2017년 3월 7일 화요일

computer network(1) - 네트워크 개요와 프로토콜

what's the Internet?

  : The Internet is an example of a network!

"nuts and bolts "view of Internet

 * millions of connected computing devices:
    hosts = end systems (네트워크의 말단에 있는 장비들을 호스트라고 함)
       ==> host is device running network apps
            ( -> 호스트는 네트워크 어플들을 작동시키는 장치이다)
            ex) PC, server, smartphone...

 * communication links
      fiber(광섬유), copper(구리선), satellite(무선), radio(무선)
           ==> component linking each other computers
                  ex) wireless links, wired links
      It's important that these components maintain bandwidth widely.
      why? because The wider the bandwidth, the higher the transmission rate.

 * packet switches (패킷 교환기)( packet is chunks of data)
    : routers(경로를 결정하는 장치) and switches ==> it's similar to Navigation

 * Internet : "network of networks"(<--> internet : interconnected network)
    : Interconnected ISPs(Internet Service Provider)
      global ISP : SKT, KT... , regional ISP : cable company...

 * protocols : "the customs and regulations dealing with diplomatic formality".
     => 컴퓨터간에 정보를 주고 받을 때에 정해진 규칙 혹은 약속
     So, we can control sending, receiving of msgs using protocols
    ex. TCP, IP, HTTP, Skype....

 * Internet standards
   RFC : Request for comments
   IETF : Internet Engineering Task Force
       -> They are Internet standard documentation.

A service view of Internet

 * Infrastructure that provides services to network applications:
    네트워크 응용프로그램들에게 서비스 기반을 제공
       ex.Web, VoIP, email,game.....

 * provides programming interface to applications:
    네트워크 응용프로그램들에게 프로그래밍 인터페이스를 제공
ex. API....


What's a protocol?

In short, the protocol defines the order and format of messages sent and received between each network, and the tasks for sending and receiving messages.

 ==> 간단히 말하면, 프로토콜은 각각의 네트워크들 간의 주고받는 메시지의 순서 와 형식 및 메시지의 전송과 수신에 대한 작업들을 정의한 것.

             human protocol <----------------------------------> network protocol
         language used by people                                 language used by machine
          questions and answers                                      questions and answers

So, human protocol and network protocol is very similar.
but, The machine can only have a conversation specified by the protocol.








































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