Date: Fri, 15 Dec 2000 16:43:48 +0100 From: Udo Erdelhoff <ue@nathan.ruhr.de> To: freebsd-net@FreeBSD.ORG Cc: Patrick Bihan-Faou <patrick@netzuno.com> Subject: Re: Strange fragmentation needed message Message-ID: <20001215164348.E85041@nathan.ruhr.de> In-Reply-To: <POEDLEGGIEKJJIOGHEJNCEPECDAA.patrick@netzuno.com>; from patrick@netzuno.com on Thu, Dec 14, 2000 at 09:54:33AM -0500 References: <POEDLEGGIEKJJIOGHEJNCEPECDAA.patrick@netzuno.com>
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Hi, On Thu, Dec 14, 2000 at 09:54:33AM -0500, Patrick Bihan-Faou wrote: > You probably need to use tcpmssd from the ports (net/tcpmssd) or use the > recently added tcpmss option of PPP for you ADSL link. no, that's not the cause of the problem and adding tcpmssd to the mix doesn't solve the problem. My normal setup includes tcpmssd and some filter rules in ppp and ipfw, I kicked them to eliminate some possible problem sources. AFAIK, tcpmssd is only needed for connections originating on boxes in your LAN. If the connection originates on the box with the ADSL line, the MSS will be correct. Anyway, this is a capture of an ftp session with tcpmssd: ] mybox.3176 > remote.21: P 38:53(15) ack 51 win 17424 (DF) [tos 0x10] The last part of the put command ] remote.20 > mybox.40699: S 2001469163:2001469163 (0) win 32120 <mss 1460,sackOK,timestamp 1248677 0,nop,wscale 0> (DF) Incoming connection from the remote box ] 16:00:53.325469 mybox.40699 > remote.20: S 2723319420:2723319420 (0) ack 2001469164 win 17520 <mss 1452> (DF) Reply: No, use mss 1452 ] remote.21 > mybox.3176: . ack 53 win 31944 (DF) ] remote.20 > mybox.40699: . ack 1 win 32120 (DF) ] remote.21 > mybox.3176: P 51:106(55) ack 53 win 31944 (DF) ] mybox.40699 > remote.20: P 1:1025(1024) ack 1 win 17520 (DF) [tos 0x8] ] mybox > mybox: icmp: mybox unreachable - need to frag (mtu 1480) ] mybox > mybox: icmp: mybox unreachable - need to frag (mtu 1480) And boom. > You can also look at http://renaud.waldura.com/doc/freebsd-pppoe/ which is a > good paper on your problem. If you can read German, take a look at my homepage, especially at the paper about using T-ISDN-DSL (the ADSL service I'm using) with FreeBSD, especially the chapters about the MSS/MTU problem and the integration of tcpmssd. /s/Udo -- "No boom today. Boom tomorrow. There's always a boom tomorrow" To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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