tcpip协议原理两套-第二套第02章osi和

Chapter

2 OSI

Model

&TCP/IPProtocol

SuiteThe

OSI/RMLayers

in

the

OSI/RMTCP/IP

protocol

suiteAddressing

in

TCP/IPTCP/IP

versions2.1 TheOSI/RMAn

ISO

standardOpen

System

Interconnection/

Reference

Model开放系统互连/参考模型Released

in

1984Ensured

greater

compatibility

and

interoperability7

layers,

each

of

which

illustrates

aparticularnetwork

functionISO

isthe

organization,

OSI

isthe

modelOSI

is

not

a

protocol,

but

a

conceptual

modelOSIModelApplicationPresentationSessionTransportNetworkData

LinkPhysical7654321WhyLayered？AdvantagesReduces

complexityStandardizes

interfacesFacilitates

modular

engineeringEnsures

interoperable

technologyAccelerates

evolutionSimplifies

teaching

and

learningDisadvantagesStrict

layered

architecture

makes

its

software

notso

efficient.…N+1NN

1…TheFeaturesofLayeringEach

layer

concerns

on

its

own

detailsEach

layer

provides

a

service

to

the

layeraboveEach

layer

communicates

with

its

peer

layerin

another

node

through

the

use

of

acorresponding

protocolPeer-to-Peer

CommunicationPeer

Entity对等进程/对等实体Peer

Layer对等层Interface接口Peer-to-Peer

Protocol对等层协议Service服务Peer

Layer

vs.

PeerEntityCutFTPFTP

ServerOutlookMail

ServerIEWWW

ServerLayer

7Layer

7OutlookIEFTP

ServerMail

ServerCutFTP

WWW

ServerMultiple

entities

in

one

layerPeer

entity：存在通信关系的对等层实体Multiple

protocols

in

one

layerProtocol：对等实体间的通信规则SMTPHTTPFTPDataExchange:EncapsulationSourceDestinationTNDLUnitAotocol

Data议数据单S数据段Segment分组Packet帧FramePhPDU：Pr

数据Data协

元Postal

Delivery交通同层间需要约定规则——协议2.2 Layers

in

theOSI/RMApplicationPresentationSessionTransportNetworkData

LinkPhysical7654321Network

processes

to

applicationsData

representationInter-host

communicationEnd-to-endconnectionsAddressing

and

best

pathAccess

to

mediaBinary

transmissionPhysical

LayerDa inkLayerPoint-to-Point

DeliveryNetwork

LayerHost-to-Host

DeliveryTransportLayerReliableEnd-to-End

Delivery

of

aMessageSession

LayerPresentation

LayerApplication

Layer2.3 TCP/IP

Protocol

SuiteOSI/RMTCP/IPThe

historical

andtechnical

openstandard

oftheInternetWanted

a

networkthat

could

surviveany

conditions,even

a

nuclear

warData

LinkPhysical7

Application6

Presentation5

Session4

Transport3

Network21ApplicationTransportInternetNetworkAccessSocketTCP/IP协议FTPHTTPSMTPDNSTCPUDPIPLANsMANsWANsDNSTFTPSNMPICMPIGMPARPRARPMultiplexing

of

TCP/IP

ProtocolsFTPSNMPTFTPTCPICMPIPARPEthernetsoftwareEthernethardwarePortProtocol

IDTypeMACnet2321SMTP2516169617UDP10800H0806H2.4 AddressinginTCP/IPAddressPhysical

address物理地址IP

addressIP地址Portaddress端口地址标识通信节点节点所属LAN或WAN指定LAN或WAN内唯一链路地址/硬件地址0x0005.5D06.1418标识通信节点的网络连接Internet指定Internet内唯一网络地址4标识通信进程操作系统指定一台计算机内唯一21,23,

25,808080,10000Relation-ship

of

Layers

andAddresses

in

TCP/IPProcessTCP

UDPIP

andotherprotocolsUnderlyingphysicalnetworksApplicationlayerTransportlayerNetworklayerNetworkAccesslayerPhysical

addressIP

addressPortaddressExample

1Example22.5 TCP/IPVersionsVersion

4（current）Insufficient

address

space:

32-bitInefficient

mechanism:

poor

QoS

and

securityVersion

5A

proposal

on

the

OSImodelNever

went the

proposal

stageVersion

6（future）Only

change

network

layer

protocols:

IPv6,

ICMPv6Large

address

space：128

bitImprove

the

weakness

of

version

42.6

Summary对分层网络协议体系的理解不同节点：层次组成不同，作用不同横向理解：虚通信，对等实体，协议，PDU纵向理解：封装与解封，服务，接口