Skip to main content

Introduction

Summary

keywords

TODO

HW

  • What is the server setup of www.gist.ac.kr Server: HTTP nginx

  • Today's P2P using service : Skype, Bittorrent, Bitcoin,

  • Microsoft in Windows 10 uses a proprietary peer-to-peer technology called "Delivery Optimization" to deploy operating system updates using end-users PCs

Exercise*

Next time P2P

Recap

Traceroute uses ICMPg protocol (same protocol as ping command)

Throughput is different to bandwidth #todo 1: what is the difference?

#todo 2 : do the excercises

Protocols

so many different machines, medias, data... How do they communicate?

We divide each services as layers each layer

OSI layer model. (just in the theory) 7 layers.

TCP/IP layer model. (of today's Internet) 5 layer model.

  • Application
  • transport
  • network
  • link
  • physical

4 lower layers (transport - physical) are implemented in each OS. Application layers are implemented in server software or browser.

Service layering

![[../images/20230907132645.png]]

Attach a header for each layer, and pass it to the lower layer. Router delivers the packet

Each chunks have different names​

  1. in transport layer :
  • Messages are wrapped with header to make a segment of the layer
  • header_transport + message = segment
  1. in network layer :
  • header_network + segment = datagram
  1. in link layer :
  • header_link + datagram = frame

Switch do not consider about network layer They only care link layer & physical layer Router do consider about network layer.

Examples​

wireshark using examples

Chapter 2. Application layer

keywords​

Web, HTTP, SMTP, IMAP, DNS, P2P, video streaming, socket programming(using UDP & TCP)

Goals​

conceptual & implementation of application layer protocols.

This semester makes a network app

text messaging, email, multi-user network games, streaming stored video, p2p, skype, zoom, internet search, remote login,

  • run on end systems.
  • communicate over network
  • encapsulate
  • no need to write software for network-core device

Client-Server paradigm​

  • server
    • always-on host
    • permanent OP address
  • clients