Ukuseta koqhagamshelo lwe-TCP
Xa sikhangela iwebhu, thumela i-imeyile, okanye udlale umdlalo we-intanethi, rhoqo asicingi malunga nonxibelelwano oluntsonkothileyo emva kwayo. Nangona kunjalo, la manyathelo amancinci abonisa ukuba aqinisekise ngonxibelelwano oluzinzileyo phakathi kwethu kunye neseva. Elinye lawona manyathelo abalulekileyo kukuseta uQhagamshelo lwe-TCP, kwaye isiseko sale yindlela yendlela emithathu.
Eli nqaku liza kuthetha ngomgaqo, inkqubo kunye nokubaluleka kweenkcukacha zendlela ezintathu. Inyathelo ngenyathelo, siza kucacisa ukuba kutheni kufuneka izandla ezintathu, indlela eqinisekisa ukuzinza kunye nokuthembeka, nokuba kubaluleke kangakanani ukudluliselwa kwedatha. Ngolwazi olunzulu lweendlela ezintathu, siya kufumana ukuqonda okungcono kweendlela ezisisiseko zonxibelelwano lwenethiwekhi kunye nembono ecacileyo yokunxibelelana kwe-TCP.
Inkqubo ye-TCP yenkqubo ye-TCP kunye noTshintsho lweLizwe
I-TCP ngumgaqo ojolise kunxibelelwano olwenziweyo, ofuna ukumiselwa konxibelelwano ngaphambi kokuhanjiswa kwedatha. Inkqubo yonxibelelwano yenziwa yindlaka ngesandla ezintathu.
Makhe siqwalasele ngokusondeleyo kwiipakethi ze-TCP ezithunyelwa kunxibelelwano ngalunye.
Ekuqaleni, bobabini abathengi kunye neseva bavaliwe. Okokuqala, umncedisi uyamamela ngenzondelelo kwizibuko kwaye ukwimeko yokuphulaphula, okuthetha ukuba i-server kufuneka iqalwe. Emva koko, umthengi sele elungele ukuqalisa ukufikelela kwiphepha lewebhu.it kufuneka aseke unxibelelwano neseva. Ifomathi yepakethi yonxibelelwano yokuqala yile ilandelayo:
Xa umthengi uqalisa unxibelelwano, kuvelisa inombolo yendlela yokulandelelana (umthengi_isn) kwaye ibeka ibala "kwinombolo yenombolo ye-TCP. Kwangelo xesha, umthengi useta isikhundla se-syn fungelo kwi-1 ukubonisa ukuba ipakethi yokuphuma yipakethi ye-Syn. Umthengi ubonisa ukuba inqwenela ukuseka unxibelelwano neseva ngokuthumela ipakethi yokuqala yeSyn kwiseva. Le pakethi ayiqulatha idatha yesicelo (oko kukuthi, idatha ethunyelwe). Okwangoku, imeko yomthengi iphawulwe njengeSyn-ithunyelwe.
Xa iseva ifumana ipakethi ye-syn evela kumthengi, iqalisa i-Down Resial inombolo ye-Srial (iseva) kwaye emva koko ibeka inani "lenombolo ye-serial" yesihloko se-TCP. Okulandelayo, i-Server ingena kubathengi_iyi-1 kwibala "Inani lokuvuma" kwaye libeka i-ack bits kunye ne-ack bit kwi-1. Ngeli xesha, umncedisi ukwimeko ye-syn-rcvd.
Nje ukuba umxhasi afumane ipakethi evela kwiseva, kufuneka enze ezi themba zilandelayo ukuze uphendule kwiPacket yokugqibela yempendulo: Okokuqala, umthengi ubeka i-AK ACK ye-TCP yePakethi ye-TCP kwi-1; Okwesibini, umxhasi ungena kwi-Server yeXabiso_Sn + 1 kwinombolo yeempendulo " Okokugqibela, umthengi uthumela ipakethe kwiseva. Le pakethi inokuphatha idatha kumthengi kwiseva. Emva kokugqitywa kwale misebenzi, umthengi uza kungena kwilizwe elimiselweyo.
Nje ukuba iseva ifumana ipakethi yempendulo evela kumthengi, ikwatshintsha ukuya kwilizwe elimiselweyo.
Njengoko unokubona kule nkqubo ingentla, xa usenza izandla ezintathu, impahla yesithathu ivunyelwe ukuba ithwale idatha, kodwa i-hards yokuqala ingekho. Lo ngumbuzo osoloko ubuzwa kudliwanondlebe. Nje ukuba i-Hander Hardheke ezintathu igqityiwe, omabini amaqela afaka ilizwe elimiselweyo, ebonisa ukuba uxhulumaniso lusekiwe ngempumelelo, apho umthengi kunye neseva unokuqalisa ukuthumela idatha omnye komnye.
