Izokuthutha ze-TCP zezokwethenjwa
Sonke sijwayelene ne-protocol ye-TCP njenge-protocol yezokuthutha ethembekile, kepha iqinisekisa kanjani ukuthembeka kwezokuhamba?
Ukuthola ukudluliselwa okuthembekile, izici eziningi ezidinga ukucatshangelwa, njengenkohliso yedatha, ukulahleka, ukuphindwaphindwa, noku-oda koku-oda. Uma lezi zinkinga zingaxazululwa, ukudluliswa okuthembekile akunakutholwa.
Ngakho-ke, i-TCP isebenzisa izindlela ezinjengenombolo yokulandelana, impendulo yokwamukela, ukuthumela kabusha izilawuli, ukuphathwa kokuxhumana, kanye nokulawula iwindi ukufezekisa ukuhambisa okuthembekile.
Kuleli phepha, sizogxila efasiteleni elishelelayo, ukulawulwa kokugeleza kanye nokulawulwa kwe-TCP. Indlela yokubuyisa isembozwe ngokwahlukana esigabeni esilandelayo.
Ukulawula Ukugeleza Kwenethiwekhi
Ukulawulwa kokugeleza kwenethiwekhi noma ukwazi njengoba ukulawulwa kwethrafikhi yenethiwekhi empeleni kuyinto ukubonakaliswa kobudlelwano obucashile phakathi kwabakhiqizi nabathengi. Cishe ufike kulesi simo esiningi emsebenzini noma ezingxoxweni. Uma umthamo womkhiqizi ukhiqiza kakhulu udlula amandla omthengi okudla, kuzodala ukuthi ulayini ukhule unomphela. Esimweni esibucayi ngokwengeziwe, ungahle wazi ukuthi lapho imiyalezo yoRabi ihlangana kakhulu, ingadala ukonakaliswa kokusebenza kwayo yonke iseva ye-MQ. Okufanayo kuyiqiniso nge-TCP; Uma kushiywe kungalawulwa, imilayezo eminingi kakhulu izofakwa kunethiwekhi, futhi abathengi bazobe bedlula amandla abo, kanti abakhiqizi bazoqhubeka nokuthumela imiyalezo ephindwe kabili, okuzothinta kakhulu ukusebenza kwenethiwekhi.
Ukubhekana nalesi simo, i-TCP ihlinzeka ngendlela yomthumeli ukulawula inani lemininingwane ethuselwe ngokususelwa kumandla wangempela wokuthola owamukelayo, owaziwa ngokuthi ukulawulwa kokuhamba. Otholayo ugcina iwindi lokwamukela, ngenkathi umthumeli egcina iwindi lokuthumela. Kumele kuqashelwe ukuthi lawa mawindi axhumene ukuxhumana okukodwa kwe-TCP hhayi ukuthi konke ukuxhumana kwabelana ngewindi.
I-TCP inikezela ngokulawulwa kokugeleza ngokusebenzisa okuguqukayo kwefasitela le-Thola. Iwindi lemiklomelo linikeza umthumeli inkomba yokuthi isikhala esingakanani senqolobane esisatholakala. Umthumeli ulawula inani ledatha elithunyelwe ngokuya ngekhono langempela lokwamukela owemukelayo.
Umgcini wezemukeli wazisa umthumeli ngosayizi wedatha ongayithola, futhi umthumeli uthumele kulo mkhawulo. Lo mkhawulo usayizi wewindows, khumbula unhlokweni we-TCP? Kukhona insimu yewindows, esetshenziselwa ukukhombisa inani lamabhayithi owamukelayo ayakwazi noma azimisele ukwamukela.
Umgcini womthumeli uzothumela ngezikhathi ezithile iphakethe le-Window Profe, elisetshenziselwa ukuthola ukuthi ngabe isitholi samukelayo sisakwazi yini ukwamukela idatha. Lapho i-buffer etholile isengozini yokuchichima, usayizi wewindows usethwe ngenani elincane ukufundisa umthumeli ukulawula inani ledatha ethunyelwe.
