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Re: [PMOL] FW: IETF Draft: SIP Performance Metrics-03
Al,
These have been corrected, thank you.
Regards,
Daryl
On 3/5/09 8:22 PM, "Al Morton" <acmorton at att.com> wrote:
> A few minor edits, below.
> Al
>
> At 06:31 PM 3/5/2009, Daryl Malas wrote:
>> All,
>>
>> Here is the updated text. Please let me know if this captures the suggested
>> changes. If so, I will post the new revision of the draft:
>>
>> Time of Day Accuracy
>>
>> As defined above, T1 is associated with the start of a request and
>> also serves as the time-of-day stamp associated with a single
>> specific measurement. The clock offset [RFC2330] is the difference
>> between T1 and a recognized primary source of time, such as UTC
>> (offset = T1- UTC).
> spacing:
> (offset = T1 - UTC).
>
>
>> When measurement results will be correlated with other results or
>> information using time-of-day stamps, then the time clock that
>> supplies T1 SHOULD be synchronized to a primary time source, to
>> minimize the clock's offset. The clocks used at the different
>> measurement points SHOULD be synchronized to each other, to minimize
>> the relative offset (as defined in RFC2330). The clock's offset and
>> the relative offset MUST be reported with each measurement.
>>
>> Time Interval Accuracy
>>
>> The accuracy of the T4-T1 interval is also critical to maintain and
>> report. The difference between clock's offsets at T1 and T4 is one
>
> report. The difference between a clock's offsets at T1 and T4 is one
> ^
>> source of error for the measurement and is associated with the
>> clock's skew [RFC2330].
>>
>> A stable and reasonably accurate clock is needed to make the time
>> interval measurements required by this memo. This source of error
>> SHOULD be constrained to less than +/- 1 ms, implying 1 part per 1000
>> frequency accuracy for a 1 second interval. This implies greater
>> stability is required as the length of the T4-T1 increases, in order
>> to constrain the error to be less than +/- 1ms.
>>
>> Regards,
>>
>> Daryl
>>
>>
>> On 3/4/09 8:52 AM, "Daryl Malas" <d.malas at cablelabs.com> wrote:
>>
>>> Mario and Al,
>>>
>>> Thank you for coming to agreement on the text. I will update the draft and
>>> submit today.
>>>
>>> Regards,
>>>
>>> Daryl
>>>
>>>
>>> On 3/4/09 1:39 AM, "Marian Delkinov" <marian.delkinov at ericsson.com> wrote:
>>>
>>>> Thanks Al!
>>>>
>>>> IMO, the definitions you proposed are accurate and in accordance with
>>>> RFC 2330.
>>>>
>>>> Best regards!
>>>> Mario.
>>>>
>>>> -----Original Message-----
>>>> From: pmol-bounces at ietf.org [mailto:pmol-bounces at ietf.org] On Behalf Of
>>>> Al Morton
>>>> Sent: Tuesday, 03 March, 2009 22:13
>>>> To: Daryl Malas; pmol at ietf.org
>>>> Subject: Re: [PMOL] FW: IETF Draft: SIP Performance Metrics-03
>>>>
>>>> Mario's comment is in the archive (and my In-box) so it appears to have
>>>> been processed by the list.
>>>>
>>>> I think that the main question, when trying to reconcile Gerald's and
>>>> Mario's comments, is whether we are talking about clock offset, or time
>>>> offset and error in time offset.
>>>>
>>>> RFC 2330 defines clock offset in section 10.1:
>>>> To begin, we define a clock's "offset" at a particular moment as the
>>>> difference between the time reported by the clock and the "true"
>>>> time
>>>> as defined by UTC. If the clock reports a time Tc and the true time
>>>> is Tt, then the clock's offset is Tc - Tt.
>>>> and since 2330 is our primary reference here, that's the way we should
>>>> go, IMO.
>>>>
>>>> Chapter 3, page 5:
>>>> As defined above, T1 is associated with the start of a request and
>>>> also serves as the time-of-day stamp associated with a single
>>>> specific measurement. The clock offset [RFC2330] is the difference
>>>> ^^^^^
>>>> between T1 and a recognized primary source of time, such as UTC
>>>> (offset = T1- UTC).
>>>>
>>>> Same page, (approx. Mario's suggested text):
>>>> When measurement results will be correlated with other results or
>>>> information using time-of-day stamps, then the time clock that
>>>> supplies T1 SHOULD be synchronized to a primary time source, to
>>>> minimize the clock's offset. The clocks used at the different
>>>> measurement points SHOULD be synchronized to each other, to
>>>> minimize the relative offset (as defined in RFC2330). The
>>>> clock's offset and the relative offset MUST be reported with
>>>> each measurement.
>>>>
>>>> Later in the same section:
>>>>
>>>> Time Interval Accuracy
>>>>
>>>> The accuracy of the T4-T1 interval is also critical to maintain and
>>>> report. The difference between clock's offsets at T1 and T4 is one
>>>> source of error for the measurement and is associated with the
>>>> clock's skew [RFC2330].
>>>>
>>>> A stable and reasonably accurate clock is needed to make the time
>>>> interval measurements required by this memo. This source of error
>>>> SHOULD be constrained to less than +/- 1 ms, implying 1 part per
>>>> 1000
>>>> frequency accuracy for a 1 second interval.
>>>>
>>>> Hope this helps,
>>>> Al
>>>> (as a participant)
>>>>
>>>> At 01:52 PM 2/24/2009, Daryl Malas wrote:
>>>>> Forwarding comments on behalf of Mario, because I never saw them hit
>>>>> the mailing list...
