Subject: [rbridge] scope of draft-tissa-trill-cmt-00

From: "Tissa Senevirathne (tsenevir)" <[email-masked]>
Date: Thu, 29 Mar 2012 04:42:36 -0700

There is considerable discussion going on in the mailing list, it
appears may be the scope of the work in the draft need bit more
explanation. Hence, thought to give a background and scope of the draft
and exact problem that we are solving

1.       This draft is only focusing on how to solve RPF issue on the
multi-homed edge that use pt-pt links.

2.       This draft does not discuss how multi-homed edge should be
implemented, it is work of future drafts.

Below is an example on how this problem can occur.

Assume there is dual homed pt-pt Edge and edge is represented by virtual
nickname

Assume there are two multi-destination trees.

Consider the following cases

case 1:  Both trees are rooted on the same RBRidge RBx

Case 2  Two trees are rooted on different RBridges RBx and RBy

Consider the topology below. In an scenario like below, virtual RB will
always be connected to the two trees through RB1, hence RB2 is unable to
associate Virtual RB to a tree. 

The CMT draft provide flexible framework to associate virtual RB to
multi-destination trees through a parent of choice.

Case 1:

                  Rbx

                   |     \  (10)

               (1)|       \---------

                   |                   |      

                 RB1 ----(1)---- RB2

                    +---------------+

                    | Virtual RB |

Case 2:

                  Rbx          Rby

             (1)   |              | (1)

              +----------------------+

              |   TRILL Campus |

              +----------------------+

                   |     \  (10)

               (1)|       \---------

                   |                   |      

                 RB1 ---(1)------ RB2

                    +---------------+

                    | Virtuak RB|

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