From: Rick Jones <[EMAIL PROTECTED]> Subject: Re: [PATCH 2.6.22-rc5] TCP: Make TCP_RTO_MAX a variable Date: Mon, 25 Jun 2007 15:29:26 -0700
> Ian McDonald wrote: > > On 6/26/07, OBATA Noboru <[EMAIL PROTECTED]> wrote: > > > >> From: OBATA Noboru <[EMAIL PROTECTED]> > >> > >> Make TCP_RTO_MAX a variable, and allow a user to change it via a > >> new sysctl entry /proc/sys/net/ipv4/tcp_rto_max. A user can > >> then guarantee TCP retransmission to be more controllable, say, > >> at least once per 10 seconds, by setting it to 10. This is > >> quite helpful on failover-capable network devices, such as an > >> active-backup bonding device. On such devices, it is desirable > >> that TCP retransmits a packet shortly after the failover, which > >> is what I would like to do with this patch. Please see > >> Background and Problem below for rationale in detail. > >> > > RFC2988 says this: > > (2.4) Whenever RTO is computed, if it is less than 1 second then the > > RTO SHOULD be rounded up to 1 second. > > > > Traditionally, TCP implementations use coarse grain clocks to > > measure the RTT and trigger the RTO, which imposes a large > > minimum value on the RTO. Research suggests that a large > > minimum RTO is needed to keep TCP conservative and avoid > > spurious retransmissions [AP99]. Therefore, this > > specification requires a large minimum RTO as a conservative > > approach, while at the same time acknowledging that at some > > future point, research may show that a smaller minimum RTO is > > acceptable or superior. > > > > (2.5) A maximum value MAY be placed on RTO provided it is at least 60 > > seconds. > > > > Your code doesn't seem to meet requirements of section 2.5 as your > > minimum is 1 second. > > (At the risk of having another Emily Litella moment entering a > discussion late...) > > I thought that those sorts of things were generally referring to the > _default_ setting? I believe so. And the requirement of section 2.5 is rather weak (it says "MAY"). Any comments from others? -- OBATA Noboru ([EMAIL PROTECTED]) - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
