[16NG] Re: multicast and IPv6 over ETHCS

["Jihoon Lee" <[e-mail]>]

Hi Alex,
I agree with that.

Thanks,
Jihoon




2007/1/15, Alexandru Petrescu <[e-mail]>om>:
>
> Hi Jihoon,
>
> Jihoon Lee wrote:
> > Hi Alex,
> >
> > Sorry for my late response. Basically I agree with your opinion. An
> > IPv6 node requires a link local multicast address in order to perform
> >  DAD, ND, and RA.
> >
> > Contrary to our expectations, 802.16/16e don't support UL multicast
> > (which means an MS forwards data directly to other MSs in the same
> > cell).
> >
> > (BTW, I think I need to clarify the UL multicast I mentioned. I
> > believe you already know this: the multicast/broadcast which is sent
> > by an MS  to other MSs in the same cell (BS) cannot be supported in
> > 802.16. However, other MSs in another cell (BS) may receive this
> > since the 802.16 backhaul (WiMAX ASN) may multicast/broadcast at ETH
> > or IP layer.)
> >
> > I agree that the document needs to specify how to deal with this
> > problem.
>
> Yes, I think the IPv6-over-ETHCS document should make clear the
> assumption of IPv6 using link-layer multicast for IPv6.  I don't think
> the IPv6-over-ETHCS document should solve the problem you mention above
> between parenthesis (uplink mc, or mc between BSs) at link layer.
>
> The IPv6-over-ETHCS document could list the behaviour of ETHCS it
> expects.  Ie:
>
> -when MS sends NS to a IP solicited-node multicast address the node who
> has joined group must receive it.
> -when BS or AR advertises an RA to all-nodes multicast address then all
> SSs who have joined that group must receive it.
> -mapping an IPv6 link-local multicast address should happen (eg sending
> a packet to IP dst ff02::1 should have the link-layer dst
> 33:33:33:0:0:0:1).
>
> The document IPv6-over-ETHCS should list what are the means for SS to
> _join_ a link-layer multicast group.  There are few of them (send a
> link-layer message, send a MLD message, establish a local filtering
> rule, always receiving all packets, etc).
>
> But I don't think the IPv6-over-ETHCS document should specify the
> link-layer behaviour for an implementation of ETHCS link-layer
> multicast.  Do you agree with this latter item?
>
> Alex
>
> >
> > Best regards, Jihoon
> >
> >
> > 2007/1/12, Alexandru Petrescu <[e-mail]
> > <mailto:[e-mail]>>:
> >
> > Hi Jihoon, thanks for reply,
> >
> > Jihoon Lee wrote:
> >> Hi Alex,
> >>
> >> Let me jump into discussion. 1) 802.16/16e MAC has no capability to
> >>  do uplink multicast. In DL, 802.16 provides multicast CIDs which
> >> is initiated by DSA messages. In UL, however, there is no way for
> >> an MS to access others' UL data fundamentally, in 802.16 PHY/MAC.
> >
> > Ok.  For one, if the 802.16MAC is not capable to do bidirectional (or
> >  normal) multicast then that is a big issue for IPv6-over-IPv6CS.
> > (and surprisingly, apparently the document IPv6-over-IPv6CS doesn't
> > seem to mention the word 'multicast'.)
> >
> > The issue is that a SS running IPv6 needs to multicast a NA, from
> > time to time.  For DAD it needs to send a NS to a multicast address
> > too.
> >
> >> In case of ETH over 802.16, the ETH(bridge) may cover this (an MS
> >> sends multicast data in UL, and then a bridge forwards it back).
> >> But, there is still a difficulty in multicasting data back except
> >> for the source MS.
> >
> > You mean the bridge in BS?  I was thinking ETHCS in SS may offer a
> > multicast interface to the IP stack.
> >
> > In both cases (bridge in BS or bridge in SS), I think it is not up to
> >  this document to specify how the ETHCS transforms a asymmetric ul/dl
> >  multicast feature into a symmetric one.  But it should be a goal for
> >  ETHCS to offer such an interface to the IPv6 stack, otherwise the
> > IPv6 stack won't work.  What do you think?
> >
> > Alex
> >
> >
>
>

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