Date: Mon, 27 Aug 2001 22:49:24 -0400 From: "Louis A. Mamakos" <louie@TransSys.COM> To: Harkirat Singh <singh@pdx.edu> Cc: Mike Silbersack <silby@silby.com>, Dave Zarzycki <zarzycki@FreeBSD.ORG>, Alfred Perlstein <bright@mu.org>, freebsd-net@FreeBSD.ORG Subject: Re: RFC: SACK/FACK patch port to Current Message-ID: <200108280249.f7S2nOZ62047@whizzo.transsys.com> In-Reply-To: Your message of "Mon, 27 Aug 2001 18:04:40 PDT." <Pine.GSO.4.33.0108271751490.27335-100000@gere.odin.pdx.edu> References: <Pine.GSO.4.33.0108271751490.27335-100000@gere.odin.pdx.edu>
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> > I agree with your comment that FCAK is only a retransmission algorithm and > many papers recommends that FACK+SACK improves the performance for > long-delay network (for more information look at 1996 SIGCOMM paper). Most of the hair in a TCP implementation is "only" the retransmission algorithm. Having been a co-author of a TCP/IP stack 20 years ago, and been through the evolution of TCP with Van Jacobson's work, I cringe everytime I see yet another hack in the FreeBSD TCP. It's hard to get right, even when you know what effect you're trying to achieve. Consider that much of the work that resulted in slow-start and other other related work that Van did was accompanied by a considerable of before and after testing to measure the effect. I sure hope someone has done that testing and analysis of this code and the effect on the FreeBSD TCP implementation. I don't think that a drive-by commit of some other related work without a commitment to understand the code in a very deep way is wise. If you consider the dynamic range that the TCP retransmit timers need to operate over, it's a truly frighting thing, and folks ought not to be anxious screw with the implementation lightly. louie To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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