Hazvina mhosva kuti ndeipi nzira inoshandiswa kuzadzisa network port kutaurirana, haigone kupatsanurwa kubva kune yakakodzera standard protocol. Nekudaro, iyo Ethernet inobatanidzwa mune yedu kambaniONUchigadzirwa chakatevedzana chinonyanya kutevedzera IEEE 802.3 chiyero. Pazasi pane sumo pfupi yeIEEE 802.3 furemu chimiro
IEEE802.3 Frame Structure
Basa reMedia Access Control sublayer (MAC) ndiyo yakakosha tekinoroji yeEthernet, iyo inosarudza iyo huru network kuita kweEthernet. Iyo MAC sublayer inowanzo patsanurwa kuita maviri anoshanda mamodule: furemu encapsulation / unpacking uye midhiya yekuwana kutonga. Kana uchibatanidza mabasa eiyi sublayer, danho rokutanga nderokunzwisisa chimiro cheEthernet
|Precode | Frame Start Delimiter | Kwekuenda Kero | Source Address | Length | Data | Frame Check Sequence|
| 7 bytes | 1 byte | 6 bytes | 6 bytes | 2 bytes | 46-1500 bytes | 4 bytes|
(1) Precode: Kodhi ine 7 bytes yebhinary "1" uye "0" intervals, kureva 1010... 10, inosvika makumi mashanu nematanhatu mabhiti. Kana iyo furemu yaiswa pane midhiya, inogamuchira inogona kumisikidza bit synchronization, nekuti mune yeManchester kodhi, iyo yekufambisa waveform ine "1" uye "0" inopindirana ndeye periodic square wave.
(2) Frame First Delimiter (SFD): Ibhinari sequence ye10101011 ine hurefu hwe1 byte. Kana iyi kodhi ikapfuura, inomiririra kutanga chaiko kwefuremu kuitira kuti mugamuchiri awane yekutanga chidimbu cheiyo chaiyo furemu. Kureva kuti, furemu chaiyo ine yasara DA+SA+L+LLCPDU+FCS.
(3) Kero Yekuenda (DA): Inotsanangura kero yekuenda iyo furemu iri kuedza kutumira kwairi, ine 6 bytes. Inogona kunge iri kero imwe chete (inomiririra chiteshi chimwe chete), kero dzakawanda (inomiririra boka rezviteshi), kana kero yakazara (inomiririra zvese zviteshi pane network yenzvimbo yenzvimbo). Kana kero dzakawanda dzichionekwa kero yekuenda, zvinoreva kuti furemu inogamuchirwa panguva imwe chete neboka rezviteshi, rinozivikanwa se "multicast". Kana kero yekuenda yaonekwa sekero yakazara, zvinoreva kuti furemu inotambirwa panguva imwe chete nezviteshi zvese pane network yenzvimbo, inozivikanwa se "nhepfenyuro". Mhando yekero inowanzo temwa neiyo yepamusoro bhiti yeDA. Kana iyo yepamusoro bhiti iri "0", inoratidza kero imwe chete; Iko kukosha kwe '1' kunoratidza kero dzakawanda kana kero yakazara. Kana kero yazara, ndima yeDA ine yakazara "1" kodhi.
(4) Kwakabva Kero (SA): Inoratidza kero yechiteshi inotumira furemu, iyo, seDA, inotora 6 bytes.
(5) Kureba (L): Mabhaiti maviri akazara, anomiririra nhamba yemabhaiti mu LLC-PDU.
(6) Data link layer protocol data unit (LLC-PDU): Inotangira pa46 kusvika ku1500 bytes. Ziva kuti iyo shoma LLC-PDU kureba kwe46 bytes iganhuriro, izvo zvinoda kuti zviteshi zvese zviri panharaunda yenzvimbo network zvikwanise kuona furemu iyi, kuve nechokwadi chekushanda kwakajairika. Kana iyo LLC-PDU iri pasi pemakumi mana nematanhatu bytes, iyo MAC sublayer yechiteshi chekutumira inongozadza "0" kodhi kuti ipedze.
(7) Frame Chengetedza Sequence (FCS): Inowanikwa kumagumo efuremu uye inotora huwandu hwe4 bytes. Iyo 32-bit redundancy cheki kodhi (CRC) inotarisa zviri mukati memafuremu ese kunze kwekutanga, SFD, uye FCS. Cheki cheCRC kubva kuDA kuenda kuDATA inoratidzwa muFCS. Kana chiteshi chekutumira chikatumira furemu, inoita CRC yekuongorora zvishoma nezvishoma ichitumira. Pakupedzisira, 32-bit CRC bvunzo inoumbwa uye inozadzwa munzvimbo yeFCS pakupera kwefuremu yekutapurirana pakati. Mushure mekugamuchira furemu pachiteshi chekugamuchira, kuongororwa kweCRC kunoitwa zvishoma nezvishoma uku uchigamuchira furemu imwechete kubva kuDA. Kana iyo cheki yakaumbwa neyekupedzisira yekugamuchira chiteshi yakafanana neyecheki yefuremu, inoratidza kuti furemu inofambiswa pane yepakati haina kuparadzwa. Pane zvinopesana, kana chiteshi chekugamuchira chichitenda kuti furemu yaparadzwa, inokumbira chiteshi chekutumira kuti chitumire zvakare furemu kuburikidza neimwe nzira.
Kureba kwefuremu ndeye DA+SA+L+LLCPDU+FCS=6+6+2+(46-1500)+4=64-1518, kureva kuti, kana LLC-PDU iine 46 bytes, furemu ndiyo idiki. kureba kwefuremu kwakasvika makoti makumi matanhatu namana; Kana LLC-PDU iri 1500 bytes, yakakura furemu saizi i1518 bytes.
Kambani yedu inoenderana netiweki zvinopisa zvinotengesa zvigadzirwa zvinovhara akasiyana marudzi eONUakatevedzana zvigadzirwa, kusanganisira ACONU/kutauriranaONU/akangwaraONU/bhokisiONU, etc. Zviri pamusoro apaONUseries zvigadzirwa zvinogona kushandiswa kunetiweki zvinodiwa mumamiriro akasiyana siyana. Gamuchirai munhu wese kuti auye kuzova neruzivo rwakadzama rwehunyanzvi hwekunzwisisa kwechigadzirwa.
