[Adult Learning Log] Network 1 – Week 1 Review

○ New Things I Learned

• I learned why IP addresses are divided into four parts (e.g., 0000.0000.0000.0000).

• I understood the relationship between hostnames and IP addresses.

• I finally understood what IPv4, IPv6, and DNS—terms often seen in router settings—actually mean.

○ IP Address

• An IP address is an address system used by the IP protocol at the network layer to identify individual hosts.

• It consists of 32 binary bits and is usually divided into four 8-bit sections, expressed in decimal format (e.g., 1111.1111.1111.1111).

• This commonly used format is called IPv4, where “v4” stands for “version 4.”

• However, with the rapid expansion of the Internet, a more scalable address system became necessary—this led to the development of IPv6.

• IPv6 is composed of 128 bits, divided into eight 16-bit blocks. Each block is expressed as four-digit hexadecimal numbers (ranging from 0 to FFFF).

• In most home networks and small websites, IPv4 is still more widely used. Therefore, both IPv4 and IPv6 are often used together in a configuration called Dual Stack.

○ Hostname

• To connect to a specific host on the Internet, you need its IP address.
  However, users prefer to use easily recognizable and meaningful text-based names instead of numeric IP addresses.

• That’s why when a user enters a hostname, a DNS (Domain Name System) server translates it into the corresponding IP address.

• A DNS structure is typically divided into four hierarchical levels: Country Domain, Organization Type, Organization Name, and Host, separated by dots (.).

• Example:

www.google.co.kr

→ www (Host), google (Organization Name), co (Organization Type), kr (Country Domain)

• Note: The term hostname can refer to the entire name (www.google.co.kr), or in a narrower sense, it may specifically refer to the host part (e.g., www for a web server).