Protocol

Reference: [Book] Network Introduction for IT Engineers

Before getting started

• The term protocol is used when referring to rules/conventions

• In networking, the term protocol is also used to refer to communication rules

Protocol

• Physical aspect

  • Data transmission media, signal conventions, line specifications, etc.

  • Ethernet is widely used

• Logical aspect

  • Protocol specifications for devices to communicate with each other

  • TCP/IP is widely used

Bit-based protocol

• Protocols were mostly developed based on binary bits to use small amounts of data efficiently

  • Strict agreements were made to transmit content with the minimum number of bits, and communication was only possible when these agreements were strictly followed

Application level protocol

• Application level protocols widely use character-based protocols rather than bit-based ones

  • HTTP and SMTP are representative protocols

  • Instead of transmitting messages in bits, they use characters to represent and transmit headers, header values, and data

  • While less efficient than bit-based protocols, they are defined in characters, allowing free header definition and extensibility

Protocol stack

• Generally, TCP/IP is called a protocol stack rather than a protocol

  • TCP and IP are protocols that operate on separate layers, but since they are used together, such a bundle of protocols is called a protocol stack

  • The TCP/IP protocol stack includes not only TCP and IP but also a wide variety of application layer protocols such as UTP, ICMP, ARP, HTTP, SMTP, and FTP

• The TCP/IP protocol stack is divided into the following 4 parts

  • Physical layer

    • Ethernet

  • Network layer

    • Helps data find its way to the destination

  • Transport layer

    • Helps properly assemble split packets into data form

  • Application layer