Re: [v6ops] ref Hosts dont MLD to join LL groups
Alexandru Petrescu <alexandru.petrescu@gmail.com> Fri, 24 July 2015 05:04 UTC
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To: Owen DeLong <owen@delong.com>
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From: Alexandru Petrescu <alexandru.petrescu@gmail.com>
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Date: Fri, 24 Jul 2015 07:04:48 +0200
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Subject: Re: [v6ops] ref Hosts dont MLD to join LL groups
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I agree unicast RA in response to RS makes sense. Ideally unicast RAs in responses to unicast RSs. Le 24/07/2015 03:28, Owen DeLong a écrit : > >> On Jul 23, 2015, at 07:34 , Alexandru Petrescu >> <alexandru.petrescu@gmail.com >> <mailto:alexandru.petrescu@gmail.com>> wrote: >> >> >> >> Le 23/07/2015 15:01, Enno Rey a écrit : >>> Hi, >>> >>>> >>>> Inform the sender willingnes to be part of the group. If not >>>> part of group, then sender will not send it. Same concept at >>>> L2 and at L3. >>> >>> wrong. the sender of a MC message just sends it out, regardless >>> if somebody listens or not. >> >> I agree. >> >>> the router(s) helping to distribute this message (in case of >>> interdomain MC) only have to know (= are interested) if there's >>> at least one interested listener on an adjacent link. neither >>> the sender nor the router(s) have any interest (or need to have >>> that) in individual listeners. >> >> YEs, that's so for multicast across multiple subnets. >> >> But on the same link (same subnet) the Router sends these RAs, so >> it must be able to know which Host would like to receive its >> multicasted RAs. > > No… It sends them to the ALL_HOSTS multicast group which it assumes > will reach every host on the link, since that’s the whole point of > the ALL_HOSTS multicast group when paired with LINK scope. YEs. But it's a matter of semantics. A Host may want to act as a Host sometimes (join all-hosts) and as a router other times (join the all-routers group only). For example, a smartphone would need to act as a Host when RS/RA but would need to be a router when doing 64share (stop its RSs, unsubscribe all-hosts, etc). To paraphrase, that's the whole point of that being a group a multicast and not using broadcast - not just a fancy word. Alex > > >> >>>>> strictly speaking MLD as a whole is only needed for >>>>> interdomain multicast anyway. >>>> >>>> Disagree - beyond just interdomain multicast, Ethernet has >>>> link-layer multicast builtin. There is no 'broadcast' address >>>> anymore in Ethernet since some time, replaced by 'multicast': >>>> supposedly better at saving battery and other advantages. >>>> >>>>> on the local link you join a MC group by kind-of self >>>>> declaration ("hey I consider myself part of that group >>>> >>>> That is an Ethernet message. >>> >>> no. that's a decision taken somewhere in the software/stack. no >>> need for any packet here. >> >> Well. I cant put my wireshark in monitor mode right now but if I >> could I would tell the name of the Ethernet message on WiFi (a >> management frame) which joins link-layer multicast. > > WiFi != Ethernet. > > 802.11 != 802.1, 802.3, etc. > > > Management Frames > > 802.11 management frames enable stations to establish and maintain > communications. The following are common 802.11 management frame > subtypes: > > > > Management frames are unique to WiFi. > > >> >>>> Some cards send that message, others don't. All should. >>>> >>>>> so I'm interested in certain traffic and hence instruct my >>>>> stack to listen to/process packets with certain addresses"). >>>>> no need of MLD for that action. >>>> >>>> How does the Ethernet layer know this is a Router, and not a >>>> Host? Only by knowing that it can join the all-hosts or >>>> all-routers link-layer address. And only the IP stack knows >>>> whether it's a Host or a Router. So the IP stack should tell >>>> the Ethernet layer to make that link-layer join. >>> >>> which it does, as a stack-internal