Ukusethwa Kokuxhumeka kwe-TCP
Uma siphequlula iwebhu, sithumela i-imeyili, noma sidlala umdlalo oku-inthanethi, sivame ukungacabangi ngokuxhumeka kwenethiwekhi okuyinkimbinkimbi ngemuva kwayo. Kodwa-ke, yilezi zinyathelo ezibonakala zincane eziqinisekisa ukuxhumana okuzinzile phakathi kwethu neseva. Esinye sezinyathelo ezibaluleke kakhulu ukusethwa kokuxhumeka kwe-TCP, futhi umongo walokhu ukuxhawulana ngezindlela ezintathu.
Lesi sihloko sizoxoxa ngesimiso, inqubo kanye nokubaluleka kokuxhawulana ngezindlela ezintathu ngokuningiliziwe. Isinyathelo ngesinyathelo, sizochaza ukuthi kungani kudingeka ukuxhawulana ngezindlela ezintathu, ukuthi kuqinisekisa kanjani ukuzinza kokuxhumana kanye nokuthembeka, nokuthi kubaluleke kangakanani ekudlulisweni kwedatha. Ngokuqonda okujulile ngokuxhawulana ngezindlela ezintathu, sizothola ukuqonda okungcono kwezindlela eziyisisekelo zokuxhumana kwenethiwekhi kanye nombono ocacile wokuthembeka kokuxhumeka kwe-TCP.
Inqubo Yokuxhawulana Ngendlela Ezintathu ye-TCP kanye Nokuguqulwa Kwesimo
I-TCP iyiphrothokholi yezokuthutha egxile ekuxhumaneni, edinga ukusungulwa koxhumano ngaphambi kokudluliswa kwedatha. Le nqubo yokusungulwa koxhumano yenziwa ngokuxhawulana ngezindlela ezintathu.
Ake sibheke ngokucophelela amaphakethe e-TCP athunyelwa kuxhumo ngalunye.
Ekuqaleni, kokubili iklayenti kanye neseva KUVALIWE. Okokuqala, iseva ilalela ngenkuthalo echwebeni futhi isesimweni SOKULALELA, okusho ukuthi iseva kumele iqalwe. Okulandelayo, iklayenti isilungele ukuqala ukufinyelela ikhasi lewebhu. Kudingeka isungule uxhumano neseva. Ifomethi yephakethe lokuqala lokuxhuma ilandelayo:
Uma iklayenti liqala uxhumano, lidala inombolo yokulandelana kokuqala okungahleliwe (iklayenti_isn) bese liyibeka ensimini ethi "Inombolo yokulandelana" yesihloko se-TCP. Ngesikhathi esifanayo, iklayenti libeka isikhundla sefulegi le-SYN ku-1 ukukhombisa ukuthi iphakethe eliphumayo liyiphakethe le-SYN. Iklayenti libonisa ukuthi lifisa ukusungula uxhumano neseva ngokuthumela iphakethe lokuqala le-SYN kuseva. Leli phakethe aliqukethe idatha yesendlalelo sohlelo lokusebenza (okungukuthi, idatha ethunyelwe). Kuleli qophelo, isimo seklayenti simakwe njenge-SYN-SENT.
Uma iseva ithola iphakethe le-SYN elivela kuklayenti, liqala ngokungahleliwe inombolo yalo yochungechunge (i-server_isn) bese lifaka leyo nombolo ensimini ethi "Inombolo yochungechunge" yesihloko se-TCP. Okulandelayo, iseva ifaka i-client_isn + 1 ensimini ethi "Inombolo yokuvuma" bese isetha amabhithi e-SYN kanye ne-ACK ku-1. Ekugcineni, iseva ithumela iphakethe kuklayenti, elingenayo idatha yesendlalelo sohlelo lokusebenza (futhi alikho idatha yeseva yokuthumela). Ngalesi sikhathi, iseva isesimweni se-SYN-RCVD.
Uma iklayenti selithole iphakethe elivela kuseva, lidinga ukwenza okulandelayo ukuze liphendule iphakethe lokugcina lempendulo: Okokuqala, iklayenti lisetha i-ACK bit yesihloko se-TCP sephakethe lempendulo ku-1; Okwesibili, iklayenti lifaka inani i-server_isn + 1 ensimini ethi "Qinisekisa inombolo yempendulo"; Okokugcina, iklayenti lithumela iphakethe kuseva. Leli phakethe lingathwala idatha kusuka kuklayenti liye kuseva. Lapho sekuqediwe le misebenzi, iklayenti lizongena esimweni se-ESTABLISHED.
Uma iseva ithola iphakethe lempendulo elivela kuklayenti, ishintshela futhi esimweni esithi ESTABLISHED.
Njengoba ubona enkambisweni engenhla, lapho kwenziwa ukuxhawulana ngezindlela ezintathu, ukuxhawulana kwesithathu kuvunyelwe ukuthwala idatha, kodwa ukuxhawulana kokuqala okubili akuvunyelwe. Lona umbuzo ovame ukubuzwa ezingxoxweni. Uma ukuxhawulana ngezindlela ezintathu sekuqediwe, izinhlangothi zombili zingena esimweni esimisiwe, okubonisa ukuthi uxhumano selusungulwe ngempumelelo, lapho iklayenti neseva bangaqala ukuthumelana idatha.