>>>>>
>>>>>
>>>>> ----------------
>>>>> Daryl Malas
>>>>> CableLabs
>>>>> (o) +1 303 661 3302
>>>>> (f) +1 303 661 9199
>>>>> mailto:d.malas at cablelabs.com
>>>>>
>>>>>
>>>>>> -----Original Message-----
>>>>>> From: Marian Delkinov [mailto:marian.delkinov at ericsson.com]
>>>>>> Sent: Friday, February 20, 2009 3:43 AM
>>>>>> To: Daryl Malas
>>>>>> Cc: pmol at ietf.org
>>>>>> Subject: RE: IETF Draft: SIP Performance Metrics-03
>>>>>>
>>>>>>
>>>>>> Daryl,
>>>>>>
>>>>>> Sorry, for my perhaps delayed feedback! (I'm back after a long
>>>>>> absence).
>>>>>>
>>>>>> I checked the new version (03) of the draft. All the texts that I
>>>>>> had comments before are fine.
>>>>>>
>>>>>> However, I found some changes in other texts, based on other
>>>>>> people's comments, that I have to disagree with.
>>>>>>
>>>>>> ---
>>>>>> Chapter 3, page 5:
>>>>>> As defined above, T1 is associated with the start of a request and
>>>>>> also serves as the time-of-day stamp associated with a single
>>>>>> specific measurement. The time offset [RFC2330] is the
>>>> difference
>>>>>> between T1 and a recognized primary source of time, such as UTC
>>>>>> (offset = T1- UTC).
>>>>>>
>>>>>> Instead of using the term "time offset" above, I suggest "clock's
>>>>>> offset". Thus the text will comply with the terminology used in
>>>>>> RFC2330, chapter 10.1.
>>>>>>
>>>>>> ---
>>>>>> Same page, the text:
>>>>>> When measurement results will be correlated with other results or
>>>>>> information using time-of-day stamps, then the time clock that
>>>>>> supplies T1 SHOULD be synchronized to a primary time source, to
>>>>>> minimize the error in the time offset. The time offset MUST be
>>>>>> reported with each measurement.
>>>>>>
>>>>>> I fail to understand the sentence "to minimize the error in the time
>>>>
>>>>>> offset". There is no ERROR in the time offset, because the time
>>>>>> offset IS the error. Moreover RFC2330 doesn't define such error, the
>>>>
>>>>>> draft doesn't define it either, so better avoid using it. I suggest
>>>>>> keeping the text as in version-02, but using "clock's offset".
>>>>>>
>>>>>> In addition, when correlating measurements, it's much more important
>>>>
>>>>>> all clocks used at the measurement sources to be synchronized to
>>>>>> each other, rather than be synchronized to primary time source. Thus
>>>>
>>>>>> the relative offset should be minimized.
>>>>>>
>>>>>> So the text should be:
>>>>>>
>>>>>> When measurement results will be correlated with other results or
>>>>>> information using time-of-day stamps, then the time clock that
>>>>>> supplies T1 SHOULD be synchronized to a primary time source, to
>>>>>> minimize clock's offset. The clocks used at the different
>>>>>> measurement sources SHOULD be synchronized to each other, to
>>>>>> minimize the relative offset (as defined in RFC2330). The
>>>>>> clock's offset and the relative offset MUST be reported with
>>>>>> each measurement.
>>>>>>
>>>>>> ---
>>>>>> Respectively and for the same reasons, the following text:
>>>>>> The accuracy of the T4-T1 interval is also critical to maintain and
>>>>>> report. The difference in errors between the time offsets at T1
>>>>>> and
>>>>>> T4 is associated with the clock's skew [RFC2330].
>>>>>>
>>>>>> Should be kept as in version -02, but use the "clock's offset" term:
>>>>>>
>>>>>> The accuracy of the T4-T1 interval is also critical to maintain and
>>>>>> report. The difference between clock's offsets at T1 and T4 is
>>>> the
>>>>>> error for the measurement and is associated with the clock's skew
>>>>
>>>>>> [RFC2330].
>>>>>>
>>>>>>
>>>>>> I'm OK with all other changes in version -03 compared to version
>>>> -02.
>>>>>>
>>>>>> Best regards!
>>>>>> Mario.
>>>>>>
>>>>>>
>>>>> _______________________________________________
>>>>> PMOL mailing list
>>>>> PMOL at ietf.org
>>>>> https://www.ietf.org/mailman/listinfo/pmol
>>>>
>>>> _______________________________________________
>>>> PMOL mailing list
>>>> PMOL at ietf.org
>>>> https://www.ietf.org/mailman/listinfo/pmol
>>>
>>>
>>> -----------------
>>> Daryl Malas
>>> CableLabs
>>> (o) +1 303 661 3302
>>> (f) +1 303 661 9199
>>> mailto:d.malas at cablelabs.com
>>>
>>>
>>> _______________________________________________
>>> PMOL mailing list
>>> PMOL at ietf.org
>>> https://www.ietf.org/mailman/listinfo/pmol
>>
>>
>> -----------------
>> Daryl Malas
>> CableLabs
>> (o) +1 303 661 3302
>> (f) +1 303 661 9199
>> mailto:d.malas at cablelabs.com
>
-----------------
Daryl Malas
CableLabs
(o) +1 303 661 3302
(f) +1 303 661 9199
mailto:d.malas at cablelabs.com