chapter7a tang ung dung

8/3/2019 Chapter7a Tang Ung Dung

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Chng 2.Giao thc tng ng dng (application layer)

Chapter 2. The Application Layer 2

Application Layer


Ch2. The Application Layer

2.1. Mt s khi nim v nguyn tc.

2.2. Web & Hyper Text Transfer Protocol.

2.3. Web design and HTTP, Web programming.

2.4. File Transfer Protocol.

2.5. Electronic Mail Protocols.

2.6. Domain Name System.


2.1. Mt s khi nim v nguyn tc

Mt s chng trnh ng dng (network applications): Email (Yahoo! Mail, MS Outlook).

Web browser (MS Internet Explorer, Netscape Navigator).

Instant messenger (Yahoo! Messenger, ICQ).

P2P file sharing (Napster, KazaA).

Internet games (Yahoo! Games).

Internet telephone (Skype, FPTFone,VNNFone).

Streaming stored video clips.

Real-time video conference.

Massive parallel computing.


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Mt s giao thc (application-layer protocols)

HTTP (Hyper Text Transfer Protocol) Giao thc web.

FTP (File Transfer Protocol) Giao thc truyn tp.

SMTP (Simple Mail Transfer Protocol) Giao thc truyn th in t.

POP (Post Office Protocol) Giao thc nhn th in t.

IMAP (Internet Mail Access Protocol) Giao thc nhn th in t (khc POP3)

DNS (Domain Name System) DNS = h thng tn min, giao thc DNS quy nhquy tc s dngtn min.

TFTP (Trivial FTP) Mt dngkhc ca FTP.


Net applications vs. application-layer protocols

Applications: Chng trnh ng dng chy trn

cc my tnh.

Trao i thng ip (message) vicc ng dng khcnhm thc thivai tr ca ng dng.

Vd: web browser, email client

Application-layer protocols: L mt thnh phn ca chng

trnh ng dng.

nh ngha cc quy tc trao ithng ip.

Giao tip vi cc dch v ccung cp bi tng di (TCP,UDP).


Cc chng trnh giao tip vi nhau ntn?

Cc chng trnh trn cng mt my tnhS dng cc dch v c cung cp bi h iu hnh

(interprocess communication).

Cc chng trnh trn cc my tnh khc nhauGiao tip thng qua giao thc ca tng ng dng

(application-layer protocol).

Chng trnh pha ngi dng = user agentGiao tip vi ngi s dng (giao din s dng).

Giao tip vi cc giao thc mng.


M hnh khch-phc v (client-server paradigm)

M hnh khch-phc v c quen gil m hnh khch-ch. Mtng dngc thbao gm hai phn:

Client Thit lplin kt vi server. Yu cu dch v t server. Nhiu clients. Vd: web browser.

Server Chvcung cpcc dch v khi client

yu cu. Thngch c 1 server, khng thay i

a ch, chy 24/7. Vd: web server.

applicationtransportnetworkdata linkphysical

applicationtransportnetworkdata linkphysical

request

reply


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M hnh ngang hng (Peer-to-peer paradigm)

Khng c my dch v c nh,cc my tnh trong mng lcny l server (nhn yu cu ktni) nhng lc khc li l client(yu cu my khc kt ni).

Cc my tnh lngang hng,

t do kt ni v giao tip i

mt. a ch ca cc my tnh tham

gia giao tip lin tc thay i.


Client-server & P2P examples

CNN.com

Yahoo! Mail

Google

Yahoo! Messenger

Internet Relay Chat (IRC)

Client-server

Client-server

Client-server

Client-server & P2P

Client-server & P2P


Dch v tng di i vi application-layer

C th coi tng application (Internet) = tng application +presentation + session trong m hnh OSI.

Cc dch v vi application: Presentation: gn lin vi application trong TCP/IP

File formats: picture (JPEG, GIF), audio (MP3, RM), video (MPEG,

MOV), document (HTML, XML). Data encryption & compression.

Session: gn lin vi application trong TCP/IP NFS (Network File System), RPC (Remote Procedure Call), SQL

(Structured Query Language), SSL (Secure Socket Layer).

Transport (*) Cung cp dch v vn chuyn cho application (TCP/IP). Hai giao thc: TCP v UDP.


Yu cu i vi vic vn chuyn dliu

Data loss

Cc ng dng audio/video c th chp nhn mt mt, sai lch dliu trong khong cho php.

Email, file transfer yu cu d liu phi chnh xc.

Timing

Cc ng dng online cn tr (delay) nh (phone, games).

Bandwidth

Cc ng dng multimedia cn ng truyn tc cao mbo cht lng.

