Iyunithi ephezulu yokuhanjiswa kolwazi kwi-Intanethi yaba yi-1500 bytes

I-Ethernet ikuyo yonke indawo, kwaye amashumi amawaka abavelisi bavelisa izixhobo eziyixhasayo. Nangona kunjalo, phantse zonke ezi zixhobo zinento enye efanayo - UMNTU:

$ 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

I-MTU (iYunithi yoThutho oluPhezulu) ichaza ubungakanani bobungakanani bepakethi yedatha enye. Ngokubanzi, xa utshintshiselana ngemiyalezo ngezixhobo kwi-LAN yakho, i-MTU iya kuba ngokomyalelo we-1500 bytes, kwaye phantse yonke i-Intanethi isebenza kwi-1500 bytes.

Umzekelo, i-802.11 (eyaziwa njenge-WiFi) ine-MTU ye-2304 bytes, kwaye ukuba inethiwekhi yakho isebenzisa i-FDDI, i-MTU yakho yi-4352 bytes. I-Ethernet ngokwayo inombono othi "izakhelo ezinkulu", apho i-MTU inokwabelwa ubukhulu obufikelela kwi-9000 bytes (ngenkxaso yale modi nge-NICs, ii-switchers kunye ne-routers).

Nangona kunjalo, kwi-Intanethi oku akuyomfuneko ngokukodwa. Kuba i-backbones eziphambili ze-Intanethi zenziwe ngokuyintloko ngoqhagamshelo lwe-Ethernet, ubukhulu bepakethi obungekho semthethweni bubekwe kwi-1500B ukunqanda ukuqhekeka kwepakethi kwezinye izixhobo.

Inani le-1500 ngokwalo liyamangalisa - umntu unokulindela ukuba izinto eziqhubekayo kwihlabathi lekhompyuter zisekelwe kumagunya amabini, umzekelo. Ngoko i-1500B ivela phi kwaye kutheni sisayisebenzisa?

Inombolo yomlingo

Impumelelo yokuqala enkulu ye-Ethernet emhlabeni yeza ngohlobo lwemigangatho. 10BASE-2 (ebhityile) kwaye 10BASE-5 (engqindilili), amanani abonisa ukuba mangaphi amakhulu eemitha icandelo lothungelwano elithile elinokufikelela kuwo.

Kuba zazininzi iiprothokholi ezikhuphisanayo ngelo xesha, kwaye ihardware yayinemida yayo, umenzi wefomathi uyavuma ukuba iimfuno zememori zepakethe buffer zidlale indima ekuveleni kwenombolo yomlingo 1500:

Xa sijonga emva, kucacile ukuba ubuninzi obungaphezulu bunokuba sisisombululo esingcono, kodwa ukuba besinyuse ixabiso le-NICs kwangethuba, ngeyithintele i-Ethernet ekubeni isasazeke.

Nangona kunjalo, eli ayililo lonke ibali. IN работе "I-Ethernet: Ukutshintshwa kwePakethi esasazwayo kwiiNethiwekhi zeKhompyutha zeNgingqi," i-1980, inika enye yohlalutyo lokuqala lokuphumelela kokusebenzisa iipakethi ezinkulu kwiinethiwekhi. Ngelo xesha, oku kwakubaluleke kakhulu kuthungelwano lwe-Ethernet, kuba babenokudibanisa zonke iinkqubo ngentambo enye ye-coaxial, okanye ziquka ii-hubs ezikwazi ukuthumela ipakethe enye kuzo zonke iindawo ezikwicandelo elinye ngexesha elinye.

Kwakuyimfuneko ukukhetha inani elingayi kubangela ukulibaziseka okuphezulu kakhulu xa uthumela imiyalezo kumacandelo (ngamanye amaxesha axakeke kakhulu), kwaye kwangaxeshanye angeke anyuse inani leepakethi kakhulu.

Kubonakala ukuba, iinjineli ngelo xesha zakhetha inombolo ye-1500 B (malunga ne-12000 bits) njengeyona ndlela "ekhuselekileyo".

Ukusukela ngoko, ezinye iinkqubo ezahlukeneyo zokuthumela imiyalezo zifikile kwaye zahamba, kodwa phakathi kwazo, i-Ethernet yayinexabiso eliphantsi le-MTU kunye ne-1500 Bytes yayo Ukugqithisa ixabiso eliphantsi le-MTU kuthungelwano kuthetha ukuba kubangele ukuqhekeka kwepakethi okanye ukuzibandakanya kwi-PMTUD [ukufumana ubukhulu bepakethe ephezulu. kwindlela ekhethiweyo]. Zombini iinketho zazineengxaki zazo ezikhethekileyo. Nokuba ngamanye amaxesha abavelisi abakhulu be-OS bathoba ixabiso le-MTU nangaphantsi.

Factor Ukusebenza

Ngoku siyazi ukuba i-Intanethi ye-MTU inqunyelwe kwi-1500B, ubukhulu becala ngenxa yeemetriki ze-latency latency kunye nokunciphisa i-hardware. Ingaba oku kukuchaphazela kangakanani ukusebenza kakuhle kwe-Intanethi?

Ukuba sibheka idatha evela kwindawo enkulu yokutshintshiselana nge-Intanethi ye-AMS-IX, sibona ukuba ubuncinane i-20% yeepakethi ezithunyelwayo zinobukhulu obukhulu. Unokujonga kwakhona kwi-trafiki ye-LAN iyonke:

Ukuba udibanisa zombini iigrafu, ufumana into efana nale ilandelayo (uqikelelo lwezithuthi kuluhlu lobungakanani bepakethi nganye):

Okanye, ukuba sijonga i-traffic yazo zonke ezi zihloko kunye nolunye ulwazi lwenkonzo, sifumana igrafu efanayo kunye nesikali esahlukileyo:

Inxalenye enkulu ye-bandwidth ichithwa kwiiheader zeepakethi kwiklasi enkulu yobukhulu. Ekubeni i-overhead ephezulu kwi-peak traffic yi-246 GB / s, kunokucingelwa ukuba sonke sitshintshele kwi-"jumbo frames" xa ukhetho olunjalo lusekho, olu luhlu luza kuba malunga ne-41 GB / s.

Kodwa ndicinga ukuba namhlanje kweyona nxalenye inkulu ye-Intanethi uloliwe sele ehambile. Kwaye nangona abanye ababoneleli besebenza kunye ne-MTU ye-9000, abaninzi abayixhasi, kwaye ukuzama ukutshintsha into kwihlabathi jikelele kwi-Intanethi kuye kwabonakala kunzima kakhulu kwaye kwakhona.

umthombo: www.habr.com