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Lp Application*Chng 5 Lp ApplicationComputer Networking: A Top
Down Approach Featuring the Internet, 3rd edition. Jim Kurose,
Keith Ross Addison-Wesley, July 2004.
All material copyright 1996-2006J.F Kurose and K.W. Ross, All
Rights ReservedSlide ny c bin dch sang ting Vit theo s cho php ca
cc tc gi
Lp Application
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Lp Application*Chng 5: Ni dung trnh by5.1 Cc nguyn l ca ng dng
mng5.2 Web v HTTP5.3 FTP 5.4 Electronic MailSMTP, POP3, IMAP5.5
DNS
5.6 Chia s file P2P5.7 Lp trnh socket viTCP5.8 Lp trnh socket vi
UDP5.9 Xy dng mt Web server
Lp Application
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Lp Application*Chng 5: Lp ApplicationMc tiu: Khi nim, cc kha cnh
hin thc ca cc giao thc ng dng mngCc m hnh dch v lp transportM hnh
client-serverM hnh peer-to-peer
Nghin cu giao thc thng qua xem xt mt s giao thc lp
applicationHTTPFTPSMTP / POP3 / IMAPDNSLp trnh ng dng mngsocket
API
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Lp Application*Mt s ng dng mngE-mailWebTin nhn nhanhng nhp t
xaChia s file P2PTr chi nhiu ngi trn mngStreaming cc video
clips
in thoi InternetHi tho video thi gian thcTnh ton ln, tnh ton
song song
Lp Application
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Lp Application*To mt ng dng mngVit chng trnh :chy trn cc h thng
u cui khc, vtruyn thng qua mngV d: Web: phn mm Web server truyn
thng vi phn mm trnh duytPhn mm nh vit cho cc thit b trung tm mngcc
thit b trung tm mng khng chy cc m ng dng ca ngi dngng dng trn cc h
thng u cui cho php pht trin ng dng nhanh, ph bin
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5.1 Cc nguyn l ca ng dng mngLp Application*
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Lp Application*Cc kin trc ca ng dngClient-serverPeer-to-peer
(P2P)Lai gia client-server v P2P
Lp Application
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Lp Application*Kin trc client-serverserver: host lun hot nga ch
IP c nhnhm cc server chia s cng vicclients:truyn thng vi serverc th
kt ni khng lin tcc th c a ch IP thay ikhng truyn thng trc tip vi
client khc
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Lp Application*Kin trc P2P thun tykhng c server lun hot ngtruyn
thng trc tip vi h thng u cui bt kcc im kt ni khng lin tc v thay i a
ch IPV d: Gnutella
linh hot cao nhng kh qun l
Lp Application
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Lp Application*Lai gia client-server v P2PSkypeng dng in thoi
InternetTm a ch ca thnh vin xa: server trung tmKt ni trc tip
Client-client (khng thng qua server) Tin nhn nhanhChat gia 2 user l
P2PM hnh client-server:User ng k a ch IP ca h vi server trung tm
khi trc tuynUser tip xc vi server trung tm tm a ch IP ca bn
Lp Application
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Lp Application*Tin trnh truyn thngTin trnh: chng trnh chy bn
trong 1 host.trong cng host, 2 tin trnh truyn thng dng truyn thng
ni b (do h iu hnh xc nh).cc tin trnh trong cc host khc nhau truyn
thng bng cch trao i cc thng ipTin trnh Client: tin trnh khi to
truyn thngTin trnh Server: tin trnh ch c tip xc
Ch : cc ng dng vi kin trc P2P c c cc tin trnh client v
server.
Lp Application
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Lp Application*Socketscc tin trnh gi/nhn cc thng ip n/t socket
ca nsocket tng t nh catin trnh gi y thng ip ra ngoi catin trnh nhn
ph thuc vo h tng lu thng mang thng ip n socket thch hpInternetiu
khin bi h iu hnhiu khin bi ngi pht trin ng dngAPI: (1) la chn giao
thc vn chuyn; (2) kh nng chnh sa mt vi tham s (xem phn sau)
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Lp Application*Tin trnh nh a ch nhn c thng ip, tin trnh phi c
nhn dng (identifier)thit b host phi c a ch IP duy nhta ch IP m trn
tin trnh ang chy c nhn dng tin trnh?KHNG, nhiu tin trnh c th chy
trn cng 1 hostNhn dng bao gm c a ch IP v cc s cng (port) lin kt vi
tin trnh trn host.V d v s port:HTTP server: 80Mail server: 25 gi
thng ip HTTP cho web server gaia.cs.umass.edu :IP address:
128.119.245.12Port number: 80
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Lp Application*nh ngha giao thc lp ng dngcc kiu ca trao i thng
ipV d: yu cu, p ngC php thng ip:Cc trng no trong thng ip v lm sao m
t?Ng ngha thng ip ngha ca thng tin trong cc trngCc quy tc khi no v
lm sao cc tin trnh gi v p ng cc thng ipCc giao thc Public-domain:nh
ngha trong RFCCho php cng tcV d: HTTP, SMTPCc giao thc c quyn:V d:
KaZaA
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Lp Application*Dch v vn chuyn no ng dng khng cnMt mt d liu mt s
ng dng (vd: audio) c kh nng chu licc ng dng khc (vd: truyn file,
telnet) yu cu d liu tin cy 100%nh thmt s ng dng (vd: in thoi
Internet, tr chi tng tc) yu cu tr thp t hiu quBandwidth (bng
thng)mt s ng dng (vd: a phng tin) yu cu bng thng t hiu qucc ng dng
khc mm do hn c th dng bt k bng thng no cng c
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Lp Application*Mt s yu cu i vi cc ng dng ph binApplication
Truyn filee-mailWebaudio/videothi gian thcaudio/video luTr chi
tng tcTin nhn nhanhData loss
khngkhngKhngchu li
chu lichu likhngBandwidth
mm do mm domm doaudio: 5kbps-1Mbpsvideo:10kbps-5MbpsNh trnMt vi
kbpsmm doTime Sensitive
khngkhngkhngc, 100 mili giy
c, mt vi giyc, 100 mili giyC v khng
Lp Application
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Lp Application*Cc dch v giao thc Internet
transportTCP:connection-oriented: cn thit lp tin trnh gia client v
server Vn chuyn tin cy: gia tin trnh gi v nhniu khin lung: ngi gi s
khng ln t ngi nhniu khin tc nghn: iu tit ngi gi khi mng qu tiKhng h
tr: nh th, bo m bng thng ti thiuUDP:truyn d liu khng tin cy gia gi
v nhnKhng h tr: thit lp kt ni, tin cy, iu khin lung, iu khin tc
nghn, nh th, bo m bng thng ti thiu
Th th sinh ra UDP lm g?
