[16NG] Re: multicast and IPv6 over ETHCS

Gabriel,

> Notice that if a link layer simply floods
> all multicast packets (essentially  using
> broadcast), things work fine.

Let's focus on the main issue. As I know, we started to discuss this
problem, because of the lack of flooding function (surely including
multicast) between MSs (uplink) in 802.16 MAC layer. So, we're trying to
discuss this problem regarding IPv6overETHCS.

Best regards,
Jihoon

2007/1/18, gabriel montenegro <gabriel_montenegro_2000@yahoo.com>om>:
>
>   Alex,
>
> The statement below is not true:
>
>    I meant links with link-layer headers.
>
>    Reading ND it says "node MUST join" before receiving an RA.  'Join' can
>
>    happen only if that link is multicast-capable.
>
> 802.15.4 (a link with link-layer header) has no multicast capability
> (only broadcast) at the link layer. Yet IPv6 can work fine. Of course,
> if one wants to optimize, one can do several things ( e.g., controlled
> flooding, sending along a spanning tree, etc), but neither is this
> required nor does the link layer have any concept of multicast.
>
> Wouldn't it be enough to simply say that multicast address mapping
> is done per http://tools.ietf.org/html/rfc2464?
>
> Should be obvious, but perhaps this is worth noting?
>
> Because this is so, regular IP-level join protocols work fine
> (e.g., MLD), no need to say more. You also mention elsewhere that a
> link-level
> "join" for multicast is necessary. This is not so.  Notice that if a
> link layer simply floods all multicast packets (essentially  using
> broadcast), things work fine. The IP layer itself will do the filtering.
> The link-layer can do filtering to avoid flooding mcast as if it were
> bcast, but it's just an optimization.
>
> Now, 802.1D does propose such a link-layer optimization (IGRP/GARP),
> but probably cuz this requires support at
> the clients (or perhaps for other reasons as well), this is not actually
> deployed, and yet things work fine over ethernet. Instead, the
> optimization to avoid flooding is possible because IPv4 and
> IPv6 procedures are followed for joins (IGMP, MLD) independently of
> link-layer.
> Typically, snooping of those sets state at the link-layer to achieve the
> desired (not required) optimization.
>
> -gabriel
>
> ----- Original Message ----
> From: Alexandru Petrescu < alexandru.petrescu@motorola.com>
>
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