Re: [Roll] ticket - 172 - clarify units of trickle timers
peter van der Stok <stokcons@xs4all.nl> Mon, 17 August 2015 07:15 UTC
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Date: Mon, 17 Aug 2015 09:15:25 +0200
From: peter van der Stok <stokcons@xs4all.nl>
To: Routing Over Low power and Lossy networks <roll@ietf.org>
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Cc: Michael Richardson <mcr+ietf@sandelman.ca>
Subject: Re: [Roll] ticket - 172 - clarify units of trickle timers
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Hi Michael, thanks for trying to solve this issue. I must confess that I had not recognized the problem. For interoperability is seems an issue when values are initialized (as you point out as well) It will be a nuisance if sets of nodes must be initialized with different Imin and Imax values to reach the same behaviour. The same problem will occur when a YANG (SMIv2) description is made for managing these parameters. Suggestion: write an ERRATA document for RFC6206 which then solves draft-ietf-roll-trickle-mcast-12 issue. Peter Michael Richardson schreef op 2015-08-14 14:27: > https://tools.ietf.org/wg/roll/trac/ticket/172 > > This ticket was opened in response to a DISCUSS from AD Alia Atlas, > on the draft-ietf-roll-mpl-parameter-configuration document. > > As a result of this DISCUSS the processing of trickle-mcast was held > up at the RFC-editor, as there was concern that we needed to fix that > document. Ines and I are looking for opinions from the WG about this > situation; better text, even just "yes, you described the problem > correctly" > > The specific confusion is that > draft-ietf-roll-mpl-parameter-configuration > and trickle-mcast are not explicit enough about the units of IMIN and > IMAX > values. > > Jonathan Hui commented that the origin of the problem is > really RFC RFC 6206, and he wrote on a thread involving the ADs: > > - On one hand, RFC 6206 says "the maximum interval size Imax", > which > is an absolute value. > - On the other hand, RFC 6206 says that Imax "is described as a > number > of doublings of the minimum interval size", which is a relative > value. > > - Later, RFC 6206 uses Imax as if it were an absolute value. For > example, "When the algorithm starts execution, it sets I to a > value in > the range of [Imin, Imax]". In another example, "Nodes with > small Imax > values will transmit faster, suppressing those with larger Imax > values. The nodes with larger Imax values, always suppressed, > will > never transmit." That statement only makes sense if Imax was an > absolute value, and not relative to Imin. > > - RFC 6206 also uses Imax as it it were a relative value. "Note > that > mismatched Imin values and matching Imax doubling constants will > lead > to mismatched maximum interval lengths." > > It seems clear to me that it doesn't really *internally* matter if Imax > is a > timer or a doubling of Imin, as long as it can be used an alarm that > causes > the trickle algorithm to run. It is only when we get to > draft-ietf-roll-mpl-parameter-configuration when we put these values > on the wire that we have to deal with it clearly. > > mpl-paramaeter-configuration says (section 2.1): > > Note that all time values (Trickle timers and expiration periods) > are > in TUNIT milliseconds precision. For example, if TUNIT is 20 and > the > data message interval minimum (DATA_MESSAGE_IMIN) is 1000ms, then > DM_IMIN shall be set to 50. > > and I suggest that it instead say: > > Note that time values DM_IMIN, DM_T_EXP, C_MIN, C_T_EXP are in units > of TUNIT. TUNIT is a multiplier, and is in units of miliseconds. > For example, if TUNIT is 20 and the > desired data message interval minimum (DATA_MESSAGE_IMIN) is 1000ms, > then DM_IMIN shall be set to 50 (1000ms/ 20 = 50). > > Time values: DM_IMAX, and C_IMAX are in multiples of the respective > DM_IMIN and C_IMIN values, so if a DM_MIN value of 50 (1000ms) is > encoded, and DM_IMAX contains the number 4, then the > DATA_MESSAGE_IMAX value > would have be 4000ms (4s). > > Also, mpl-parameter-configuration needs a reference to 6206. > > As such I don't think we need to fix anything in the trickle-mcast > document > itself. > > -- > Michael Richardson <mcr+IETF@sandelman.ca>, Sandelman Software Works > IETF ROLL WG co-chair. http://datatracker.ietf.org/wg/roll/charter/ > > > _______________________________________________ > Roll mailing list > Roll@ietf.org > https://www.ietf.org/mailman/listinfo/roll
- [Roll] ticket - 172 - clarify units of trickle ti… Michael Richardson
- Re: [Roll] ticket - 172 - clarify units of trickl… peter van der Stok
- Re: [Roll] ticket - 172 - clarify units of trickl… Michael Richardson
- Re: [Roll] ticket - 172 - clarify units of trickl… Kerry Lynn
- Re: [Roll] ticket - 172 - clarify units of trickl… Michael Richardson
- Re: [Roll] ticket - 172 - clarify units of trickl… Kerry Lynn
- Re: [Roll] ticket - 172 - clarify units of trickl… Michael Richardson
- Re: [Roll] ticket - 172 - clarify units of trickl… Yusuke DOI