Le 23 oct. 2011 à 18:25, Maoke a écrit : > hi Remi, > > 2011/10/21 Rémi Després <[email protected]> > Maoke, > Please see below. > > Le 20 oct. 2011 à 16:48, Maoke a écrit : > >> hi Remi, >> >> thanks a lot for the reply! it is very helpful and my latest understanding >> almost approach it. but still some minor clarifications. >> 2011/10/20 Rémi Després <[email protected]> >> Hi Maoke, >> >> Thank you for your questions concerning relationships between IPv6 and IPv4 >> addressing plans. >> >> Here are address-planning steps that illustrate how an IPv6 addressing plan >> can be kept independent from IPv4 prefixes used for IPv4 residual >> deployment, even if CEs must be able to have different sharing ratios. >> >> (A) IPv6 considerations >> (A1) Determine the maximum number N of CEs you want to support, a power of 2 >> (N = 2 ^ n). >> (A2) Choose the length x of IPv6 prefixes you want to assign to ordinary >> customers (e.g. x = 60) >> (A2) Multiply M by a margin coefficient K, a power of two (K = 2 ^ k), to >> take into account that: >> >> >> here the M should be a typo of "N", right? ;-) > > Yes, thanks. > >> >> >> - Some privileged customers may be assigned IPv6 prefixes of length x', >> shorter than x, to have larger addressing spaces than ordinary customers, >> both in IPv6 and IPv4. >> - Due to the hierarchy of routable prefixes, many theoretically delegatable >> prefixes may not be actually delegatable (ref: host density ratio of RFC >> 3194). >> >> (B) IPv4 considerations >> (B1) List all (non overlapping) IPv4 prefixes Hi that are available for IPv4 >> residual deployment. >> (B2) Take enough of them, among the shortest ones, to get a total space >> whose size M is a power of two (M = 2 ^ m), and includes a good proportion >> of the available IPv4 space (ref >> www.ietf.org/mail-archive/web/softwires/current/msg02261.html). >> (B3) For each IPv4 prefix Hi of length hi, choose a "Rule index" Ri of >> length ri = m - hi. All these indexes must be non overlapping prefixes (e.g. >> 0, 10, 110, 111 for one /10, one /11, and two /12). > > Oops, another bug :-(. > The right formula for ri is: ri = m - (32 - hi) > >> >> (C) After (A) and (B) >> (C1) Derive the length c of the "Common prefix" C that will appear at the >> beginning of all delegatable prefixes (c = n + k - m) >> > > > is this another bug? i think:
> > |<------------ x ---------------->| > | |<--------- n ----------->|<k>| > +------------+---------+-------------+-----+---+ > |Common Pref.|Rule idx | IPv4 suffix |PSID | | > +------------+---------+-------------+-----+---+ > | |<--------- m ------>| > |<--- c ---->|<-- ri ->|<--- hi ---->| Correct (with the correction made in your next mail: hi replaced by 32 - hi) > and thus c = x - (n + k), right? ;-) Indeed. Thanks fot the careful review. Cheers, RD
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