Ko da wace hanya ake amfani da ita don cimma nasarar sadarwar tashar jiragen ruwa, ba za a iya raba ta da daidaitattun ka'idoji ba.Koyaya, Ethernet yana da hannu a cikin kamfaninmuONUjerin samfuran galibi suna bin ka'idodin IEEE 802.3.A ƙasa akwai taƙaitaccen gabatarwa ga tsarin firam ɗin IEEE 802.3
IEEE802.3 Tsarin Tsarin
Ayyukan Media Access Control sublayer (MAC) shine ainihin fasahar Ethernet, wanda ke ƙayyade babban aikin cibiyar sadarwa na Ethernet.Ana rarraba sublayer na MAC zuwa nau'ikan aiki guda biyu: firam encapsulation/buɗewa da sarrafa damar mai jarida.Lokacin haɗa ayyukan wannan sublayer, mataki na farko shine fahimtar tsarin firam ɗin Ethernet
|Kafin farko |Matsakaicin Fara Fara Firam |Adireshin Zuwa |Adireshin tushe |Tsawon |Data |Tsare-tsare Tsare-tsare |
|7 bytes |1 byte |6 bytes |6 bytes |2 bytes |46-1500 bytes |4 bytes|
(1) Precode: Lambar da ke ɗauke da bytes 7 na tazara "1" da "0", watau 1010... 10, jimlar 56 bits.Lokacin da aka ɗora firam ɗin akan kafofin watsa labarai, mai karɓar zai iya kafa aiki tare na ɗan lokaci, saboda a cikin yanayin lambar Manchester, tsarin watsawa tare da tazara "1" da "0" shine tazara mai murabba'i na lokaci-lokaci.
(2) Tsarin Farko na Farko (SFD): Yana da jerin binaryar 10101011 tare da tsawon 1 byte.Da zarar wannan lambar ta wuce, tana wakiltar ainihin farkon firam don baiwa mai karɓa damar gano farkon ɗan firam ɗin.Wato ainihin firam ɗin ya ƙunshi ragowar DA+SA+L+LLCPDU+FCS.
(3) Adireshin Wuta (DA): Yana ƙayyadaddun adireshin wurin da firam ɗin ke ƙoƙarin aikawa zuwa gare shi, wanda ya ƙunshi bytes 6.Yana iya zama adireshi ɗaya (mai wakiltar tashar guda ɗaya), adireshi masu yawa (wakiltar rukunin tashoshi), ko cikakkun adireshi (wakiltar duk tashoshi a cibiyar sadarwar yankin).Lokacin da adireshi da yawa suka bayyana a adireshin inda aka nufa, yana nufin cewa rukunin tashoshi yana karɓar firam lokaci guda, wanda aka sani da "multicast".Lokacin da adireshin da aka nufa ya bayyana a matsayin cikakken adireshin, yana nufin cewa ana karɓar firam lokaci guda ta duk tashoshi na cibiyar sadarwar yankin, wanda aka sani da "watsawa".Nau'in adireshin yawanci ana ƙaddara ta mafi girman bit na DA.Idan mafi girman bit shine "0", yana nuna adireshin guda ɗaya;Ƙimar '1' tana nuna adireshi da yawa ko cikakkun adireshi.Lokacin da adireshin ya cika, filin DA yana da cikakkiyar lambar "1".
(4) Adireshin tushe (SA): Yana nuna adireshin tashar da ke aika firam, wanda, kamar DA, ya mamaye 6 bytes.
(5) Tsawon (L): bytes biyu a duka, wakiltar adadin bytes a cikin LLC-PDU.
(6) Data link Layer Data Unit (LLC-PDU): Ya tashi daga 46 zuwa 1500 bytes.Lura cewa mafi ƙarancin tsawon LLC-PDU na 46 bytes shine iyakancewa, wanda ke buƙatar duk tashoshi a cibiyar sadarwar yankin don samun damar gano wannan firam, tabbatar da aikin cibiyar sadarwa na yau da kullun.Idan LLC-PDU bai wuce 46 bytes ba, MAC sublayer na tashar aikawa za ta cika lambar "0" ta atomatik don kammalawa.
(7) Tsare-tsare Tsararraki (FCS): Yana nan a ƙarshen firam ɗin kuma ya mamaye jimlar 4 bytes.Lambar rajistan sake sakewa mai 32-bit (CRC) ce wacce ke bincika abubuwan da ke cikin duk firam ban da gabatarwa, SFD, da FCS.Sakamakon binciken CRC daga DA zuwa DATA yana nunawa a cikin FCS.Lokacin da tashar aikawa ta aika firam, tana yin tabbacin CRC bi da bi yayin aikawa.A ƙarshe, an ƙirƙiri gwajin 32-bit CRC kuma an cika shi a matsayin FCS a ƙarshen firam don watsawa akan matsakaici.Bayan karɓar firam ɗin a tashar karɓa, ana yin tabbacin CRC da ɗan bita yayin karɓar firam iri ɗaya farawa daga DA.Idan checksum ɗin da tashar karɓa ta ƙarshe ta yi daidai da lissafin firam ɗin, yana nuna cewa firam ɗin da aka watsa akan matsakaici bai lalace ba.Akasin haka, idan tashar karɓa ta yi imanin cewa an lalata firam ɗin, za ta buƙaci tashar aikewa da ta sake tura firam ɗin ta wata hanya.
Tsawon firam shine DA+SA+L+LLCPDU+FCS=6+6+2+(46-1500)+4=64-1518, wato lokacin da LLC-PDU ke 46 bytes, firam din shine mafi kankanta. kuma tsayin firam ɗin shine 64 bytes;Lokacin da LLC-PDU ke 1500 bytes, matsakaicin girman firam shine 1518 bytes.
Kamfanonin mu masu dacewa da samfuran siyar da zafi mai zafi suna rufe nau'ikan iri daban-dabanONUjerin samfurori, ciki har da ACONU/ sadarwaONU/mai hankaliONU/akwatinONU, da sauransu. Na samaONUAna iya amfani da samfuran jerin samfuran don buƙatun cibiyar sadarwa a yanayi daban-daban.Maraba da kowa da kowa ya zo kuma ya sami ƙarin fahimtar fasaha game da samfurin.
