Date: Sat, 19 Oct 2002 21:17:28 +0200 From: Marco van Tol <bsd-mobile@tols.org> To: freebsd-mobile@FreeBSD.ORG Subject: Re: 100 Mbit/s is (a lot) slower than 10 Mbit/s Message-ID: <20021019211728.B55151@tols.org> In-Reply-To: <20021019210804P.hanche@math.ntnu.no>; from hanche@math.ntnu.no on Sat, Oct 19, 2002 at 09:08:04PM %2B0200 References: <20021019210804P.hanche@math.ntnu.no>
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On Sat, Oct 19, 2002 at 09:08:04PM +0200, Harald Hanche-Olsen wrote: > I have a Linksys ethernet card in my laptop. It can to 10 or 100 > Mbit/s. But when it's in 100 Mbit/s mode, transfers into the laptop > are lots slower than at 10 Mbit/s, at least as long as the sender is > on the same local net and has a 100 Mbit/s interface. > > The reason is obvious enough: Snooping on the ethernet traffic reveals > that packets are lost, with frequent timeouts and waits for > retransmissions as a result. The timeouts are easily visible by > watching the blinkenlights on the dongle. I am assuming this is a > result of the Linksys' puny buffer being overrun, perhaps due to the > bandwidth from the PCMCIA slot to the CPU not being big enough to > cope. > > So why don't I just use 10 Mbit/s then? Well, at home that is what I > do, since I can tell my stationary PC to run its interface at 10 > Mbit/s, and the Linksys will automatically follow suit. But at work > we recently upgraded our network to 100 Mbit/s, and hence the > difficulty: The ed driver has no provision (it seems) for setting the > speed. (Maybe there is no way to ask the card to pick the lower > speed.) > > Could anyone suggest a reasonable workaround? I though maybe I could > set some kernel variables to make the window size in TCP smaller and > hence stop the buffer overrun from happening so often, but I am not > sure what knob to twiddle or even if there is one. (Yes, recompiling > the kernel is okay, too.) > > Is this a common problem? I don't see a lot of complaints about it on > the list. Maybe it's just the card that's crappy, and I should get > another one? FWIW, the card calls itself an EtherFast (ha!) 10/100 PC > Card. I got it back in 1999 because it was cheap, so I have got > enough use out of it and won't be unduly upset if I need to scrap it. Hi, perhaps this response is absolutely worthless, in which case I'd like to ask you to silently ignore it. But: if your ethernet card is connected to a switch, as opposed to a hub, did you check the duplex settings? I know from personal experience that if your duplex settings don't match on both the network card and the switch, packet loss will occur. If you did, pretend I never sent this e-mail. ;-) > - Harald > > PS. If the ethernet cable or dongle is disconnected for any reason, > the laptop hangs until I lean on the power button. Very annoying. Can't comment on this one. Sorry. :( -- Marco van Tol [mailto:bsd-mobile@tols.org] [http://www.tols.org] To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-mobile" in the body of the message
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