Tochcmangvadchvu vi ent hong 189 Chng 8: DCH VUI NTERNET 8.1Can ban I nt er net 8.1.1Gii t hieu I nt er net Trongnhngnamganay,I nternetl anguonthongti nngaycangquan trong trong nghi en cu, thng mai , gi ao duc vatrong moigi a nh. Songisdung truyxuatI nternetchocongvi ec,nghi encu,gi ai trakhongngngtang l en mot cach an tng en hang tri eu ngitren thegi i . Cung l uc oth sodch vu I nternetngaycangtangtheonhucaucuangi sdung.Ngi sdung I nternet cothedung I nternet nh mot hethong th tn i en ttoan cau, cong cunghi en cu hi eu qua, dch vugi aitr trc tuyen hay thng maii en t. Nguyen nhanchnhcuas bungnovengi sdungvadchvu I nternethi ennayl aI nternet aket hp c nhi eu mang may tnh khac nhau. Do oI nternet khong phai ci euhanhbi motcquanhaymottochcri engl enao.Cacmang thanhphancuaI nternetci euhanhbi nhi eutochcvanhi eucanhannhng vung khac nhau tren toan thegi i . Cohang ngan mang nh vay tren toan thegi ivachung ket noivinhau hnh thanh nen I nternet. I nternet l amot mang cuacacmangmaytnh.ThuatngI nternetconghal akhongcocquanchuquan ch thc cua I nternet, hay noimot cach khac khong cothevemot ban on gi an cua I nternet hoac tham ch khong thecoc mot danh sach chnh xac hang tri eu may tnh hay ngisdung cotrong I nternet.Motmangl i enmang(I nternetwork)l amothethongcacmangcucboLAN(Local AreaNetwork)noi vi nhaubangmotnghi thcl i enl acchungvacl i enketbi cacthi etbgoi l acacbonhtuyen(router)haycaccaul i en ket (bri dge). Ngisdung c ket noivimot mang LAN cua mang l i en mang cothetruyxuattai nguyencuabatcmangLANnaokhackhi ccapphep. Vanh vay, mang l i en mang aket hp c cac mang may tnh ri eng l ethanh motmangkhongl o.ui emvematnguyenl ycuamangl i enmangl as gi a tangayantngcuacacnguontai nguyenhudungoi vi ngi sdung. i eunaycungl atrnghpcuaI nternet,vnguontai nguyenkhongl ocuanococ tpham vitoan cau cua no. V dunh, I nternet a ra nhng ti eu chuan mchothtni enttoancaunhSMTP(Si mpl eMai l Transf erProtocol ) chang han. Nh vay, ngisdung I nternet cothechuyen th i en ten bat cautrenmangbangbatcphanmemngdungthi entnaokhi ho angsdung mot ti eu chuan I nternet mnh SMTP. I nternetl amotcongcu nghi encugi atr,changhangongnhng thong ti n cua vosocac chuekhac nhau. Cac trnh tm ki em ngay hoan thi en aD ch vu I n t er n et 190 vi ectruyxuatdedang,nhanhchongennhngthongti nnaytnhari enghay van phong. I nternet cung l amot nguon hotrkythuat vacac l ikhuyen quygi a. Hi en nay, rat nhi eu cong ty ang cung cap thong ti n ti ep th, cap nhat phan mem vahotrkythuat tren I nternet. I nternet atrthanh mot phng ti en dedang vahi euquaki nhtetrongvi echotr kythuatchocacacnhacungcapvakhach hang. Do I nternet cokhanang tng hp tren toan cau nen ngisdung chcan truy xuat I nternet qua truy xuat noihat bang mot ng day i en thoai .Co3cacheketnoi vi I nternetl a:f i rstcl ass,busi nesscl assvacoach cl ass. -Fi rstcl ass:ayl acachthccaocapenoi vi I nternet,phng thcnayrattonkem,chdanhchocactochc,doanhnghi epl n haycactochccuachnhphuKhi sdungphngthcnayth bancanmaso(account)cuamnhevaomangcucbo.Truyxuat theocachnaynhanhhnnhi eusovi cacki eunoi ketkhacvanochophepbansdungcacchngtrnhvatandungcacgi aodi en taidch vuban ang sdung. -Busi nesscl ass:Phngthcnaychophepmotmaytnhhaymot mang nhocac may tnh cotheket noiviI nternet via chI P cua ri engmnh.Dangketnoi naysdungphanmemgi aoti epcua ri engnovamotmodemtococaoeketnoi vi motmaytrung gi an qua ng day i en thoai . -Coach cl ass:Ban sesdung chng trnh gi ao ti ep cua may ban vamotmodemenoi vi maytnhdchvu,ketnoi ki eunaythmay tnh cua ban sekhong trthanh mot thanh vi en cua I nternet manochtruy xuat en may tnh ang noitrc ti ep en I nternet cua dch vu. 8.1.2Lch shnh t hanh vaphatt r ien I nt er net DuI nternetl amothethongtruyxuattoancauvaphobi ennhngnguon goc cua I nternet l aikhong nh vay. I nternet l asan pham cua cac cong nghec boquoc phong Hoa Ky(DoD: Department ofDef ense) phat tri en vao thap ky60 cua thekytrc. i eu quan trong nhat cua nhng cong nghenay l anghithc ket mangtococaocthi etkesaochomangvanhoatongtotngaycakhi conhi euphancuamangkhongsdunghaybhonghoc.BoquocphongHoaKymuon sdung cong nghenay egi cho hethong thong ti n phong thucua hovan hoatongtotngaycakhi ha tangcsbphahuy.Vaonam1969,Cucd an nghi encuti enti en(ARPA:AdvancedResearchProj ectsAgency)trongDoD thi etl apmangARPANETsdungcongnghenay.MangARPAnet(Advanced Research Proj ects Agency network) ra ivinhi eu u i em:-Mang van hoat ong khiconhi eu ket noibh hong. Tochcmangvadchvu vi ent hong 191 -Nhng may tnh khac l oainhau van cothel i en l ac c vinhau. -Mang phaicokhanang ti eu chnh hng truyen thong ti n. -ARPAnet l amot mang cua cac mang chkhong phaichn thuan l amot mang may tnh. NhngnutmangARPANETauti encxaydngvaonam1971tai 4 trng aihoc taiHoa Ky. Tc snay trong nhng nam cua thap ky70 thekytrc,ARPANETaphattri envanhi euvi ennghi encu,trngai hocaket noimang LAN cua hoen mang ARPANET. Ngay trong gi aioan nay, mot l oat cacnghi thcgoi l aTransmi ssi onControl Protocol /I nternetProtocol (TCP/I P) trthanh ti eu chuan cho thong ti n l i en mang. Cho en ngay nay, TCP/I P van con l anghithc ti eu chuan cho l i en l ac tren Internet. Noahnh thanh nen tang cua nhi eu ng dung chuyen gi ao thong ti n sol i eu van con c sdung tingay nay nh FTP (Fi l e Transf er Protocol ) vaGopher. Vao thap ky80 cua thekytrc, ARPANET c thay thebang mo tmang tococaocTochcKhoahocQuocgi aHoaKy(NSF:Uni tedStates Nati onal Sci enceFoundati on)hotr.Cungl uco,cacsi tecuaquanoi tachra khoi hethongcuaNSFNETmi ehnhthanhmangl i enmangri engcuamnh goil aMI LNET. Trong thap kynay vosocac cong ty vacac tochc ket noimang cua mnh viNSFNET. Gi aioan phat tri en cuoicung cua I nternet cho en ngay nay l astchoihotrI nternet cua NSF vao nam 1995. 