Re: [dhcwg] Re: PD lifetimes
JINMEI Tatuya / 神明達哉 <jinmei@isl.rdc.toshiba.co.jp> Wed, 05 February 2003 11:16 UTC
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Date: Wed, 05 Feb 2003 18:00:07 +0900
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From: JINMEI Tatuya / 神明達哉 <jinmei@isl.rdc.toshiba.co.jp>
To: Ole Troan <ot@cisco.com>
Cc: rdroms@cisco.com, dhcwg@ietf.org
Subject: Re: [dhcwg] Re: PD lifetimes
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>>>>> On Tue, 04 Feb 2003 23:17:36 +0000, >>>>> Ole Troan <ot@cisco.com> said: >> 0. (I once discussed this point privately, but I could not help >> raising this again. Please forgive me for this repetition.) (snip) >> It would be much simpler to have a single "lifetime" only, which >> controls T1 and T2, and loosely affects the RA lifetimes. > I believe this was brought up during the DHC meeting in Yokohama. the > main argument (coming from Thomas I think) for including the preferred > lifetime was to simplify renumbering. it also allows for more granular > control if PD is used in other contexts than the one specified in the > draft. Okay, according to the discussion in this thread, it seems that I'm in the minority on this. So, I'm okay to keep the preferred lifetime in the PD specification. > the draft specifies how a prefix is delegated but has intentionally > left unspecified (apart from suggesting some defaults) how it is to be > used within the site. the only requirement is that the valid lifetime > is adhered to, anything else can be configured in any way the local > administrator (if there is one) wants. As I said in a separate message, this approach treats the preferred lifetime as (a kind of) optional information, while the preferred lifetime takes an essential role in address assignment. In the PD spec, the valid and preferred lifetimes are sometimes essential and sometimes informational, which make me confused: - the PD valid lifetime specifies the "lease duration" of the site prefix. (this is essential) - the PD valid lifetime also specifies the upper bound of the RA valid lifetime. (this is a bit strong, but still informational) - the PD preferred lifetime controls the (recommended) default values of T1 and T2. (this is essential) - the PD preferred lifetime specifies a suggestion of the RA preferred lifetime. (this is informational) Thus, it would most make sense to me if the essential and informational parts are clearly separated. For example, - we have three parameters for a prefix; lease duration, valid lifetime, and preferred lifetime. we also have T1 and T2 for an IA_PD. - the lease duration is an essential information, which specifies the "lifetime of the site prefix" and must be specified in Reply messages. It also controls the default value of T1 and T2. - the valid and preferred lifetimes are informational, which may or may not be (concretely) specified in Reply messages. If specified, those values mean the suggested values of the RA lifetimes. - there are of course some trivial relationship between the parameters. For instance, the valid and preferred lifetimes must not be larger than the lease duration. (we may need additional bits for the valid and preferred lifetimes as Erik suggested, but I omitted the additional bits here for simplicity.) Doesn't this make much sense? >> In the following comments, however, I'll assume the current valid + >> preferred scheme. >> >> 1. Section 9 says >> >> In a message sent by a delegating router the preferred and valid >> lifetimes should be set to the values specified in section "Router >> Configuration Variables" of RFC2461 [3], unless administratively >> configured. >> >> Technically, the wording 'values specified in section "Router >> Configuration Variables"' is not clear, because the router >> configuration variables of RFC 2461 do not contain the valid and >> preferred lifetimes. The intended variables should probably be >> AdvValidLifetime and AdvPreferredLifetime, respectively. Even so, >> however, I still suspect these are appropriate values. >> AdvXXXLifetimes are for each end host (in a site), but the lifetimes >> given by PD affect the entire site. In general (and IMO), the latter >> should be larger than the former. > section 6.2.1 of RFC2461 does indeed include AdvValidLifetime and > AdvPreferredLifetime, so I'm not sure what is not clear. My point is that the text should be like this: In a message sent by a delegating router the preferred and valid lifetimes should be set to AdvValidLifetime and AdvPreferredLifetime, respectively, as specified in section "Router Configuration Variables" of RFC2461 [3], unless administratively configured. (though I'd like larger default value as I said below.) >> I believe the default values of PD lifetimes should keep the default >> values of RA lifetimes in the typical configuration. Thus, I would >> recommend the following values: (snip) > I don't see decrementing lifetimes in RA's as abnormal, nor do I see > the benefit of advertising fixed values in RA's. there is nothing > prohibiting an requesting router implementation to use fixed values, > as long as it behaves correctly when the PD valid lifetime < RA > lifetime. Regarding this point, please refer to the succeeding discussion in this thread. However, if we clarified the essential and informational parameters (see above), this part might not be an issue. JINMEI, Tatuya Communication Platform Lab. Corporate R&D Center, Toshiba Corp. jinmei@isl.rdc.toshiba.co.jp _______________________________________________ dhcwg mailing list dhcwg@ietf.org https://www1.ietf.org/mailman/listinfo/dhcwg
- [dhcwg] PD lifetimes JINMEI Tatuya / 神明達哉
- [dhcwg] Re: PD lifetimes Ralph Droms
- Re: [dhcwg] Re: PD lifetimes Jun Xie
- Re: [dhcwg] Re: PD lifetimes Ralph Droms
- Re: [dhcwg] Re: PD lifetimes Erik Nordmark
- Re: [dhcwg] Re: PD lifetimes JINMEI Tatuya / 神明達哉
- Re: [dhcwg] Re: PD lifetimes JINMEI Tatuya / 神明達哉
- Re: [dhcwg] Re: PD lifetimes Erik Nordmark
- Re: [dhcwg] Re: PD lifetimes JINMEI Tatuya / 神明達哉
- [dhcwg] Re: PD lifetimes Ole Troan
- Re: [dhcwg] Re: PD lifetimes JINMEI Tatuya / 神明達哉
- Re: [dhcwg] Re: PD lifetimes Erik Nordmark
- Re: [dhcwg] Re: PD lifetimes JINMEI Tatuya / 神明達哉
- Re: [dhcwg] Re: PD lifetimes Erik Nordmark
- PD lifetime issues again (Re: [dhcwg] WG last cal… JINMEI Tatuya / 神明達哉