Iyo yakakura sei unit yekufambisa ruzivo paInternet yakava 1500 bytes

Ethernet iri kwese kwese, uye makumi ezviuru zvevagadziri vanogadzira michina inoitsigira. Nekudaro, zvinenge zvese izvi zvishandiso zvine chinhu chimwe chakafanana - MUNHU:

$ 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 (Maximum Transmission Unit) inotsanangura hukuru hwehukuru hwepaketi imwe chete yedata. Kazhinji, kana iwe uchitsinhanisa mameseji nemidziyo paLAN yako, iyo MTU ichave iri pahurongwa hwe1500 bytes, uye inenge Internet yese inoshanda pamabhayiti 1500. Zvisinei, izvi hazvirevi kuti aya matekinoroji ekukurukurirana haakwanise kutumira hukuru hwepaketi.

Semuenzaniso, 802.11 (inowanzozivikanwa seWiFi) ine MTU ye2304 bytes, uye kana network yako ichishandisa FDDI, ipapo MTU yako i4352 bytes. Ethernet pachayo ine pfungwa ye "giant frames", apo MTU inogona kugoverwa saizi inosvika 9000 bytes (nerutsigiro rweiyi modhi neNICs, switch uye routers).

Zvisinei, paInternet izvi hazvisi kunyanya kudiwa. Sezvo mabhesi makuru eInternet achinyanya kugadzirwa neEthernet yekubatanidza, iyo de facto unofficial yakakura saizi yepakiti yakaiswa ku1500B kudzivirira kupatsanurwa kwepaketi pane zvimwe zvishandiso.

Nhamba 1500 pachayo inoshamisa - munhu angatarisira kuti zvinogara munyika yekombuta zvichange zvichibva pamasimba maviri, semuenzaniso. Saka 1500B yakabva kupi uye nei tichiri kuishandisa?

Nhamba yemashiripiti

Kubudirira kukuru kweEthernet kwekutanga munyika kwakauya nenzira yezviyero. 10BASE-2 (mutete) uye 10BASE-5 (yakakora), nhamba dzinoratidza kuti mangani mazana emamita chikamu chetiweki chinogona kuvhara.

Sezvo pakanga paine akawanda aikwikwidza maprotocol panguva iyoyo, uye Hardware yaive nezvaisingakwanisi, mugadziri wefomati anobvuma kuti zvinodiwa zvekurangarira zvepacket buffer zvakabata basa mukubuda kwenhamba yemashiripiti 1500:

Tichitarisa kumashure, zviri pachena kuti yakakura yaigona kunge iri mhinduro iri nani, asi dai tainge tawedzera mutengo weNICs kutanga, ingadai yakadzivirira Ethernet kubva pakupararira.

Zvisinei, iyi haisi nyaya yacho yose. IN work "Ethernet: Distributed Packet Switching in Local Computer Networks," 1980, inopa imwe yekuongorora kwekutanga kwekubudirira kwekushandisa mapaketi makuru mumambure. Panguva iyoyo, izvi zvainyanya kukosha kune Ethernet network, sezvo vaigona kubatanidza masisitimu ese netambo imwe chete coaxial, kana kuve nemahubs anokwanisa kutumira pakiti imwe kune ese manode pane imwechete segment panguva imwe.

Zvakanga zvakafanira kusarudza nhamba yaisazokonzera kunonoka kwakanyanya pakutumira mameseji muzvikamu (dzimwe nguva zvakabatikana), uye panguva imwechete yaisazowedzera huwandu hwemapaketi zvakanyanya.

Sezviri pachena, mainjiniya panguva iyoyo vakasarudza nhamba 1500 B (inenge 12000 bits) seyakanyanya "yakachengeteka" sarudzo.

Kubva ipapo, mamwe maitiro akasiyana-siyana ekutumira mameseji akauya uye aenda, asi pakati pawo, Ethernet yaive neMTU yakaderera kukosha neBytes yayo 1500. Kupfuura huwandu hweMTU hukoshi mumambure zvinoreva kukonzeresa kupatsanurwa kwepakiti kana kuita PMTUD [kuwana iyo yakakura saizi yepakiti. yenzira yakasarudzwa]. Zvose zviri zviviri zvakanga zvine matambudziko azvo. Kunyangwe dzimwe nguva hombe OS vagadziri vakadzikisa kukosha kweMTU kunyangwe kuderera.

Efficiency factor

Isu tave kuziva kuti iyo Internet MTU inogumira ku1500B, zvakanyanya nekuda kwenhaka latency metrics uye zvisingakwanisi. Izvi zvinokanganisa sei kushanda kweInternet?

Kana tikatarisa data kubva kune yakakura Internet exchange point AMS-IX, tinoona kuti ingangoita 20% yemapaketi anotumirwa ane saizi yakakura. Iwe unogona zvakare kutarisa iyo yakazara LAN traffic:

Kana iwe ukabatanidza magirafu ese, unowana chimwe chinhu senge chinotevera (kufungidzira kwetraffic kune yega yega saizi yepakiti renji):

Kana, kana tikatarisa traffic yeiyi misoro yese uye rumwe ruzivo rwesevhisi, tinowana iyo yakafanana girafu ine chiyero chakasiyana:

Chikamu chikuru che bandwidth chinopedzerwa pamisoro yemapaketi mukirasi yakakura saizi. Sezvo iyo yepamusoro yepamusoro pakakwirira traffic iri 246 GB/s, zvinogona kufungidzirwa kuti dai isu tese takachinjisa ku "jumbo mafuremu" kana sarudzo yakadaro ichiripo, iyi yepamusoro ingangove ingangoita 41 GB/s.

Asi ndinofunga nhasi kune chikamu chikuru cheInternet icho chitima chakatosiya. Uye kunyangwe vamwe vapeji vachishanda neMTU ye9000, vazhinji havaitsigire, uye kuedza kushandura chimwe chinhu pasi rose paInternet kwakaratidza kuve kwakaoma zvakanyanya kakawanda.

Source: www.habr.com