8.1.3WWW TkhiNSFNET trthanh I nternet th vi ec hotrvai eu hanh coc tnhi eu tochc t nhan vacac nut mang ket noivino. Hau het cac may tnh hnh thanhnenmangARPANETvamangNSFNETeuhoatongtrennentang hei eu hanh UNI X. i eu ocongha l anhng ngisdung I nternet au ti en phaicohi eubi ettoi thi euvehei euhanhUNI Xecothetmki emthongti ntren I nternet. Tuy nhi en, i eu nay athay oitrong nhng nam gan ay kecung visphat tri en cua Worl d Wi de Web hay con c goil adch vuWWW hay Web. Web sdung mot cong nghexuat ban i en tgoil asi eu van ban (hypertext), ac bi etl aHypertextTransportProtocol (HTTP).Tho ngti ncxuatbantrenhethong si eu van ban c chi a thanh nhi eu tail i eu nhogoil aWeb hay trang Web. Moitrang Web nay cothecha cac ket noigoil ahyperl i nk en cac tail i eu khac. Hyperl i nkcothel amott,motcumthaymothnhanhcphanbi etbang ong khung hay gach chan. Khingisdung cl i ck chuot vao hyperl i nk th trang web nol i en ket sec hi en th. i eu nay cho phep ngisdung t chon con ngchomnhkhi octai l i eu,chuyenoi quacactai l i eukhacnhaucothenamtrenmaytnhnhi euni khacnhautrenthegi i .Nguontai nguyentren trangwebcothel avanban,amthanh,hnhanh,vi deohayhoathoa.Ngi sdungcothetruyxuatencacnguontai nguyennaybangmotcongcu goi l aD ch vu I n t er n et 192 trnhduyet(browser)hauheteucungcapcactrangwebcogi aodi enohoanen chcan trochuot en vacl i ck tren cac hyperl i nk hay nut an l enh. Vi ectruy xuat dedang val i nh ong cua trang web l amot moitrng l ytng cho xuat ban tren I nternet. Vanoaong gop to l n vao sbung nodan c I nternet trong cac l nh vc gi a nh, gi ao duc vathng mai . 8.2Kien t r uc I nt er net 8.2.1Backbone Mang truc (backbone) cua I nternet l amang l i en mang toan cau goil acac Net. Cac mang thuoc shu cua cac trng aihoc vacac chnh phungay cang nhi eucungcapdl i euvathi etbthongti nvangi sdungcuaho ctruy xuat mi en ph. Hocung hotrcac nghithc I nternet phobi en nh HTTP, FTP vaGopher.Moi Netvungcketnoi vi nhi euNetvungkhacbangcacng truyensol i eutococao.Nhngketnoi nhi eungnaycungcapnhtuyen ongchothongti nkhi mottrongcacNetb tacnghenhaykhonghoatong. Nhng mang khac cotheket noitrc ti ep vao backbone I nternet bang mot cong (gateway)trencacngtruyentococaogi acacNetvung.Tuynhi en,ki eu ketnoi nayratmacti envanamngoai khanangcuanhi eutochcvacanhan. Nhngngi sdungthongthngkhongcokhanangketnoi cnhvaycothetruy xuat I nternet bang cach thuebao vinhacung cap dch vuI nternet (I SP: I nternet Servi ce Provi der). Cac I SP l acac cong ty thi et l ap gateway cua mnh vibackboneI nternethayho cothecocactruyxuattheothoathuanvi gateway cua cac cong ty khac. Cac I SP cung cap cho ngisdung hay cac cong ty thuebao cua hotruy xuat I nternet vimot cc ph nhat nh. 8.2.2Nghi t hc I nt er net Mot khiac ket noiviI nternet, cac may tnh eu cothetng tac vitatcacacmaytnhkhactrenmangbangmohnhkhachchu(cl i ent/server). Trongmohnhnay,cactacvu xl ybaogomvi ecchaytrnhngdungtren I nternet c chi a ra cho may khach (cl i ent) vamot hay nhi eu may chu(server). aubenki acuatacvu xl ynhtmki emcsdl i euchanghancthc hi en bicac may chu. Cac may chucung shu cac nguon tainguyen nh thong ti n, dch vuecothechi a sevicac may tnh khac tren I nternet. Cac may khach xl ypha khach hang cua tac vuxl ymot ng dung cua I nternet nh gi ao ti ep vingisdung chang han. May khach sdung cac chng trnh khach etruy xuattai nguyentrencacmaychuInternetvatraooi thongti nvi cacmay khach khac tren I nternet.Tochcmangvadchvu vi ent hong 193 TatcacacmaytnhtrenI nterneteul i enl acvi nhaubangnghi thc TCP/I P c thi et keeket noicac hethong khac nhau. Loat nghithc TCP/I P cungcapnentangchonhi euti enchketnoi ti euchuannhFTPcothechuyen dl i eugi acachethongmaytnhhoantoankhacnhau.Nghi thci eukhi en truyen dan (TCP) l amot nghithc nh hng ket noi(connecti on ori ented) phan chi athongti ncanchuyenchatrongcacgoi nhogoi l aI Ppacket.Noanhsocac goiI P ecothec xac nhan vasap xep ung thtau thu. Nosegil ai cacgoi I Pbsai hongtrongquatrnhtruyen.Nghi thcI nternet(I P)l amot nghithc phiket noi(connecti onl ess) chu trach nhi em nh tuyen cac goiI P qua mang I nternet een c ch cua chung. a.Het hong t en vung vacac a chI P MoigoiI P eu comot phan au goi goil aheader bao gom a chI P cua nigivaninhan. V vay moimay tnh ket noiviI nternet eu phaicomot a chI P ri eng bi et. a chnay dung exac nh may tnh vamang noket noi . a chI P codang sonhphan 32 bi t c chi a l am 4 octer, moioctet co8 bi t. Moioctetl amotsonhphanri engbi etvi gi atrthapphant0en255.ethuan ti en, a chI P thng c vi et didang thap phan. V dunh: 194.125.109.32. Cungnhmoi dongtrenphanachcuamotl athxacnhthanhpho,ng phovasonhath moioctet trong a chI P aidi en cho mang hay may tnh c nhvti .Co5l oai achI Pkhacnhau:A,B,C,DvaE.Moi l oai dungcac phankhacnhaucuaphanachexacnhmaychuhaymangcannhv. Chang han, vil oaia chA th octet au ti en l asonhan dang mang. Nh vay 3 octet con l aidung exac nh a chcua may tnh trong mang.TrongI nternetngaynaynhngtenmaychul anhngchakhoadungexac nh ten cua cac may tnh cocac dch vumata muon khaithac.V du: home.vnn.vnMoi maytnhcungcganachIP-motachbangso.Changhan, may tnh coten gopher.msu.edu c gan so35.8.2.61 Taisao mot may tnh can haiten? V a chI P bang so, chung c hi eu vathao tac dedang biphan cng vaphan mem, nokhong hp visdung cua con ngi . Tuy nhi en,home.vnn.vn l aidenhhn nhi eu so via chI P. Nh thea chI P thch hp vimay tnh hn, vaa chvung thch hp vicon ngi . MucchchnhcuaI Pl acungcapkhanangketnoi cacmangconthanh l i enmangetruyendl i eu.Vai trocuaI Ptngt vai trocuagi aothctang mangtrongmohnhOSI ,tatcacachethongthanhvi encual i enmangoi hoiphaicaiat I P tang mang. Mot sov duvenhng ten chudang vung tng ng via chI P: D ch vu I n t er n et 194 Ten may chua chI P Msu.edu35.8.2.2 Spacel i nk.msf c.nasa.gov192.153.156.15 Theocachtren,achI Pbaogi cunggom4nhomso,cacconsonay c bi eu di en bang 4 phan gi atrthap phan c phan cach bicac dau cham. Moi phancuaachI Pl amotgi atrtrongkhoang0va255,nocbi euthbang mot byte tren bonhmay tnh. Nh thea chI P vemat vat l ycothechay t0.0.0.0 en 255.255.255.255 Trail aiten vung khong nhat thi et co4 phan. Cong vi ec cua hethong ten vung l achuyen ten thanh a chI P. Khiban oc mot a chI P ttraiqua phai , ban phaiitphan chung nhat en phan ri eng nhat cua ten. Ngc l ai , khiban oc mot ten chul oaivung, ban itphan ri eng bi et nhat en phan chung