[16NG] Re: multicast and IPv6 over ETHCS

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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