Date: Sun, 28 Nov 1999 04:49:30 +1100 From: death <death@southcom.com.au> To: "Erik Stainsby" <stainsby@lets.net> Cc: <freebsd-questions@FreeBSD.ORG> Subject: Re: pppd, mtu, lag, and icmp "need to frag" packets Message-ID: <4.2.1.19991128044007.0181deb0@mail.southcom.com.au> In-Reply-To: <000901bf38fc$128fef00$339fefcc@vpl.vancouver.bc.ca> References: <4.2.1.19991128030900.00a9f380@mail.southcom.com.au>
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At 09:23 AM 27/11/1999 -0800, you wrote: >This wreaks of M$ F.U.D. This wreaks of Anti-M$ F.U.D. >o The calm reasoned asides that insist M$ product has no problem. Err. It doesn't. If you read you'd notice that the lag appears on the FreeBSD machine too. I suppose i should've mentioned that it's lagged even without using the windows machine at all. Even with it disconnected. >o The technical pitch being -just- that much beyond what joe consumer >might understand. The technical pitch is based totally on what my problem is. I can't go any more or less technical. >o The fact that the essence of the issue in debate is a few >milliseconds of performance Incorrect. We're talking almost thousands here, and that can make a HELL of a lot of difference. > ~~ and this being cast in the context of >IRC and telnet ~~ is pitched at a trivial home-user frame of mind. So? What's wrong with running FreeBSD at home as a gateway? I need a stable machine for my internet. Don't know how much it costs for YOU to make a local phone call, but for me it's $0.25. >o Even the lame dramatic wannabe nickname (death) is calculated to >identify the message as coming from a 'power user'. The nickname is my nickname IRL - i've had it for about 4 years. Interpret it to your own limitations - but it simply means that i LOOK like death. Pale as death and in black. Cheers >----- Original Message ----- >From: death <death@southcom.com.au> >To: <freebsd-questions@FreeBSD.ORG> >Sent: Saturday, November 27, 1999 9:04 AM >Subject: pppd, mtu, lag, and icmp "need to frag" packets > > > > > > Hi, > > > > I'm having a major problem trying to defeat lag over my 56k modem > > connection with FreeBSD.. Once upon a time when i was using Windows >98 it > > was as simple as downloading a program, clicking 'optimize', and >voila, > > it's now about 5 times as smooth/lagless as i've ever managed to get >FreeBSD. > > > > I'm running 3.3-STABLE on a p166, 32MB ram, 1GB HDD. Connected to >that, via > > a 'pppd' serial link, is a Windows 2000 machine. Both serial ports >are at > > 115,200bps. The MTU/MRU setting in both ppp and pppd are 576 (which >causes > > a problem for pppd which i'll discuss soon). > > > > Is there any way, apart from setting the MTU and MRU values in 'ppp' >(i've > > set them to 576 - which seems to be a common, good number) - to >decrease > > lag? When receiving data, lag rises to about 600-1000ms. When >sending data, > > lag goes through the roof at ~1750ms. > > > > And strangely, when running cvsup, and even when it's only >downloading, the > > lag is launched into orbit and sits at 2500ms MINIMUM. I thought >that it > > might've been CPU usage doing this. A quick check reveals ~95% idle. > > > > This lag is present on both computers btw. > > > > So, any advice to lower this lag? Yes, i know 56k modems are slow, >but it's > > still very possible to kill lag with say telnet and IRC, whilst i'm > > downloading via ftp at 5KB/s. I know i'm not going to get more than >5KB/s, > > i just want IRC and telnet to run smoother. I've done it with >Windows 98 - > > even downloading 5 things at a time had no affect on anything else. > > > > > > Also, when the MTU of ppp0 is 576, FreeBSD keeps sending icmp "need >to > > frag" packets to whatever sent me a packet that was supposedly too >big. > > Here's a snippet from tcpdump: > > > > 00:47:52.999475 203.102.135.200.80 > 192.168.1.2.1142: P 1:645(644) >ack 326 > > win 32120 (DF) (ttl 58, id 37803) > > 00:47:52.999753 210.84.240.102 > 203.102.135.200: icmp: 192.168.1.2 > > unreachable - need to frag (mtu 576) (DF) (ttl 255, id 51301) > > 00:47:53.089502 203.102.135.200.80 > 192.168.1.2.1141: P 1:610(609) >ack 322 > > win 32120 (DF) (ttl 58, id 37804) > > 00:47:53.089700 210.84.240.102 > 203.102.135.200: icmp: 192.168.1.2 > > unreachable - need to frag (mtu 576) (DF) (ttl 255, id 51302) > > > > > > How do the packets get 644 or 609 bytes long? The MTU on tun0 is >576. > > > > Can't FreeBSD just fragment the packets and pass them through? I've >looked > > everywhere for an option on this but to no avail.. > > > > BTW just a few configuration notes, i hope i cover them all: > > > > * i'm running ppp as 'ppp -nat'. i've only got one IP (which in the >above > > example is 210.84.240.102) > > * ipfw is up and running, although it's only denying port 21, 23, >and 25, > > and diverting port 113 to natd which then passes it on the windows >machine. > > * 192.168.1.1 == freebsd.. 192.168.1.2 == windows. > > * the icmp frag packets don't appear on ppp0 at all when i use >tcpdump. so > > i'm assuming that FreeBSD is creating them. > > > > > > I'm forced to change the MTU to 1500 which doesn't give me any of >those > > frag errors. Considering that i'm only linked to FreeBSD via a >115,200bps > > serial cable, it's important that i get rid of lag on ppp0 too - >which i > > was hoping i could do by setting the MTU down. It's only 12KB/s >after all. > > Not a 100Mbps NIC. > > > > > > Thanks in advance. > > > > Cheers > > > > Death > > > > > > > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > > with "unsubscribe freebsd-questions" in the body of the message > > > > > > >To Unsubscribe: send mail to majordomo@FreeBSD.org >with "unsubscribe freebsd-questions" in the body of the message To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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