nhat. V du: a) www.pti thcm.edu.vn www: worl d wi de web pti thcm: ten cua mot tochc edu: ten domai n vn: ten nc b) 35.8.1.212 35: network address8.1.212: host address I P l amot gi ao thc ki eu khong l i en ket congha l akhong can cogi aioan l i enkettrckhi truyendl i eu.nv dl i eudungtrongI Pcgoi l adatagram, cokhuon dang chra nh sau: VERI HL Type ofServi ceTotall ength I denti f i cati onFl agsFragment of f set Ti me to l i veProtocol Header checksum Source address Desti nati on address Opti ons + paddi ng Data -VER (4 bi ts): chversi on hi en hanh cua I P c caiat. -I HL(4 bi ts): chodaiphan au cua datagram, tnh theo n vt(word=32 bi ts). odaitoithi eu l a5 t(20bytes). -Type ofservi ce (8 bi ts): ac tacac tham sovedch vu . Tochcmangvadchvu vi ent hong 195 -Total l ength(16bi ts):chodai toanbodatagram,kecaphan header (tnh theo n vbytes). -I denti f i cati on(16bi ts):cungvi cacthamsokhac(nhsource addressvadesti nati onaddress)dungenhdanhduynhatcho mot datagram trong khoang thigi an novan con tren l i en mang. -Fl ags (3bi ts): l i en quan en sphan oan (f ragment) cac datagram. -Fragmentof f set(13bi ts):chv trcuaoan(f ragment)trong datagram,tnhtheonv64bi ts,conghal amoi oan(troan cuoi cung)phai chamotvungdl i eucoodai l aboi socua64 bi ts. -Ti me to l i ve (8 bi ts): quinh thigi an ton tai(tnh bang gi ay) cua datagram trong l i en mang etranh tnh trang mot datagram bquan trenmang.Thi gi annaycchobi tramgi vacgi ami(thng quic l a1 n v) khidatagram iqua moirouter cua l i en mang. -Protocol(8bi ts):chgi aothctangtrenketi epsenhanvungdl i eu tram ch. -Headerchecksum(16bi ts):maki emsoatl oi 16bi tstheophng phap CRC, chcho vung header. -Source address (32 bi ts): a chcua tram nguon. -Desti nati on address (32 bi ts): a chtram ch. -Opti ons(odai thayoi ):khai baocacopti onstuychondongigiyeu cau. -Paddi ng(odai thayoi ):vungem,cdungebaoamcho phan header l uon ket thuc mot moc 32 bi ts. -Data (odaithay oi ): vung dl i eu, coodail aboisocua 8 bi ts, vatoia 65535 bytes. Tom l ai , moia chI P coodai32 bi ts c tach thanh 4 vung (moivung 1byte),cothecbi euthdi dangthapphan,batphan,thapl ucphanhoac nhphan. Cach phobi en nhat l adung thap phan codau cham etach cac vung. Muc ch cua I P l aenh danh duy nhat cho mot host bat kytren l i en mang. achI Pcgantheomotsocochunhchophepcacmangl n quanl ynhi eusol nachvacacmangnhoquanl ynhngphannhocua khoangtrongachI P.achI Pcchi athanhnhi eul oai .Cumsobentraicua a chI P xac nh l oai .Ngita chi a cac a chI P thanh 5 l p, k hi eu l aA, B, C, D, vaE. D ch vu I n t er n et 196 Lp A: 07 8 1516 232431 Neti dHosti d Lp B: Neti dHosti d Lp C: Neti dHosti d Lp D: Mul ti cast address Ma ng l oaiA gom nhng sot0 en 127, vemat l ythuyet mang l oaiA cotheco16.777.216 may chuMang l oaiB gom nhng sot128 en 191. Vemat l ythuyet l oainay cotheco65.536 may chu. Mangl oai Cgomnhngsot192en223vamoi mangcotheco256 may chu. Lp D dung egiI P datagram timot nhom cac host tren mot mang. Lp D edphong trong tng l ai . Mot a chcohosti d = 0 c dung ehng timang nh danh bivung neti d. Mot a chI P covung hosti d gom hoan toan so1 c dung ehng titat cacac host noivao mang neti d, vaneu vung neti d cung gom toan so1 th nohng en tat cacac host trong l i en mang. V du: 00001010000010100000101000001010 10 . 0.0.0 Lp A, neti d = 10

10000000000000110000001000000011 128.3 .2 . 3 Lp B, neti d = 128.3, hosti d =2.3 11000000000000000000000111111111 192.0 . 1 . 255 Lp C, neti d = 192.0.1, hosti d = 255 hng titat cacac host. Tochcmangvadchvu vi ent hong 197 Trongnhi eutrnghpmotmangcothechi athanhnhi eumangcon (subnet), l uc ocothea them cac vung subneti d enh danh cac mang con. Vung subneti d c l ay tvung hosti d. V du: Lp A: 078 151631 Neti dSubneti dHosti d Lp B: 23, 24 Neti dSubneti dHosti d Lp C: 26 27Neti dSubneti dHosti d b.Giao t hc ieu khien t r uyen TCP TCP l amot gi ao thc ki eu col i en ket(connecti on-ori ented), ngha l acan phaithi et l ap l i en ket (l ogi c) gi a mot cap thc theTCP trc khichung trao oidl i eu vinhau. n vdl i eu dung trong TCP l asegment, cokhuon dang: Source portDesti nati on port Sequence number Acknowl edgment number Data of f set Reserv-ed U R G A C K P S H R S T S Y N F IN Wi ndow ChecksumUrgent poi nter Opti onsPaddi ng TCP data Y ngha cac tham so: -Source port (16 bi ts): sohi eu cong cua tram nguon. -Desti nati on (16 bi ts): sohi eu cong cua tram ch. -Sequence number (32 bi ts): sohi eu cua byte au ti en cua segment trkhibi t SYN c thi et l ap. -Acknowl edgmentnumber(32bi ts):sohi eucuasegmentti eptheo matram nguon ang chenhan. -Dataof f set(4bi ts):sol ngt32bi tstrongTCPheaderchravtr bat au vung dl i eu. D ch vu I n t er n et 198 -Reserved (6 bi ts): dung trong tng l ai . -Controlbi ts: +URG: vung con trokhan (Urgent Poi nter) cohi eu l c. +ACK: vung bao nhan cohi eu l c. +PSH: chc nang PUSH. +RST: khi ong l ail i en ket (reset). +SYN: ong bohoacac sol i eu tuan t. +FI N: khong con dl i eu ttram nguon. -Wi ndow(16bi ts):capphatcredi teki emsoatl uongdl i eu.ay chnh l asol ng cac byte dl i eu, bat au tbyte c chra trong vung Ack number, matram nguon asan sang enhan. -Checksum(16bi ts):maki emsoatl oi theoCRCchotoanbosegment. -UrgentPoi nter(16bi ts):controtroti sohi eutuant cua byte itheosaudl i eukhan,chophepbennhanbi etcodai cuadl i eu khan. Vung nay chcohi eu l c khibi t URG c thi et l ap. -Opti ons (odaithayoi ): khaibao opti ons cua TCP. -Paddi ng (odaithay oi ): phan chen them vao header ebao am phanheaderl uonketthucmotmoc32bi ts.Phanthemnaygom toan so0. -TCP data (odaithay oi ): cha dl i eu cua tang tren, coodaitoiangamnhl a536bytes.Gi atrnaycothekhai baotrongphan opti ons. Trc khitruyen dl i eu gi a haitram can phaithi et l ap mot l i en ket TCP gi a chung vakhikhong con nhu cau truyen dl i eu th l i en ket osec gi aiphong. Cunggi ongnhnhnggi aothckhac,cacthcthetangtrensdung TCP thong qua cac ham dch vunguyen thuy (pri mi ti ve servi ce). Mot soham nguyen thuy: Requestpri mi ti ve:Unspeci f i edpassi veopen,Acti