Kungakhathaliseki ukuba yeyiphi indlela esetyenziswayo ukufezekisa unxibelelwano lwezibuko lothungelwano, ayinakohlulwa kwiiprothokholi ezisemgangathweni ezifanelekileyo. Nangona kunjalo, i-Ethernet ibandakanyeka kwinkampani yethuI-ONUuthotho imveliso ikakhulu ilandela IEEE 802.3 umgangatho. Ngezantsi sisingeniso esifutshane kwi-IEEE 802.3 isakhelo sesakhelo
IEEE802.3 Ulwakhiwo lwesakhelo
Umsebenzi we-Media Access Control sublayer (MAC) yiteknoloji engundoqo ye-Ethernet, emisela ukusebenza kwenethiwekhi ye-Ethernet. I-sublayer ye-MAC idla ngokuhlula kwiimodyuli ezimbini ezisebenzayo: i-frame encapsulation / unpacking kunye nolawulo lokufikelela kwimidiya. Xa udibanisa imisebenzi yale sublayer, isinyathelo sokuqala kukuqonda isakhiwo sesakhelo se-Ethernet
|Ikhowudi yangaphambili | Isakhelo sokuQalisa iDelimiter | Idilesi yendawo yokufikela | Idilesi yomthombo | Ubude | Idatha | Ulandelelwano lokuHlola isakhelo|
|7 iibhayithi | 1 ibhayithi | iibyte ezi-6 | iibyte ezi-6 | iibyte ezi-2 | 46-1500 bytes | iibyte ezi-4|
(1) Ikhowudi yangaphambili: Ikhowudi equlethe i-7 bytes yokubini "1" kunye ne-"0" intervals, okt 1010... 10, iyonke 56 bits. Xa isakhelo silayishwe kumajelo eendaba, umamkeli unokuseka ulungelelwaniso lwebit, kuba kwimeko yekhowudi yaseManchester, i-waveform yokuhanjiswa kunye ne-"1" kunye ne-"0" ye-intervals yi-periodic square wave.
(2) I-Frame First Delimiter (SFD): Lulandelelwano lwebhinari ye-10101011 kunye nobude be-byte ye-1. Nje ukuba le khowudi idlulile, imele isiqalo sokwenyani sesakhelo ukwenzela ukuba umamkeli afumane indawo yokuqala yesakhelo esisiso. Oko kukuthi, eyona isakhelo siqulathe i-DA+SA+L+LLCPDU+FCS eseleyo.
(3) Idilesi yendawo ekusingwa kuyo (DA): Icacisa idilesi yendawo ekuyiwa kuyo isakhelo esizama ukuthumela kuyo, equka iibhayithi ezi-6. Inokuba yidilesi enye (emele isikhululo esinye), iidilesi ezininzi (ezimele iqela lezitishi), okanye iidilesi ezipheleleyo (ezimele zonke izikhululo kuthungelwano lwendawo yendawo). Xa iidilesi ezininzi zivela kwidilesi yendawo ekuyiwa kuyo, oko kuthetha ukuba isakhelo sifunyanwa ngaxeshanye liqela lezitishi, ezaziwa ngokuba yi "multicast". Xa idilesi yendawo ekuyiwa kuyo ibonakala njengedilesi epheleleyo, oko kuthetha ukuba isakhelo sifunyanwa ngaxeshanye zizo zonke izitishi kuthungelwano lwendawo yendawo, eyaziwa ngokuba "lusasazo". Uhlobo lwedilesi luqhele ukumiselwa yeyona bits iphezulu yeDA. Ukuba eyona bit iphezulu ngu "0", ibonisa idilesi enye; Ixabiso lika-'1' libonisa iidilesi ezininzi okanye iidilesi ezipheleleyo. Xa idilesi igcwele, indawo yeDA inekhowudi epheleleyo ethi "1".
(4) Idilesi yomthombo (SA): Ibonisa idilesi yesikhululo esithumela isakhelo, esifana neDA, sithatha iibytes ezi-6.
(5) Ubude (L): Iibhayithi ezimbini zizonke, ezimele inani leebhayithi kwi-LLC-PDU.
(6) Uluhlu lwedatha yedatha yedatha yedatha yedatha (LLC-PDU): Isuka kwi-46 ukuya kwi-1500 bytes. Qaphela ukuba ubuncinci be-LLC-PDU ubude be-46 bytes buyithintelo, efuna zonke izitishi kuthungelwano lwendawo yendawo ukuba zikwazi ukubona esi sikhokelo, ukuqinisekisa ukusebenza kwenethiwekhi eqhelekileyo. Ukuba i-LLC-PDU ingaphantsi kwe-46 bytes, i-MAC sublayer yesikhululo sokuthumela iya kuzalisa ngokuzenzekelayo ikhowudi ethi "0" ukugqiba.
(7) Ulandelelwano lokuHlolwa kweSakhelo (FCS): Ifumaneka ekupheleni kwesakhelo kwaye ithatha i-4 bytes iyonke. Yikhowudi yokutshekisha ye-32-bit ye-redundancy (CRC) ejonga imixholo yazo zonke izakhelo ngaphandle kwentshayelelo, i-SFD, kunye ne-FCS. Iziphumo zokutshekishwa kwe-CRC ukusuka kwi-DA ukuya kwi-DATA zibonakaliswe kwi-FCS. Xa isitishi sokuthumela sithumela isakhelo, senza ungqinisiso lwe-CRC kancinci kancinci ngelixa uthumela. Ekugqibeleni, uvavanyo lwe-32-bit CRC luyenziwa kwaye luzaliswe kwindawo ye-FCS ekupheleni kwesakhelo sosasazo oluphakathi. Emva kokufumana isakhelo kwisikhululo esifumanayo, uqinisekiso lweCRC lwenziwa kancinci kancinci ngelixa ufumana isakhelo esifanayo siqala kwiDA. Ukuba i-checksum eyenziwe yisikhululo sokugqibela sokufumana ifana ne-checksum yesakhelo, ibonisa ukuba isakhelo esihanjiswe kwi-medium asizange sibhujiswe. Ngokuchasene noko, ukuba isikhululo esifumanayo sikholelwa ukuba isakhelo sitshatyalalisiwe, siya kucela isikhululo sokuthumela ukuba siphinde sithumele isakhelo ngendlela ethile.
Ubude besakhelo yiDA+SA+L+LLCPDU+FCS=6+6+2+(46-1500)+4=64-1518, oko kukuthi, xa i-LLC-PDU ingama-46 bytes, isakhelo sesona sincinci. ubude benqwanqwa baba ngama-64 eebhayithi; Xa i-LLC-PDU iyi-1500 bytes, ubukhulu besakhelo esiphezulu yi-1518 bytes.
Inethiwekhi yenkampani yethu efanelekileyo ethengisa iimveliso ezishushu zigubungela iintlobo ezahlukeneyo zeI-ONUiimveliso series, kuquka ACI-ONU/unxibelelwanoI-ONU/ekrelekreleI-ONU/ibhokisiI-ONU, njl. Oku kungasentlaI-ONUiimveliso zothotho zingasetyenziselwa iimfuno zenethiwekhi kwiimeko ezahlukeneyo. Wamkelekile wonke umntu ukuba eze kwaye abe nolwazi oluthe kratya lobugcisa bemveliso.
