[16NG] Re: multicast and IPv6 over ETHCS

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.

Best regards,
Jihoon

2007/1/12, Alexandru Petrescu <alexandru.petrescu@motorola.com>om>:
>
> 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
>