veopen,Send,Cl ose, Al l ocate, Response pri mi ti ves: Open I D, Status response, Termi nate, Del i ver, Error,.. c.Quat r nh chuyen dl i eu cua TCP/I P Quatrnh l i en quan en vi ec chuyen dl i eu tmay tnh cua ban en may tnh khac tren mang cuc bohoac mang I nternet khaphc tap. TCPvaI Pl anhnggi aothcri engbi etl amnhngvi ecri engbi et.Cong vi ec cua TCP l acung cap mot c cheti n cay cho may tnh echuyen vanhan dl i eu, dl i eu phaic gi ao nhan mot cach ti n cay, theo trnh t, ay uvakhong l ap l ai . Tochcmangvadchvu vi ent hong 199 I P l am cong vi ec l achuyen nhng oan dl i eu goil adatagram tren mang I nternet. Ta xet cach TCP hoat ong: Khimot may tnh muon oithoaivimay tnh khac tren mang I nternet, nomketnoi TCPvi maytnho.Ketnoi cungcapbi TCPgi ahai maytnh hoat ong cho phep dichuyen dl i eu dichuyen theo cahaihng cung mot l uc. TCP ki em tra vi ec l u thong emay tnh nhan khong btran ay dl i eu tmay tnh gichuyen en. TCPchophepchngtrnhcuahai maytnhtraooi thongti ntrenmot mang,haytrenmotnhomcacmang- mangI nternet.Moi thongbaochuyenicchi arathanhmothaynhi eudatagram.Moi datagramcothecanphaiqua nhi eu mang trc khien ch. Taisao dl i eu cua ban c phep dichuyen theo nhi eu ng dan een ch? V tnh hi eu quacono.Neu mot ng dan btac nghenvaconhi eungkhaceeno,dl i eusectruyentheong khac.Khi conhi eungdanthi etb danngchonmotngdantotda tren c stoc ol i en quan hoac theo cac ssap xep hanh chanh. d.TCP oi vi giao t hc dat agr am cua ngisdung Nhac l airang mot ket noiTCP tng tnh mot cuoc goii en thoai . ay l aket noiconh hng. Ngc l ai , I P l askhong ket noi . Nogitng datagram imot cach oc l ap khong l i en quan g en vi ec chuyen toan bothong ti n.Tren quan i em l am vi ec gi a haimay tnh, TCP cung cap sket noil i en tuc, I P gi up TCP thehi en sket noil i en tuc ao. Tngphan,gi aothcDatagramcuangi dungUDP(UserDatagram Protocol )l as khongketnoi .Comotchi phnhatnhethchi envabaotr mot ket noiTCP. UDPchophepnhngngdungnhthegi mi enphcacdl i euencac maychuxa.ThcchatUDPl acachchngtrnhngdunggi cacI P datagram.Luonl uonnhthevi I Pdatagram,khongcovi ecbaoamchuyen gi ao. Bivay mot chng trnh dung UDP phaisan sang chap nhan l uc thong bao khong en c val uc ophaixoay sthanh cong. Langisdung, noichung ban khong thenhan thay ng dung dung UDP hay TCP. Vi ec nay c quyet nh bingil ap trnh vanothng dehi eu viban. 8.2.3Chuyen mach I nt er net Cac goiI P ien a chnhan tren I nternet qua mot ki en truc mang goil achuyenmachgoi .Ki entrucchuyenmachgoi chophepcacmangcketnoiviI nternet cothetrao oicac goiI P ngay cakhichung khong c ket noitrc D ch vu I n t er n et 200 ti epvi nhau.Vi ecchuyenoi cacgoi I Pnaycthchi enquahethongcac may chuvacac bonh tuyen I nternet gi ong nh mot hethong bu chnh. Bat cthi et bnao cothegivanhan cac goidl i eu I P eu l ahost, chang han nh cac maytnhcl i enthayserver.Hostl acacmaygi vamaynhansdunghethong buchnh I nternet.Cacbonhtuyen(router)gi ongnhcactrungtambu chnhvungchuyenthtnchoti khi noencachcanchuyen.Cacbonhtuyencatgi acacmangketnoi vi I nternetvacacngthongti n I nternetsdung.Vay,cacgatewayI nternetcungl acacbonhtuyenI nternet. Nh vay thong ti n I nternet can thi et phaicoquatrnh xl ycac goiI P quagi ang gi a cac bonh tuyen. Khimot goiI P c mot host chuyen ith cac trnh ng dung cua mang hoan toan khong hi eu no. Noti ep tuc dichuyen cho en mot bonh tuyen oc c a chI P cua no. Bonh tuyen so sanh a chI P oc c vi bangnhtuyencuanochacactuyenencacachenmanochuyen c.Neubonhtuyennaykhongthetmramotachentrongtatcacac mang manoket noivith nochvi ec chuyen goiI P ang xl ycho mot bonh tuyen khac. 8.2.4Cac bonh t uyen t nh vaong Cacbonhtuyencothehoatongcheotnhhaycheothchng. Cac bonh tuyen tnh c thi et kegi aioan au cobang nh tuyen conh trkhi nocthayoi nhancongbi nhaquanl y.Macducacbonhtuyen nay khahi eu quavimang I nternet con nhonhng khiI nternet phat tri en nhanh chong th vi ec sdung cac bonh tuyen cap nhat nhan cong trnen khong thc te.Ngaynay,hauhetcacbonhtuyentrenI nterneteul acacbonhtuyen ong.Cacbonhtuyenongxacnhtuyentotnhatchocacgoi I Pdothng xuyen trao oithong ti n nh tuyen vicac bonh tuyen khac. V vay, neu mot bonhtuyennaookhongdungchaybtacnghenthcacbonhtuyen khactrenI nternetsecthongbaot ongvacothet ongcapnhatbang nh tuyen cua mnh. Cac goiI P cotheiqua nhi eu bonh tuyen tren I nternet, cchuyenti epnhi eul antrckhi encachencuano.Thcra,cac goi I Pkhacnhaucuacungmotthongi epcothectruyentrennhi eung truyen vat l ykhac nhau. 8.2.5Ten mien (domain name) MacduachI Pratdesdungoi vi cachostvacacbonhtuyen nhngnol ai khonhvaxal a oi vi ngi sdung.Vdu nhachwww.i nterswi f t.com l adenhvathan thi en vingisdung hn nhi eu so viachI Pcuanol a194.125.109.32.I nternetsdunghethongtenmi en(DNS: Domai n Name System) con goil aten mi en enh vcho cac a chI P. NgoaiTochcmangvadchvu vi ent hong 201 vi ec desdung vadenh, ten mi en con tang hi eu quado ngisdung t gay ra l oihn.Hethong ten mi en gi up cho ngisdung ti ep tuc dung ten mi en ngay cakhi achI Pcuamnhthayoi .Hethongtenmi enhoatongbangmotquatrnh goil aphan gi aiten mi en etng ng ten cua host vicac a chI P. Phan gi aiten mi en c thc hi en bang server ten mi en tren mang ket noiviI nternet eduytrcsdl i eunhngtenmi envacacachI Ptngngcuano. Server ten mi en tong dch ten mi en sang a chI P vangc l aitrong suot quatrnh l i en l ac viI nternet.VkchthcmangI nternetval ngthongti nnotruyentai qual nnen hethongtenmi enphai cchi athanhnhi eumi enkhacnhau.Cacmi enc sap xep theo dang phan cap hnh cay vamoiten mi en c phuc vu bimot c chechuyen dch ten mi en sang a chI P. Cao nhat cua phan cap nay l agoc ten mi en l aikhong coten g. Digoc l acac mi en cap cao nhat. Nhng ten mi en cap cao nhat nay chi a cac mang ket noiviI nternet thanh nhi eu l oainh net ng vicac mang hay cac I SP, edu ng vicac c sgi ao duc, Ten mota Loaitochc shu mang comD oanhnghi ep(Commerci al Busi ness)eduGi aod uc(Ed ucat i on al I n st i t ut i on s)govCh nhphu(Gover nment ) m i l Q uan oi (M i l i t ar y) orgTochc(Or gani zat i on)n et N hacungcapt ruyxuat mang Vi I