Ingabe i-MTU ye-VPN encane iyahesha? Qhathanisa ubufakazi bangempela
I-MTU ephansi ingagwema umkhawulo wendlela futhi isabize umthamo. Qhathanisa umkhawulo wangempela, izindleko zezinhloko kanye nomthwalo womsebenzi ngaphambi kokugcina ushintsho.
Ithuluzi lilahla ukudluliswa okukhulu kodwa livumela i-ping ukuba idlule, ngakho iseluleko sifika ngokushesha: yehlisa i-MTU. Ukulungiswa kwesinye isikhathi kuyasebenza, bese kusetshenziswa kuwo wonke amaphrofayili kuyo yonke inethiwekhi. Yilapho ukulungiswa okuqondiwe kuphenduka intela yaphakade yokusebenza. Ukuqhathanisa okufanele kwenziwe kuphakathi komkhawulo wangempela wendlela kanye nezindleko zokunciphisa iphakethe ngalinye ngaphansi kwayo.
Yini encipha ngempela lapho wehlisa i-MTU
Iphakethe ngalinye lithwala izinhloko ngaphambi kokuthwala idatha yakho. Emkhondweni we-Ethernet wamabhayithi angu-1500, i-IPv4 ne-TCP zisebenzisa amabhayithi angu-40 zishiye angu-1460 womthwalo; ukufakwa kunezela izinhloko zangaphandle ze-IP, UDP kanye nethuluzi phezulu, ngakho isabelomali sangaphakathi somthwalo sehla futhi. Ukwehlisa i-MTU yesikhombi kunciphisa leso sabelomali ngamabomu.
Izindleko zilingana nenani lamaphakethe, hhayi inani lamabhayithi. Ifayela elifanayo lihlukaniswe ngamaphakethe amaningi lidinga iziphazamiso ezengeziwe, izinqumo ezengeziwe zokuhlela kanye nokucutshungulwa okwengeziwe kwephakethe ngalinye kudivayisi ngayinye endleleni. Kwiseva ehlelayo esivele iseduze nomkhawulo wayo wamaphakethe ngomzuzwana, lokho ukwehlisa ijubane kwangempela hhayi iphutha lokuhlanganisa. Izindleko ziyabonakala ngisho nalapho ukudluliswa uqobo kuphumelela.
Yingakho i-MTU encane iyindlela yokugwema umkhawulo, hhayi ukwenza ngcono okuvamile. Ithenga ukuthembeka emkhondweni ongakwazi ukuthwala uhlaka olukhulu, futhi ikhokhisa izindleko ezengeziwe kuwo wonke iphakethe elingadingi ukuncishiswa.
Nini i-MTU encane iwukulungiswa okufanele
Uphawu lwakudala lucacile: ukuxhawula kwe-TCP kuqedwa, izimpendulo ezincane zifika, futhi ukulanda okukhulu kuyama noma kusethwe kabusha. I-ping enebhithi yokungahlukanisi ku-1472 bhayithi yehluleka kuyilapho i-ping yamabhayithi angu-1400 iphumelela, lokho kukhombisa umkhondo ongakwazi ukuthwala iphakethe elisayizi egcwele futhi ongaledlulisi umyalezo we-ICMP obungatshela umthumeli ukuba anciphise.
Ukutholakala kwe-MTU yomkhondo kuncike kuleyo miyalezo ye-ICMP yedinga lokuhlukanisa. Uma i-firewall iyilahla, umthumeli uqhubeka nokuzama iphakethe elikhulu futhi uxhumano lubonakala lulenga. Ukwehlisa i-MTU ohlangothini lwethuluzi kugwema ukuphindaphinda, futhi lokho kuwukulungiswa okusemthethweni kuleyo nethiwekhi.
Ubuchwepheshe bokufinyelela nabo babeka imikhawulo yabo: i-PPPoE ivamise ukuphela ku-1492, eminye imikhondo yeselula ne-DSL iphansi, futhi amathuluzi afakwe ngaphakathi akhipha izindleko kabili. Linganisa umkhondo wangempela esikhundleni sokukopisha inombolo encwadini yokuhola, futhi khumbula ukuthi i-IPv6 idinga okungenani amabhayithi angu-1280 e-MTU kukho konke ukuxhumana okuthwalayo, njengoba i-RFC 8200 icacisa.