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Lp Application*Cc giao thc lp application,
transportApplication
e-mailTruy cp terminal t xaWeb Truyn filestreaming
multimedia
in thoi Internet
Giao thc lpApplicationSMTP [RFC 2821]Telnet [RFC 854]HTTP [RFC
2616]FTP [RFC 959]c quyn(vd: RealNetworks)c quyn(vd:
Vonage,Dialpad)Giao thc di lptransport
TCPTCPTCPTCPTCP / UDP
UDP
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5.2 Web v HTTPLp Application*
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Lp Application*Web v HTTPMt s thut ng chuyn mnWeb page (trang
Web) bao gm cc objects (i tng)i tng c th l file HTML, hnh nh JPEG
image, Java applet, file audio,Trang Web file HTML c bn s cha mt s
i tng c tham chiuMi i tng c th nh a ch bng mt URLV d URL:
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Lp Application*Tng quan HTTPHTTP: hypertext transfer
protocolGiao thc lp ng dng ca WebM hnh client/serverClient: trnh
duyt yu cu, nhn v hin th cc i tng WebServer: Web server gi cc i tng
p ng cho yu cuHTTP 1.0: RFC 1945HTTP 1.1: RFC 2068PC
chyExplorerServer chyApache WebserverMac chyNavigatorYu cu HTTPYu
cu HTTPp ng HTTPp ng HTTP
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Lp Application*Tng quan HTTPDng TCP:client khi to kt ni TCP (to
socket) n server, port 80server chp nhn kt ni TCP t clientCc thng
ip HTTP (thng ip giao thc lp application) trao i gia trnh duyt
(HTTP client) v Web server (HTTP server)ng kt ni TCPHTTP l khng
trng thiserver khng gi thng tin v cc yu cu trc ca clientCc giao thc
no gi trng thi l phc tp!lch s qu kh (trng thi) phi gi linu
server/client b s c, cch nhn ca n v trng thi mu thun, phi c iu
chnh
vn lin quan
Lp Application
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Lp Application*Cc kt ni HTTPHTTP khng bn vngCh c ti a l 1 i tng
c gi qua 1 kt ni TCP.HTTP/1.0 dng HTTP khng bn vngHTTP bn vngNhiu i
tng c th c gi qua 1 kt ni TCP n gia client v server.HTTP/1.1 mc
nhin dng HTTP bn vng
Lp Application
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Lp Application*HTTP khng bn vngGi s user nhp vo URL nh sau:
www.someSchool.edu/someDepartment/home.index1a. HTTP client khi to
kt ni TCP connection n HTTP server (tin trnh) ti www.someSchool.edu
trn port 802. HTTP client gi HTTP thng ip yu cu (cha URL) vo trong
socket kt ni TCP. Thng ip ch rng client mun cc i tng
someDepartment/home.index1b. HTTP server ti host www.someSchool.edu
ch kt ni TCP ti port 80. chp nhn kt ni, thng bo cho client3. HTTP
server nhn thng ip yu cu, nh dng thng ip p ng cha i tng c yu cu v
gi thng ip vo trong socket ca nThi gian(cha text, tham chiu n 10
hnh)
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Lp Application*HTTP khng bn vng5. HTTP client nhn thng ip p ng
cha file HTML, hin th n. Phn tch c php html file, tm ra 1 tham chiu
n i tng jpeg6. Lp li cc bc t 1-5 cho cc i tng jpeg khc4. HTTP
server ng kt ni TCP. time
Lp Application
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Lp Application*HTTP khng bn vng: thi gian p ngnh ngha RTT: thi
gian gi mt gi nh i t client n server v quay li.Thi gian p ng:Mt RTT
khi to kt ni TCPMt RTT cho yu cu HTTP v mt vi byte u tin ca p ng
HTTP c tr vThi gian truyn fileTng cng = 2RTT+ Thi gian truyn
file
Lp Application
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Lp Application*HTTP bn vngVn vi HTTP khng bn vng:Yu cu 2 RTT mi
i tngH iu hnh lin quan n mi kt ni TCPCc trnh duyt thng m song song
cc kt ni TCP em v cc tham chiu n cc i tngHTTP bn vngserver b kt ni
sau khi m gi p ng leavescc thng ip HTTP ca tin trnh con cng m hnh
client/server gi thng qua kt ni m
Bn vng khng c pipelining:client pht ra yu cu mi ch khi p ng trc
nhn xong1 RTT cho mi i tng tham chiuBn vng c pipelining:mc nhin
trong HTTP/1.1client gi yu cu ngay sau khi gp mt i tng tham chiut
nht 1 RTT cho tt c i tng tham chiu
Lp Application
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Lp Application*Thng ip yu cu HTTP2 kiu thng ip HTTP: yu cu, p
ngThng ip yu cu HTTP:ASCII ( dng thc con ngi c th c c)GET
/somedir/page.html HTTP/1.1Host: www.someschool.edu User-agent:
Mozilla/4.0Connection: close Accept-language:fr
(thm mt k t xung dng)dng yu cu(cc lnh GET, POST, HEAD)cc dng
header k t xung dng, v u dng mi ch im cui cng ca thng ip
Lp Application
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Lp Application*HTTP thng ip yu cu: dng thc tng qut
Lp Application
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Lp Application*Ti ln form inputPhng php Post:Web page thng cha
