Re: Question about IPv6 over UDLR

[Emmanuel Duros <Emmanuel.Duros@UDcast.com>]

I am CC-ing this mail to the ip-dvb@erg.abdn.ac.uk mailing list because
it deals with IP over DVB issues.

As far as I understand: "the neighbor discovery of IPv6 does not work",
this due to the lack of information in the data link layer framing. The
header does not contain the MAC address of the sender and for that
reason, correct layer 2 filtering cannot be applied.

This is especially true when implementing RFC 3077 (UDLR) over a DVB
link. The MPE link layer format does not carry the source mac address of
the sender. A receiver which sends multicast traffic through the GRE
tunnel is not capable to drop (at layer 2) its own packets coming from
the UDL.

Please, correct me if I am wrong, but the IPv6 neighbor discovery
protocol works over a UDL if the datalink format contained a source mac
address (similarly to Ethernet frame format).

More generally, to obtain full bidirectional connectivity implementing
RFC 3077 over a unidirectional link, it is necessary that the datalink
header format contains at least the following information: 
 - MAC destination address
 - MAC source address
 - Ether_type-like field which specifies the content of the frame (e.g:
ARP, pppoe, IPv4, IPv6, etc.).

Emmanuel
--
Hidetaka IZUMIYAMA wrote:
> 
> Hello,
> 
> I'm Izu of JSAT.
> 
> At 18:06 01/11/06 +0100, Laurent Roullet wrote:
> >Hello,
> >
> >I am trying to gather information on IPv6 over UDL. Can anyone point me to
> >documents giving information of the current status (experiments and
> >achievements). I have had a look at the JSAT presentations made during last
> >meeting in London. It is said at the end that "the neighbor discovery of
> >IPv6 does not work". Do we know the reason of this limitation ?
> 
> UDLR emulates the broadcast link.
> If a receiver(receiver-1) sends the multicast packet to UDL, this packet
> send to Feed BDL via GRE tunnel, and forwards to UDL for other receivers.
> Receiver-1 receive this packet via UDL. If the datalink layer frame does not
> carry the source mac address, receiver-1 cannot discard this packet in
> datalink layer.
> That means Receiver-1 does not know this muticast packet was send by himself.
> 
> The neighbor discovery use multicast address.
> If datalink frame does not have source mac address,
> Receiver-1 consider that some one use same IP address.
> 
> This the reason I write last slide of my presentations in last IETF.
> 
> -- izu --
> 
> _______________________________________________
> UDLR mailing list
> UDLR@udcast.com
> http://www.udcast.com/mailman/listinfo/udlr

-- 
Emmanuel Duros                  http://www.udcast.com
2455 Route des Dolines BP355  | Tel : +33 (0)4 93 00 16 60
06906 Sophia Antipolis France | Fax : +33 (0)4 93 00 16 61
            ** Full IP over Broadcast Media **