Date: Wed, 28 May 2003 12:55:47 -0400 From: "kfl" <kfl@xiphos.ca> To: "freebsd - net" <net@FreeBSD.org> Subject: FW: TCP for transaction Message-ID: <JCEDLMKGMLLELHAJNIHJKEGHEJAA.kfl@xiphos.ca>
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> -----Original Message----- > From: kfl [mailto:kfl@xiphos.ca] > Sent: Wednesday, May 28, 2003 12:53 PM > To: freebsd - net > Subject: TCP for transaction > > > > Here is a tcpdump output from one FreeBSD box with TCP for > transaction enabled and a client supporting the NO_PUSH > setsockopt with a windows box: > > 19:00:15.357281 192.168.3.200.1247 > 192.168.2.7.microsoft-ds: SP > 4208572194:420 > 8572331(137) win 65535 <mss 1460,nop,wscale 2,nop,nop,ccnew 2> (DF) > 19:00:15.357514 192.168.2.7.microsoft-ds > 192.168.3.200.1247: S > 2795532295:2795 > 532295(0) ack 4208572195 win 61680 <mss 1460,nop,wscale 2> (DF) > 19:00:15.357911 192.168.3.200.1247 > 192.168.2.7.microsoft-ds: . > ack 1 win 52560 > (DF) > 19:00:18.356736 192.168.3.200.1247 > 192.168.2.7.microsoft-ds: P > 1:138(137) ack > 1 win 52560 (DF) > 19:00:18.357465 192.168.2.7.microsoft-ds > 192.168.3.200.1247: P > 1:90(89) ack 13 > 8 win 61646 (DF) > 19:00:18.456659 192.168.3.200.1247 > 192.168.2.7.microsoft-ds: . > ack 90 win 5256 > 0 (DF) > 19:00:20.611227 192.168.3.200.1247 > 192.168.2.7.microsoft-ds: P > 138:336(198) ac > k 90 win 52560 (DF) > 19:00:20.612037 192.168.2.7.microsoft-ds > 192.168.3.200.1247: P > 90:359(269) ack > 336 win 61597 (DF) > > I see two problems here (in fact its only one problem with a side effect): > > 1) When sending the ccnew option T/TCP send data with it. > 2) As a results the sender times out and retransmit at > 19:00:18.356736 > adding 3 seconds to the connection data transfer. > > Now, in the rfc1644 it is stipulated that a host can send data > with the cc.new option. I am a bit confused here since T/TCP > should accelerate data transfer for small transaction (saving 1 > RTT) and not timing out if the destination host does not support it. > > I think we should avoid sending data with the cc.new option. > > Any thoughs? > > Karim Fodil-Lemelin > Network Engineering. > Xiphos Technologies > www.xiphos.com >
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