Date: Wed, 11 Jul 2007 14:40:47 +0200 From: "Heiko Wundram (Beenic)" <wundram@beenic.net> To: freebsd-questions@freebsd.org Subject: Re: Some hosting weirdness... Message-ID: <200707111440.47637.wundram@beenic.net> In-Reply-To: <AF5B51BD-997A-45AE-84C6-41B2D1798632@secure-computing.net> References: <AF5B51BD-997A-45AE-84C6-41B2D1798632@secure-computing.net>
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On Wednesday 11 July 2007 14:19:09 Eric F Crist wrote: > <snip> > What should I look for? Is there possibly some weird caching issues > at their ISPs? How can I fix this? Do a tcpdump when someone connects from their network and check for TCP-MSS= =20 issues, which would be my first guess when small files/items load fine over= =20 HTTP but items larger than a single TCP-packet won't (which basically fits= =20 the symptoms you describe). As some ISPs will do IP fragmentation when a packet too large to fit over t= he=20 downlink to a customer arrives, you'll not see this problem with these. Tho= se=20 ISPs that don't do IP fragmentation on the downlink (quite a few) generally= =20 should send out an ICMP-message with a "Fragmentation needed" error (which= =20 appears in the tcpdump), but some don't do that either. Generally, the MSS in their SYN-packet when connecting to your webserver=20 should be below 1460; most probably at 1452 (which is DSL and cable AFAIK),= =20 or more generally speaking (their) MTU-40, and the _IP_ packet size your ho= st=20 sends back should always be equal to or below the minimum of your MSS (whic= h=20 is sent in the SYN/ACK packet) and their MSS, plus 40. If this is not the=20 case, you have an issue. =2D-=20 Heiko Wundram Product & Application Development =2D------------------------------------ Office Germany - EXPO PARK HANNOVER =20 Beenic Networks GmbH Mail=E4nder Stra=DFe 2 30539 Hannover =20 =46on +49 511 / 590 935 - 15 =46ax +49 511 / 590 935 - 29 Mail wundram@beenic.net Beenic Networks GmbH =2D------------------------------------ Sitz der Gesellschaft: Hannover Gesch=E4ftsf=FChrer: Jorge Delgado Registernummer: HRB 61869 Registergericht: Amtsgericht Hannover
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