decision. "once I'm a router >>> get me everything sent to ff02::1/33:33:00:00:00:01. in addition >>> - given I'm a node anyway - get me everything for ff02::2". no >>> need to send any packet for all this. >> >> In that same way, the Host must be able to tell everybody else >> whether or that Host is interested in receiving the multicasted >> RAs. > > Nope… It either listens or it doesn’t. According to IPv6, a host must > listen to all hosts and a router must listen to all routers and all > hosts, but that’s merely by convention. > > Nothing in the hardware. > > No packets sent to say “I’m now listening for this.” It just starts > listening. > > It’s like changing channels on your TV…. You don’t tell the old TV > station that you’re tuning out and the new station that you’re tuning > in. You just change which frequency your local tuner is listening > to. > > Owen > >> >> Alex >> >>> >>> best >>> >>> Enno >>> >>> >>> >>> >>> >>>> >>>> Yours, >>>> >>>> Alex >>>> >>>>> but "joining" on the local-link doesn't need MLD. >>>>> >>>>> best >>>>> >>>>> Enno >>>>> >>>>> >>>>> >>>>> >>>>> >>>>>> >>>>>> Alex >>>>>> >>>>>> Le 23/07/2015 13:51, Ole Troan a ??crit : >>>>>>> Alexandru, >>>>>>> >>>>>>> I???m afraid I couldn???t interpret your message. would >>>>>>> someone else be able to translate? >>>>>>> >>>>>>> cheers, Ole >>>>>>> >>>>>>>>> >>>>>>>>> I do wonder if we should expand that exception to >>>>>>>>> all link-scope multicast addresses. >>>>>>>>> >>>>>>>> >>>>>>>> I would beg to disagree. >>>>>>>> >>>>>>>> If we expand that to all link-scoped groups, may lead >>>>>>>> to dismantling IPv6 dependence on 33::1 - >>>>>>>> ff:ff:ff:ff:ff would be sufficient. >>>>>>>> >>>>>>>> My oppinion would rather be to modify the MLD RFC to >>>>>>>> mandate MLD joins for all scopes. >>>>>>>> >>>>>>>> Ethernet has primitives for joining the corresponding >>>>>>>> link-layer groups, and in some cases they are used. >>>>>>>> Maybe all should use them. >>>>>>>> >>>>>>>>> the bridge implementors I speak to tell me that they >>>>>>>>> don???t have enough state to do MLD snooping for >>>>>>>>> link-local scoped multicast addresses anyway... >>>>>>>> >>>>>>>> This may be dumb from my side, but why dont bridge >>>>>>>> implementers use link-layer multicast? They shouldnt >>>>>>>> implement MLD, and not snoop it. The Hosts should send >>>>>>>> the necessary link-layer multicast joins (triggered by >>>>>>>> themselves sending MLD REPORT for these groups) to the >>>>>>>> bridge addresses. >>>>>>>> >>>>>>>> Alex >>>>>>>> >>>>>>>>> cheers, Ole >>>>>>> >>>>>> >>>>>> _______________________________________________ v6ops >>>>>> mailing list v6ops@ietf.org <mailto:v6ops@ietf.org> >>>>>> https://www.ietf.org/mailman/listinfo/v6ops >>>>> >>>> >>>> _______________________________________________ v6ops mailing >>>> list v6ops@ietf.org <mailto:v6ops@ietf.org> >>>> https://www.ietf.org/mailman/listinfo/v6ops >>> >> >> _______________________________________________ v6ops mailing list >> v6ops@ietf.org <mailto:v6ops@ietf.org> >> https://www.ietf.org/mailman/listinfo/v6ops >
- [v6ops] ref Hosts dont MLD to join LL groups Alexandru Petrescu
- Re: [v6ops] ref Hosts dont MLD to join LL groups Ole Troan
- Re: [v6ops] ref Hosts dont MLD to join LL groups Enno Rey
- Re: [v6ops] ref Hosts dont MLD to join LL groups Andrew 👽 Yourtchenko
- Re: [v6ops] ref Hosts dont MLD to join LL groups Alexandru Petrescu
- Re: [v6ops] ref Hosts dont MLD to join LL groups Ole Troan
- Re: [v6ops] ref Hosts dont MLD to join LL groups Alexandru Petrescu
- Re: [v6ops] ref Hosts dont MLD to join LL groups Enno Rey
- Re: [v6ops] ref Hosts dont MLD to join LL groups Alexandru Petrescu
- Re: [v6ops] ref Hosts dont MLD to join LL groups Enno Rey
- Re: [v6ops] ref Hosts dont MLD to join LL groups Alexandru Petrescu
- Re: [v6ops] ref Hosts dont MLD to join LL groups Owen DeLong
- Re: [v6ops] ref Hosts dont MLD to join LL groups Owen DeLong
- Re: [v6ops] ref Hosts dont MLD to join LL groups Alexandru Petrescu
- Re: [v6ops] ref Hosts dont MLD to join LL groups Owen DeLong