Cc ng dng email, file transfer mm do hn, tu theo tc .


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Cc yu cu giao vn ca mt s ng dng


Internet Transport protocols: TCP & UDP

TCP (Transmission Control Protocol)

connection-oriented: setuprequired between client, server.

reliable transportbetweensending and receiving process.

flow control: sender wontoverwhelm receiver.

congestion control: throttlesender when networkoverloaded.

does not providing: timing,minimum bandwidthguarantees.

UDP (User Datagram Protocol)

unreliable data transferbetween sending and receivingprocess

does not provide: connectionsetup, reliability, flow control,congestion control, timing, orbandwidth guarantee.


Internet applications: TCP or UDP?





2.3. Web design and programming.





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2.2. Web & HTTP

Trang web (web page): mt loi ti liu c cha trong nhiu i tng: text, image, audio, Java applet, HTML

V cbn, web page = HTML file (base HTML).HTML = Hyper Text Markup Language.

HTML s dng cc th (tag) m t i tng cha trong n.

Mi i tng c ch ra bi a ch URL (UniformResource Locator)

http://www.hau1.edu.vn:80/cs/index.htm

http://www.hau1.edu.vn:80/cs/images/calendar.jpg

Protocol Host name & port Path


HTTP (Hyper Text Transfer Protocol)

Giao thc tng ng dng web. S dng m hnh client/server.

Client (user agent): Trnh duyt web (web browser) Yu cu truycp web thng qua

URL (URL request).

Server My phc v web (web server). Gi cc i tng ti client thng

quan phn hi (response).

HTTP version:

HTTP 1.0: RFC 1945

HTTP 1.1: RFC 2068


HTTP: Qu trnh trao i thng ip

Client (browser) thit lp lin kt ti web server(TCP connection) qua cng 80 (mc nh).

Serverng kt ni (accept).

Cc thng ip (HTTP messages) c trao igia browser v server.

Ngt kt ni.


HTTP example

1a. http client thit lplin ktTCP vi http server (process)ti a ch www.hau1.edu.vn,cng 80 (ngm nh vi httpserver).

2. http client gihttp requestmessage (bao gm c URL) tiTCP connection socket

1b. http server ti my phc vwww.hau1.edu.vn chyu cu

kt ni TCP ti cng 80, chpnhn kt ni ri thng bo viclient.

3. http server nhn requestmessage, to rahttp responsemessage c cha cc i tngc yu cu ri gi vosocket.

time

Gi s ngi dng truy cp URL: www.hau1.edu/cs/index.htm

(trang web c text v 10 hnh nh jpeg)


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5. http client nhn responsemessage c cha html file, hinth html. Sau , phn tch htmlfile, tm URL ca 10 hnh nh

jpeg trong ti liu.

6. Bc 1-5 c lp li vi tng

hnh nh.

4. http server ngt lin kt.

time


HTTP Connection: Persistent & Non-persistent

Non-persistent HTTP

Nhiu nht l mt itng c truyn qualin kt TCP.

HTTP 1.0

Persistent HTTP

Cho php nhiu i tngc truyn trn cng mt linkt.

Client phn tch, tm ra v giyu cu ti tt c cc itng ngay sau khi nhn c

trang HTML ban u (baseHTML).

HTTP 1.1 s dng lin kt loiny ch mc nh.


HTTP Message Format: request & response

Hai loi message:request vresponse. HTTP request message: dng ASCII (c c!)

GET /somedir/page.html HTTP/1.0

User-agent: Mozilla/4.0Accept: text/html, image/gif,image/jpeg

Accept-language:fr

(extra carriage return, line feed)

request line(GET, POST,

HEAD commands)header

lines

Carriage return,line feed

indicates endof message


HTTP request message


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HTTP response message

HTTP/1.0 200 OK

Date: Thu, 06 Aug 1998 12:00:15 GMT

Server: Apache/1.3.0 (Unix)

Last-Modified: Mon, 22 Jun 1998 ...