form inputInput c ti ln vo server trong thn thc thPhng php URL:Dng
GETInput c ti ln trong trng URL ca dng yu cu:
www.somesite.com/animalsearch?monkeys&banana
Lp Application
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Lp Application*Cc kiu phng php HTTP/1.0GETPOSTHEADhi server mc i
tng yu cu m khng p ngHTTP/1.1GET, POST, HEADPUTti ln file trong thn
thc th n ng dn c xc nh trong trng URLDELETExa file c xc nh trong
trng URL
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Lp Application*Thng ip p ng HTTPHTTP/1.1 200 OK Connection
closeDate: 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 ... dng trng
thi(giao thcm trng thicm t trng thi)cc dngheaderD liu, vd: fileHTML
yu cu
Lp Application
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Lp Application*Cc m trng thi p ng HTTP200 OKyu cu thnh cng, i
tng yu cu nm pha sau thng ip ny301 Moved Permanentlyi tng yu cu di
chuyn, v tr mi xc nh pha sau thng ip ny (Location:) 400 Bad
Requestthng ip yu cu server khng hiu404 Not Foundti liu yu cu khng
c trong server 505 HTTP Version Not SupportedTrong dng u tin ca
thng ip p ng server-> client.Mt s mu:
Lp Application
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Lp Application*Kim tra HTTP (pha client)1. Telnet n Web server a
thch ca bn:
M kt ni TCP port 80(port HTTP server mc nhin) ti cis.poly.edu.Mi
th nhp vo gi n port 80 ti cis.poly.edutelnet cis.poly.edu 802. Nhp
vo yu cu trong lnh GET HTTP:
GET /~ross/ HTTP/1.1Host: cis.poly.eduDo nh lnh ny (enter 2 ln),
bn gi yu cu GET ti thiu (nhng y ) n HTTP server3. Xem thng ip p ng
gi t HTTP server!
Lp Application
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Lp Application*Kho st hnh ng ca HTTPtelnetEthereal
Lp Application
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Lp Application*Trng thi User-server: cc cookieNhiu Web sites dng
cc cookie4 thnh phn:1) cookie header line ca thng ip p ng HTTP2)
cookie header line trong thng ip p ng HTTP3) cookie file lu trong
host ca user, qun l bi trnh duyt ca user 4) c s d liu back-end ti
Web siteV d:Susan truy cp Internet lun t mt PCShe ln u tin vo mt
e-commerce site xc nh Khi yu cu khi to HTTP n site, site to mt ID
duy nht v to mt im ng nhp trong c s d liu back-end cho ID
Lp Application
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Lp Application*cc cookie: lu gi trng thi (tt.)serverto ID1678
cho userim ng k trong c s d liu backend
truy cptruy cpmt tun sau:
Lp Application
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Lp Application*cc cookie (tip)Cc cookie em li:s cp phpgi mua
hngcc khuyn cotrng thi phin lm vic ca user (Web e-mail)cc cookie v
s ring t:cc cookie cho php cc site bit nhiu hn v bnbn c th cung cp
tn v e-mail cho sitesngoi raLm th no gi trng thi:cc thi im kt thc
giao thc: bo tr trng thi ti sender/receiver thng qua nhiu giao tccc
cookie: trng thi mang cc thng ip http
Lp Application
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Lp Application*Web caches (proxy server)user thit lp trnh duyt:
truy cp Web thng qua cachetrnh duyt gi tt c yu cu HTTP cho cachei
tng trong cache: cache tr v i tngngc li cache yu cu i tng t server
ngun, sau tr v cho clientMc tiu: tha mn yu cu ca client khng cn lin
quan n server ngunclientProxyserverclientHTTP yu cuHTTP yu cuHTTP p
ngHTTP p ngHTTP yu cuHTTP p ngserverngunserverngun
Lp Application
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Lp Application*Web cachingCache hot ng ti c client v serverTiu
biu cache c ci t bi ISP (trng hc, cng ty, ISP ring)Ti sao dng Web
caching?Gim thi gian p ng cho yu cu ca clientGim lu thng trn lin kt
truy cpInternet rt ng nghch vi caches: cho php nhng ngi cung cp ni
dung ngho nn phn pht hiu qu ni dung (cng vy i vi P2P file
sharing)
Lp Application
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Lp Application*V d CachingGi skch thc trung bnh i tng= 100,000
bitstc trung bnh yu cu t trnh duyt n server = 15/s tr t router ni
gi yu cu n server ngun ri quay li = 2 sKt qu kh dng ca LAN = 15% kh
dng trn lin kt truy cp= 100%tng thi gian tr = tr Internet + tr truy
cp+ tr LAN = 2 s + cc pht+ mili s
serversngun Internetcng cngnetwork gi yu cu10 Mbps LAN1.5 Mbps
lin kt truy cpcache ni gi yu cu
Lp Application
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Lp Application*V d Caching (tip)Gii php c thtng bng thng truy cp
ln, v d 10 MbpsKt qu kh dng ca LAN = 15% kh dng trn lin kt truy cp
= 15%tng thi gian tr = tr Internet + tr truy cp+ tr LAN = 2 s +
mili s + mili sthng tng chi ph
serversngun Internetcng cngnetwork gi yu cu10 Mbps LAN10 Mbps