Nalu umdwebo wokulawula wenethiwekhi:
Ukulawulwa kwe-Network Control
Ngaphambi kokwethula ukulawulwa kwe-conution, kudingeka siqonde ukuthi ngaphezu kwewindows etholile kanye newindows le-Send, kukhona okusetshenziswa kakhulu ukuxazulula inkinga yokuthi umthumeli uqala ukuthumela idatha efasiteleni le-Thola. Ngakho-ke, iwindi le-conglesion libuye ligcinwe ngumthumeli we-TCP. Sidinga i-algorithm ukunquma ukuthi ingakanani idatha efanele ukuthumela, ngoba ukuthumela idatha encane kakhulu noma eningi kakhulu akuyona into ekancane kakhulu, yingakho umqondo wewindi lokuxubha.
Ekulweni kwenethiwekhi yangaphambilini yokugeleza, esikugwemeyo kwakuwumthumeli ogcwalisa i-cache yesitholi ngedatha, kodwa sasingazi ukuthi kwenzekani kunethiwekhi. Imvamisa, amanethiwekhi ekhompyutha asendaweni eyabiwe. Ngenxa yalokhu, kungahle kube nokuhlangana kwenethiwekhi ngenxa yokuxhumana phakathi kwamanye amabutho.
Lapho inethiwekhi igcwele, uma inani elikhulu lamaphakethe liyaqhubeka lithunyelwe, kungadala izinkinga ezinjengokubambezeleka nokulahlekelwa amaphakethe. Ngalesi sikhathi, i-TCP izobuyela emuva idatha, kepha ukubuyiselwa emuva kuzokwandisa umthwalo kunethiwekhi, okuholela ekubambezezeleni okukhulu nokulahleka kwamaphakethe amaningi. Lokhu kungangena kumjikelezo omubi futhi uqhubeke ube mkhulu.
Ngakho-ke, i-TCP ayikwazi ukungakunaki okwenzekayo kunethiwekhi. Lapho inethiwekhi igcwele, i-TCP imihlatshelo ngokwayo ngokunciphisa inani ledatha elithumela.
Ngakho-ke, ukulawulwa kwe-conustion kuhlongozwayo, okuhlose ukugwema ukugcwalisa yonke inethiwekhi ngedatha evela kumthumeli. Ukulawula inani ledatha umthumeli okufanele athumele, i-TCP ichaza umqondo obizwa nge-Conglesion Window. I-algorithm yokulawula ukugcwala izolungisa usayizi wewindows yokuhlangana ngokuya nge-conglesion degree yenethiwekhi, ukuze ulawule inani ledatha ethunyelwe ngumthumeli.
Liyini iwindi lokuhlanza? Kumele kwenziweni lokhu ngefasitela lokuthumela?
Iwindi leConeGion liguqulwa umbuso eligcinwe ngumthumeli elinquma inani ledatha umthumeli angathumela. Iwindi le-conglesion lishintsha ngamandla ngokwezinga elihlanganisiwe lenethiwekhi.
Iwindi lokuthumela livunyelelekile ngosayizi wewindi phakathi komthumeli nowemukeli okhombisa inani ledatha umuntu owemukelayo angayithola. Iwindi lokuhlangana kanye newindi lokuthumela lihlobene; Iwindi lokuthumela livame ukulingana nobuncane bokuxinana nokwamukela amawindi, okungukuthi, i-SWND = Min (CWND, RWND).
Iwindi le-conglesion CWND lishintsha kanjena:
Uma kungekho ukuxinana kunethiwekhi, okungukuthi, akukho sikhathi sokugcina senzeka, iwindi le-conglesion lenyuka.
Uma kunokuxinana kunethiwekhi, iwindi lokuxubha liyancipha.
Umthumeli unquma ukuthi ngabe inethiwekhi ihlanganiswe ngokubheka ukuthi iphakethe elivumayo le-ACK litholwa ngesikhathi esibekiwe. Uma umthumeli engatholi iphakethe lokuvuma le-ACK ngesikhathi esibekiwe, kubhekwa ukuthi inethiwekhi ihlanganisiwe.
Ngaphezu kwewindi lokuhlanza, sekuyisikhathi sokuxoxa nge-algorithm yokulawula ye-TCP. I-algorithm yokulawula ye-TCP iqukethe izingxenye ezintathu eziphambili:
Qala kancane:Ekuqaleni, iwindi leCWND conethion lincane, futhi umthumeli unyusa iwindows yokuhlangana ngokuningiliziwe ukuze ivumelane ngokushesha nomthamo wenethiwekhi.
