0बीटी इन्फिनिटी के लिए वान MTU अनुकूलन

मेरी बीटी SmartHub से एक pfSense रूटर से स्विच करने के बाद मैं कुछ मामूली पेश आने वाली समस्याओं लिया है. One of which has been the squid proxy ser­vice caus­ing a prob­lem where I can­’t access the BBC web­site with an error. जबकि मैं अंत में एक से थोड़ा अजीब विधि के माध्यम से इसे ठीक किया, मैं इस समस्या का संभावित स्रोत जो अपने आप पर फिक्सिंग के लायक था का सामना करना पड़ा

When I turned squid off I was imme­di­ately able to access the BBC web­site, but with it turned on I con­sist­ent received an error from squid that there had been a “Zero Sized Reply”. यह व्यंग्य लग रहा था बीबीसी से कोई जवाब प्राप्त करने में असमर्थ था. One pos­sible cause of this could be frag­men­ted pack­ets being dropped, and the cause of frag­ment­a­tion is nor­mally MTU size.

The default MTU for Eth­er­net is 1500 and most mod­ern oper­at­ing sys­tems man­age things on the LAN auto­mat­ic­ally. It is pos­sible to use sizes up to 9000 to increase through­put (थोड़ा) लैन के लिए. कैसे कभी, this was of less interest to me than mak­ing sure pack­ets wer­en’t get­ting frag­men­ted mul­tiple times, or being frag­men­ted after leav­ing the router.

pfSense के साथ वान MTU डिफ़ॉल्ट करने के लिए सेट (1500) I tried some pinging from win­dows to see what the max­im­um size was without frag­ment­a­tion. The com­mand to use is ping google.com -f -l 1500, chan­ging the last num­ber to find the optim­um. My BT Infin­ity con­nec­tion uses PPPoE which typ­ic­ally has a max­im­um value of 1492 (यह वास्तव में सच में PPPoA उपयोग कर सकते हैं के रूप में PPPoE pfSense के लिए जो मेरे पाट मॉडेम पेश कर सकते हैं, dif­fer­ent sources say dif­fer­ent things about this), and when using ping it is neces­sary to take into account some over­head which has a value of 28, so I was expect­ing a ping MTU of 1464 सबसे बड़ा मैं इस्तेमाल कर सकते हैं होने के लिए. To my sur­prise this still res­ul­ted in frag­ment­a­tion and I even­tu­ally found the max­im­um I could use was 1456.

मैं इस मान का उपयोग किया (साथ 28 पीठ पर जोड़ा) की एक MTU मान सेट करने के 1484 में वान inter­face set­tings of pfsense. Now the only frag­ment­a­tion should be done by the router to LAN pack­ets, with no risk of any later frag­ment­a­tion from a router some­where between me and any par­tic­u­lar web­site. After clear­ing my browser cache and the squid cache I was then able to load the BBC web­site suc­cess­fully. I sus­pect the issue was caused by a router black­hol­ing issue some­where between my आईएसपी and the BBC serv­ers which was drop­ping the frag­men­ted pack­ets. A nice descrip­tion of the phe­nomen­on can be found on RCL के ब्लॉग