This blog is defining The DNS & Network Routing: Amazon Route 53 & Amazon CloudFront-1. DNS is Domain Name System.
The Domain Name System
DNS is responsible for mapping human-readable domain names (like example.com) to the machine-readable IP addresses (like 93.184.216.34) they represent.
Whenever you launch a new network-facing service on AWS—or anywhere else—and want it to make it accessible through a readable name, you need to satisfy some configuration requirements. But before you can learn to do that, it’s important to be familiar with the basic concepts on which name services are built.
In this section, we’ll define the key elements of DNS infrastructure, particularly the way they’re used within Amazon Route 53.
Namespaces
The addressing structure organizing the billions of objects making up the Internet is managed through naming conventions. If, for instance, there was more than one website called amazon.com or more than one resource identified by the IP address 205.251.242.103, then things would quickly get chaotic. So, there’s got to be a reliable, top-down administration authority. The Internet naming system is maintained within the domain name hierarchy namespace, which controls the use of human-readable names. It’s a hierarchy in the sense that the Internet can be segmented into multiple smaller namespaces through the assignment of blocks of public or private IP addresses or through the use of top-level domains (TLDs). Both the Internet Protocol and the domain name hierarchy are administrated through the Internet Corporation for Assigned Names and Numbers (ICANN).
Name Servers
Associating a domain name like amazon.com with its actual IP address is the job of a name server. All computers will have a simple name server database available locally. That database might contain entries associating hostnames (like localhost) with an appropriate IP address. The following code is an example of the /etc/hosts file from a typical Linux machine. It includes a line that allows you to enter fileserver.com in your browser to open the home page of a web server running within the local network with the IP 192.168.1.5. 127.0.0.1 localhost 127.0.1.1 MyMachine 192.168.1.5 fileserver.com
The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
If a query isn’t satisfied by a local name server, it will be forwarded to one of the external DNS name servers specified in your computer’s network interface configuration. Such a configuration might point to a public DNS server like Google’s at 8.8.8.8 or OpenDNS at 208.67.222.222. Their job is to provide an IP address matching the domain name you entered so your application (a web browser, for instance) can complete your request.
Domains and Domain Names
In terms of Internet addressing, a domain is one or more servers, data repositories, or other digital resources identified by a single domain name. A domain name is a name that’s been registered for the domain that’s used to direct network requests to the domain’s resources.
Domain Registration
Top-level name servers must be made aware of a new domain name before they can respond to related queries. Propagating domain name data among name servers is the job of a domain name registrar. Registrars work with registry operators like VeriSign so that domain registrations should be globally authoritative. Among its other roles, Amazon Route 53 acts as a domain name registrar.
Also read this topic: Introduction to Cloud Computing and AWS -1
Domain Layers
A domain name is made up of multiple parts. The rightmost text of every domain address (like .com or .org) indicates the top-level domain (TLD). The name to the left of the TLD (the amazon part of amazon.com) is called the second-level domain (SLD). This SLD designation would also refer to the unique second-level domains used by some countries, like the .co of .co.uk that’s used for UK-based businesses. A subdomain identifies a subset of a domain’s resources. Web and email servers from the administration department of a college, for instance, might all use the administration .school.edu name. Thus, [email protected] might be a valid email address, while administration.school.edu/apply.pdf could point to a file kept in the web root directory of the administration.school.edu server. www.school.edu, api.school.edu, and ftp.school.edu are all common examples of subdomains (sometimes referred to as hosts). Figure 8.1 illustrates the parts of a simple subdomain.
Fully Qualified Domain Names
Based on the default DNS settings on many systems, the system’s default domain name will be automatically appended when resolving requests for partial domain names. As an example, a request for workstation might be resolved as workstation.localhost. If, however, you want to request a domain name as is, without anything being appended to it, you’ll need to use a fully qualified domain name (FQDN). An FQDN contains the absolute location of the domain including, at the least, a subdomain and the TLD. In addition, convention will often require a trailing dot after the TLD—which represents the domain root—to confirm that this is, indeed, an FQDN. Addresses in DNS zone files, for instance, will fail without a trailing dot. Here’s how that might look: administration.school.edu.
Zones and Zone Files
A zone (or hosted zone as Route 53 calls it) is a subset of a DNS domain. A zone file is a text file that describes the way resources within the zone should be mapped to DNS addresses within the domain.
Record Types
The record type you enter in a zone file’s resource record will determine how the record’s data is formatted and how it should be used. There are currently around 40 types in active use
Alias Records
It’s also possible to route traffic from one domain to another using an alias record. While the use of alias records has not yet been standardized across providers, Route 53 makes them available within record sets, allowing you to connect directly with network-facing resources running on AWS.
Amazon Route 53
With those DNS basics out of the way, it’s time to turn our attention back to AWS. Route53 provides more than just basic DNS services. In fact, it focuses on four distinct areas: domain registration, DNS management, availability monitoring (health checks), and routing policies (traffic management). In case you’re curious, the “53” in Route 53 reflects the fact that DNS traffic uses network port 53 to do its job.
Domain Registration
While there’s nothing stopping you from registering your domains through any ICANN-accredited registrar—like GoDaddy—you can just as easily use Route 53. For domains that will be associated with AWS infrastructure, using Route 53 for registration can in fact help simplify your operations. You can transfer registration of an existing domain from your current registrar by unlocking the domain transfer setting in the registrar’s admin interface and then requesting an
authorization code. You’ll supply that code to Route 53 when you’re ready to do the transfer. If you’d prefer to leave your domain with its current registrar, you can still use Route 53 to manage your DNS configuration. Simply copy the name server addresses included in your Route 53 record set and paste them as the new name server values in your registrar’s admin interface.
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