Content-Length: 6821

Content-Type: text/html

data data data data data ...

status line(protocol

status codestatus phrase)

headerlines

data, e.g.,requestedhtml file


HTTP response message


HTTP response message: status codes

200 OK

request succeeded, requested object later in this message

301 Moved Permanently

requested object moved, new location specified later inthis message (Location:)

400 Bad Request

request message not understood by server

404 Not Found

requested document not found on this server

505 HTTP Version Not Supported


V d thc hnh

1. Telnet ti web server:

Mmt kt ni (TCP) ti cng 80 ti web server ca trng HDN.Sau khi kt ni, tt c k t gvo s c gi ti cng 80.

telnet www.ud.edu.vn 80

2. Nhp vo GET http request:GET /cs/index.htm HTTP/1.0

y l mthttp request n gin.Nhp xongg 2 ln Enter gi ti server

3. Kim tra k t qu nhn c (http response message)!


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User-server interaction: authentication & cookies

client server

usual http request msg

401: authorization req.WWW authenticate:

usual http request msg+ Authorization:

usual http response msg

usual http request msg+ Authorization:

usual http response msgtime

Authenthication


Cookies: keeping state

Server pht sinh mt con sno (#) khi client request,ng thi ghi nhs ny s dng sau ny: Chng thc

(authentication)

Ghi nhsthch, thiquen, la chn truy cpln trc.

server gi cookie ti

client qua response msg, vd:Set-cookie: 1678453

Ln sau truy cp website,client gi km cookie, vd:cookie: 1678453

client server

usual http request msg

usual http response +Set-cookie: #

usual http request msgcookie: #


usual http request msgcookie: #


cookie-spectific

action

cookie-spectific

action


Conditional GET: client-side caching

M: server khng cn giobj ti client khi client cphin bn cp nht (up-to-date) ca obj.

Client phi ch ra thi giansa gn y nht ca objtrong http request msg.If-modified-since:

Server s tr v response msgkhng cha obj nu obj lcp nht:HTTP/1.0 304 Not Modified

client server

http request msgIf-modified-since:

http response

HTTP/1.0304 Not Modified

objectnot

modified

http request msgIf-modified-since:

http responseHTTP/1.1 200 OK

objectmodified


Web Caches (proxy server)

Client gi http requests tiweb cache thay v ti server. Nu obj c ti web cache:

web cache to http responsemsg gi v cho client.

Nu khng, web cache to gi

http request ti server, nhnobj, lu tr, ri gi httpresponse msg ti client.

Web cache s khin ngidng c cm gic duyt webnhanh hn, gim nghnmng.

Vd: proxy server trong IE.

client

Proxyserver

client

httprequest

http

reque

st

httpresponse

http

respon

se

httpreque

st

httpr

esponse

originserver

originserver


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Why Web Caching?

Assume: cache is close to

client (e.g., in same

network)

smaller response time:

cache closer to client

decrease traffic to distant

servers

link out ofinstitutional/local ISP

network often bottleneck

originservers

publicInternet

institutionalnetwork 10 Mbps LAN

1.5 Mbpsaccess link

institutionalcache


Web servers

IIS (Microsoft Internet Information Server)

Chy trn mi tr ng Windows

i km Windows 2000 Server (IIS 5.0).

Apache web server

M ngun m.

Linux/Windows

http://www.apache.orgWeb serverc dng nhiu nht.

Tomcat, Netscape, Xitami





2.3. Web design and HTTP, Web programming.





Web design: HTML

Thit k web: To ra ti liu HTML HTML (Hyper Text Markup Language)

Trong ti liu HTML c th c nhiu i tng Text

Images

Hyper link

S dng th (tag) din t i tng. Th m, vd: ; ; ; Th ng, vd: ; ;;

Cng c: Text editor: Notepad, Ultra Edit...

Microsoft FrontPage

Macromedia Dreamweaver

http://www.w3schools.org (http://www.w3schools.com)


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Web programming

HTML = trang web tnh (Static web): Web serverlun tr v mt trang HTML c nh khi nhn cyu cu ca ngi dng.

Lp trnh web: tng tc vi ngi s dng thngqua web.

LT web # LT Pascal, C:

Tng tc thng qua HTTP Message.Client-side scripts: Java script, VB script.

Server-side scripts: ASP, JSP, PHP, Perl


HTML Form: Send user requests

Simple Form

Simple ASP


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TCP Socket Programming

Giao thc HTTP: application-layer protocol

Hai ng dng application mun giao tip phi s dngdch v ca tng giao vn: Socket: a door between application process and end-end-transport

protocol (UCP or TCP).

process

TCP withbuffers,variables

socket

controlled byapplicationdeveloper

controlled byoperating

system

host orserver

process

TCP withbuffers,variables

socket

controlled byapplicationdeveloper

controlled byoperatingsystem

host orserver

internet


TCP Socket: Client/server

Server socket msn v i ti mt cng (port)no .Port c s dng ch mt process c th s dng

TCP trn mt host.

Client phi thit lp kt ni vi server (request).

Khi server nhn yu cu kt ni, n to r a mt

socket mi tip nhn (cho php nhiu clients). Microsoft Visual Basic:

Winsock: Windows Socket Component.


Winsock & OSI

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