lin kt truy cpcache ni gi yu cu
Lp Application
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Lp Application*V d Caching (tip)ci t cachetc h tr l 0.4kt qu40%
yu cu s c tha mn hu nh ngay lp tc60% yu cu s c tha mn bi server
ngun kh dng trn lin kt truy cp gim n 60%, do tr khng ng k (vd 10
mili s)tng thi gian tr = tr Internet + tr truy cp+ tr LAN =
0.6*(2.01) s + 0.4*mili s < 1.4 s
serversngun Internetcng cngnetwork gi yu cu10 Mbps LAN1.5 Mbps
lin kt truy cpcache ni gi yu cu
Lp Application
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Lp Application*GET c iu kinMc tiu: khng gi i tng nu cache cp
nhtcache: xc nh ngy ca bn sao cache trong yu cu
HTTP:If-modified-since: server: p ng khng cha i tng nu bn sao cache
cp nht: HTTP/1.0 304 Not ModifiedcacheserverHTTP request
msgIf-modified-since: i tngkhngsa iHTTP request
msgIf-modified-since: HTTP responseHTTP/1.0 200 OK
i tngcsa i
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5.3 FTPLp Application*
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Lp Application*FTP: giao thc truyn filetruyn file n/t host t xam
hnh client/server client: pha khi to truyn (n/t host xa)server:
host xaftp: RFC 959ftp server: port 21truyn fileh thng file t
xauser ti host
Lp Application
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Lp Application*FTP: kt ni d liu, iu khin ring bitFTP client tip
xc FTP server ti port 21, xc nh TCP nh giao thc transportClient ly
giy php thng qua kt ni iu khinClient xem th mc xa bng vic gi cc lnh
thng qua kt ni iu khin.Khi server nhn lnh truyn file, server m kt
ni TCP th 2 (cho file) n clientSau khi truyn 1 file, server ng kt
ni d liu Server m kt ni d liu TCP khc truyn file khciu khin kt ni:
out of bandFTP server gi li trng thi: th mc hin hnh, giy php
trc
Lp Application
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Lp Application*Cc lnh, phn hi FTPV d cc lnh:gi nh vn bn ASCII
trn knh iu khinUSER usernamePASS passwordLIST tr v danh sch ca file
trong th mc hin hnhRETR filename trch chn (ly) fileSTOR filename lu
(t) file vo trong host xaV d m tr vm trng thi v cm (nh HTTP)331
Username OK, password required125 data connection already open;
transfer starting425 Cant open data connection452 Error writing
file
Lp Application
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5.4 Electronic MailLp Application*
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Lp Application*Electronic Mail3 thnh phn quan trng: user agents
mail servers simple mail transfer protocol: SMTPUser Agentcn gi l
mail readervit, sa i, c cc thng ip mailV d: Eudora, Outlook, elm,
Netscape Messengercc thng ip i v n c lu trn server
Lp Application
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Lp Application*Electronic Mail: mail serversMail Servers mailbox
(hp th) cha cc thng ip n userhng thng ip cho cc thng ip email ra
ngoi (chun b gi)giao thc SMTP gia cc mail servers gi cc thng ip
email client: mail server giserver: mail server nhn
Lp Application
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Lp Application*Electronic Mail: SMTP [RFC 2821]dng TCP truyn tin
cy thng ip email t client n server trn port 25truyn trc tip: server
gi n server nhn3 knh truynbt tay (cho hi)truyn thng ip ngtng tc
lnh/phn hilnh: vn bn ASCIIphn hi: m trng thi v cm cc thng ip phi
dng m ASCII 7-bit
Lp Application
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Lp Application*Tnh hung: Alice gi cho Bob1) Alice dng UA vit
thng ip v gi n [email protected]) UA ca Alice gi thng ip ca c y n
mail server; thng ip c gia nhp vo hng i3) Pha Client ca SMTP m kt
ni TCP vi mail server ca Bob4) SMTP client gi thng ip ca Alice trn
kt ni TCP5) mail server ca Bob t thng ip vo hp th ca Bob6) Bob kch
hot trnh user agent c thng ip
123456
Lp Application
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Lp Application*V d tng tc SMTP S: 220 hamburger.edu C: HELO
crepes.fr S: 250 Hello crepes.fr, pleased to meet you C: MAIL FROM:
S: 250 [email protected]... Sender ok C: RCPT TO: S: 250
[email protected] ... Recipient ok C: DATA S: 354 Enter mail, end
with "." on a line by itself C: Do you like ketchup? C: How about
pickles? C: . S: 250 Message accepted for delivery C: QUIT S: 221
hamburger.edu closing connection
Lp Application
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Lp Application*Th nghim tng tc SMTP:telnet servername 25thy 220
tr li t servernhp cc lnh HELO, MAIL FROM, RCPT TO, DATA, QUITlnh
trn cho php bn gi email khng cn dng email client (reader)
Lp Application
