Date: Fri, 04 Aug 2000 15:16:22 -0700 From: bmah@cisco.com (Bruce A. Mah) To: Garrett Wollman <wollman@khavrinen.lcs.mit.edu> Cc: bmah@cisco.com, freebsd-net@FreeBSD.ORG Subject: Re: cvs commit: src/sys/netinet tcp_output.c Message-ID: <200008042216.e74MGMk14703@bmah-freebsd-0.cisco.com> In-Reply-To: <200008042131.RAA33779@khavrinen.lcs.mit.edu> References: <200008042014.QAA05452@cholla.INRS-Telecom.UQuebec.CA> <200008042107.e74L7Tu13995@bmah-freebsd-0.cisco.com> <200008042131.RAA33779@khavrinen.lcs.mit.edu>
next in thread | previous in thread | raw e-mail | index | archive | help
--==_Exmh_-2095522332P Content-Type: text/plain; charset=us-ascii If memory serves me right, Garrett Wollman wrote: > <<On Fri, 04 Aug 2000 14:07:29 -0700, bmah@cisco.com (Bruce A. Mah) said: > > > A RED queue would drop a random packet from the full queue. > > Actually, no. A RED queue would drop a packet as it is enqueued, at > random intervals which depend on the current length of the queue. > Many people get this wrong when the idea is first explained to them; I > know I did. Read the paper for a full explanation of how this works.[1] Mea culpa, thanks for the correction. It's been too long since I read the paper. If it makes you feel any better, I have *nothing* to do whatsoever with the RED implementation in any Cisco product. :-p > > If you can get those flows to back off (e.g. TCP congestion > > control), > > Specifically, I think the problem with Archie's patch is that it might > result in TCP not backing off at all. I think I see your concern but I am not sure whether or not this is true. Given that I started off my previous email with a totally false statement, I'm not sure if I should venture out on a limb again, but: From the commit log, the error case Archie is concerned with is if ip_output returns with ENOBUFS. If this is true, then after Archie's patch gets executed, the code below the out: label will call tcp_quench(), which closes the congestion window down to one segment. The fact that the patch already reset tp->snd_nxt doesn't change that. > RED doesn't deal well with > unresponsive flows. Agreed. Bruce. --==_Exmh_-2095522332P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: PGPfreeware 5.0i for non-commercial use MessageID: HuZKOCkYKe88R65elv+ql4bPbwEyn4xc iQA/AwUBOYtAttjKMXFboFLDEQJlkwCfTiMVV4cCrBWxlUDLG+vtRwHq1yoAoJAb wbp/u8hqqDGPdcSbe8NpXDhQ =d0l+ -----END PGP SIGNATURE----- --==_Exmh_-2095522332P-- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200008042216.e74MGMk14703>