nternet,tencuami encapcaonhatcti euchuanhoaecothenh vc dedang. Cohaidang ten cua mi en l aten mota(descri pti ve) vaten vtr(l ocati ve).Tenmotachobi etl oai tochcquanl ymaychucontenvtr cho bi et vtr cua may chuat quoc gi a nao. Bang sau l acac ten motathong dung. Cac ten mi en dang vtr thng co2 kytnh vn l aVi et Nam, se l aThui en, ca l aGi a Naai , j p l aNhat Ban, Tren thc teten mi en cap cao nhat khong phail uc nao cung chnh xac. Rat nhi eu cac nhacung cap truy xuat mang khong conet cho ten mi en cap cao nhat cua hovangc l ai , mot caiten mi en cap cao nhat edu cothec dung cacho mot tochc thng maihay tham ch quan s. Moi mi encaocapnhatl ai cchi athanhnhi eumi encaphai (second l eveldomai n). Nhng ten mi en cap haithng dung cho camot tochc hay mot congty.Vdu:tenmi eni nterswi f tai di enchoachcuacongtykhovan i nterswi f t tren I nternet vaten nay nam diten mi en cap cao nhat l acom. Mc D ch vu I n t er n et 202 ten mi en cap 3 hoac thap hn thng dung cho cac phong ban trong cong ty hay trong mot tochc. Chang han nh vicong ty I nterswi f t th cobophan taichnh, bophan kho van, Ten mi en c vi et vimc thap nhat ben trai , mc cao nhat benphai vamoi tenmi encachnhaubi daucham.Vdu,bophanchuyenvan cua cong ty I nterswi f t coten l adi spatch.i nterswi f t.com Cac thong i ep cua I nternet seil en vaixuong phan cap mi en cho en l ucti cchen.Gi asmotngi naoobophanchuyenvancua I nterswi f tmuongi mottho ngi epchomotkhachhangmotkhoatrongmot trng aihoc. Khiothong i ep sec chuyen tmi en chuyen van sang mi en i nterswi f tquami encomengoccuahethongphancap.Tai goccuahethong phancapnol ai cchuyenti epchomi enedu,chomi enai hoccanenvacuoicung l acho mi en khoa trong trng aihoc can en. 8.2.6URL Cac nguon tainguyen danh cho truy xuat oihoikhong chl avi ec nh vtenmi encanthi etmotcachngi annhvay.Khi ocanphai xacnhcach thcti epcannguontai nguyennayvaphai xacnhcu thecantruyxuattainguyen nao trong a chcan en. Mc chiti et hn c cung cap trong nh vtai nguyentho ngnhat(URL:Uni f ormResourceLocator).ol acacxaukytcung cap cac thong ti n can thi et exac nh tainguyen tren I nternet. Mot v duve URLtrangwebchu cuahangI nterswi f ttrenworl dwi dewebl a: http://www.i nterswi f t.com/i netpub/i nterswi f t.html .Phanauti encuaURLnh trong v ducua ta l ahttp:// xac nh phng phap truy xuat nguon tainguyen. Noxac nh nghithc c sdung nh http cho dch vuWWW, f tp cho dch vuFTP vagopherchodchvu Gopher.Phanthhai cuaURLxacnhvtrnguontainguyentrenI nternetvathngl acsdungl aachmi encuatai nguyen. Trongvdu URLtren,ol awww.i nterswi f t.com,vtrcuawebserverwww trongmi eni nterswi f tdi mi encom.Cuoi cungURLxacnhbanthantainguyen. Trong v ducua ta th ol atap ti n i nterswi f t.htmltrong th muc i netpub. 8.3Quan lyI nt er netvacac t ieu chuan 8.3.1I SOC KhiI nternet cang phat tri en th nhu cau xac nh ti eu chuan vaduy tr dch vu cang trnen khan thi et. Nhi eu tochc ac hnh thanh eganh vac trach nhi em nay. Khong cotochc nao trong sooshu I nternet cavahau het cac tochc duy tr cac ti eu chuan nay eu l acac tochc phil inhuan. Nhng ngisdungI nternetcotochctruyxuatI nternetquatrungtamthongti nl i enmang (I nterNI C:I nterNetworkI nf ormati onCenter).I nterNI CcungcapcacdchvuTochcmangvadchvu vi ent hong 203 thong ti n l i en mang nh dch vudanh ba(di rectory servi ce) chang han cho cong ong I nternet. I nterNI C cung chu trach nhi em vevi ec ang kyten mi en m ivaxac nh cac a chI P.I nterNI C sap xep cac ten mi en cap cao nhat nh com, edu, org, net, vabaoamrangcactenmi encaphai noangkyl aduynhat.Hauhetcacquyet nh veti eu chuan vadch vuI nternet eu c i eu hanh biHi ep hoiI nternet (I SOC: I nternet SOCi ety). ay l amot tochc phil inhuan thc hi en duy tr vaphat tri en I nternet. I SOC c i eu hanh bimot hoiong gom cac uy vi en c tuyen chon tcac thanh vi en cua hi ep hoi . Bat ccanhan hay tochc nao cung cothetrthanhthanhvi enchnhthccuaI SOC.Cacthanhvi enhi entai cua I SOCbaogomcacnhacungcapdchvu I nternet,cactrngai hoc,cacnhacungcapsanpham,caccquancuachnhphu,I SOCtruyenattonch,muc chcuamnhquacaccuochoi nghthngni envavosocacanpham.I SOC cung hp tac hanh ong vinhi eu nhom ang i eu hanh vaxac nh ti eu chuan cho I nternet khac. 8.3.2Cac t ochc khac Mot trong nhng nhom hp tac viI SOC l aNhom Quy hoach vaKythuat I nternet(I EPG:I nternetEngi neeri ngandPl anni ngGroup).NhomI EPGchu trachnhi emvevi ecxucti enhptackythuatcuahoatonghangngaytren I nternet.Cacthanhvi encuanhomI EPGcl aytcacnhacungcapdchvubackbone I nternet. NhomdandatkythuatI nternet(I ESG:I nternetEngi neeri ngSteeri ng Group) l amot bophan cua I SOC etong hp cac ti eu chuan danh cho I nternet. Nhng ti eu chuan I nternet nay c cac n vHoiong Ki en truc I nternet (I AB: I nternetArchi techtureBoard)banhanh.I ABcI SOCthanhl apecungcap mottongketchungves phattri enkythuatcuaI nternetvaephanxetcac tranhcai .Mottrongnhi euchcnangkhaccuaI ABl axuatbancacBaocao I nternethangthang(I MR:I nternetMonthl yReport)etongkethi entrangcua I nternet.I MRbaogomcactai li eumotacacthachthcvematkythuatmaI nternet phaing au vacac bao cao cua cac uyban kythuat khac nhau vecac thach thc o. Cac uyban kythuat l ail acac ti eu ban cua I AB chu trach nhi em vephat tri en kythuat nhi eu l nh vc khac nhau.Mot trong cac uyban nh vay l aTi eu ban Xuc ti en Nhi em vuNghi en cu I nternet (I RTF: I nternet Research Task Force) l i en quan en l nh vc phat tri en l audai cuaI nternet.ChanghannhI RTFchutrachnhi emgi ai quyets thi eu hi eu quacua cac a chI P trong vi ec ap ng cac nhu cau phat tri en I nternet.UybancapphepachI nternet(I ANA:I nternetAssi gnedNumbers Authori ty)cungl amvi ecdi quyeni euhanhcuaI AB.I ANAgi amsatvi ec cap phat a chI nternet, a chport vacac l oaiti eu chuan sokhac cua I nternet. D ch vu I n t er n et 204 Trong khioI ETF l aitap trung vao cac thach thc kythuat hi en thimaI nternet phaioimat. I ETFthanhl apcacnhoml amvi ecexacnhrocacthachthcnayvamoinhom sequan tam timot chueri eng. Chang han nh secocac nhom phutrach cac l nh vc an toan mang, nh tuyen mang vaquan l ymang, I ETF xuat ban cac tail i eu chnh thc cua mnh qua cac I nternet Draf t truyen batren mang I nternet. Cacti euchuanthcs cuaI nternetcxuatbanl acacRFC(Request For Comment) ac I AB vaI ESG phechuan. 