Kungani nixhawulana kathathu? Hhayi kabili, kane?
Impendulo evamile ithi, "Ngoba ukuxhawulana kwabantu abathathu kuqinisekisa ikhono lokwamukela nokuthumela." Le mpendulo ilungile, kodwa yisizathu esingaphandle nje, ayivezi isizathu esiyinhloko. Okulandelayo, ngizohlaziya izizathu zokuxhawulana kwabantu abathathu ezicini ezintathu ukuze ngijulise ukuqonda kwethu le nkinga.
Ukuxhawulana ngezindlela ezintathu kungagwema ngempumelelo ukuqaliswa kokuxhumana okuphindaphindiwe ngokomlando (isizathu esiyinhloko)
Ukuxhawulana kwabantu abathathu kuqinisekisa ukuthi bobabili amaqembu bathole inombolo yokuqala yochungechunge ethembekile.
Ukuxhawulana kwabantu abathathu kugwema ukuchitha izinsiza.
Isizathu 1: Gwema Ukujoyina Okuphindwe Kabili Komlando
Kafushane nje, isizathu esiyinhloko sokuxhawulana ngezindlela ezintathu ukugwema ukudideka okubangelwa ukuqaliswa kokuxhumeka okudala okuphindwe kabili. Endaweni yenethiwekhi eyinkimbinkimbi, ukudluliswa kwamaphakethe edatha akuhlali kuthunyelwa kumphathi wendawo ngokuya ngesikhathi esibekiwe, futhi amaphakethe edatha amadala angafika kumphathi wendawo kuqala ngenxa yokuminyana kwenethiwekhi nezinye izizathu. Ukuze kugwenywe lokhu, i-TCP isebenzisa ukuxhawulana ngezindlela ezintathu ukuze kusungulwe uxhumano.
Uma iklayenti lithumela amaphakethe amaningi okusetha uxhumano lwe-SYN ngokulandelana, ezimweni ezifana nokuminyana kwenethiwekhi, okulandelayo kungenzeka:
1- Amaphakethe amadala e-SYN afika kuseva ngaphambi kwamaphakethe akamuva e-SYN.
2- Iseva izophendula iphakethe le-SYN + ACK kuklayenti ngemuva kokuthola iphakethe elidala le-SYN.
3- Uma iklayenti lithola iphakethe le-SYN + ACK, linquma ukuthi uxhumano luwuxhumano lomlando (inombolo yokulandelana iphelelwe yisikhathi noma isikhathi sokuphelelwa yisikhathi) ngokuya ngomongo walo, bese lithumela iphakethe le-RST kuseva ukuze liyeke uxhumano.
Ngokuxhumeka kokuxhawulana okubili, ayikho indlela yokunquma ukuthi uxhumano lwamanje luwuxhumano lomlando yini. Ukuxhawulana okuthathu kuvumela iklayenti ukuthi linqume ukuthi uxhumano lwamanje luwuxhumano lomlando yini ngokusekelwe kumongo lapho selilungele ukuthumela iphakethe lesithathu:
1- Uma kuwukuxhumana komlando (inombolo yokulandelana iphelelwe yisikhathi noma isikhathi sokuphelelwa yisikhathi), iphakethe elithunyelwe ngokuxhawulana kwesithathu liyiphakethe le-RST ukuze kumiswe ukuxhumana komlando.
2- Uma kungelona uxhumano lomlando, iphakethe elithunyelwe okwesithathu liyiphakethe le-ACK, futhi amaqembu amabili axhumanayo asungula uxhumano ngempumelelo.
Ngakho-ke, isizathu esiyinhloko sokuthi i-TCP isebenzise ukuxhawulana ngezindlela ezintathu ukuthi iqala ukuxhumana ukuze ivimbele ukuxhumana okungokomlando.
Isizathu sesi-2: Ukuvumelanisa izinombolo zokuqala zokulandelana kwamaqembu womabili
Zombili izinhlangothi zephrothokholi ye-TCP kumele zigcine inombolo yokulandelana, okuyisici esibalulekile ukuqinisekisa ukudluliswa okuthembekile. Izinombolo zokulandelana zidlala indima ebalulekile ekuxhumaneni kwe-TCP. Zenza okulandelayo:
Umamukeli angasusa idatha ephindaphindiwe futhi aqinisekise ukunemba kwedatha.
Umamukeli angathola amaphakethe ngokulandelana kwenombolo yochungechunge ukuqinisekisa ubuqotho bedatha.
● Inombolo yochungechunge ingakhomba iphakethe ledatha elitholwe yilowo omunye umuntu, okwenza kube lula ukudluliswa kwedatha okuthembekile.
