Re: [mpls] Spencer Dawkins' No Objection on draft-ietf-mpls-residence-time-14: (with COMMENT)
Greg Mirsky <gregimirsky@gmail.com> Tue, 07 March 2017 17:42 UTC
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From: Greg Mirsky <gregimirsky@gmail.com>
Date: Tue, 07 Mar 2017 09:42:46 -0800
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To: Spencer Dawkins at IETF <spencerdawkins.ietf@gmail.com>
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Cc: draft-ietf-mpls-residence-time@ietf.org, Alexander Vainshtein <vainshtein.alex@gmail.com>, mpls-chairs@ietf.org, "iesg@ietf.org" <iesg@ietf.org>, "mpls@ietf.org" <mpls@ietf.org>
Subject: Re: [mpls] Spencer Dawkins' No Objection on draft-ietf-mpls-residence-time-14: (with COMMENT)
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Hi Spencer, I've uploaded the new version of the draft. It includes changes we've discussed as well as to address comments from Alia, Mirja, Ben, and Benjamin. I hope that I haven't missed anything. Regards, Greg On Mon, Feb 27, 2017 at 1:36 PM, Spencer Dawkins at IETF < spencerdawkins.ietf@gmail.com> wrote: > Keeping in mind that these are non-blocking comments (so, do the right > thing) ... > > > On Feb 27, 2017 14:53, "Alexander Vainshtein" <vainshtein.alex@gmail.com> > wrote: > > Spencer and all, > I concur with Eric. > > The RTM mechanism defined in this spec does not depend on the protocol - > NPT, PTP or something else - that is carried over an LSP. > > > Right, and the Introduction starts out that way, but the Abstract calls > out PTP specifically, and a quick string search turns up 4 "NTP" strings > and 70 "PTP" strings in the document (counting the table of contents but > you get the idea). That's probably what misled me. > > But the good news is that I'm not likely to be your typical reader ;-) > > Thanks, > > Spencer > > However, PTP by design can use the information about accummulated on-path > delay (the Correction field in its PDUs has been defined for just this > purpose), while NTP, in its present form, cannot do that. > > If/when the NTP spec is updated so that it can use measured on-path delay, > it would be able to benefit from RTM as well - as I see it, without any > substantial changes to this spec. > > Hopefully this helps. > > My 2c, > Sasha > > On Feb 27, 2017 21:41, "Eric Gray" <eric.gray@ericsson.com> wrote: > > Spencer, > > > > While the reference to NTP is forward looking (as Greg > suggested) – there is no strong reason to suspect that additional work > relative to this specification will _*necessarily*_ be required. > > > > Transparent Clock (again as Greg mentioned) has not yet been defined for > NTP. > > > > The essential element of transparent clock is that there > needs to be a way to determine the amount of time a message spends at each > hop (this is the variable component of delay for any given path) so that > this delay can be corrected for. The more hops for which you have this > information, the more accurate the corrected time values will be. > > > > If you can determine the variable delay experienced by a > time message, you can combine this information with the measurable fixed > delay (associated mostly with light-speed delays) to provide a very precise > corrected time value. > > > > Transparent Clock is quite elegant in that sense, as long > as it can be done without layer-violations. J > > > > -- > > Eric > > > > *From:* Spencer Dawkins at IETF [mailto:spencerdawkins.ietf@gmail.com] > *Sent:* Monday, February 27, 2017 12:47 PM > *To:* Greg Mirsky <gregimirsky@gmail.com> > *Cc:* iesg@ietf.org; draft-ietf-mpls-residence-time@ietf.org; Loa > Andersson <loa@pi.nu>; mpls-chairs@ietf.org; mpls@ietf.org > *Subject:* Re: Spencer Dawkins' No Objection on > draft-ietf-mpls-residence-time-14: (with COMMENT) > > > > Hi, Greg, > > > > On Feb 27, 2017 11:13, "Greg Mirsky" <gregimirsky@gmail.com> wrote: > > Hi Spencer, > > yes, only PTP has defined operation of the transparent clock and how to > use the residence time to improve accuracy of distributed time. > > > > (Remembering that this is a no-blocking comment) > > > > I'd suggest removing the text reference to NTP in the Introduction, and > mentioning that you're allocating the value for NTP in Section 7.2, but > that NTP can't make use of this mechanism unless it adds support for > transparent clock. > > > > Does that make sense? > > > > Spencer > > > > Regards, > > Greg > > > > On Mon, Feb 27, 2017 at 9:06 AM, Spencer Dawkins at IETF < > spencerdawkins.ietf@gmail.com> wrote: > > Hi, Greg, > > > > On Feb 27, 2017 09:55, "Greg Mirsky" <gregimirsky@gmail.com> wrote: > > Hi Spencer, > > thank you for your thorough review and the question. > > NTP yet doesn't use transparent clock paradigm but in section 3 G-ACh for > Residence Time Measurement we've noted that NTP may be one type of TLV and > have requested appropriate allocation by IANA in the new sub-registry MPLS > RTM TLV Registry (section 7.2). Thus, if NTP will be enhanced to use > transparent clock, the RTM over MPLS will be capable to support it. > > We're open to your suggestions to make it clearer. > > > > So, is it correct to say that PTP is the only time protocol that uses the > transparent clock paradigm today? > > > > Spencer > > > > Kind regards, > > Greg > > > > On Sun, Feb 26, 2017 at 1:54 PM, Spencer Dawkins < > spencerdawkins.ietf@gmail.com> wrote: > > Spencer Dawkins has entered the following ballot position for > draft-ietf-mpls-residence-time-14: No Objection > > When responding, please keep the subject line intact and reply to all > email addresses included in the To and CC lines. (Feel free to cut this > introductory paragraph, however.) > > > Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html > for more information about IESG DISCUSS and COMMENT positions. > > > The document, along with other ballot positions, can be found here: > https://datatracker.ietf.org/doc/draft-ietf-mpls-residence-time/ > > > > ---------------------------------------------------------------------- > COMMENT: > ---------------------------------------------------------------------- > > I'm a bit confused on one point. There's one reference to NTP in the > Introduction, everything else is about PTP, but the specification never > actually says if this mechanism is intended to be usable for NTP as well. > Could that be clearer? > > > > > > > > > > > >
- [mpls] Spencer Dawkins' No Objection on draft-iet… Spencer Dawkins
- Re: [mpls] Spencer Dawkins' No Objection on draft… Greg Mirsky
- Re: [mpls] Spencer Dawkins' No Objection on draft… Spencer Dawkins at IETF
- Re: [mpls] Spencer Dawkins' No Objection on draft… Greg Mirsky
- Re: [mpls] Spencer Dawkins' No Objection on draft… Spencer Dawkins at IETF
- Re: [mpls] Spencer Dawkins' No Objection on draft… Greg Mirsky
- Re: [mpls] Spencer Dawkins' No Objection on draft… Eric Gray
- Re: [mpls] Spencer Dawkins' No Objection on draft… Alexander Vainshtein
- Re: [mpls] Spencer Dawkins' No Objection on draft… Spencer Dawkins at IETF
- Re: [mpls] Spencer Dawkins' No Objection on draft… Greg Mirsky