The basic link of computer network

What is a computer network

Wikipedia: Computer network (computer network) is the use of communication equipment and lines will be geographically different, functional independent of multiple computer systems connected to a fully functional network software to achieve network hardware, software and resource sharing and information transmission system. A simple system that connects two or more computers to communicate with each other.

Direct-attached networks:

Point-to-point networking (Point-to-Point network): Dedicated media. Unidirectional, half duplex, full duplex.

Multiple access networks (Multiple access Network): Shared media. Broadcast, collision. Unicast, multicast, broadcast.

Indirectly connected networks.

Network interconnection: The Interconnection network (internetwork or the Internet) is made up of networks connected by routers (or gateways). The Internet (Internet) is an interconnected network.

System domain network, LAN, metropolitan area network, WAN.

What is the Internet:

Terminal System: Host (Running network application).

Communication link: optical fiber, copper wire, radio, satellite. Transfer rate = bandwidth.

Router.

The structure of the Internet:

The top-level ISP is also known as the backbone network. The 2nd tier ISP is a smaller ISP (often a regional ISP), a client of the top-level ISP, and can connect to a top-level ISP or other 2nd-tier ISP. The terminal system is connected to the Internet via an ISP network (access network). Note: ISP (Internet service Provider) Internet services provider.

Services provided by the network:

Reliable service: File transfer, web browsing, e-mail, e-commerce

Unreliable services: Video streaming, IP telephony, Web conferencing

Connection-oriented services no connected services

There is no confirmed service for confirmed services

Datagram Service: No connection no acknowledgement

Request response and Message Flow service

What is an agreement?

The Protocol (Protocol) defines the rules for transmitting messages between network entities (entities), such as the message format, the order in which messages are sent and received.

Hierarchical structure of the network
Why is the network layered? Modularity simplifies system maintenance and modification. Each layer of service is implemented through the services provided at lower levels and the functionality of this layer.

Internet Architecture:

Application Layer Application: Provides support file Services (FTP) for some specialized applications, mail (SMTP), Web pages (HTTP)

Transport Layer Transport: data transfer between processes (end-to-end) TCP, UDP

Network layer networks: Routing datagrams from the source host to the destination host (host to host) IP, routing protocols

Data Link layer Data Link: transfer (jump to jump, node to node) in the physical network PPP, Ethernet

Physical layer Physical: bits on the line (transmits raw bitstream)

Package (encaptualtion):

Each layer transmits data units called packets (packets), which belong to a protocol, also known as the Protocol Data Unit (protocol).

The basic link of computer network