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RE: Hashing function for PSAMP
Dear all,
now that the meaning of "selection" is clarified I think
there is still the need of recommending one of the hash functions,
therefore I think the discussion we had still applies (just keep in mind
that instead of "mandatory" we have a "recommended"):
just make BOB recommended for packet selection and packet digest.
Best regards,
Saverio
> -----Original Message-----
> From: owner-psamp@ops.ietf.org
> [mailto:owner-psamp@ops.ietf.org] On Behalf Of Tanja Zseby
> Sent: Wednesday, February 16, 2005 10:41 AM
> To: Benoit Claise
> Cc: Juergen Quittek; psamp@ops.ietf.org
> Subject: Re: Hashing function for PSAMP
>
> Hi Benoit,
>
> I fully agree. The discussion can be only about what we
> recommend IF someone decides to implement a hash-based packet
> selection.
>
> Regards
> Tanja
>
> Benoit Claise wrote:
>
> > Hi Tanja,
> >
> > Thanks for the clarification/confirmation.
> > So I'm confused by the discussion in this thread, as it
> seems that we
> > are discussing a mandatory hash function? Doesn't it contradict the
> > statement "you MUST implement at least one of the selection method
> > described in the draft in order to be PSAMP compliant."?
> >
> > Regards, Benoit.
> >
> >> Hi Benoit,
> >>
> >> I remember that we decided that you MUST implement at least one of
> >> the selection method described in the draft in order to be PSAMP
> >> compliant.
> >> So I agree, it is sufficient to implement either a sampling or a
> >> filtering method. We explicitely decided not to favor one
> scheme over
> >> another. The hash-section just gives recommendations for the case
> >> that someone decided to implement a hash-based scheme. I see no
> >> reason to change this decision.
> >>
> >> Regards
> >> Tanja
> >> P.S.: if you have time, can you call me and give me the
> list of typos
> >> that you have on your paper version ? Or we make a short editing
> >> session at the IETF ?
> >>
> >> Benoit Claise wrote:
> >>
> >>> Dear all,
> >>>
> >>> Regarding PSAMP compliance, I was under the impression that the
> >>> agreement was (even If I could not find a trace of it,
> after looking
> >>> approx. 30 sec ;)):
> >>> If you want to be PSAMP compliant, you MUST implement at
> least one
> >>> of the "method" described in the draft.
> >>> So I concluded that one filtering or one sampling
> mechanism would be
> >>> sufficient.
> >>>
> >>> Now, the discussion below is about a compulsory hash function.
> >>>
> >>> Can we please clarify the situation regarding PSAMP
> compliance, so
> >>> where is/are the MUST(s):
> >>> - MUST implement one of the filtering or sampling
> mechanism (note:
> >>> hashing is a filtering function)?
> >>> - Or MUST implement one of the filtering and one of the sampling
> >>> mechanism (note: hashing is a filtering function)?
> >>> - Or MUST implement one of the filtering, sampling, or hashing
> >>> mechanism?
> >>> - Or MUST implement one of the filtering, sampling, and hashing
> >>> mechanism?
> >>> - Or something else?
> >>>
> >>> From there, we will deduce if we even need a compulsory hash
> >>> function...
> >>>
> >>> Regards, Benoit.
> >>>
> >>>> Dear all,
> >>>>
> >>>> Currently, the packet selection document has IPSX mandatory for
> >>>> packet selection and CRC32 mandatory for packet digest.
> >>>>
> >>>> The problem I see with this recommendation is that IPSX is not
> >>>> suitable for IPv6. It does not sound like a good idea
> to have it
> >>>> mandatory for
> >>>> IPv6 systems.
> >>>>
> >>>> Here are two alternatives:
> >>>>
> >>>> 1. Make IPSX mandatory for IPv4 packet selection and BOB
> mandatory
> >>>> for IPv6 packet selection.
> >>>> Then, with BOB implemented anyway, we should then replace CRC32
> >>>> with BOB for packet digest, because both perform similarly and
> >>>> there is no good reason for forcing implementors to
> support also
> >>>> a third hash function.
> >>>>
> >>>> 2. Just make BOB mandatory for packet selection and
> packet digest.
> >>>> This would simplify implementation, because only a
> single function
> >>>> is required. For packet digest this should be OK, see 1.
> >>>> A disadvantage is that BOB is slower than IPSX by factor 7.
> >>>> An advantage is, that BOB is free of IPR, while IPSX
> is protected
> >>>> by a patent.
> >>>>
> >>>> Does anybody have a preferences for 1., 2., or the
> current choice?
> >>>>
> >>>> Thanks,
> >>>>
> >>>> Juergen
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
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> >>
> >>
> >>
> >>
> >
> >
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>
> --
> Dipl.-Ing. Tanja Zseby
> Fraunhofer Institute FOKUS Email:
> zseby@fokus.fraunhofer.de
> Kaiserin-Augusta-Allee 31 Phone: +49-30-3463-7153
> D-10589 Berlin, Germany Fax:
> +49-30-3463-8153
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