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Lp Application*SMTPSMTP dng cc kt ni bn vngSMTP yu cu cc thng ip
(header & body) phi dng thc 7-bit ASCIISMTP server dng
CRLF.CRLF xc nh kt thc thng ipSo snh vi HTTP:HTTP: koSMTP: ytt c u
c tng tc lnh/p ng, cc m trng thi ASCIIHTTP: mi i tng c ng kn trong
thng ip p ng ca nSMTP: nhiu i tng c gi trong thng ip nhiu phn
Lp Application
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Lp Application*Dng thc thng ip email SMTP: giao thc cho trao i
cc thng ip emailRFC 822: chun cho dng thc vn bn:cc dng header, v
d:To:From:Subject:khc vi cc lnh SMTP!bodythng ip, ch c cc k t
ASCIIheaderbodydng trng
Lp Application
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Lp Application*Dng thc thng ip: cc m rng multimediaMIME: m rng
email multimedia, RFC 2045, 2056cc dng b sung trong header ca thng
ip khai bo kiu ni dung MIMEkiu, kiu con, khai bo tham sd liu
multimedia phng php dng m ha d liuphin bn MIMEd liu m ha
Lp Application
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Lp Application*Cc giao thc truy cp email SMTP: truyn dn/lu tr vo
server ca ngi nhnGiao thc truy cp email: trch xut t serverPOP: Post
Office Protocol [RFC 1939]cp php (agent server) v download IMAP:
Internet Mail Access Protocol [RFC 1730]nhiu tnh nng (phc tp hn)iu
khin cc thng ip lu trn serverHTTP: Hotmail , Yahoo! Mail,
SMTPgiao thctruy cpmail server ca ngi nhn
Lp Application
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Lp Application*Giao thc POP3giai on cp phpcc lnh pha client:
user: khai bo usernamepass: passwordcc p ng pha server+OK-ERRgiai
on giao dch, client:list: lit k cc s thng ip retr: trch xut thng ip
theo sdele: xaquit C: list S: 1 498 S: 2 912 S: . C: retr 1 S: S: .
C: dele 1 C: retr 2 S: S: . C: dele 2 C: quit S: +OK POP3 server
signing off
S: +OK POP3 server ready C: user bob S: +OK C: pass hungry S:
+OK user successfully logged on
Lp Application
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Lp Application*POP3 v IMAPnghin cu thm v POP3V d trc dng ch ti
xung v xa.Bob khng th c li email nu thay i clientti xung-v-gi: sao
chp cc thng ip trn cc client khc nhauPOP3 khng gi trng thi ca cc
phin lm vicIMAPGi tt c thng ip ti 1 v tr: serverCho php user t chc
cc thng ip theo dng th mcIMAP gi trng thi xuyn sut cc phin lm
vic:cc tn ca th mc v nh x gia ID ca thng ip v tn th mc
Lp Application
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5.5 DNSLp Application*
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Lp Application*DNS: Domain Name SystemCon ngi: nhiu cch nhn
dng:SSN, tn, #h chiuInternet hosts, routers:a ch IP (32 bit) dng
cho cc gi nh a chtn, v d: www.yahoo.com dng bi con nginh x gia a ch
IP v tn?Domain Name System:c s d liu phn b hin thc theo t chc phn
cp ca nhiu servers tngiao thc lp application host, routers, name
servers truyn thng vi cc tn phn gii (a ch/dch ra tn)lu : chc nng li
Internet, hin thc nh giao thc lp applicationphc tp bin mng
Lp Application
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Lp Application*DNS Ti sao khng tp trung ha DNS?mt im chu lilu
lngkhong cch c s d liu tp trungbo tr
khng linh hot!Cc dch v DNSTn Host chuyn thnh a ch IPB danh
Hostcc tn ng chun v b danhB danh Mail serverTi phn bCc Web server
bn sao: tp cc a ch IP cho 1 tn ng chun
Lp Application
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Lp Application*C s d liu cu trc, phn bClient mun IP cho
www.amazon.com:Client hi mt server gc (root) tm com DNS
serverClient hi com DNS server ly amazon.com DNS serverClient hi
amazon.com DNS server ly a ch IP ca www.amazon.com
Lp Application
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Lp Application*DNS: cc server tn gctip xc qua server tn cc b no
khng th phn gii tnserver tn gc:tip xc server tn c thm quyn nu nh x
tn khng xc nhly nh xtr v nh x n server tn cc b
Lp Application
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Lp Application*TLD v Server c thm quynCc server Top-level domain
(TLD) : chu trch nhim cho tn min com, org, net, edu, v cc tn min
quc gia nh uk, fr, ca, jp.Lnh vc gio dc cho edu TLDCc DNS server c
thm quyn: DNS server ca t chc, cung cp cc tn host c thm quyn nh x
IP cho server (v d: Web v mail).Khng th duy tr bi t chc hoc ngi
cung cp dch v
Lp Application
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Lp Application*Server tn cc bKhng hon ton theo cu trc phn cpMi
ISP (ISP c nhn, cng ty, trng hc) c mt server cc b nh vy.cng gi l
server tn mc nhinKhi mt host to mt truy vn DNS, truy vn c gi ti DNS
server cc b ca nHot ng nh mt proxy, chuyn truy vn vo cho t chc phn