Kutheni ezintathu ezintathu? Ayiphindwe kabini, kane?
Impendulo eqhelekileyo yile, "kuba izandla ezintathu ziqinisekisa amandla okufumana nokuthumela." Le mpendulo ichanekile, kodwa sisizathu somhlaba kuphela, asisibeka phambili esona sizathu siphambili. Kwezi zinto, ndiza kuzihlaziya izizathu zokwenza ngesandla izandla ezivela kwiinkalo ezintathu zokwenza ukuba siqonde ukuqonda kwethu ngalo mbandela.
Ukusela ngesandla ezintathu kunokuphepha ngokufanelekileyo ukuqaliswa konxibelelwano oluphindaphindiweyo (esona sizathu siphambili)
Ukuchitha izandla ezintathu ziqinisekisa ukuba omabini amaqela afumene inombolo yofundiso lokuqala enokuthenjwa.
Indlakazi ezintathu zithintela izixhobo.
Isizathu soku-1: Kulumkele ukuzonwabisa ngokwemvelo
Kwi-nyhele, esona sizathu siphambili sezinto ezintathu-ezinesithathu kukuthintela ukudideka okubangelwa kukuqala konxibelelwano oludala. Kwimeko entsonkothileyo yenethiwekhi, ukuhanjiswa kweepakethi zedatha akusoloko kuthunyelwa kumzi wexesha lokufika ngokungqinelana nexesha elichaziweyo, kwaye iipakethi zedatha ezindala zinokufika kwindawo yokuya kwindawo oya kuyo kuqala ngenxa yengqungquthela yenethiwekhi kunye nezinye izizathu. Ukuthintela oku, i-TCP isebenzisa izandla ezintathu zokuseka unxibelelwano.
Xa umthengi uthumela iipakethi zoqhagamshelo lwe-Syn ngokulandelelana, kwiimeko ezinje ngengqungquthela yenethiwekhi, oku kulandelayo kunokwenzeka:
1- Iipakethi ze-Syn ezindala zifika kwiseva phambi kweepakethi zeSyn zamva nje.
I-2- Umncedisi uza kuphendula ipakethi ye-Ack ye-Ack kumthengi emva kokufumana ipakethi yeSyn.
3- Xa umthengi efumana ipakethi ye-Syn + igqiba ukuba uxhulumaniso luqhagamshelo lwembali (ulandelelwano lwenombolo ephelelwe lixesha, kwaye emva koko ithumela ipakethi ye-RST ukulahla unxibelelwano.
Ngoqhagamshelo lwezandla ezimbini, akukho ndlela yokufumanisa ukuba uqhagamshelo lwangoku lunxibelelwano lwembali. Indlakazi ezintathu ivumela umthengi ukuba aqwalasele ukuba ngaba uqhagamshelo lwembali lusekwe kumxholo xa sele ilungele ukuthumela ipakethi yesithathu:
1- Ukuba lusuku oluphawulayo (ukulandelelana kwenombolo ekuphelelwe lixesha okanye ixesha lokuphuma), ipakethi ethunyelwa ngesandla sisixhobo sesithathu yipakethi ye-RST ukulahla unxibelelwano lwembali.
2- Ukuba ayisiyo uqhagamshelo lwembali, ipakethi ethunyelwe okwesihlandlo sesithathu yipakethi ye-ACK, kwaye amaqela amabini odlulisayo ahlaziya ngempumelelo uqhagamshelo.
Ke ngoko, esona sizathu sokuba i-TCP isebenzisa indawo ezintathu zendlela kukuba uqalisa unxibelelwano ukuthintela unxibelelwano lwembali.
Isizathu 2: Ukulungelelanisa iinombolo zokulandelelana kokuqala zawo omabini amaqela
Omabini la macala e-TCP kufuneka agcine inombolo yokulandelelana, eyinto ephambili ukuqinisekisa usulelo oluthembekileyo. Iinombolo zokulandelelana zidlala indima ebalulekileyo kunxibelelwano lwe-TCP.Benza oku kulandelayo:
Umamkeli unokuphelisa idatha ephindwe kabini kwaye uqinisekise ukuchaneka kwedatha.
Umamkeli unokufumana iipakethi ngokomyalelo wenombolo yokulandelelana ukuqinisekisa ukuthembeka kwedatha.
● Inombolo yokulandelelana inokuchonga ipakethi yedatha efunyenwe kwelinye iqela, inika amandla osulelo lwedatha ethembekileyo.