Ukugwema Ukugxeka:Ngemuva kokuthi iwindi le-conglesion lidlula umkhawulo othile, umthumeli wenyusa iwindi le-conglesion ngendlela eqondile yokunciphisa ijubane izinga lokukhula kwewindi le-conglesion futhi uvikele ukulayisha ngokweqile inethiwekhi.
Ukuvuselelwa okusheshayo:Uma kuqubukana, umthumeli ugcina iwindi le-conglesion futhi ungena ezweni lokubuyisa okusheshayo ukuthola indawo yokubuyiselwa kwenethiwekhi ngokusebenzisa ama-amps atholakele.
Ukuqala kancane
Lapho uxhumano lwe-TCP lusunguliwe, iwindi le-Conglesion CWND ekuqaleni lisethwe ku-MSS okungenani (ubukhulu besigaba se-Event). Ngale ndlela, inani lokuthumela lokuqala limayelana ne-MSS / RTT Byte / Okwesibili. I-bandwidth yangempela etholakalayo ivame ukuba makhulu kakhulu kune-MSS / RTT, ngakho-ke i-TCP ifuna ukuthola isilinganiso esifanele sokuthumela, esingatholakala nge-Start-Start.
Enqubweni yokuqalisa kancane, inani le-Conglesion Window CWND lizoqalwa ku-1 MSS, futhi isikhathi ngasinye lapho ingxenye yepakethe edlulisiwe iyavunywa, inani le-CWND lizokwandiswa yi-MSS eyodwa, okungukuthi, inani le-CWND lizoba ama-2 mss. Emva kwalokho, inani le-CWND liphindwe kabili ekudluliseleni ngakunye kwengxenye yephakethe, njalonjalo. Inqubo ethile yokukhula ikhonjiswa kulokhu okulandelayo.
Kodwa-ke, izinga lokuthumela alikwazi ukukhula njalo; Ukukhula kufanele kuphele ngesinye isikhathi. Ngakho-ke, isilinganiso sokuthumela sikhula nini? Ukuqala okuhamba kancane kuvame ukuqeda ukwanda kwezinga lokuthumela kwenye yezindlela ezimbalwa:
Indlela yokuqala yicala lokulahleka kwepakethe ngesikhathi senqubo yokuthumela ehamba kancane. Lapho kwenzeka ukulahleka kwephakethe, i-TCP ibeka iwindi le-Sender Conglesion cwnd ku-1 bese liqala kabusha inqubo yokuqala. Ngalesi sikhathi, kwenziwa umqondo we-Slow Start Threshold SSTresh wethulwa, inani lakhe lokuqala liyingxenye yenani le-CWND elenza ukulahleka kwephakethe. Okungukuthi, lapho kutholwa ukugcwala, inani le-ssthresh liyingxenye yenani lewindows.
Indlela yesibili ukuxhumanisa ngokuqondile nenani leThreshold SSTreshold SSTreshesh. Njengoba inani le-SSthresh liyingxenye yenani lewindows lapho kutholwa ukugcwala, ukulahleka kwepakethe kungavela kabili lapho i-CWND inkulu kakhulu kune-SSTresh. Ngakho-ke, kungcono ukusetha i-CWND ku-SSthresh, ezodala ukuthi i-TCP ishintshele kumodi yokulawula ukugcwala bese uqeda ukuqala kabusha.
Indlela yokugcina yokuthi ukuqala kancane kungaphela uma kutholwa ama-acks amathathu, i-TCP yenza ukubuyiselwa okusheshayo futhi ingena ezweni kabusha. (Uma kungacaci ukuthi kungani kunamaphakethe amathathu e-ACK, azochazwa ngokwahlukana ngendlela etholwayo.)
