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

["David Johnston" <[e-mail]>]

I was disagreeing with the statement that 802.16e doesn't support UL
multicast. It doesn't down in the depths of the 802.16 MAC, but at the
MAC service it does, using the existing 802 rules of addressing,
bridging and point to point LANs.

I don't think it is necessary for the IETF to specify how link layer
multicast is implemented, since 802 already does.

DJ



> -----Original Message-----
> From: Alexandru Petrescu [mailto:[e-mail]]
> Sent: Tuesday, January 16, 2007 8:52 AM
> To: David Johnston
> Cc: Jihoon Lee; [e-mail]; [e-mail]
> Subject: Re: [16NG] Re: multicast and IPv6 over ETHCS
> 
> David Johnston wrote:
> > I don't agree with that.
> 
> David, I'm trying to identify whether your disagreement matches my
> understanding.
> 
> What don't you agree with?  You don't agree that IP-over-ETHCS
> document should not specify how the link-layer implements link-layer
> multicast?  In other words do you suggest that the document _should_
> specify how the link-layer implements link-layer multicast?
> 
> > An UL Ethernet MSDU with a multicast or broadcast DA should get sent
> > to members of the multicast group/everyone in the bridged LAN.
> 
> Yes.  Is this a problem?
> 
> > Since 802.16 implements a point to point Ethernet similarly to
modern
> >  cat 5 ethernet, then either everyone=the Ethernet termination in
the
> >  BS, or it hits an 802.1D bridge in the BS and so the bridge deals
> > with sending it to the other 802 LANs to which is it has bridge
> > ports, including other SSs.
> 
> I sense this is a way of implementing it.  It is however a link-layer
> method.
> 
> > As I mentioned before, an 802.16 BS does not implement one network,
> > it implements a bunch of point to point networks that may be joined
> > by a bridge or IP routing or any other scheme that is implemented in
> > the BS.
> 
> What is that IP routing scheme that implements a link-layer?  Is it
> MPLS?  What other?
> 
> Do you suggest that the draft IP-over-ETHCS recommends the 802.16 BS
to
> implement a bunch of point to point networks joined by an IP router?
> 
> I think the draft _could_ list some means by which the link-layer
> multicast  _could_ be implemented (major use of word 'MAY') but not to
> make any recommendation about that.
> 
> Alex
> 
> >
> >
> > DJ
> >
> >
> >
> >
> >
> >
> >
> >
------------------------------------------------------------------------
> >
> >
> >
> >
> >
> > *From:* Jihoon Lee [mailto:[e-mail]] *Sent:* Monday,
> > January 15, 2007 4:12 PM *To:* Alexandru Petrescu *Cc:*
> > [e-mail]; [e-mail] *Subject:* [16NG] Re: multicast
and
> >  IPv6 over ETHCS
> >
> >
> >
> > Hi Alex,
> >
> > I agree with that.
> >
> >
> >
> > Thanks,
> >
> > Jihoon
> >
> >
> >
> >
> >
> >
> >
> > 2007/1/15, Alexandru Petrescu <[e-mail]
> > <mailto:[e-mail]> >:
> >
> > 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]>
> >> <mailto:[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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