cp
Lp Application
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Lp Application*host yu cucis.poly.edugaia.cs.umass.eduDNS server
gc123456DNS server c thm quyndns.cs.umass.edu78TLD DNS serverV
dHost ti cis.poly.edu mun a ch IP ca gaia.cs.umass.edu
Lp Application
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Lp Application*Cc truy vn quytruy vn quy:y trch nhim phn gii tn
cho server tn tip xc cti qu nng?truy vn tun t:tn tip xc c tr li vi
tn ca server Ti khng bit tn , nhng c th hi server ny
Lp Application
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Lp Application*DNS: caching v cp nht cc recordmt khi server tn
hc cch nh x, n cache nh xim ng nhp cache s thot ra (bin mt) sau mt
vi lnTLD servers in hnh s c cache trong cc server tn cc bDo server
tn gc s khng thng xuyn c truy cpc ch cp nht/thng bo bn di c thit k
bi IETFRFC
2136http://www.ietf.org/html.charters/dnsind-charter.html
Lp Application
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Lp Application*Cc DNS recordDNS: c s d liu phn b lu tr cc record
ti nguyn (RR)Type=NSname l tn min (vd: foo.com)value l tn host ca
server tn c thm quyn cho tn min ny
Type=Aname l tn hostvalue l a ch IP
Type=CNAMEname l b danh ca tn chun (tn thc) www.ibm.com l tn thc
servereast.backup2.ibm.comvalue l tn chun
Type=MXvalue l tn ca email server lin kt vi name
Lp Application
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Lp Application*Giao thc v cc thng ip DNSGiao thc DNS: cc thng ip
truy vn v tr li, u c cng dng thc thng ip header thng ip
identification: 16 bit # cho truy vn, tr li cho truy vn dng cng
#flags:truy vn hoc tr li quy mong ch quy sn sngtr li c cp php
Lp Application
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Lp Application*Giao thc v cc thng ip DNScc trng Name, type cho 1
truy vncc RR trong p ng cho truy vncc record cho cc server c thm
quynthng tin hu ch b sung c th s dng
Lp Application
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Lp Application*Chn cc record vo DNSV d: mi to Network Utopiang k
tn min networkuptopia.com ti mt registrar (v d: Network
Solutions)Cn cung cp cho registrar tn v a ch IP ca server tn c thm
quyn (primary v secondary) ca bnRegistrar chn 2 RR vo trong com TLD
server: (networkutopia.com, dns1.networkutopia.com,
NS)(dns1.networkutopia.com, 212.212.212.1, A) a vo trong server c
thm quyn record Type A cho www.networkuptopia.com v bn ghi Type MX
cho networkutopia.comLm sao ngi khc c th bit c a ch IP Web site ca
bn?
Lp Application
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5.6 Chia s file P2PLp Application*
-
Lp Application*Chia s file P2PV dAlice chy ng dng P2P client trn
my tnh xch tay ca cKt ni khng lin tc vo Internet; ly a ch IP cho mi
kt niHi v Hey Judeng dng s hin th nhng peer khc c bn sao ca Hey
Jude.
Alice chn 1 trong nhng peer, l Bob.File c sao chp t my tnh ca
Bob: HTTPTrong khi Alice ti xung, cc user khc ti ln t Alice.Alice l
1 peer ng c vai tr Web client v Web server tm thi.Tt c peer l
server = linh hot cao!
Lp Application
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Lp Application*P2P: directory tp trungu tin do Napster thit k1)
khi peer kt ni, n thng bo cho server trung tm:a ch IPni dung2)
Alice truy vn Hey Jude3) Alice yu cu file t Bob
Lp Application
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Lp Application*P2P: cc vn vi directory tp trungMt im chu liHin
tng tc nghn c chaiXm phm bn quyn
truyn file khng tp trung nhng tm kim ni dung th tp trung cao
Lp Application
-
Lp Application*Trn ngp truy vn: Gnutellahon ton phn bkhng c
server tp trunggiao thc tn min chungnhiu Gnutella client hin thc
giao thc
overlay network: thc cnh gia peer X v Y nu c 1 kt ni TCPtt c cc
peer ang hot ng v cc cnh l mng overlay networkcnh khng phi l mt lin
kt vt lpeer s kt ni vi < 10 peer ln cn
Lp Application
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Lp Application*Gnutella: giao thcTruyn File:HTTPTruy vn thng ip
gi trn cc kt ni TCP ang c peer chuyn thng ip truy vn QueryHit gi
trn ng ngc chiu linh hot:hn ch trn ngp theo phm vi
Lp Application
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Lp Application*Gnutella: hi t PeerHi t peer X phi tm mt s peer
khc trong Gnutella network: dng mt danh sch cc peer d tuynX ln lt
th to TCP vi cc peer trn danh sch cho n khi kt ni thit lp c vi YX
gi thng ip Ping n Y; Y chuyn thng ip Ping. Tt c cc peer nhn thng ip
Ping s tr li bng thng ip PongX nhn c nhiu thng ip Pong. N sau c th
thit lp thm cc kt ni TCP.Peer leaving: xem mt s vn mng gia nh!
