Facebook imiphumela yokuhlolwa nge-algorithm entsha yokulawula ukuminyana - , elungiselelwe ukudlulisa okuqukethwe kwevidiyo. I-algorithm yahlongozwa abacwaningi abavela eMassachusetts Institute of Technology. I-COPA prototype ethunyelwe ukuze ihlolwe ibhalwe ngo-C++. ngaphansi kwelayisense ye-MIT futhi ifakwe kuyo - ukuqaliswa kwephrothokholi ye-QUIC eyenziwa ku-Facebook.
I-algorithm ye-COPA yakhelwe ukubhekana nezinselelo zokudluliswa kwevidiyo kunethiwekhi. Kuye ngohlobo lwevidiyo, ama-algorithms okulawula ukuminyana abhekana nezidingo ezibonakala zingqubuzana: ividiyo esebenzisanayo idinga ukubambezeleka okuncane, ngisho nezindleko zekhwalithi, kuyilapho ividiyo ekhiqizwe kusengaphambili, enekhwalithi ephezulu ibeka kuqala ukugcinwa kwekhwalithi. Ngaphambilini, abathuthukisi bohlelo lokusebenza bebekhawulelwe ekusebenziseni ama-algorithms ahlukene asuselwa kukhwalithi noma izimfuneko zokubambezeleka. Abacwaningi abathuthukise i-COPA bazame ukudala i-algorithm yendawo yonke yokulawulwa kokuminyana kwe-TCP phakathi nokudluliswa kwevidiyo okungashunwa kuzidingo ezithile zevidiyo.
I-algorithm yokulawula ukuminyana inquma ibhalansi efanele lapho kuthunyelwa amaphakethe. Ukuthumela amaphakethe amaningi kakhulu kungaholela ekulahlekelweni kwephakethe kanye nesijeziso sokusebenza ngenxa yesidingo sokuwathumela kabusha, kuyilapho ukuthumela kancane kakhulu kuholela ekubambezelekeni, okuphinde kube nomthelela omubi ekusebenzeni. Iphrothokholi ye-QUIC yakhethelwa ukuhlolwa ngoba ivumela ama-algorithms okulawula ukuminyana ukuthi asetshenziswe endaweni yomsebenzisi ngaphandle kokuphazamisa i-kernel.
Ukuze kuvinjwe ukuminyana kwesiteshi, i-COPA isebenzisa ukumodela kokusebenza kwesiteshi okusekelwe ekuhlaziyweni kokuhlukahluka kokulibaziseka kokulethwa kwephakethe (i-COPA inciphisa usayizi wewindi lokuminyana njengoba ukubambezeleka kuyanda, isebenzisa iqiniso lokuthi ukubambezeleka kuqala ukwanda ngisho nangaphambi kokulahlekelwa kwephakethe). Ibhalansi phakathi kokubambezeleka kanye nokuphumayo kulawulwa kusetshenziswa ipharamitha ekhethekile, i-delta. Ukwandisa i-delta kukhulisa ukuzwela kokubambezeleka kodwa kunciphisa ukuphuma, kuyilapho ukuncipha kwe-delta kuvumela ukuphuma okuphezulu ngezindleko zokulibaziseka okukhulayo. Inani le-delta elingu-0.04 lichazwa njengebhalansi ephelele phakathi kwekhwalithi nokubambezeleka.
I-COPA ihlolwe ngokumelene nama-algorithms adumile e-CUBIC kanye ne-BBR kusetshenziswa isevisi yokusakaza bukhoma ye-Facebook. I-algorithm ye-CUBIC isetshenziswa ngokuzenzakalelayo ku Linux futhi kwehla kancane kancane kusayizi wefasitela lokuminyana kuze kube yilapho kwenzeka ukulahleka kwephakethe, ngemva kwalokho usayizi wefasitela ubuyiselwa emuva enanini ngaphambi kokuqala kokulahleka.
Ukubhafa kwephakethe okuphakathi kwe-CUBIC emishinini yenethiwekhi yesimanje kushiya okuningi okungafunwa, njengoba kunciphisa ukwehla kwephakethe. I-algorithm yokulawula ukuminyana ayiqapheli lokhu kubhafa futhi iyaqhubeka nokwandisa isivinini ngisho noma isixhumanisi sesivele siminyene ngokomzimba. Amaphakethe angathunyelwanga afakwa kubhafa kunokuba awiswe, futhi i-algorithm yokulawula ukuminyana kwe-TCP iqala kuphela lapho ibhafa isigcwele futhi ayikwazi ukulinganisa izinga lokugeleza ngendlela efanele nesivinini sokuxhumanisa esibonakalayo. Ukuze kubhekwane nale nkinga, i-Google iphakamise i-algorithm ye-BBR ethuthukisiwe ebikezela umkhawulokudonsa otholakalayo ngokuhlolwa okulandelanayo kanye nokulinganisa kwesikhathi sokuya nokubuya (RTT).
Ku-delta=0.04, ukusebenza kwe-COPA bekusondele kulokho kwe-CUBIC ne-BBR. Ezivivinyweni ezenziwe ngoxhumo lwenethiwekhi olunesivinini esikhulu ngokubambezeleka kwephakethe eliphansi, i-COPA ithole ukubambezeleka okuphansi (479 ms) kune-CUBIC (499 ms), kodwa yasala ngemuva kancane kwe-BBR (462 ms). Lapho ikhwalithi yokuxhuma iwohloka, i-COPA ibonise imiphumela engcono kakhulu—ukubambezeleka kwaba ngaphansi ngo-27% kunaleyo ye-CUBIC ne-BBR.
Ngaphezu kwalokho, esiteshini sokuxhumana esingesihle, i-COPA ne-BBR bathole ukusebenza okuphezulu kakhulu uma kuqhathaniswa ne-CUBIC. Izinzuzo zokuphuma kwe-BBR nge-CUBIC bezingu-4.8% kanye no-5.5%, kanti ama-COPA abe ngu-6.2% no-16.3%.
Source: opennet.ru
