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Add AWS execrises and questions

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Mostly about VPC and Route 53.
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exercises/dns/README.md
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<summary>What is DNS? What is it used for?</summary><br><b>
DNS (Domain Name Systems) is a protocol used for converting domain names into IP addresses.<br>
As you know computer networking is done with IP addresses (layer 3 of the OSI model) but for as humans it's hard to remember IP addresses, it's much easier to remember names. This why we need something such as DNS to convert any domain name we type into an IP address. You can think on DNS as a huge phonebook or database where each corresponding name has an IP.
computer networking (at layer 3 of the OSP model) is done with IP addresses but for as humans it's hard to remember IP addresses, it's much easier to remember names. This why we need something such as DNS to convert any domain name we type into an IP address. You can think on DNS as a huge phonebook or database where each corresponding name has an IP.
</b></details>
<details>
@ -14,29 +14,13 @@ The process of translating IP addresses to domain names.
</b></details>
<details>
<summary>What is a DNS record?</summary><br><b>
<summary>What is a name server?</summary><br><b>
A mapping between domain name and an IP address.
A server which is responsible for resolving DNS queries.
</b></details>
<details>
<summary>How DNS works?</summary><br><b>
In general the process is as follows:
* The user types an address in the web browser (some_site.com)
* The operating system gets a request from the browser to translate the address the user entered
* A query created to check a local entry of the address exists in the system. In case it doesn't, the request is forwarded to the DNS resolver
* The Resolver is a server, usually configured by your ISP when you connect to the internet, that responsible for resolving your query by contacting other DNS servers
* The Resolver contacts the root nameserver (aka as .)
* The root nameserver responds with the address of the relevant Top Level Domain DNS server (if your address ends with org then the org TLD)
* The Resolver then contacts the TLD DNS and TLD DNS responds with the IP address that matches the address the user typed in the browser
* The Resolver passes this information to the browser
* The user is happy :D
</b></details>
<details>
<summary>Explain the resolution sequence of: www.site.com</summary><br><b>
<summary>What is the resolution sequence of: www.site.com</summary><br><b>
It's resolved in this order:
@ -46,6 +30,61 @@ It's resolved in this order:
4) www.site.com
</b></details>
<details>
<summary>What is a domain name registrar?</summary><br><b>
[Cloudflare](https://www.cloudflare.com/en-gb/learning/dns/glossary/what-is-a-domain-name-registrar): "A domain name registrar provides domain name registrations to the general public. A common misconception is that registrars sell domain names; these domain names are actually owned by registries and can only be leased by users."
</b></details>
<details>
<summary>Given the following fqdn, <code>www.blipblop.com</code>, what is the root?</summary><br><b>
`.` is the root
</b></details>
<details>
<summary>Given the following fqdn, <code>www.blipblop.com</code>, what is the top level domain?</summary><br><b>
`.com.` is the top level domain
</b></details>
<details>
<summary>Given the following fqdn, <code>www.blipblop.com</code>, what is the second level domain?</summary><br><b>
`blipblop.com.` is the second level domain
</b></details>
<details>
<summary>Given the following fqdn, <code>www.blipblop.com</code>, what is the domain?</summary><br><b>
`www.blipblop.com.` is the domain
</b></details>
<details>
<summary>Describe DNS resolution workflow in high-level</summary><br><b>
In general the process is as follows:
* The user types an address in the web browser (some_site.com)
* The operating system gets a request from the browser to translate the address the user entered
* A query created to check if a local entry of the address exists in the system. In case it doesn't, the request is forwarded to the DNS resolver
* The Resolver is a server, usually configured by your ISP when you connect to the internet, that responsible for resolving your query by contacting other DNS servers
* The Resolver contacts the root nameserver (aka as .)
* The root nameserver either responds with the address you are looking for or it responds with the address of the relevant Top Level Domain DNS server (if your address ends with org then the org TLD)
* The Resolver then contacts the TLD DNS. TLD DNS might respond with the address you are looking for. If it doesn't has the information, it will provide the address of SLD DNS server
* SLD DNS server will reply with the address to the resolver
* The Resolver passes this information to the browser while your OS also stores this information in the cache
* The user cab browse the website with happiness and joy :D
</b></details>
##### DNS - Records
<details>
<summary>What is a DNS record?</summary><br><b>
A mapping between domain name and an IP address.
</b></details>
<details>
<summary>What types of DNS records are there?</summary><br><b>
@ -61,7 +100,9 @@ A more detailed list, can be found [here](https://www.nslookup.io/learning/dns-r
<details>
<summary>What is a A record?</summary><br><b>
A (Address) Maps a host name to an IP address. When a computer has multiple adapter cards and IP addresses, it should have multiple address records.
A (Address): Maps a host name to an IPv4 address.
When a computer has multiple adapter cards and IP addresses, it should have multiple address records.
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<details>
@ -70,6 +111,14 @@ A (Address) Maps a host name to an IP address. When a computer has multiple adap
An AAAA Record performs the same function as an A Record, but for an IPv6 Address.
</b></details>
<details>
<summary>What is a CNAME record?</summary><br><b>
CNAME: maps a hostname to another hostname.
The target should be a domain name which must have an A or AAAA record. Think of it as an alias record.
</b></details>
<details>
<summary>What is a PTR record?</summary><br><b>
@ -78,9 +127,26 @@ While an A record points a domain name to an IP address, a PTR record does the o
<details>
<summary>What is a MX record?</summary><br><b>
MX (Mail Exchange) Specifies a mail exchange server for the domain, which allows mail to be delivered to the correct mail servers in the domain.
</b></details>
<details>
<summary>What is a NS record?</summary><br><b>
NS: name servers that can respond to DNS queries
</b></details>
##### DNS - TTL
<details>
<summary>Explain DNS Records TTL</summary><br><b>
[varonis.com](https://www.varonis.com/blog/dns-ttl): "DNS TTL (time to live) is a setting that tells the DNS resolver how long to cache a query before requesting a new one. The information gathered is then stored in the cache of the recursive or local resolver for the TTL before it reaches back out to collect new, updated details."
</b></details>
##### DNS - Misc
<details>
<summary>Is DNS using TCP or UDP?</summary><br><b>
@ -97,10 +163,6 @@ True.
<summary>Which techniques a DNS can use for load balancing?</summary><br><b>
</b></details>
<details>
<summary>What is DNS Record TTL? Why do we need it?</summary><br><b>
</b></details>
<details>
<summary>What is a zone? What types of zones are there?</summary><br><b>
</b></details>