Internet Applications

Introduction

What is the Internet?

Internet vs. internet

internet: a set of computer networks that are connected to each other.

泛指多个计算机网络互连而组成的网络

Internet: a worldwide sets of networks that interoperate using TCP/IP protocols.

指当前世界上最大的、开放的、由众多网络相互连接而成的特定计算机网络

Internet vs. WWW

WWW万维网:An information sharing model on top of the Internet

一个由许多互相链接的超文本组成的系统，通过互联网访问。

Internet :a networking infrastructure and the related communication standards

How does the Internet work?

Components of the Internet

沙漏型

Internet applications

◼ telnet, ftp, Email, Web browser

Internet protocols

◼ TCP/IP, FTP, SMTP,HTTP

Internet addresses

◼ IPv4, IPv6, Domain Name System

Physical infrastructure

◼ hosts, routers, wiring

Internet addressing

IP Address：network interface address

Be assigned by IANA

Hostname：Be assigned to a host for the benefit of humans

Internet protocols

Protocol = A set of rules for communicating

• Internet Protocol (IP)

  ​ ◼ Basic data transport: the glue of the Internet

  ​ ◼ Unreliable delivery

  ​ ◼ Versions

  ​ ◼ IPv4 with 32 bit/4 Byte address

  ​ ◼ IPv6 with 128 bit/16 Byte address

• Transport layer

  Transmission Control Protocol (TCP)

    ◼ Reliable data transmission
  

  ​ ◼ Connection-oriented

  User Datagram Protocol (UDP)

  ​ ◼ Unreliable data transmission

  ​ ◼ Connectionless-oriented

All Internet Applications use at least IP, most use TCP/UDP and IP

• Application protocols

  ​ File Transfer Protocol (FTP)

  ​ ◼ Used by file exchange applications

  ​ Simple Mail Transfer Protocol (SMTP)

  ​ ◼ Used by email applications

  ​ HyperText Transfer Protocol (HTTP)

  ​ ◼ Used by WWW applications

• Internet applications

  ftp, telnet, email, www(www是所有超文本网页文件的集合)

  大多基于CS架构

  application对应的protocol：

  

Layered networking model

Client-server paradigm（典范）

• Client – the user of the service

  ​ Initiates interaction through requests

• Server – the provider of the service

  ​ Must be listening

  ​ Waits and responds to the incoming requests

quiz

Basic Network Definitions

Terms for Network Devices

• Node:a device that is connected as part of a network with a network address

  E.g. Computer, PDA, Cell Phone, router, switch, bridge etc.

• Host Node:the computer attached directly to the Internet

• Link :the inter-connection between network devices

• Network Component:the equipment that is part of the network infrastructure

• Bandwidth:Indicates how much stuff you can send through a connection

• Delay:is an expression of how much time it takes for a packet of data to get from one designated point to another

  

• Jitter 晃动:The variation in delay

• Error Rate:错误传输、丢失或重传输的数据单元的概率

  ◼ BER (Bit Error Rate)

  ◼ FER (Frame Error Rate)

  ◼ PER (Packet Error Rate)

Terms for Network Performance Parameters

• Throughput : the average rate of successful message delivery over a communication channel

• QoS (Quality of Service)

• PLR (Packet Loss Rate)

Ways to connect to the Internet

• Dialup拨号：Via twisted pair phone lines

  MODEM (MOdulator-DEModulator，调制解调器)

• ISDN：Integrated Services Digital Network (64-128Kbps)

  ISDN（综合业务数字网）是传统电话服务的替换产品，提供从终端用户到终端用户的全数字服务，实现了语音、数据、图形、视频等综合业务的一个全数字化传递方式。

• (A)DSL：(Asymmetric) Digital Subscriber Line 非对称数字用户环路

  ◼ 8 Mbps download, 2Mbps upload – 1M bps download, 256Kbps upload

• Cable Modem

  CATV: 500 Kbps - 30 Mbps

  FTTH: Fiber to the Home

• LAN

  Ethernet connections

• Satellite

• Cellular（蜂窝）

• Broadband wireless access（宽带无线接入）

Terms for network types

switching function in the network

Circuit switching network(面向连接)：专用线路

Message switching network（报文交换）：发送整体报文

Packet switching network（无连接）：分成package

Hybrid switching network

Different channel access technologies

• Multi-access means shared medium

  Many end-systems share the same physical communication resources

  There must be some arbitration mechanism

  Example: LANs

• point-to-point

  Between two points in the network, there must exists a physical channel

  bandwidth waste

  Example: WANs

range of the network

• WAN (Wide Area Network，广域网) - network that spans a large geographic area

  • Range: 10 - 1000 km

  • Point-to-point ring or partial mesh

• MAN (Metropolitan Area Network，城域网) - network that spans a medium area such as a campus to a city

  • Range: < 10 km

  • multi-access

    Microwave, IEEE802.16/WiMAX

• LAN (Local Area Network，局域网) - network that spans a limited area such as a lab, or a building

  • multi-access

  • Range: < 1 km

  • high speed

  ◼ Ethernet: IEEE 802.3, 10 M, 100M,

  ◼ Wireless LAN: IEEE802.11b/a/g/n/ac

• PAN (Personal Area Network，个人区域网) – network that spans a small space such a room, less than 10m

According to the user of the network

• Public network

  The large scale network built by the telecommunication companies

• Private network

  The network built by a certain agency for its special requirements

Layered Architecture

OSI Layer Model

TCP/IP Layer Model