Sida cutubka ugu badan ee gudbinta macluumaadka ee internetka uu u noqday 1500 bytes

Ethernet waa meel walba, iyo tobanaan kun oo warshadeeyayaal ah ayaa soo saara qalab taageeraya. Si kastaba ha ahaatee, ku dhawaad ​​dhammaan qalabkan ayaa leh hal shay oo ay wadaagaan - QOFKA:

$ ip l
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 state UNKNOWN
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp5s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP 
    link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff

MTU (Utubta Gudbinta ugu badan) ayaa qeexaysa cabbirka ugu badan ee xirmo xogeed keliya. Guud ahaan, marka aad farriimaha ku kala beddesho aaladaha LAN-gaaga, MTU-gu waxa uu noqonayaa 1500 bytes, inta badan Internetku waxa uu ku shaqeeyaa 1500 bytes. Si kastaba ha ahaatee, tani macnaheedu maaha in tignoolajiyada isgaadhsiintu aanay gudbin karin cabbirro waaweyn.

Tusaale ahaan, 802.11 (oo loo yaqaan WiFi) wuxuu leeyahay MTU oo ah 2304 bytes, haddii shabakadaadu isticmaasho FDDI, markaa MTU-gaagu waa 4352 bytes. Ethernet lafteedu waxay leedahay fikradda "xeemooyinka waaweyn", halkaas oo MTU lagu meelayn karo cabbir gaaraya ilaa 9000 bytes (oo ay taageerayaan habkan NICs, furayaasha iyo router).

Si kastaba ha ahaatee, internetka tani maahan mid si gaar ah loo baahan yahay. Maadaama laf-dhabarta ugu weyn ee internetka ay ka kooban yihiin isku xirka Ethernet, cabbirka ugu badnaan ee baakidhka aan rasmiga ahayn ayaa loo dejiyay 1500B si looga fogaado kala qaybsanaanta baakooyinka aaladaha kale.

Nambarka 1500 laftiisa waa yaab - mid ayaa filan kara joogteynta adduunka kombuyuutarku inay ku saleysan yihiin awoodaha laba, tusaale ahaan. Haddaba xagee 1500B ka yimid maxaan wali u isticmaalnaa?

Lambarka sixirka

Horumarka weyn ee Ethernet ee ugu horreeya adduunka wuxuu ku yimid qaab heerar ah. 10BASE-2 (dhuuban) iyo 10BASE-5 (qararan), tirooyinka tilmaamaya inta boqollaal mitir ee qayb shabakad gaar ah ay dabooli karto.

Maaddaama ay jiraan borotokool badan oo tartamaya wakhtigaas, qalabkuna wuxuu lahaa xaddidaadkiisa, abuuraha qaabka ayaa qiray in shuruudaha xusuusta ee xirmooyinka xirmooyinka ay door ka ciyaaraan soo bixitaanka lambarka sixirka 1500:

Marka dib loo eego, way caddahay in ugu badnaan weyn laga yaabo inay ahayd xal wanaagsan, laakiin haddii aan kordhin lahayn qiimaha NICs goor hore, waxay ka hortagi lahayd Ethernet inuu noqdo mid baahsan.

Si kastaba ha ahaatee, tani maaha sheekada oo dhan. IN shaqada "Ethernet: Baakadaha Qaybsan ee Isku-xidhka Kombuyuutarrada Gudaha," 1980, wuxuu bixiyaa mid ka mid ah falanqaynta ugu horreeya ee waxtarka isticmaalka baakadaha waaweyn ee shabakadaha. Waqtigaas, tani waxay si gaar ah muhiim ugu ahayd shabakadaha Ethernet, maadaama ay ku xidhi karaan dhammaan nidaamyada oo leh hal fiilo coaxial ah, ama waxay ka kooban yihiin hub awood u leh inay u soo diraan hal baakidh dhammaan qanjidhada isla qaybta isku mid ah hal mar.

Waxay ahayd lagama maarmaan in la doorto tiro aan keeni doonin dib u dhac aad u sarreeya marka la gudbinayo farriimaha qaybaha (mararka qaarkood aad mashquul u ah), isla markaana aan kordhinayn tirada baakidhka aad u badan.

Sida muuqata, injineerada wakhtigaas waxay doorteen lambarka 1500 B (qiyaastii 12000 bits) ikhtiyaarka ugu "nabdoon".

Tan iyo markaas, nidaamyada kale ee fariimaha kala duwan ayaa yimid oo baxay, laakiin iyaga ka mid ah, Ethernet wuxuu lahaa qiimaha ugu hooseeya ee MTU oo leh 1500 Bytes. Ka gudubka qiimaha ugu yar ee MTU ee shabakada macnaheedu waa inuu keeno jajabinta baakadaha ama ku lug lahaanshaha PMTUD [helitaanka cabbirka ugu badan ee xirmada waddo la doortay]. Labada doorashoba waxay lahaayeen dhibaatooyin gaar ah oo iyaga u gaar ah. Xitaa haddii marmarka qaarkood shirkadaha waaweyn ee OS ay hoos u dhigeen qiimaha MTU xitaa ka hooseeya.

Qodobka waxtarka leh

Waxaan hadda ognahay in MTU-ga intarneetka uu ku kooban yahay 1500B, taasoo ay ugu wacan tahay cabbirada daahitaanka dhaxalka ah iyo xaddidnaanta qalabka. Intee in le'eg ayay tani saamaynaysaa waxtarka internetka?

Haddii aan eegno xogta laga helay barta sarrifka Internetka ee weyn AMS-IX, waxaan aragnaa in ugu yaraan 20% xirmooyinka la kala qaado ay leeyihiin cabbirka ugu badan. Waxa kale oo aad eegi kartaa wadarta guud ee taraafikada LAN:

Haddii aad isu geyso labada garaaf, waxaad heleysaa wax la mid ah kuwan soo socda (qiyaasaha taraafikada ee kala duwanaanshaha cabbirka xirmo kasta):

Ama, haddii aan eegno taraafikada dhammaan madaxyadan iyo macluumaadka kale ee adeegga, waxaan helnaa garaaf isku mid ah oo leh miisaan kala duwan:

Qayb weyn oo xajmiyeedka ayaa lagu kharash gareeyaa madaxyada xirmooyinka fasalka ugu weyn. Maadaama taraafikada ugu sarreysa ee taraafikada ugu sarreysa ay tahay 246 GB/s, waxaa loo qaadan karaa in haddii aan dhammaanteen u wareejin lahayn "jumbo frames" marka ikhtiyaarka noocan oo kale ah uu weli jiro, dusha sare waxay noqon doontaa oo keliya 41 GB/s.

Laakiin waxaan u maleynayaa maanta qaybta ugu weyn ee internetka ee tareenku mar hore ka tagay. In kasta oo bixiyeyaasha qaarkood ay la shaqeeyaan MTU ee 9000, badankoodu ma taageeraan, oo isku dayga in ay wax ka beddelaan wax caalami ah oo internetka ah ayaa la caddeeyay inay aad u adag tahay marar badan.

Source: www.habr.com