Ukugwema Ukugxeka
Lapho i-TCP ingena ezweni lokulawula ukugcwala, i-CWND isethwe kuhhafu weThregion Thregion SSTreshesh. Lokhu kusho ukuthi inani le-CWND alikwazi ukuphindwa kabili njalo lapho ingxenye yepakethe itholwa. Esikhundleni salokho, indlela egciniwe egciniwe yamukelwa lapho inani le-CWND lenyuswa nge-MSS eyodwa kuphela (ubukhulu bepakethe yepakethe yepakethe) ngemuva kokudluliswa ngakunye. Isibonelo, noma ngabe izingxenye eziyishumi zephakethe zivunywa, inani le-CWND lizokwanda kuphela nge-MSS eyodwa. Le imodeli yokulahla eqondile futhi iphinde ibe nesandla phezulu ekukhuleni. Lapho kuncipha kwephakethe, inani le-CWND lishintshwa libe yi-MSS, futhi inani le-SSthresh lisethwe kuhhafu we-CWND. Noma kuzovimba nokukhula kwe-MSS lapho izimpendulo ezi-3 ze-ACK Redundant zitholwa. Uma ama-acks amathathu angafuneki asatholwa ngemuva kokunciphisa inani le-CWND, inani le-SSthresh liqoshwe njengengxenye yenani le-CWND kanye nombuso wokuvuselela okusheshayo.
Ukululama okusheshayo
Esimweni sokululama okusheshayo, inani lewindi le-conglesion CWND lenyuswe nge-MSS eyodwa yalowo ngakunye, okungukuthi, i-ACK engafiki ngokulandelana. Lokhu ukusebenzisa izingxenye zephakethe ezidluliselwe ngempumelelo kunethiwekhi ukuthuthukisa ukusebenza kahle kokuhambisa ngangokunokwenzeka.
Lapho i-ack yengxenye yephakethe elahlekile ifika, i-TCP yehlisa inani le-cwnd bese lingena ezweni lokugwema ukuthuthumela. Lokhu ukulawula usayizi wewindi lokuhlanza futhi ugweme ukwandisa ukuxinana kwenethiwekhi.
Uma kwenzeka isikhathi ngemuva kombuso wokulawula ukugcwala, isimo senethiwekhi siba sibi kakhulu futhi i-TCP sisuka esimweni sokugwema ukuthuthumela esimweni sokuqalisa kancane. Kulokhu, inani lewindi le-conlesion CWND lisethelwe ku-1 MSS, ubude obuphakeme kakhulu bepakethe, kanye nenani leThreshold Supshold SSWreshesh isethwe kuhhafu we-CWND. Inhloso yalokhu ukuphinda ukhule kancane kancane usayizi wewindows yokuhlangana ngemuva kokuthola kabusha inethiwekhi ukulinganisa isilinganiso sokudlulisa kanye nezinga lokuxinana kwenethiwekhi.
Ukubeka kafushane
Njenge-protocol yezokuxhumana ethembekile, i-TCP isebenzisa ukuthutha okuthembekile ngenombolo yokulandelana, ukuvuma, ukubuyiselwa kabusha, ukuphathwa kokuxhumeka kanye nokulawulwa kwefasitela nokulawulwa kwefasitela. Phakathi kwazo, indlela yokulawula ukugeleza ilawula inani ledatha elithunyelwe ngumthumeli ngokuya ngomthamo wangempela wokuthola owamukelayo, okuvimbela izinkinga zokuxinana kwenethiwekhi kanye nokuwohloka kokusebenza. Indlela yokulawula ukugcwala igwema ukwenzeka kokuxinana kwenethiwekhi ngokulungisa inani ledatha ethunyelwe ngumthumeli. Imiqondo yewindi le-conlesion kanye nokuthumela iwindi ihlobene nomunye, futhi inani ledatha ku-Sender lilawulwa ngokushintshana ngosayizi wewindi le-conglesion. I-Slow Start, ukugwema ukuthuthumela kanye nokubuyiselwa okusheshayo yizingxenye ezintathu eziphambili ze-algorithm control control algorithm, elungisa usayizi wewindows yokuhlangana ngamasu ahlukile ukuze uvumelane namakhono kanye ne-coxion degree yenethiwekhi.
Esigabeni esilandelayo, sizohlola indlela yokubuyisa kabusha ye-TCP ngokuningiliziwe. Indlela yokubuyisa iyingxenye ebalulekile ye-TCP ukufezekisa ukuhambisa okuthembekile. Iqinisekisa ukuhanjiswa okuthembekile kwedatha ngokubuyisa okulahlekile, konakalisiwe noma idatha ebambezelekile. Umgomo wokuqalisa kanye necebo lendlela yokubuyisa kuzokwethulwa futhi kuhlaziywe ngokuningiliziwe esigabeni esilandelayo. Hlala ubukele!
Isikhathi sePosi: Feb-24-2025