8.4Sphatt r ien t r ong t ng lai cua I nt er net Khi cautrucachI PcuaI nternetcphattri envaonhngnamau cuathapky80thekytrcnonhamennhucautrcmatvatrongtngl aicua ngisdung. 32 bi t a chtrong phi en ban hi en hanh cua I P (I pv4) cothenh vc tren 4 tya chcua ti16,7 tri eu mang may tnh. Sphat tri en ang ki nh ngac cua I nternet trong may nam gan ay anhanh chong l am can ki et caihoa chI P c I pv4 cung cap. Nh ng ngiphat tri en ban au cua TCP/I P akhong l ng trc c quy movatoc ophat tri en I nternet trong may nam gan ay. Con socac mang may tnh ket noiviI nternet tang l en theo tng nam vanhngcongcu quanl ymangdatrenNghi thcQuanl yMangngi an (SNMP:Si mpl eNetworkManagementProtocol )yeucautatcacachub,card gi ao ti ep, server vacac bonh tuyen eu phaic gan bang cac a chI P. Sphat tri en trong tng l aicu a thtrng gi aitr dan dung e doa en baitoan nay. Truyen hnh cap, mua sam tainhavacac dch vuthong ti n ang gi aioan phat tri en dan en tnh hnh moiTV vathi et bI nternet eu phaicomot a chI P. eoi phovithach thc nay nam 1992 I ETF aa ra l ikeu goil ap kehoachchomotphi enbanmi cuaI Pgoi l aI Pthehemi (I Png:I PNext Generati on). I Png hay con goil aI Pv6 ang c nh ngha l aexuat cuoicung trong rat nhi eu cac exuat ap ng l ikeu goinay. Mot trong nhng muc ti eu thi et kecuaI Pv6l aduytrtnhtnghpvi cacnghi thccapcaonhHTTPvaFTP. i eunaysel amchoquatrnhchuyenoi sangI Pv6sel amots ti entri enchkhong phail amot cuoc cach mang. Vanocung congha l anhng ngisdung cotheti ep tuc dung bat cng dung nao ang dung cung viI Pv4. u i em noibat nhat cua I Pv6 so viI Pv4 l amrong khong gi an nh va ch. I Png sdung trng a chdai128 bi t vimuc ch ap ng sothi et bc nh vnhi eu hn rat nhi eu. Trong thc tesoa chmaI Png cothenh vc nhi eu hn gap 4 tyl anconso4tyachcnhvbi I Pv4.Khonggi anachnaycsdung cho 3 l oaia ch: Tochcmangvadchvu vi ent hong 205 -uni cast, -anycast, -mul ti cast. Cac a chuni cast nham en vi ec xac nh mot gi ao ti ep cuthecho tng thi et b. Do ochcomot thi et bc gan cho moia chuni cast cuthe. Trong khi othanycastvamul ti castl ai nhamenvi ecnhvachchocacnhom gi aodi en.Motgoi I Pgi chomotachanycastchcphanphatti thanh vi encuanhommabonhtuyenphanxetcanchuyenentrongkhi motgoi I P gi ti motachmul ti castsecphanphatchotatcacacthanhvi entrong nhom. V I Png c thi et keetoithi eu hoatac ong cua nol en cac nghithc vacongnghekhacnentacongcuanol encacbonhtuyenseratnho.ephuhpvi cacachI Pv6dai hncacnghi thcnhtuyenhi enthi ci eu chnh hn l athay mi . I Pv6 em l ainhi eu khanang minhcau truc l aiheader cuagoi I P.Changhan,trngnhtuyen(routi ngheader)chophepmotnguon xac nh tuyen itich quan trong hn cac tuyen khac do nghithc nh tuyen xac nh. I Pv6 cung cothem mot trng anh dau (authenti cati on header) ebao am rang: -Cac may thu nhan dl i eu tng thch vidl i eu ac may phat gii , -May gixac nh trong a chnguon l axac thc. Trngencapsul ati oncungcaptnhbaomatgi ongnhtrnganhdau nhngcungcungcapthems ti ncaygi amaygi vamaynhan.i eunayat cbangvi ecmatmahoadl i eucotronggoi I P.Vi ecthemvaotrngnhan l ul ng(f l owl abel )vatrnguti envaoheadercuaI Pv6aapngc cac nhu cau ng dung tren cac dl i eu thigi an thc (real -ti me data). Nhng tnh nang nay gi up caithi en chat l ng cua cac dch vuI nternet nh cac ng dung a phng ti en, mul ti cast vavi deo. I Pv6cungeml ai nhi eucai thi enangkevechcnangcanthi etcho mangdi ongangcI Pv4hotr.Vdu nhngi sdungdi ongcothenhan tn hi eu theo doitmot server hay mot bonh tuyen cuc bovathong bao chonhabi etcvtrhi enthi cuaho.Nhvay,e- mai l haybatcdl i eu nao en a chnhaeu cothec chuyen ti ep en vtr hi en thicua ho. 8.5FTP vaGopher Lydo chnh engita bat au ket noiviI nternet l achi a secac tap ti n vatruy xuat thong ti n. Cohaidch vuc phat tri en ehotrcac chc nang nay l aNghithc chuyen tap ti n (FTP: Fi l e Transf er Protocol ) vaGopher.FTP c thi et keecho phep ngisdung cotheket noivimot maytnhtrenI nternetvatai l en(upl oad)haytai xuong(downl oad)cactapti n. Gopher c thi et kenh mot dch vuphan phoithong ti n val amot phng phap D ch vu I n t er n et 206 tngoi thanthi enhnetruyxuatthongti nthongquahangl oatthcn (menu). 8.5.1FTP FTPl amottrongnhngdchvu rai auti encuaI nternet.FTPc phat tri en echo phep truy xuat, sao chep hay dichuyen cac tap ti n dl i eu tninay tinikhac.FTP ac bi et rat ac l c cho vi ec chuyen van cac tap ti n dl i eu gi acachethongmaytnhkhacnhaunhgi amotmaytnhUNI Xvamothethong MS-DOS chang han. Mac duWWW athay thekhanhi eu cac chc nang cua FTP nhng FTP van l aphng phap phobi en nhat esao chep cac tap ti n tmay server en mot may tnh cl i ent qua I nternet. FTP caiat rat n gi an vadechay.oil uc ngita xem FTP l amot nghithc nhng oil uc ngita l aicho rangFTPl amotchngtrnh.ThcraFTPcungl amotnghi thc,cungl amot chng trnh. FTP l amot nghithc hay mot ti eu chuan cho vi ec chuyen gi ao cac tapti ngi acacmaytnhvael amci eunaytacanphai comotchng trnh FTP.Motcl i entFTPl i enl acvi motserverFTPtrenmotmayhost.Maytnh hostcungcapcactai nguyeneupl oadhaydownl oadf i l e.Ngi sdung I nternetcochngtrnhcl i entFTPcotheketnoi vi serverethchi entruy xuat. Ngoai vi ectruyxuatquamottai khoan(account)sdungcu the,cothetruyxuatFTPquaangnhapmi enph.ayl adchvu FTPacbi etchophep truy xuat thong ti n makhong can phaicotaikhoan tren may host. Nhai eu hanh server FTP sequyet nh nhng tap ti n vathong ti n nao l acho phep truy xuat tmaycuaho vanhngai cothetruyxuatcchung.Gi aoti epsdungeket noi vi serverFTPphu thuocvaophanmemtrenmaytnhtruyxuat(chng trnh cl i ent). CacchngtrnhFTPauti encogi aoti epdatrennentangkyt.Nh vay, ngisdung govao cac l enh DOS hay UNI X eket noi(l og on) vimay tnh pha ben ki a val uc tm th muc, chuyen tap ti n roigi aitoa(l og of f ). Visra icua hypertext vaWorl d Wi de Web aphat tri en gi ao di en ohoa l amchoFTPtrnendesdunghnbaogi het.Batcdangtapti nnao cungcothedungcvi FTPchodul atapti ntai l