Date: Tue, 19 Feb 2013 10:51:38 -0800 From: Chuck Swiger <cswiger@mac.com> To: Alex Yong <annonymouse+freebsd@gmail.com> Cc: freebsd-net@freebsd.org Subject: Re: Wallclock vs monotonic time in v6 expiry times? Message-ID: <D1912C84-78AF-46B9-9B4B-3871EEC782F9@mac.com> In-Reply-To: <CAJW_4zAszUermNQ0Xmz_G2A1X9Oz-2WhbrRj3UNKtCnDu-obmg@mail.gmail.com> References: <CAJW_4zAszUermNQ0Xmz_G2A1X9Oz-2WhbrRj3UNKtCnDu-obmg@mail.gmail.com>
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Hi-- On Feb 19, 2013, at 10:42 AM, Alex Yong wrote: > I've been looking around in the IPv6 code recently and I noticed that > time_second seems to be the clock of choice for calculating expiry times > for prefixes, routers and addresses. Is there any specific reason it uses > wall clock time and not time_uptime as this makes more sense to me? Sure. Sequence #s, retry timers, etc do better if based off of wall clock time than if based off of uptime because realtime persists in moving forward but uptime gets reset if the host crashes/reboots. RFC-793 discusses "Quiet Time" concept for TCP, but it applies elsewhere. Regards, -- -Chuck
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