목차

• 1. 용어 정리
  • 1.1 Process
  • 1. 2 Sockets
• 2. transport services that an app needs
• 3. 대표적 프로토콜: HTTP(Hypertext transfer protocol) - web

1. 용어 정리

1.1 Process

: program running within a host

• process within same host
  • communicate using inter-process communication (defined by OS)
• process in different hosts
  • communicate by exchanging messages
• applications with P2P architectures have client/server processes
  • client process
    : process that initiates communication
  • server process
    : process that waits to be contacted

1. 2 Sockets

• process sends/receives messages to/from its socket

  

2. transport services that an app needs

• throughput
• timing
• security
• data integrity → 현재 전송 계층은 이 기능만 제공!
  • 데이터가 유실되지 않고 온전히 전달하는 기능

3. 대표적 프로토콜: HTTP(Hypertext transfer protocol) - web

• HTTP: web’s application layer protocol

• client/server model

  • client : browser that requests, receives(using HTTP Protocol) and displays Web objects
    
  • server
    : web server sends objects in response to requests (using HTTP Protocol)

• uses TCP

  • client initiates TCP connection(creates socket) to server, port 80
  • server accepts TCP connection from client
  • HTTP messages (application-layer protocol messages) exchanged between browser(HTTP client) and Web server
  • TCP connection closed

• HTTP is “stateless”

  • server maintains no information about client requests

• HTTP connections

  • non-presistent HTTP

    • object 한 개만 보내고 TCP connection을 끊는 경우

    • RTT
      : time for a small packet to travel from client to server and back

    • non-persistent HTTP response time

      = 2 * RTT + file transmission

      
      • to initiate TCP connection → 1 RTT
      • HTTP request and first few bytes of HTTP response to return → 1 RTT
      • file transmission time

  • persistent HTTP

    • TCP connection을 재사용하여 여러 object을 보내는 경우