Date: Tue, 11 Oct 2005 16:43:52 +0200 From: "Rehsack Jens \(ext\)" <jens.rehsack.ext@siemensvdo.com> To: "Tobias Roth" <roth@iam.unibe.ch> Cc: freebsd-mobile@freebsd.org Subject: RE: Help needed: cannot send packets larger 230 bytes via vodafone umts Message-ID: <CE3682EF98A64140B2BF376C39461E0A02FA6C@krbdf7ma.ww011.siemens.net>
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-----Original Message----- From: Tobias Roth [mailto:roth@iam.unibe.ch]=20 Sent: Tuesday, October 11, 2005 4:16 PM To: Rehsack Jens (ext) Cc: freebsd-mobile@freebsd.org Subject: Re: Help needed: cannot send packets larger 230 bytes via vodafone umts > On Tue, Oct 11, 2005 at 02:19:42PM +0200, Rehsack Jens (ext) wrote: > > > >=20 > > > > I started some diagnostics why my web wont work, and detected > > > > that packets larger than 229 byte payload via ping will swallowed > > > > by the connection (I don't know where). > > >=20 > > > Did you try traceroute with a packetlength larger than your 229 bytes > > > to see where the packets get dropped and for what reason? > > >=20 > > > greets, t. > >=20 > > Now I did ;) > >=20 > > And horribly I had to see, that traceroute seems to transport even > > larger packets an get's the wanted answers. I also tried after that > > shock >traceroute -P TCP< and seen, that it works, too. >=20 > Initially, my theory was that you have a problem with pathMTU, but I > am not so sure anymore. If pathMTU is broken, telnetting to port 80 > won't work, since the packets sent have the DF bit set and thus cannot > be fragmented. When tracerouting with udp or tcp, they don't have that > bit set, so they get fragmented and things work. >=20 > However, this does not explain why your icmp pings don't get through > if larger than 229 bytes. >=20 > One last idea: You may try to lower the mtu of your ppp interface > with ifconfig down to 229 and see if telnet then works. If so, you > might have an mtu problem after all, if not, something else is rotten. >=20 > good luck, t. setting net.inet.tcp.path_mtu_discovery=3D0 didn't change anything, but # ifconfig tun0 mtu 200 changes something. Now the DNS lookup wont work anymore, but I get response from my webserver. It's really slow, but it is there ;) And MTU 230 works both - dns & web. Now I think it could be time to look how to speed up the thing ;)
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