Brian, Sheng, The proposal seems nicely stabilized as regards the MSB=0 case. IMHO though, more than proposed so far could be done concerning the MSB=1 case.
In sec 3, instead of "If the MSB of the flow label is 1, the remaining 19 bits MAY obey a locally defined set of rules and those bits MAY be changed en route", we could have: "If the MSB of the flow label is 1, the remaining 19 bits MAY obey a different defined set of rules. Each such set will have to be identified by a specific value of the 3 bits that follow the MSB." We therefore: - avoid to exclude some new rule sets that would apply end to end; - prevent that some new rule set would take for itself all possible values having MSB = 1. Sorry to have this a little late, but better late than never, right? RD Le 25 févr. 2010 à 00:15, Sheng Jiang a écrit : > > >> -----Original Message----- >> From: Brian E Carpenter [mailto:brian.e.carpen...@gmail.com] >> Sent: Thursday, February 25, 2010 4:10 AM >> To: Rémi Després >> Cc: Sheng Jiang; '6man' >> Subject: Re: [Fwd: I-D Action:draft-carpenter-6man-flow-update-00.txt] >> >> On 2010-02-25 02:39, Rémi Després wrote: >>> Le 23 févr. 2010 à 22:02, Brian E Carpenter a écrit : >>> >>>> I think we can make this OK by the following type of rule >> (I really >>>> haven't worked out all the possible cases carefully, however). >>>> >>>> If a packet arrives with all 0, then local use is allowed but if >>>> the packet leaves the local domain the label MUST be set >> back to all >>>> 0. >>>> >>>> That actually requires that the local use method MUST >> include a flag >>>> bit meaning "this was originally all 0", but that seems >> easy enough. >>>> Then the current default behaviour is perfectly preserved >> when viewed >>>> outside the local domain. >>> >>> What makes the most sense to me is: >>> - first bit =0 ==> Must be preserved end to end. >>> - If there is some local use to traverse a domain, the >> value at entrance has to be restored at exit. >>> >>> Now, if the entrance value is all 0, this fact can be coded >> in the local-use format, so that it is easy to restore the >> entrance value at exit. >>> On the other hand, if the entrance value is E2E and non 0, >> some means to keep this value in the modified packet has to >> be found. How to do it has to be taken care of when designing >> each particular local use. >>> >>> Reasonable? >> >> 100%, in my humble opinion. So there are actually three cases >> when a packet arrives in a local-use domain (either from a >> local host or from a border router): >> >> Flow label is zero: local use allowed (with MSB=1) but label >> must be set to zero on exit from the domain. >> >> Value between 1 and 0x7FFFF: local use not allowed, label >> must not be changed >> >> MSB=1: local use allowed. > > This is petty good. It solves our original worry: local use is not allowed > when flow label is all zero. I guess we can update the draft with this > design now. > > Cheers, > > Sheng > -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
