Networking, Protocols, and Domain Name Service (DNS)

 

The letter "HTTP" found on the URL (Uniform Resource Locator) while surfing the internet is the abbreviation of the Hyper Text Transfer Protocol. There is a term "IP address" required for the internet access, and the IP is short for the Internet Protocol. These are the protocol of transferring data via the network connection: the IP is for the internet layer and the HTTP is for the application layer. There are also the other various networking protocols. The layer structure description here mainly follows the OSI Reference Model.

 

The protocols for the application layer are not only the HTTP but also the FTP for the data transfer to the file server, the POP3 for E-mail, and SSL/TLS for the data transfer with encryption for example. The AWS network architecture provides the ostensible sample. The Application Load Balancer (ALB) deals with the internet-facing side of the traffic with the HTTP to the public subnet directly connected to the internet to distribute the traffic access volume to those inside the public subnet. The Network Load Balancer (NLB) deals with the internal side of the traffic with the SSL/TLS to distribute the traffic access volume coming from those in the public subnet to those inside the private subnet. 

 

The SSL/TLS is the protocol also used for the transport layer connecting between the application layer (via the session layer and the presentation layer) and the network layer. The network layer represents the inside network of the on-premises environment connecting the physical layer via the data link layer. The network layer requires its protocol for its data transfer among these physical devices by linking their data together. The network layer is the gateway to outside the on-premises via either the internet connection or the Direct Connect via the transport layer, and this requires the protocol too.

 

 

As shown in the the URL, the HTTP is followed by the domain such as "art-blue-liberalism.blogspot.com".  This is addressing the website with the name which humans are accustomed with while computers are not. Computers understand and process various tasks by means of numbers so they address the website by the number such as the IP address. 

 

Therefore, the networking needs the domain name service (DNS) resolving a name to numbers.  The DNS resolves the domain name such as "art-blue-liberalism.blogspot.com" to the IP address such as 192.0.2.1 in IPv4, and 2001:db8:0:1234:0:567:8:1 in IPv6 (Ref. Wikipedia).

 

There is the DNS allocated in order to transform to manage the domains and the IP addresses among these access connections.  It is similar to the phone book while looking for a telephone number by searching the name of a person or an organisation in the index.

 

The DNS server checks its own cache memory to find an IP address for the domain name when it receives the query. If not found there, then, this query is sent to the root servers, the root of the DNS hierarchy, which are operated by a number of the organization and evenly allocated in the world. But, instead of directly providing the DNS server with the IP address, the root server requests the Top Domain Server (TDS) to instruct the DNS server to find how and where to look for the IP address matching with the queried domain name.