Date: Thu, 22 Feb 1996 20:43:28 -0800 From: David Greenman <davidg@Root.COM> To: Stephen Hovey <shovey@buffnet.net> Cc: "Garrett A. Wollman" <wollman@lcs.mit.edu>, Superuser <root@buffnet.net>, freebsd-questions@freebsd.org Subject: Re: Telnet Slowdown (fwd) Message-ID: <199602230443.UAA00295@Root.COM> In-Reply-To: Your message of "Thu, 22 Feb 1996 13:16:36 EST." <Pine.BSD.3.91.960222130621.18258C-100000@buffnet7.buffnet.net>
next in thread | previous in thread | raw e-mail | index | archive | help
>On Thu, 22 Feb 1996, Garrett A. Wollman wrote: >> >> > Im not out to start a fight - I think FreeBSD has many wonderful features >> > and I use it for a few things even though the tcp/ip has troubles. >> >> I have seen no evidence to support this claim. Pony up. >> > >The basic symptom is a stall - as though the sockets werent any good >anymore without an error message. > >If my trumpet users do not have van jacobson compression turned on for >instance, they can connect to my freebsd news server, but cannot >successfully pull over the entire active headers - it stops after a >couple records. (freebsd's virtual memory and disk buffering and the fact >that linux crashed too much under the load is why i use freebsd anyways >and make everybody turn on van jacobson) So you are saying that it works fine if people are using VJ compression? Hmmm...this doesn't sound like a problem with the networking code. Maybe with hardware flow control... >If I ftp to ftp.cdrom.com using a freebsd on my ethernet ring to theirs, >I can connect ok, and things seem ok, unless I cd and ls too many times. >I can maybe do 10 or 15 commands, and then it stalls. I can issue ls and >it returns back like there are no files there or something. But I can cd >and ls till Im blue with one of my sco's connected to that same ftp server. This sounds a lot like the connections are waiting for the 2MSL timer. This can happen if you trip over your own un-timedout connections by connecting to wcarchive, doing a bunch of quick ls's, disconnecting, and then reconnecting and doing the same thing. It will take 60 seconds for the old connections to timeout...there is nothing that can be done about this and still be compliant with the TCP/IP RFCs. There's a good discussion of this problem in the W. Richard Stevens book "TCP/IP Illustrated, volume 1". >If I have a web site installed on a freebsd wherein the pages contains a >lot of large graphics, they will come over half way and stall. Moving to >sco or linux and it stops stalling. Can't explain this...I'd like to see some hard information/analysis to back this up. I know of several FreeBSD WWW servers that are among the busiest on the Net and haven't heard of/seen this problem. In fact, "www.yahoo.com" is using FreeBSD and they swear by it (as opposed to "at" it :-)). In your case you might be running out of mbuf clusters. This is a very common mis- configuration problem that people make when using FreeBSD in WWW servers. It's easy to fix - just set the parameter correctly in the kernel config file. Try: options "NMBCLUSTERS=4096". On the other hand, it might a simple matter of some packets getting dropped. It would be worth your time to look at the TCP statistics via 'netstat -s' and interface statistics via 'netstat -i'. This may show some errors or packet lossage that might be caused by a slow network card, buggy driver in FreeBSD, or defective ethernet cabling. It would also help if you could provide more information about the hardware (especially the ethernet card) that you are using - we already know about most of the driver bugs and might be able to make some suggestions. >I dont know enough of the underlying protocol(s) to know why it would do >this. I theorize that some form of timeout or retry count somewhere is >too tight or isnt getting reset or something. I think you are seeing a variety of different problems all with different causes. Some of which are inherent in the TCP/IP protocol and some of which are caused by misconfigured hardware and software. -DG David Greenman Core-team/Principal Architect, The FreeBSD Project
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199602230443.UAA00295>