Ngakho-ke, lapho sekusungulwe uxhumano lwe-TCP, iklayenti lithumela amaphakethe e-SYN anenombolo yokuqala yokulandelana futhi lidinga iseva ukuthi iphendule ngephakethe le-ACK elibonisa ukwamukelwa ngempumelelo kwephakethe le-SYN leklayenti. Ngemuva kwalokho, iseva ithumela iphakethe le-SYN elinenombolo yokuqala yokulandelana kuklayenti bese ilinda iklayenti ukuthi liphendule, unomphela, ukuqinisekisa ukuthi izinombolo zokuqala zokulandelana zivumelaniswa ngokuthembekile.
Nakuba ukuxhawulana ngezindlela ezine kungenzeka futhi ukuze kuvumelaniswe ngokuthembekile izinombolo zokuqala zokulandelana kwezinhlangothi zombili, izinyathelo zesibili nezesithathu zingahlanganiswa zibe yisinyathelo esisodwa, okuholela ekuxhawulaneni ngezindlela ezintathu. Kodwa-ke, ukuxhawulana okubili kungaqinisekisa kuphela ukuthi inombolo yokuqala yokulandelana kweqembu elilodwa yamukelwe ngempumelelo elinye iqembu, kodwa akukho siqinisekiso sokuthi inombolo yokuqala yokulandelana kwezinhlangothi zombili ingaqinisekiswa. Ngakho-ke, ukuxhawulana ngezindlela ezintathu kuyindlela engcono kakhulu ongayithatha ukuze kuqinisekiswe ukuzinza nokuthembeka kokuxhumeka kwe-TCP.
Isizathu 3: Gwema Ukuchitha Izinsiza
Uma kukhona "ukuxhawulana okubili" kuphela, lapho isicelo se-SYN seklayenti sivinjiwe kunethiwekhi, iklayenti alikwazi ukuthola iphakethe le-ACK elithunyelwe yiseva, ngakho-ke i-SYN izophinde isetshenziswe. Kodwa-ke, njengoba kungekho ukuxhawulana okwesithathu, iseva ayikwazi ukunquma ukuthi iklayenti lithole yini ukuvuma kwe-ACK ukuze kusungulwe uxhumano. Ngakho-ke, iseva ingasungula uxhumano kuphela ngemva kokuthola isicelo ngasinye se-SYN. Lokhu kuholela kokulandelayo:
Ukumosha izinsiza: Uma isicelo se-SYN seklayenti sivinjiwe, okuholela ekudlulisweni okuphindaphindiwe kwamaphakethe amaningi e-SYN, iseva izosungula ukuxhumana okuningi okungavumelekile ngemuva kokuthola isicelo. Lokhu kuholela ekumosha izinsiza zeseva okungadingekile.
Ukugcinwa kwemiyalezo: Ngenxa yokuntuleka kokuxhawulana okwesithathu, iseva ayinayo indlela yokwazi ukuthi iklayenti lithole kahle yini imvume ye-ACK ukuze kusungulwe uxhumano. Ngenxa yalokho, uma imiyalezo inamathela kunethiwekhi, iklayenti lizoqhubeka nokuthumela izicelo ze-SYN ngokuphindaphindiwe, okubangela ukuthi iseva ihlale isungula uxhumano olusha. Lokhu kuzokwandisa ukuminyana kwenethiwekhi nokubambezeleka futhi kuthinte kabi ukusebenza kwenethiwekhi iyonke.
Ngakho-ke, ukuze kuqinisekiswe ukuzinza nokuthembeka kokuxhumeka kwenethiwekhi, i-TCP isebenzisa ukuxhawulana okunezindlela ezintathu ukusungula uxhumano ukuze kugwenywe ukwenzeka kwalezi zinkinga.
Isifinyezo
IUmthengisi Wephakethe LenethiwekhiUkwakhiwa koxhumano lwe-TCP kwenziwa ngokuxhawulana ngezindlela ezintathu. Ngesikhathi sokuxhawulana ngezindlela ezintathu, iklayenti liqala ngokuthumela iphakethe elinefulegi le-SYN kuseva, okubonisa ukuthi lifuna ukusungula uxhumano. Ngemva kokuthola isicelo esivela kuklayenti, iseva iphendula iphakethe elinamafulegi e-SYN ne-ACK kuklayenti, okubonisa ukuthi isicelo soxhumano samukelwe, bese ithumela inombolo yayo yokuqala yochungechunge. Ekugcineni, iklayenti liphendula ngefulegi le-ACK kuseva ukukhombisa ukuthi uxhumano lusungulwe ngempumelelo. Ngakho-ke, amaqembu amabili asesimeni ESIQINILE futhi angaqala ukuthumela idatha komunye nomunye.
Ngokuvamile, inqubo yokuxhawulana ngezindlela ezintathu yokusungulwa koxhumano lwe-TCP yenzelwe ukuqinisekisa ukuzinza nokuthembeka koxhumano, ukugwema ukudideka nokuchitha izinsiza ngokuxhumana komlando, nokuqinisekisa ukuthi zombili izinhlangothi ziyakwazi ukuthola nokuthumela idatha.
Isikhathi sokuthunyelwe: Jan-08-2025