i eu,tapti naphngti en haytapti ncuatrnhngdung.FTPchopheptruyentatcacacl oai tapti nnay didang kyt ASCI Ihay nhphan. Khita truyen cac tap ti n van ban gi a cac hethongkhacnhaunhDOSvaUNI Xchanghanthcactapti nnayphai c chuyen oisang dang ASCI Itrc a. Tochcmangvadchvu vi ent hong 207 Cacdangtapti nkhongphai l avanbanthcchuyenthanhdangnhphan.FTPsdungTCPl anghi thcchuyenvanchotatcacacthongti nvachuyen oidl i eu gi a server vacl i ent. Trong FTP cohaiphng phap: -Thi et l ap taikhoan pha server, -Sdung FTP nac danh. Neutacomottai khoanphamayserverthtaphai l ogonvaomang cua server. u i em cua truy xuat qua taikhoan l ata cothetruy xuat c nhi eu thong ti n hn l aoivicac ngisdung nac danh. Mot taikhoan mi en ph cung cho phep ket noivimay server vadownl oad cac tap ti n. Ngisdung chcan l ogonvaohethongvi usernamel a anonymous .Dungtai khoanmi enph ngisdung phainhap vao password l aa che-mai lcua mnh. Dnhi en cac server FTP conhi eu han checac taikhoan mi en ph truy xuat mot sotap ti n dl i eu nao o. Khokhanchuyeucuacahai l oai FTPketrenl athongti nvenguondl i eu.Coenhangngancacsi teFTPtrenI nternetvangi sdungphai bi et csi tenaochanhngthongti ncanthi et.Saukhi atmcsi tecanthi et th van el aphaitm cho ra th muc nao cocha thong ti n can truy xuat. Nhi eu si te FTP khong codanh muc cac tap ti n dl i eu theo bat cmot thtnao.ekhac phuc cac khokhan khitruy xuat thong ti n qua FTP, ngita phat tri enArchi e.Archi el amotchngtrnhtruyxuatthongti nketnoi nhkyvimoisi te FTP tren toan mang I nternet. Nodownl oad tat cacac danh muc cac tap ti n cac si te nay vacap nhat vao mot c sdl i eu cothetm ki em tmay cua ngisdung bang chng trnh Archi e cl i ent. 8.5.2Gopher Gopher l amot dch vuda tren menu gi up ngisdung tm ki em tap ti n, chng trnh vacac tainguyen khac tren I nternet. Cung gi ong nh FTP, Gopher l amot dch vuI nternet l au i . Mac dungisdung cotheket noivihethong menucuaGopherbangTel net,phanl nchcothel i enl accti cacserver Gopher qua chng trnh Gopher cl i ent.u i em chnh cua dch vuGopher so vidch vuFTP vaArchi e l akhitm ki emmottapti ndl i eungi sdungkhongcanphai bi ettencuatapti no. Gopherhotr tmki embangtkhoa(keyword)vachophepngi sdungl uc tm qua cac menu vadanh muc cac tap ti n cho tikhitm thay tap ti n can thi et. Sauongi sdungcothedownl oadtapti nki emcbangtai khoanFTP mi en ph. MacduGophercungtngt nhFTPnhngnol ai phctaphnnhi eu. Ngi sdungkhongnhngchcotheduyetquadanhmuccactapti nvath D ch vu I n t er n et 208 muc macon cothel i en ket vicac server Gopher khac vadch vuI nternet gi ong nh Tel net vaWWW. S l i enketcacserverGophergoi l akhonggi anGopher(Gopherspace). Khimot si te Gopher mic thi et l ap th cac nhai eu hanh cua si te nay sel i en ketvi nhai euhanhphanmemGopherl atrngai hocMi nnesota (Uni versi ty ofMi nnesota). Si te Gopher misec cap nhat vao danh sach cac server Gopher. Veroni ca l amot c sdl i eu cha thong ti n vecac si te Gopher. Nocungcapmotki eudchvu oi vi GophercungnhArchi ecungcapcho FTP. C sdl i eu cua Veroni ca c bi en dch bang vi ec quet tat cacac server Gopher tren toan thegi ival i et ketat cacac danh muc cua chung. etm ki em thong ti n qua Veroni ca ngisdung phail og on vao mot server Veroni ca. Sau oVeroni ca setm ki em trong khong gi an Gopher vabi en dch cac menu Gopher cha thong ti n can tm ki em. 8.6Mohnh giao t iep client /ser ver 8.6.1Ser verva cl i ent Hai khai ni emquantrongehi eurocautruccuaI nternetl aservervacl i ent. Ser verl amot may tnh dung ethc hi en mot socong vi ec cho mot may tnh khac.Cl i entl amotmaytnhyeucauserverthchi encongvi ecchomnh. ay l anh ngha rong, ngoaira con mot nh ngha thch hp hn da vao mi enl amvi eccuaservervacl i ent.i euquantrongchungtaphai ghi nhvemoiquan hegi a server vacl i ent l acl i ent khong can bi et cach server thc hi en cong vi ec omanochquan tam en ket quacong vi ec manoyeu cau. Cac server cothethc hi en cac cong vi ec n gi an cung nh phc tap. V du mot cl i ent yeu cau server nhan mot tap ti n ac bi et. Neu tap ti n onam tren may tnh cua cua server th nochcan l ay tap ti n ora ta vaginoen cl i ent. Tuy nhi en neu tap ti n okhong nam tren may tnh cua server th nosebi et cach tm tap ti n ovachuyen noen cl i ent. Neu server khong thel am vi ec nay th server phaibi et cach tral il ataisao khong l am c. Nhngtngtacnhvaycol ehi roi ramnhngnogi upchovi ectruy xuat thong ti n tren I nternet trnen dedang hn . Neu ban muon comot cau tral icho mot cau hoinao o, ban khong can bi et cau tral iay nam tren may tnh cuabanhayl atrenmaytnhxavabancungkhongcanhoccachtmno. Serverbannoi ketti cangthongmi nhvamanh(hayl aservermaservercua bansenoi ketti cangthongmi nhvamanh)thnocangnhanhchongchoban cautral i .Bi vcohangnganhethongthongmi nhtrenI nternetnenvi ectm cau tral itrnen rat dedang. V du : ti me-of -day server chn gi an travegi hi en hanh bat ckhi nao cl i entgi ti servernaymotthongti n.MotwebservernhannhngyeucautTochcmangvadchvu vi ent hong 209 mot trnh duyet web browser el ay mot ban sao cua trang web, server l ay c ban sao cua tap ti n cho trang nay vatranovecua trnh duyet web. V duvemohnh cl i ent/server: Ti meserverthi etl aponghoti meof daycuamaytnh.onghothikhac trong ngay l athi et bphan cng eduy tr thikhac vangay hi en hanh, cho phepchngtrnhsdungno.Motkhi cthi etl ap,onghothi khactrong ngay bao am thigi an chnh xac. Cach thehi en ngay gi : hei eu hanh duy tr ngay vagi trong ngay bang cach em sogi ay ketmot thii em khiau. V du : hei eu hanh Uni x l ay gi ay th0 cua ngay 1/1/1970 l am thii em khiau, viTCP/I P thii em nay l agi ay th0 cua ngay 1/1/1990. 8.6.2Tnh phc t ap cua ser ver Cac v dutren ta chxet server mc n gi an v chung tuan theo mot tht nhatnh,baygi chungtagi anhranghei euhanhsesaphangcacyeu caugi enchomotserverkhi servernayangban,vahangi naysekhong trnen qua daiv khanang l am vi ec cua server l anhat nh. Mot server cotnh phc tap hn nhi eu so vicl i ent v chung cokhanang chap nhan nhi eu yeu cau cung mot l uc. Vdu :xetserverchuyentapti nconhi emvu saocheptapti nenmay khac theo yeu cau chi em mot thigi an xl yr at l au. Thongthngmotservercohai phan:chngtrnhchucotrachnhi em nhancacyeucaumi ,mottaphpcacchngtrnhphu cotrachnhi emxl ytng yeu cau. Server chuyeu thc hi en 5 bc sau ay: -Mcong, -icl i ent, -Chon cong, -Khiong chng trnh phu, -Ti ep tuc (quay trvebc i ). 