RE: [ippm] Comments on draft-ietf-ippm-framework-compagg-00
Anura Jayasumana <anura@engr.colostate.edu> Wed, 22 March 2006 02:48 UTC
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Date: Tue, 21 Mar 2006 19:45:25 -0700
From: Anura Jayasumana <anura@engr.colostate.edu>
To: "Philip F. Chimento Jr." <vze275m9@verizon.net>
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Subject: RE: [ippm] Comments on draft-ietf-ippm-framework-compagg-00
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>===== Original Message From "Philip F. Chimento Jr." <vze275m9@verizon.net> ===== >Hi Anura: >You can add means, whether the relevant RVs are dependent or not, so >average delays add. >Higher order statistics, as you point out, do not add simply. >Convolution ASSUMES that the RVs are independent. > > >Regards, >Phil Chimento Phil, Yes, you are right. Based on very limited results we have for delay, it looks like the delays are independent if the inter-packet gaps of the stream is large; when ipg is small, such as with a burst, the delays appear to be highly correlated. This is when convolution breaks down. Cheers! AJ > >On Mar 21, 2006, at 12:31, Anura Jayasumana wrote: > >> >> >> Henk Uijterwaal wrote: >>> Phil, >>> >>> The problem that I have with this section is that it doesn't give me >>> very strong or concrete reasons for why I want to combine metrics. >>> >>> Suppose I have a path A-B-C. I'm interested in the delays between >>> them. >>> Now, I can measure all 3 (A-B, B-C and A-B-C) separately. >>> However, if >>> there is a way to add up the delays between A-B and B-C, and get the >>> overall delay, then i can see myself some work and diskspace. In >>> general, >>> I'd be interested in the minimum set of measurements that still gives >>> me information about the entire network. >>> >>> Section 5.1: The problem here is that piece-wise measurements do >>> not necessarily combine. IPDV and re-ordering are examples where one >>> subsection of a network can "undo" what a previous one has done. >>> Putting these together in a straightforward way doesn't give you the >>> right answer. >> >> With delays, if the packet delays in the two networks are not >> correlated, it is still possible to measure statistics of delays >> of segments and combine them to provide end-to-end delay >> statistics. When delays are correlated, it becomes necessary to >> measure correlation as well.... which would be more complex. >> Reordering is somewhat of a harder problem. But, when captured >> using RD (reorder density), you can combine the reordering in >> different segments and still come up with end-to-end reordering. >> Combination is done using >> convolution, which would be the case for delay also. One thing >> going for RD is the fact that reordering in two network segments >> are less likely to be correlated compared to delay. We have >> carried out many mesurements on Internet, planet-lab, simulations, >> etc., and are yet to see a case where it did not work - for >> reordering. >> (See http://www.cnrl.colostate.edu/packet_reorder.html ) >> Cheers! >> AJ >> >>> >>> I agree but can't we just say so? >>> >>> Henk >>> >>> >>> --------------------------------------------------------------------- >>> --------- >>> Henk Uijterwaal Email: henk.uijterwaal >>> (at)ripe.net >>> RIPE Network Coordination Centre http:// >>> www.amsterdamned.org/~henk >>> P.O.Box 10096 Singel 258 Phone: +31.20.5354414 >>> 1001 EB Amsterdam 1016 AB Amsterdam Fax: +31.20.5354445 >>> The Netherlands The Netherlands Mobile: +31.6.55861746 >>> --------------------------------------------------------------------- >>> --------- >>> >>> 1160438400. Watch this space... >>> >>> _______________________________________________ >>> ippm mailing list >>> ippm@ietf.org https://www1.ietf.org/mailman/listinfo/ippm >> >> Anura P. Jayasumana >> Professor, Electrical & Computer Engineering >> and Computer Science >> Department of Electrical and Computer Engineering >> Colorado State University >> Fort Collins, CO 80523 >> Phone: (970) 491-7855 >> Fax: (970) 491-2249 >> Email: <Anura.Jayasumana@Colostate.edu> > > >_______________________________________________ >ippm mailing list >ippm@ietf.org >https://www1.ietf.org/mailman/listinfo/ippm _______________________________________________ ippm mailing list ippm@ietf.org https://www1.ietf.org/mailman/listinfo/ippm
- [ippm] Comments on draft-ietf-ippm-framework-comp… Philip F. Chimento Jr.
- Re: [ippm] Comments on draft-ietf-ippm-framework-… Henk Uijterwaal
- Re: [ippm] Comments on draft-ietf-ippm-framework-… Philip F. Chimento Jr.
- Re: [ippm] Comments on draft-ietf-ippm-framework-… Anura Jayasumana
- Re: [ippm] Comments on draft-ietf-ippm-framework-… Philip F. Chimento Jr.
- RE: [ippm] Comments on draft-ietf-ippm-framework-… Anura Jayasumana
- Re: [ippm] Comments on draft-ietf-ippm-framework-… Al Morton
- Re: [ippm] Comments on draft-ietf-ippm-framework-… Philip F. Chimento Jr.
- RE: [ippm] Comments on draft-ietf-ippm-framework-… Fardid, Reza
- Re: [ippm] Comments on draft-ietf-ippm-framework-… Anura Jayasumana