Re: [16NG] Re: multicast and IPv6 over ETHCS

Hi, sorry for popping up,

On Fri, 2007-01-12 at 12:19 +0100, Alexandru Petrescu wrote:
> 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.

Do you think this is an accidental design choice (i.e. no uplink
multicast)? Or 802.16/16e MAC designers had very good fundamental
reasons? 

(I'm sorry. This question looks out-of IETF scope. But I think we may 
learn something more general i.e. useful to IP perhaps?)

Thank you.
pars

> 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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