8.6.3u iem cua mohnh client /ser ver Mohnh thc hi en phan chi a hi eu quagi a cac may tnh cl i ent vaserver. May cl i ent quan l yvan ehi en ththong ti n. May server nhokhong can phaiquan l ysqua taitha thaitren mot sol n ngitham nhap. Nhcocachchuanhoathongti n,cacnhaphattri encothethnghi em nhi eu cach caiat khac nhau. Cac nhacungcap(provi der)thongti ncotnhl i nhongratl n.Mohnh cl i ent / server l amot phan quan trong trong khuynh hng phat tri en cong nghi ep D ch vu I n t er n et 210 tcachethongongsangm,vmotthongti ncothexembangmotngonngkhac, mot c sdl i eu khac, van tng oidedang chuyen hay tham ch cail aihotrcua server. 8.7I nt er nete-mail Thtni entatrthanhphanphobi ennhattrenmangI nternet.Mot phng phap trc ti ep enhan thong ti n l ahoinhng ngiban bi et thong ti n ecoccautral i .Khi ngi ochapnhanthsetral i trcti ep.i eunaycothethchi entrenI nternetvagoi l athtni ent(e-mai l ).Mottrongnhng thuan l icua e-mai ll avi ec tral irat dedang ngay cakhikhong bi et ngigi , hayngi ngi gi bi etngi nhanl aai .Cacchngtrnhe-mai l eucochc nangtral i khongcangol ai achvatatnhi enl ahoantoanmi e nph.Vdu: gith cho tac gi anh sau:To:dqanh@pti thcm.edu.vn Subj ect:Bat cvan eg Message:Bat cthong ti n g Mot a che-mai lc tao thanh tten do ngisdung at, dau @ vamottenmi en(domai nname)cuamaytnhmangi sdungangky.Chang han, tac gi aat ten cho hop th e-mai lcua mnh l adqanh, a chcua may tnh chul apti thcm.edu.vn th a che-mai lcua tac gi al adqanh@pti thcm.edu.vn. 8.7.1Khaini em Trong l ch sl i en l ac th i en t(e-mai l ) c xem l ahoang tng, nhng chsau mot thigi an ngan nhng hethong th i en ta dang acung phat tri en trennhi euthi etbtnhtoankhacnhau.ARPANETl ahethongcphatmi nh sm nhat khihaingikhaithac bat au ginhng thong bao en vinhau tren mang l imithi et l ap. Tothi enttrthanhmotkhai ni emquenthuoc.Thi entc cungcaptrennhngmangcucbokhacnhauecacthanhvi encuanhoml am vi ec l i en l ac vinhau, vanocung em l ainhi eu ti en ch thong ti n aichung nh Compuserve. ac bi et l atoan bonhng thi et bnay cung cothecung cap nhi eu cong (gateway) etrao oith tren mang I nternet. Mac duconhi eu net ac trng vahnh dang ri eng bi et, nhng hau het cac hethong th i en tconhng u i em gi ong nhau: -Ban cothegith i en tvao l uc thuan ti en, gi ong nh gith bu i en, quatrnh nay chxay ra trong vaiphut hoac vaigi sau o. -Ngi nhancotheocrorangthongbaocuabankhi ranhroi .Cothegi nhngghi chucuangi gi hoacnhnghnhanhcol i en quan. Tochcmangvadchvu vi ent hong 211 -Thi entcothegi enmothoacnhi eungi hoacennhom ngi thchhpkhac.Phanmemthi entcungcapchobankythuateambaodanhsachtenvaachcanhangi upbanginhngghi chuennhomngi nhankhacnhaubangnhngten hi eu n gi an. -Ngi nhancothel ugi nhngthongbaotbanbe,banong nghi ep. Ngidung th i en tcothegap mot sotrngaisau: -Thcothemati dosai sotl ucanhachhoactrenphancng, phan mem khiithong bao iqua nhng mang khac nhau. -Th cothec chuyen nham hoac nhan sai . -Thi entdedangbhi eul amdothi eunhngyeutonh:gi ong noivanet mat, ol anhng yeu tomata phaitha nhan trong l i en l ac oimat. Cho en nay th i en tvan ang can dang van ban, ban giivanhan nhng tchkhong phail ahnh anh, am thanh hay ban tnh. egihoac theo doith ang en, ban sdung vail oaichng trnh ng dung th i en ttren may vitnh cua ban, nhng chng trnh nay c xem nh l anhng nhanvi ensdung (useragents).Chungnhnhngngi l achon thvasauogi quanhi euuseragentstruyenkhaptrenmangI nterneten nginhan. Ban vanhng nginhan th khong can sdung cung mot phan mem th i en tvacothesdung nhng cong cukhac nhau. 8.7.2anh a chI nt er net egimot thong bao th i en tqua I nternet,ban can phainhan rongisegith en vanien phaic xac nh tren I nternet. Hnh thc l ap a chn gi an nhat nh sau: User@host User l amot ten nhap adung binginhan cua ban Host thng l aten hethong ac phan (Domai n Name System) quen thuoc. V du: Wi ggi n@msu.edu trenl avdu tenachthi entngi anmabangap,vatenmay chucokhidaihn (v du: l bm.cl .msu.edu) Trong trng hp phc tap ban can ghironi truy xuat phc tap hn thay vtenmaychungi annhtren,vanhi euhethongqui nhtenuserkhonhhn na (v du: Smi th 964 hoac 12345 ABC). Chuyrang ten ngidung l aquan trong, thong thng ban can ghia chung vachnh xac neu khong bc th cua ban seil ac. D ch vu I n t er n et 212 8.7.3Soan t hao t h i en t Moithong bao th i en ttren I nternet eu cha ng muc etrc nhng g nothong bao, bao gom nhng thong ti n chnh xac nh thong bao tnginao, gien cho ai , ngay gi vi et th vachue. V du: Date: Sat, 25 Sep 2002 19: 37: 51 GMT From: Al astai r Smythe Subj ect: My next masterpi ece To: Ri ch Wi ggi ns Nhngchngtrnhthi entkhacnhauthsdungdangkhacnhau trong nhng a ch Fromva to . Cotheconhi eu hn mot nginhan trong emuc To , dau phaydung ephan cach nhng a chtrong trng hp nay. Date :ccungcapbi chngtrnhthi ent,nol angayvathigi an mabc thong i ep c soan thao. Subj ect : cha tom tat ngan gon cua thong bao mangigisecung cap.Nhng subj ect ayusegi upngi occhonl avi nhngthongbao phc tap. V du: Mot Subj ect : ayl abanphatthaochobaocaomucti eu seayuhn l a: Ban phat thaoMot vaiemuc khac ban cothegap trong phan th i en tcua ban: Cc:ghi rotencuanhngngi nhanthemvao,ol angi nhannhng ban sao (carbon copy). Bcc:(bl i ndcarboncopy)gi chonhngngi naybansaonhngachvaten cua hokhong hi en tren nhng ban sao khac. Message-I d:vungnaycchophepbi bonhandangduynhattrong thong bao, cung cap binhan vi en gii . Repl y-To: muc nay ghia chth i en testral icho ban thong bao nay c gien. Sender: ngigimot bc th thong bao cothekhac vimuc Fromkhimot chng trnh gith bisthay themot nginao khac. 8.7.4Pham vi t r ong bc t h t r ali Nhi euchngtrnhthi entcungcapmotbi euobaogomnhngl inhanxetcuangi gi trongbcthtral i cuaban,nogi i hanmotphamvi . Thong thng noc gi ihan bidau V du: >ban nghg? Tochcmangvadchvu vi ent hong 213