Aia ʻo Ethernet ma nā wahi āpau, a hana nā ʻumi kaukani o nā mea hana i nā lako e kākoʻo iā ia. Eia naʻe, ʻaneʻane hoʻokahi mea like o kēia mau mea hana - :
$ 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) e wehewehe i ka nui o ka nui o ka waihona ʻikepili hoʻokahi. Ma keʻano laulā, ke hoʻololi nei ʻoe i nā memo me nā polokalamu ma kāu LAN, aia ka MTU ma ke kauoha o 1500 bytes, a kokoke i ka pūnaewele holoʻokoʻa e hana pū ana ma 1500 bytes. Akā naʻe, ʻaʻole ia he manaʻo ʻaʻole hiki i kēia mau ʻenehana kamaʻilio ke hoʻouna i nā nui packet nui aʻe. .
No ka laʻana, 802.11 (ʻike mau ʻia ʻo WiFi) he MTU o 2304 paita, a inā hoʻohana kāu pūnaewele i FDDI, a laila ʻo kāu MTU he 4352 paita. Loaʻa iā Ethernet ka manaʻo o "nā papa nunui", kahi e hiki ai i ka MTU ke hāʻawi i ka nui a hiki i 9000 bytes (me ke kākoʻo no kēia ʻano e nā NIC, nā hoʻololi a me nā mea ala).
Eia naʻe, ma ka Pūnaewele ʻaʻole pono kēia. No ka mea, ʻo nā iwi kuamoʻo nui o ka Pūnaewele i hana ʻia me nā pilina Ethernet, ua hoʻonohonoho ʻia ka nui o ka ʻeke kiʻekiʻe de facto unofficial i 1500B e pale aku i ka ʻāpana packet ma nā mea ʻē aʻe.
He mea ʻē ka helu 1500 ponoʻī - manaʻo kekahi e hoʻokumu ʻia nā mea mau i ka honua kamepiula ma luna o nā mana ʻelua, no ka laʻana. No laila mai hea mai ka 1500B a no ke aha mākou e hoʻohana mau ai?
helu kupua
ʻO ka holomua nui mua o Ethernet i ka honua i hele mai ma ke ʻano o nā kūlana. ( lahilahi) a (ka mānoanoa), nā helu e hōʻike ai i ka nui o nā haneli mika e hiki ke uhi ʻia i kahi ʻāpana pūnaewele.
Ma muli o ka nui o nā protocols hoʻokūkū i kēlā manawa, a ua loaʻa i ka hāmeʻa kona mau palena, ua ʻae ka mea nāna i hana i ke ʻano o ka hoʻomanaʻo ʻana o ka packet buffer i hana i ka puka ʻana o ka helu kilokilo 1500:
I ka ʻike ʻana, ʻike maopopo ʻia paha he hopena ʻoi aku ka nui o ka nui, akā inā mākou i hoʻonui i ke kumukūʻai o nā NIC i ka wā ma mua, ua pale ʻia ʻo Ethernet mai ka laha ʻana.
Akā naʻe, ʻaʻole kēia ka moʻolelo holoʻokoʻa. IN "Ethernet: Distributed Packet Switching in Local Computer Networks," 1980, hāʻawi i kekahi o nā loiloi mua loa o ka pono o ka hoʻohana ʻana i nā ʻeke nui ma nā pūnaewele. I kēlā manawa, he mea koʻikoʻi kēia no nā ʻupena Ethernet, no ka mea hiki iā lākou ke hoʻohui i nā ʻōnaehana āpau me kahi kaula coaxial hoʻokahi, a i ʻole nā hubs hiki ke hoʻouna i hoʻokahi ʻeke i nā node āpau ma ka ʻāpana like i ka manawa hoʻokahi.
Pono e koho i kahi helu e hiki ʻole ai ke hoʻolōʻihi i ka wā e hoʻouna ai i nā leka i nā ʻāpana (i kekahi manawa paʻa loa), a i ka manawa like ʻaʻole e hoʻonui nui i ka helu o nā ʻeke.
ʻIke ʻia, koho nā ʻenekinia i kēlā manawa i ka helu 1500 B (ma kahi o 12000 bits) ʻo ia ka koho "palekana".
Mai ia manawa, ua hele mai a hala nā ʻōnaehana memo ʻē aʻe, akā i waena o lākou, ua loaʻa iā Ethernet ka waiwai MTU haʻahaʻa loa me kāna 1500 Bytes. no ke ala i koho ʻia]. Ua loaʻa i nā koho ʻelua ko lākou mau pilikia kūikawā. ʻOiai i kekahi manawa ua hoʻohaʻahaʻa nā mea hana OS nui i ka waiwai MTU i lalo.
Kumu Hoʻokō
Ua ʻike mākou i kēia manawa ua kaupalena ʻia ka Internet MTU i 1500B, ma muli o nā metric latency hoʻoilina a me nā palena o ka lako. Pehea ka hopena o kēia i ka pono o ka Pūnaewele?
Inā mākou e nānā i ka ʻikepili mai kahi wahi hoʻololi pūnaewele nui ʻo AMS-IX, ʻike mākou aia ma ka liʻiliʻi he 20% o nā ʻeke i hoʻouna ʻia ka nui loa. Hiki iā ʻoe ke nānā i ka huina o ka huakaʻi LAN:
Inā hoʻohui ʻoe i nā kiʻi ʻelua, loaʻa iā ʻoe kekahi mea e like me kēia (nā kuhi kaʻahele no kēlā me kēia pae nui):
A i ʻole, inā mākou e nānā i ke kaʻa o kēia mau poʻomanaʻo a me nā ʻike lawelawe ʻē aʻe, loaʻa iā mākou ka pakuhi like me kahi ʻano ʻokoʻa:
Hoʻohana ʻia ka hapa nui o ka bandwidth ma nā poʻo no nā ʻeke i ka papa nui loa. No ka mea ʻo 246 GB/s ka piʻi kiʻekiʻe ma luna o ke kaʻa, hiki ke manaʻo ʻia inā ua hoʻololi mākou a pau i nā "jumbo frames" i ka wā i loaʻa ai kēlā koho, ʻo kēia overhead ma kahi o 41 GB/s wale nō.
Akā, ke manaʻo nei au i kēia lā no ka hapa nui loa o ka Pūnaewele i haʻalele mua ke kaʻaahi. A ʻoiai ke hana nei kekahi mau mea hoʻolako me kahi MTU o 9000, ʻaʻole kākoʻo ka hapa nui iā ia, a ʻo ka hoʻāʻo ʻana e hoʻololi i kekahi mea ma ke ao holoʻokoʻa ma ka Pūnaewele ua hōʻike ʻia he paʻakikī loa.
Source: www.habr.com