Subject: mixed L2/L3

From: Ali Boudani <[email-masked]>
Date: Thu, 04 Jan 2001 09:44:11 +0100

Hello,
I was reading the draft
http://www.ietf.org/internet-drafts/draft-ietf-mpls-multicast-04.txt
(framework for IP multicast in MPLS)
and I didnt understand what is the meaning for this paragraph 4 :

Assume LSR A (Figure 8) is an MPLS edge node for the branch
   towards LSR B and an MPLS root node for the branch towards LSR C.
   The mixed L2/L3 forwarding allows that the branch towards C is not
   disturbed by a return to L3 in LSR A.

                           +-------------+
                           | MPLS cloud  |
                           |     N       |
                           |    / \      |
                           |   /   \     |
                           |  /     \    |
                           | A       N   |
                           |/ \       \  |
                           |   \       \ |
                          /|    \        |
                         B |     C       |
                           |             |
                           +-------------+

                Figure 8.  Mixed L2/L3 forwarding in node A

   b) Enables the use of the traffic driven trigger with the Downstream
   Unsolicited or Upstream on Demand label distribution mode, as
   explained in section 5.3.1.

Can anybody explain it please ??