Qhathanisa izilawuli ezintathu ngaphambi kokushintsha esisodwa
I-MTU, i-MSS nokuhlukanisa kuyizilawuli ezahlukene ezigabeni ezahlukene, futhi ukushintsha okungalungile kushiya uphawu endaweni yalo.
| Control | Layer | What it changes | Where it misleads |
|---|---|---|---|
| Interface MTU | IP link | Largest frame the interface will send | Penalizes every protocol, not just the one that failed |
| TCP MSS clamp | TCP | Segment size advertised in the handshake | Leaves UDP and QUIC untouched |
| DF and fragmentation | IP | Whether a router may split a packet | Can break path MTU discovery and security assumptions |
| Tunnel overhead | Encapsulation | Inner MTU after outer headers | Mismatch shows up only for large inner packets |
Ukukhawulela i-MSS kuvame ukuba ukulungiswa okungangeni ndlela, ngoba kuthinta i-TCP kuphela futhi kushiya isikhombi sikhululekile kwezinye izinto ezihambayo. I-MTU yesikhombi ephansi ibanzi futhi kulula ukucabanga ngayo, yingakho ijwayelekile kuma-router abasebenzisi, kodwa ikhokhisa iphrothokholi ngayinye inkinga yephrothokholi eyodwa.
Ukucisha ukuziphatha kokungahlukanisi kufihla uphawu ngokuvumela ukuhlukanisa, futhi ngokuvamile kwenza ukubambezeleka kube kubi nakakhulu ngenkathi kuphula impendulo ebiyothola usayizi ofanele. Gwema lokho njengokulungiswa okungunaphakade.
Linganisa ukushintshana esikhundleni senombolo eyodwa
Thola umkhawulo womkhondo ngesihloli sokungahlukanisi, qala phezulu futhi wehle kuze kufike impendulo:
ping -M do -s 1472 203.0.113.10
ping -M do -s 1400 203.0.113.10
tracepath 203.0.113.10Bese uqhathanisa umsebenzi wangempela kuzo zombili izilungiselelo: ukudluliswa kwefayela elifanayo, indawo yokugcina efanayo kanye nenethiwekhi efanayo. Bhala isikhathi sokuqeda nokudluliswa kabusha, isibonelo nge-nstat -az TcpRetransSegs, futhi ubheke i-CPU yedivayisi uma ithuluzi liphela ku-router encane. Ukuhlola umthamo okwenziwe okwesikhashana kungase kuphuthelwe ukuma okuvela kuphela ngemva kwamamegabhayithi ambalwa.
Izibali zamaphakethe zizokhula ngemva kokuncishiswa ngoba ukudluliswa okufanayo manje kusebenzisa amaphakethe amaningi. Lokho kulindelekile futhi akubona ubufakazi bomthamo ophakeme. Qhathanisa idatha yohlelo eqediwe, inani lokudluliswa kabusha kanye nokuphendula, hhayi izinga lamaphakethe kuphela.
Letha ushintsho ngezigaba futhi ulugcine lunomkhawulo
Bhala inani lokuqala, shintsha isilawuli esisodwa, futhi uphinde ukulinganisa ngaphambi kokwenza kwaba unaphakade. Uma ubufakazi bungabonisi nzuzo, buyisela inani langaphambili ngomyalo wesikhombi ofanayo owawusebenzisa ukuze ulisethe:
ip link set dev wg0 mtu 1420
ip link set dev wg0 mtu 1500Khawulela umphumela kunethiwekhi eyayiwudinga. Iphrofayili okufanele isebenze ku-Wi-Fi yehhotela, ku-hotspot yeselula kanye ne-LAN yasehhovisi akufanele izuze ifa inani eliphansi kakhulu elidingwa yinoma yikuphi kulokho, ngaphandle uma iklayenti ingakwazi ukuthola umkhondo.
Inani elifanele i-MTU enkulu kunazo zonke ephila emkhondweni, hhayi encane kunazo zonke eyenza uphawu lunyamalale. Bhala umkhondo, umphumela wesihloli kanye nokubuyisela emuva, futhi ubehlule ukulungiselela lapho inethiwekhi yokufinyelela ishintsha.