The OSI (Open Systems Interconnection) 7-layer model is a conceptual framework that divides the process of network communication into seven distinct layers. Standardized by the ISO in 1984, it serves as the reference model for modern networks. Layer 7 - Application Layer The layer closest to the user, the Application Layer is where the user-facing applications we interact with operate. Key Protocols: HTTP: Web service communication FTP: File transfer SMTP: Email transfer DNS: Domain name resolution Practical Use Cases: ...

The concept of a subnet mask was introduced in the evolution of TCP/IP protocols around 1985. The early internet used a classful addressing system (A, B, C classes), which was proving to be too rigid, and inefficient for IP address allocation. Subnet masks came into the picture to address this issue. History and Need for Subnet Masks In the early days of the internet, the class of an IP address was determined by looking at just the first octet (byte) of the address: ...

CIDR (Classless Inter-Domain Routing) was introduced to overcome the limitations of the existing class-based IP allocation. It allows flexible allocation of IP addresses as needed, preventing address waste. CIDR Notation and Structure CIDR represents the network bit count with the ‘/’ symbol followed by the IP address: 192.168.1.0/24 Network part: 192.168.1 (24 bits) Host part: Last 8 bits Available IPs: 254 192.168.1.0/25 Network part: 192.168.1.0 (25 bits) Host part: Last 7 bits Available IPs: 126 Relation with Subnet Mask CIDR prefixes correspond one-to-one with subnet masks: ...

Basic Structure of an IP Address An IP address is broadly divided into two parts: a ’network portion’ that distinguishes between networks, and a ‘host portion’ that identifies individual devices within that network. It’s similar to the address system of an office building. If ‘123 Main Street, New York City’ is the network portion, then ‘Suite 301, 3rd Floor’ is the host portion. Devices that share the same network portion belong to the same network. ...

tar is the most widely used compression/decompression tool in Linux. The name tar is short for ‘Tape Archive’, and it was originally created for tape backups. However, it is now the most common tool used to bundle and compress files. Essential Basic Options You Should Know tar commands are broadly divided into action specification options and action modifiers. All tar commands use a combination of these two types of options. ...