Kungakhathaliseki ukuthi iyiphi indlela esetshenziswayo ukuze kuzuzwe ukuxhumana kwembobo yenethiwekhi, ayikwazi ukuhlukaniswa nezimiso ezijwayelekile ezifanele.Kodwa-ke, i-Ethernet ibandakanyeka enkampanini yethuI-ONUuchungechunge lomkhiqizo lulandela ngokuyinhloko izinga le-IEEE 802.3.Ngezansi isingeniso esifushane sesakhiwo sefreyimu ye-IEEE 802.3
IEEE802.3 Uhlaka Lohlaka
Umsebenzi we-Media Access Control sublayer (MAC) ubuchwepheshe obuyinhloko be-Ethernet, obunquma ukusebenza kwenethiwekhi okuyinhloko kwe-Ethernet.I-sublayer ye-MAC ivamise ukuhlukaniswa ngamamojula amabili asebenzayo: ukubethelwa kozimele/ukuqaqa kanye nokulawula ukufinyelela kwemidiya.Uma uxhuma imisebenzi yalesi sakhi esingaphansi, isinyathelo sokuqala ukuqonda uhlaka lohlaka lwe-Ethernet
|Ikhodi yokuqala |I-Frame Start Delimiter |Ikheli Lendawo |Ikheli Lomthombo |Ubude |Idatha |Ukulandelana Kokuhlola Uhlaka|
|7 amabhayithi |1 ibhayithi |6 amabhayithi |6 amabhayithi |2 amabhayithi |46-1500 amabhayithi |4 amabhayithi |
(1) Ikhodi yangaphambili: Ikhodi equkethe amabhayithi angu-7 wezikhawu kanambambili "1" kanye no-"0", okungukuthi 1010... 10, isamba samabhithi angu-56.Uma uhlaka lulayishwa kwabezindaba, umamukeli angakwazi ukusungula ukuvumelanisa kancane, ngoba esimweni sekhodi ye-Manchester, i-waveform yokudlulisela enezikhawu ezithi "1" kanye "no-0" iyigagasi lesikwele lesikhathi.
(2) I-Frame First Delimiter (SFD): Iwukulandelana kanambambili kuka-10101011 nobude bebhayithi elingu-1.Uma le khodi isidlulile, imele isiqalo sangempela sohlaka ukuze umamukeli akwazi ukuthola ingxenye yokuqala yohlaka lwangempela.Okusho ukuthi, uhlaka lwangempela luqukethe i-DA+SA+L+LLCPDU+FCS esele.
(3) Ikheli Lendawo (DA): Icacisa ikheli lendawo uhlaka oluzama ukuthumela kulo, elihlanganisa amabhayithi angu-6.Kungaba ikheli elilodwa (elimele isiteshi esisodwa), amakheli amaningi (amele iqoqo leziteshi), noma amakheli agcwele (amele zonke iziteshi kunethiwekhi yendawo yendawo).Uma amakheli amaningi evela ekhelini okuyiwa kulo, kusho ukuthi ifreyimu itholwa ngesikhathi esisodwa iqembu leziteshi, elaziwa ngokuthi "i-multicast".Uma ikheli lendawo livela njengekheli eligcwele, kusho ukuthi ifremu itholwa kanyekanye yizo zonke iziteshi kunethiwekhi yendawo, eyaziwa ngokuthi "ukusakaza".Uhlobo lwekheli ngokuvamile lunqunywa ingxenye ephakeme kakhulu ye-DA.Uma ibhithi eliphakeme kakhulu lingu-"0", libonisa ikheli elilodwa;Inani '1' libonisa amakheli amaningi noma amakheli agcwele.Uma ikheli seligcwele, inkambu ye-DA inekhodi "1" egcwele.
(4) Ikheli Lomthombo (SA): Libonisa ikheli lesiteshi esithumela uhlaka, okuthi, njenge-DA, luthathe amabhayithi angu-6.
(5) Ubude (L): Amabhayithi amabili esewonke, amele inani lamabhayithi ku-LLC-PDU.
(6) Iyunithi yedatha yephrothokholi yesendlalelo sedatha (LLC-PDU): Isukela ku-46 kuya ku-1500 bytes.Qaphela ukuthi ubuncane be-LLC-PDU ubude bamabhayithi angu-46 buwumkhawulo, obudinga zonke iziteshi kunethiwekhi yendawo yendawo ukuthi zikwazi ukuthola lolu hlaka, ukuqinisekisa ukusebenza okuvamile kwenethiwekhi.Uma i-LLC-PDU ingaphansi kwamabhayithi angu-46, isisetshenziswa esingaphansi se-MAC sesiteshi esithumelayo sizogcwalisa ngokuzenzakalelayo ikhodi ethi "0" ukuze siqedele.
(7) Ukulandelana Kokuhlola Uhlaka (FCS): Itholakala ekugcineni kohlaka futhi ithatha isamba samabhayithi angu-4.Kuyikhodi yokuhlola yokuphindaphindeka okungamabhithi angu-32 (CRC) ehlola okuqukethwe kwabo bonke ozimele ngaphandle kwesethulo, i-SFD, ne-FCS.Imiphumela yokuhlola ye-CRC esuka ku-DA kuya ku-DATA ibonakala ku-FCS.Uma isiteshi esithumelayo sithumela uhlaka, senza ukuqinisekiswa kwe-CRC kancane kancane ngenkathi sithumela.Ekugcineni, kwakhiwa ukuhlolwa kwe-32-bit CRC futhi kugcwaliswe endaweni ye-FCS ekugcineni kohlaka ukuze kudluliselwe esimaphakathi.Ngemva kokuthola uhlaka esiteshini sokwamukela, ukuqinisekiswa kwe-CRC kwenziwa kancane kancane kuyilapho kuthola uhlaka olufanayo oluqala ku-DA.Uma isheke esakhiwe isiteshi sokugcina sokwamukela sifana neshekesum yohlaka, kukhombisa ukuthi ifremu edluliselwe phakathi nendawo ayizange ichithwe.Ngokuphambene nalokho, uma isiteshi sokwamukela sikholelwa ukuthi uhlaka lucekeleke phansi, sizocela isiteshi esithumelayo ukuthi sithumele kabusha uhlaka ngomshini othile.
Ubude bohlaka buyi-DA+SA+L+LLCPDU+FCS=6+6+2+(46-1500)+4=64-1518, okungukuthi, lapho i-LLC-PDU ingamabhayithi angu-46, uhlaka luncane kakhulu. ubude bamapulangwe bangamabhayithi angamashumi ayisithupha nane;Uma i-LLC-PDU ingamabhayithi angu-1500, ubukhulu bosayizi wozimele bungamabhayithi angu-1518.
Inethiwekhi yenkampani yethu efanele imikhiqizo edayiswayo eshisayo ihlanganisa izinhlobo ezahlukene zeI-ONUimikhiqizo yochungechunge, kuhlanganise ne-ACI-ONU/ukuxhumanaI-ONU/ehlakaniphileI-ONU/ibhokisiI-ONU, njll. OkungenhlaI-ONUimikhiqizo yochungechunge ingasetshenziselwa izidingo zenethiwekhi ezimeni ezahlukahlukene.Yamukela wonke umuntu ukuthi eze futhi abe nolwazi oluningiliziwe lobuchwepheshe lomkhiqizo.
