UDLR: Items to be discussed

[Emmanuel Duros <Emmanuel.Duros@sophia.inria.fr>]

Concerning the ID draft-ietf-udlr-lltunnel-00.txt
(http://www.inria.fr/rodeo/udlr/documents/draft-ietf-udlr-lltunnel-00.txt)
We received comments and had off line discussions.

I summarize here the list of items which have been addressed and could
be discussed during the UDLR meeting in LA:

1) Intercommunication between unidirectional feeds: 

The ID proposes to use the "Send Only Feed" multicast group to exchange
packets between unidirectional feeds. If the feeds are not connected to
the MBone (can this be a requirement?) we should consider to set up mesh
tunnels among feeds. This could be a little bit tricky since a
unidirectional feed cannot hear feed tunnel end-point announcements...


2) Choosing the "Send-Only Feed" multicast group:

It is not clear in the draft that every UDL should have its own
"Send-Only Feed" multicast group. Feeds MUST send encapsulated packets
to other feeds which are connected to the same UDL. How to choose this M
group per UDL ?


3) Feeds with several bidirectional interfaces:

A feed could announce a list of bidirectional interfaces (tunnel
end-points) associated with metrics instead of a unique IP addr. At the
mean time they could announce if it has a receive capability.


4) Layered representation:

For clarity we should add to the ID a layered representation of a feed
and a receiver including the link layered tunneling mechanism.


5) Scalability issues:

To be added/discussed.


6) Paragraph concerning the DTCP protocol not clear:

-----
From: Yongguang Zhang <ygz@hrl.com>
>6.3.2. DTCP at the feed: sending HELLO packets
>
>   The DTCP protocol runs on top of UDP. Packets are sent to the "DTCP
>   announcement" multicast address on the unidirectional link on port
>   HELLO_PORT, and on the "Send-Only Feed" multicast group on the
>   bidirectional interface.

This may be confusing.  According to 6.2.1, 3), quoted here:

     3) a broadcast/multicast destination (Scenario 5). The packet is
        sent over the unidirectional link with a link layer header
        corresponding to the broadcast/multicast addressing scheme. A
        copy of this packet is encapsulated behind an IP header whose
        destination address is the "Send-Only Feeds" multicast group. It
        is then sent via its bidirectional interface.

if "DTCP announcement" is sent to a multicast address on the UDL, it
should automatically be forwarded to the "Send-Only Feed" by the link
layer driver.  Maybe we don't need to mention The "Send-Only Feed" here.
-----

Emmanuel
--
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