Protocol

Background and History of NAT NAT (Network Address Translation) is a core technology that translates between private and public IP addresses in network communications. It emerged in the mid-1990s to address the IPv4 address depletion problem and was first standardized through the IETF’s RFC 1631 document in 1994, later revised as RFC 2663 in 1999 to take its current form. The original internet design assumed all devices would have unique public IP addresses, but rapid internet expansion from the late 1980s led to the quick depletion of the 32-bit IPv4 address space (approximately 4.3 billion addresses). NAT was developed as a short-term solution to this problem and has become an essential technology forming the foundation of global network infrastructure. NAT is widely used in everything from home routers to large-scale corporate networks, cloud infrastructure, and mobile communication networks, and even with IPv6 transition underway, it continues to play an important role for legacy system support and security purposes. ...

What is NDP NDP (Neighbor Discovery Protocol) is a core protocol for IPv6 networks officially standardized in 2007 through the IETF’s RFC 4861 document. It integrates the functions of several IPv4 protocols such as ARP (Address Resolution Protocol), ICMP Router Discovery, and ICMP Redirect into one, enabling more efficient and secure network management. Operating on the basis of ICMPv6 (Internet Control Message Protocol version 6), it performs various functions including neighbor node discovery, router discovery, automatic address configuration, duplicate address detection, and path optimization. ...

What is ARP ARP (Address Resolution Protocol) is a network protocol officially standardized in 1982 through the IETF’s RFC 826 document. In TCP/IP network environments, it dynamically discovers the MAC address (physical address) corresponding to a given IP address as an address translation protocol. It operates at the boundary between Layer 2 (Data Link Layer) and Layer 3 (Network Layer) of the OSI 7-layer model, performing the core role of mapping logical addresses (IP) to physical addresses (MAC). ...

Overview When accessing websites on the internet, we use domain names instead of IP addresses. DNS (Domain Name System) is the system that translates these domain names into actual server IP addresses. Often compared to the internet’s phone book, DNS was designed by Paul Mockapetris in 1983 and has since become a core internet infrastructure. It processes billions of DNS queries daily, enabling users to access web services using intuitive domain names like www.example.com without memorizing complex IP addresses like 192.168.0.1 or 2001:4860:4860::8888. ...

Overview Network communication involves complex processes, and understanding these processes systematically requires a standardized reference model. The OSI (Open Systems Interconnection) 7-layer model is a network communication standard published by the International Organization for Standardization (ISO) in 1984. It divides communication between different systems into seven layers, defining how each layer operates independently while cooperating with others to transmit data. This model serves as a fundamental conceptual framework for network engineers and software developers to understand complex communication processes and diagnose problems. ...

HTTP status codes are standardized three-digit numeric response codes that a server returns to indicate the result of processing a client’s request. These codes play a crucial role in all HTTP-based communications including web browsers, API clients, and search engines, clearly conveying whether requests succeeded, require redirection, or encountered client or server-side errors. In RESTful API design, selecting appropriate status codes is a key factor that significantly impacts API intuitiveness and developer experience. ...

HTTP (HyperText Transfer Protocol) methods are core elements of client-server communication protocols that have continuously evolved since Tim Berners-Lee first introduced them when designing the World Wide Web in 1991. The HTTP/1.1 standard (RFC 7231) defines 9 standard methods: GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS, CONNECT, and TRACE. Each method has important characteristics of idempotency and safety, playing essential roles in RESTful API design and web application development. History and Evolution of HTTP Methods What is HTTP (HyperText Transfer Protocol)? ...