Date: Tue, 26 Oct 1999 16:19:23 +0200 (MET DST) From: David Przybylak <em8david@etek.chalmers.se> To: freebsd-net@FreeBSD.ORG Subject: Window scale option Message-ID: <Pine.OSF.3.96.991026160021.13716B-100000@quarl0>
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I am working on a Long Fat Network and I would like to be able to advertise large windows thanks to the window scale option of TCP. I have increased both the receiving and the sending buffer size to 200000 bytes with the commands "sysctl -w net.inet.tcp.sendspace=200000" and "sysctl -w net.inet.tcp.sendspace=200000" on my two computers (FreeBSD 3.2). I am using the "sock" program to create a socket between the two computers and both SO_SNDBUF and SO_RCVBUF are set to 200000 on the two computers while creating the socket (I use the options -R200000 and -S200000 of "sock" to do that). I thought that TCP automatically set the scale factor based on the size of the receive buffer. So, I expected TCP to advertise a window of 65535*2^2 and to see "wscale 2" in the option field of the SYN segment. But the problem is that, looking at the tcpdump output, it seems that TCP doesn't send any scale factor with the SYN, and the window advertised is only 65535 bytes long. Does anyone understand what the problem is? How can I use the window scale option? How can I send window advertisements up to 264144 bytes (which is the maximum value fixed by the sysctl MIB variable "kern.ipc.maxsockbuf")? Regards, David Przybylak To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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