Re: Comment on DestinationMac in draft-mmm-bfd-on-lags

[Donald Eastlake <[e-mail]>]

Hi,

On Fri, Sep 28, 2012 at 6:45 AM, JOVELPONNAIEN, ARULMOHAN (ARULMOHAN)
<[e-mail]> wrote:
> Hi All,
>
> Micro-BFD session would use dedicated destination MAC address allocated for
> IANA range (RFC 5342). But this MAC address range is not link-level and would
> allow forwarding of Link-Level BFD packets by intermediate L2 switches.
>
> Assume case below, here it is possible that 3 micro BFD sessions from
> Router1 could be forwarded on single-port to Router2.
> Router1 ------------(3-port) LAG------------L2 Switch-------(1-port
> LAG)-----------Router2
>
> If MAC-address is chosen from range 01:80:c2:xx:xx:xx, then this case would
> not arise. Micro-BFD session would then be terminated by L2 switch
> immediately. By 802.1d standard 01:80:c2:xx:xx:xx would be terminated by L2
> switch.

I believe you will find that the range of addresses that are blocked
by 802.1 bridges if they do not understand them is MUCH narrower. It
is, in fact, only the block of 16 addresses from 01:80:C2:00:00:00 to
01:80:C2:00:00:0F. For example, 01-80-C2-00-00-14 and
01-80-C2-00-00-15 are the addresses used by IS-IS for All Level 1 and
All Level 2 Intermediate Systems, respectively, and which must be
transparently handled by bridges or you couldn't have a bridge in
between two Layer 3 IP routers.

> Is it not better if we choose a MAC address in 01:80:c2 range similar to
> LACP to make sure micro-BFD session remains link-level protocol?

If you want an address of that type, you could apply to the IEEE
Registration Authority although the WG should probably coordinate that
with you AD. Only a tiny fraction of those addresses, which are
intended for standards use, have been allocated. But, as I say, it
will not make any difference to the behavior and it seems easier for
an IETF WG to get a 48-bit multicast address using the procedures in
RFC 5342.

Thanks,
Donald
=============================
 Donald E. Eastlake 3rd   [phone] (cell)
 155 Beaver Street, Milford, MA 01757 USA
 [e-mail]

> Regards,
> Arul Mohan.
>
>