

So that's an overview of zones, which are an area of administrative control of a portion of the DNS namespace and records, which are the entries or the rows in the database that actually provide the data. So now let's talk a little bit about the different types of records that are available. So if I go over here and let's talk about the format of records. So records have a number of fields. First they have the owner field, which is like the www. They then have a class. So let's fill this in as I go. So this is w the class would be in. There are a number of classes defined, but the only one you'll ever see used is in, which stands for Internet. The other ones are mainly experimental, are used for odd use cases, which you almost never see.

Then we then have a type. The most common example you'll see is the a record. And then you'll have a value. And the value is the number here. One dot, one dot, one dot, one. For example, let's go through a few different types just to give you a feel for what are the types out there. I'm not going to cover them all, but before I get started, I want to refer you to a website, ayanna.org dot. That's the official body that maintains the list of all the different record types. And you can go there and see the full list of what's available, but I'll cover the main ones that people tend to use.

So the next one we have is called the quad a record, which is written as four as. And it's for an ipv six address. So something like 2001 colon colon 127 would be an ipv six address. Another common type we have is the mail server address, which is an MX record that has two portions to the value. It's got a priority and the mail server name. So something like mail dot IBM.com. it allows you to set up multiple name servers. So maybe I have another one that's priority two, that's maybe mail two dot IBM.com. what that means is that the sender will first try the priority one entry. If that doesn't work, then it'll try the priority two entry.

So there's kind of built in redundancy enabled through the DNS. Another common type is called the cname. So if I have one, just take a label foo in cname and this one stands for canonical name. It's essentially a redirection. So in this case it if someone types in foo dot IBM.com comma, I'll redirect them to www dot ns one.com. and that's just a straight text replacement. Foo dot IBM.com gets replaced with www.IBM.com.

You'll often see this used when you're deploying your website into a CDN, where the CDN will provide you the value to use for your canonical name or your cname record. Another common one is a text record. And so if we have a record like this text and we can just say hello world, if someone types in hello dot IBM.com they'll get back the text hello world. And the last one which I showed over here is just the ns record, just for completeness, we'll add it in and we'll have subzone ns dot IBM.com and again that's for delegating your zone to a different entity so that they can also work on the zone.

Again, these are just a few examples. Check out the site iana.org for the full list and hopefully now you have a good idea of the terminology of DNS and you're on your way to becoming a DNS administrator.

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