Ke ngoko, ekumiseleni uqhagamshelo lwe-TCP, umthengi uthumela iipakethi zeSyn ngenombolo yokuqala yenombolo kwaye ufuna iseva yokuphendula ngepakethi ye-ACK ebonisa i-Syn yepakethi yomthengi. Emva koko, umncedisi uthumela ipakethi ye-Syn ngenombolo yokuqala yomnikezeli ukuya kumthengi kwaye ulinde umthengi ukuba aphendule, kube kanye, ukuqinisekisa ukuba amanani ofundiso lokuqala angqinelana ngokuthembekileyo.
Nangona isandla sendlela ezine kunokwenzeka ukuba silungelelanise ngokuthembekileyo inani lokulandelelana kwawo omabini la maqela, amanqanaba okwesibini neyesibini anokudityaniswa kwinyathelo elinye, okukhokelela kwindawo ezintathu. Nangona kunjalo, i-hands ezimbini inokuqinisekisa kuphela ukuba inani lokuqala leqela lifunyenwe ngempumelelo kwelinye iqela, kodwa akukho siqinisekiso sokuba ulandelelwano lokuqala lwawo omabini la maxesha onke anokuqinisekiswa. Ke ngoko, indawo ezintathu-ezinesithathu yeyona ndlela ilungileyo yokuthatha ukwenzela ukuqinisekisa uzinzo kunye nokuthembeka konxibelelwano lwe-TCP.
Isizathu 3: Kulumkele ukuchitha izibonelelo
Ukuba kukho kuphela "izandla ezimbini", xa isicelo se-Syn sivinjiweyo kwinethiwekhi, umthengi akanakufumana ipakethi ye-AK ACK ethunyelwe yiseva, ke i-syn iyakukhathazeka. Nangona kunjalo, ekubeni kungabikho sandla sesithathu, umncedisi akakwazi ukugqiba ukuba umxhasi ufumene i-ACK ACDECGMFment ukumisela unxibelelwano. Ke ngoko, umncedisi unokuseka kuphela unxibelelwano emva kokufumana isicelo ngasinye syn. Oku kukhokelela koku kulandelayo:
Inkunkuma yezixhobo: Ukuba isicelo somthengi sivaliwe, sibangelwa kukutshintshwa okuphindiweyo kweepakethi ezininzi ze-Syn, umncedisi uza kuseka unxibelelwano olungasebenziyo emva kokufumana isicelo. Oku kukhokelela kwinkunkuma engafunekiyo yezixhobo zeseva.
Ukugcinwa komyalezo: Ngenxa yokunqongophala kwezandla yesithathu, umncedisi akanandlela yokwazi ukuba umxhasi uyifumene ngokuchanekileyo i-ACK ACKEGGGMGMFMENT YOKWAMKELWA UKUVUNYELWA. Ngenxa yoko, ukuba imiyalezo ibambekile kwinethiwekhi, umthengi uza kuqhubeka nokuthumela izicelo zeSyn kwaye zibangela ukuba iseva isebenze rhoqo. Oku kuya kukonyusa ukuxinana kwenethiwekhi kunye nokulibaziseka kwaye kuchaphazela kakubi ukusebenza kwenethiwekhi.
Ke ngoko, ukwenzela ukuqinisekisa uzinzo kunye nokuthembeka konxibelelwano lwenethiwekhi, i-TCP isebenzisa indawo ezintathu ezihamba-hamba ukumisela unxibelelwano ukuthintela ukwenzeka kwezi ngxaki.
Isishwankathelo
IIpakethi yenethiwekhi yenethiwekhiUkumiselwa koqhagamshelo lwe-TCP kwenziwa ngendlakazi ezintathu. Ngexesha leendlela ezintathu, umthengi uqala uthumela ipakethi kunye neflegi ye-Syn kwiseva, ebonisa ukuba ifuna ukuseka unxibelelwano. Emva kokufumana isicelo kumthengi, umncedisi uphendula ipakethi kunye ne-Syn kunye ne-ACK FLAGS kumthengi, ebonisa ukuba isicelo soqhagamshelo samkelwe, kwaye uthumela inombolo yalo yokulandelelana. Okokugqibela, umthengi uphendula ngeflegi ye-ACK kwiseva ukubonisa ukuba unxibelelwano luye lwamiselwa ngempumelelo. Ke, la mathewo mabini akwimo esenyuliweyo kwaye anokuqalisa ukuthumela idatha omnye komnye.
Ngokubanzi, inkqubo yenkqantosi yendlela ezintathu yoqhagamshelo ye-TCP yenzelwe ukuqinisekisa ukuzinza kunye nokuthembeka, ukunqanda ukudideka kunye nokuchitha izibonelelo kunxibelelwano lwembali, kwaye omabini amaqela ayakwazi ukufumana kwaye athumele idatha.
IXESHA LOKUQALA: UJan-08-2025