Lp Application
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Lp Application*KaZaAMi peer l mt hoc c gn thnh ch huy nhmTCP kt
ni gia peer v nhm ch huy ca nTCP kt ni gia mt s cp nhm ch huy.Nhm
ch huy theo di ni dung trong tt c thnh vin bn trong
Lp Application
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Lp Application*KaZaA: Truy vnMi file c mt bm (hash) hoc mt m
tClient gi t kha truy vn n nhm ch huy ca nNhm ch huy p ng vi truy
vn ca nhm: ng vi mi so trng: metadata, hash, a ch IPNu nhm ch huy
chuyn truy vn cho nhm khc, chng phn hi thch hpClient sau chn cc
file downloadCc yu cu HTTP dng hash nh mt nhn dng gi n cho peer qun
l file mong mun
Lp Application
-
Lp Application*KaZaA: cc th thutHn ch khi ti ln ng thiXp hng yu
cuKhch l u tinti xung song songTm hiu thm thng tin :J. Liang, R.
Kumar, K. Ross, Understanding KaZaA,(Web site:
cis.poly.edu/~ross)
Lp Application
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5.7 Lp trnh socket viTCPLp Application*(xem thm slide Lp trnh
socket)
-
Lp Application*Lp trnh socketSocket API c gii thiu trong BSD4.1
UNIX, 1981r rng ti, s dng v gii phng bi ng dngm hnh client/server2
kiu dch v lu thng qua socket API: datagram khng tin cytin cy, truyn
byte theo streaming Mc tiu: nghin cu cch xy dng ng dng truyn thng
client/server dng sockets
Lp Application
-
Lp Application*Lp trnh socket dng TCPSocket: mt cnh ca gia tin
trnh ng dng v giao thc transport (UCP hoc TCP)Dch v TCP: truyn tin
cy cc bytes t mt tin trnh n tin trnh khciu khin bingi pht trinng
dngiu khin bih iu hnhhost hoc serveriu khin bingi pht trinng dngiu
khin bih iu hnhhost hocserverinternet
Lp Application
-
Lp Application*Lp trnh socket vi TCPClient phi tip xc vi
servertin trnh server phi chy trcserver phi to socket (ca) mi
client n tip xcClient tip xc server bng:to socketTCP client cc bxc
nh a ch IP, s port ca tin trnh serverKhi client to socket: client
TCP thit lp kt ni vi server TCP
Khi c tip xc bi client, server TCP to socket mi cho tin trnh
server truyn thng vi clientcho php server ni chuyn vi nhiu clients
port dng phn bit cc client (xem tip trong chng 3)
Lp Application
-
Lp Application*Giao tip socket Client/server: TCPServer (chy trn
hostid)Client
Lp Application
-
Lp Application*tin trnh Clientclient TCP socketThut ng StreamMt
stream l mt chui cc k t c chy vo hoc ra khi mt tin trnhMt input
stream ch ngun vo ca mt tin trnh, vd: bn phm hoc socket.Mt output
stream ch ngun ra ca mt tin trnh, vd: mn hnh hoc socket.
Lp Application
-
Lp Application*Lp trnh socket dng TCPV d ng dng client-server
:1) client c cc dng t input chun (inFromUser stream) , gi n server
thng qua socket (outToServer stream)2) server c cc dng t socket3)
server chuyn cc dng thnh ch hoa, gi ngc tr li cho client4) client
c, in cc dng sa i t socket (inFromServer stream)
Lp Application
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Lp Application*V d: Java client (TCP)import java.io.*; import
java.net.*; class TCPClient {
public static void main(String argv[]) throws Exception { String
sentence; String modifiedSentence;
BufferedReader inFromUser = new BufferedReader(new
InputStreamReader(System.in));
Socket clientSocket = new Socket("hostname", 6789);
DataOutputStream outToServer = new
DataOutputStream(clientSocket.getOutputStream());
toinput streamtoclient socket, kt ni vo servertooutput streamgn
vo socket
Lp Application
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Lp Application*V d: Java client (TCP) BufferedReader
inFromServer = new BufferedReader(new
InputStreamReader(clientSocket.getInputStream()));
sentence = inFromUser.readLine();
outToServer.writeBytes(sentence + '\n');
modifiedSentence = inFromServer.readLine();
System.out.println("FROM SERVER: " + modifiedSentence);
clientSocket.close(); } } toinput streamgn vo socketGi dngn
serverc dngt server
Lp Application
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Lp Application*V d: Java server (TCP)import java.io.*; import
java.net.*;
class TCPServer {
public static void main(String argv[]) throws Exception { String
clientSentence; String capitalizedSentence;
ServerSocket welcomeSocket = new ServerSocket(6789); while(true)
{ Socket connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient = new BufferedReader(new
InputStreamReader(connectionSocket.getInputStream()));
tosocket mi tip xcti port 6789Ch, clienttip cn viserverTo
inputstream, gn vosocket
Lp Application
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Lp Application*V d: Java server (TCP)
DataOutputStream outToClient = new
DataOutputStream(connectionSocket.getOutputStream());
clientSentence = inFromClient.readLine();
capitalizedSentence = clientSentence.toUpperCase() + '\n';
outToClient.writeBytes(capitalizedSentence); } } } c dngt
socketTo outputstream, gn vosocketVit dng rat socketkt thc vng lp
whilequay li v ch chokt ni ca client khc
Lp Application
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5.8 Lp trnh socket vi UDPLp Application*(xem thm slide Lp trnh
socket)
-
Lp Application*Lp trnh socket vi UDPUDP: khng kt ni gia client v
serverkhng bt tayngi gi r rng gn a ch IP v port ca ch vo mi giphi
trch a ch IP, port ca ngi gi t gi nhnUDP: d liu truyn c th khng
theo th t, hoc b mt mtUDP cung cp vic truyn khng tin cy mt nhm cc
byte (datagrams) gia client v server
Lp Application
-
Lp Application*Giao tip socket Client/server: UDPServer (chy trn
hostid)
Lp Application
-
Lp Application*V d: Java client (UDP)Output: gi gi (cn gi l TCP
gi dng byte)Input: nhn gi (cn gi l TCP nhn dng
byte)Clientprocessclient UDP socket
Lp Application
-
Lp Application*V d: Java client (UDP)import java.io.*; import
java.net.*; class UDPClient { public static void main(String
args[]) throws Exception { BufferedReader inFromUser = new
BufferedReader(new InputStreamReader(System.in)); DatagramSocket
clientSocket = new DatagramSocket(); InetAddress IPAddress =
InetAddress.getByName("hostname"); byte[] sendData = new
byte[1024]; byte[] receiveData = new byte[1024]; String sentence =
inFromUser.readLine(); sendData = sentence.getBytes(); toinput
streamtoclient socketdch hostname thnha ch IP dng DNS
Lp Application
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Lp Application*V d: Java client (UDP). DatagramPacket sendPacket
= new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
clientSocket.send(sendPacket); DatagramPacket receivePacket = new
DatagramPacket(receiveData, receiveData.length);
clientSocket.receive(receivePacket); String modifiedSentence = new
String(receivePacket.getData()); System.out.println("FROM SERVER:"
+ modifiedSentence); clientSocket.close(); } } to datagram vid liu
gi, di, a ch IP, port
gi datagramn serverc datagramt server
Lp Application
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Lp Application*V d: Java server (UDP)import java.io.*; import
java.net.*; class UDPServer { public static void main(String
args[]) throws Exception { DatagramSocket serverSocket = new
DatagramSocket(9876); byte[] receiveData = new byte[1024]; byte[]
sendData = new byte[1024]; while(true) { DatagramPacket
receivePacket = new DatagramPacket(receiveData,
receiveData.length); serverSocket.receive(receivePacket);
Todatagram socketti port 9876To khng gian nhn
datagramnhndatagram
Lp Application
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Lp Application*V d: Java server (UDP)
String sentence = new String(receivePacket.getData());
InetAddress IPAddress = receivePacket.getAddress(); int port =
receivePacket.getPort(); String capitalizedSentence =
sentence.toUpperCase();
sendData = capitalizedSentence.getBytes(); DatagramPacket
sendPacket = new DatagramPacket(sendData, sendData.length,
IPAddress, port); serverSocket.send(sendPacket); } } } ly a ch
IPport #, cangi givitdatagramvo socketkt thc vng lp while,quay li v
chdatagram khcto datagram gi ti client
Lp Application
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5.9 Xy dng mt Web serverLp Application*
-
Lp Application*Xy dng 1 Web server n ginqun l 1 yu cu HTTPchp
nhn yu cu phn tch c php headerly file c yu cu t h thng file ca
server to thng ip p ng HTTP:cc dng header + filegi p ng n clientsau
khi to server, bn c th yu cu file dng trnh duyt (v d: IE)xem gio
trnh bit thm chi tit
Lp Application
-
Lp Application*Chng 5: Tng ktCc kin trc ng
dngclient-serverP2Plaicc yu cu dch v: tin cy, bandwidth, trm hnh
dch v Internet transportconnection-oriented, tin cy: TCPkhng tin
cy, datagrams: UDPTng quan mt s vn v ng dng mng!cc giao thc c
bit:HTTPFTPSMTP, POP, IMAPDNSlp trnh socket
Lp Application
-
Lp Application*Chng 5: Tng kttrao i thng ip yu cu/tr li in
hnh:client yu cu thng tin hoc dch v serviceserver p ng vi d liu, m
trng thicc dng thng ip:headers: cc trng cho bit thng tin v d liu d
liu: thng tin truyn thngPhn quan trng: nghin cu v cc giao thciu
khin vi cc thng ip d liu in-band, out-of-bandtp trung v khng tp
trungkhng trng thi v c trng thitruyn thng ip tin cy v khng tin cys
phc tp ca cc vn lin quan n mng
Lp Application
*
