Active-Active Problem Statement
-------------------------------

In a TRILL campus, communications between TRILL switches can

(1) use multiple parallel links and/or paths,

(2) load spread over different links and/or paths at a fine grained
flow level through equal cost multipathing of unicast traffic and
multiple distribution trees for multi-destination traffic, and

(3) rapidly re-configure to accomodate link or node failures or
additions.

Active-active is the extension, to the extent practical, of similar
load spreading and robustness to the connections between end stations
and the TRILL campus. Such end stations may have multiple ports and
will be connected, directly or via bridges, to multiple edge TRILL
switches. It must be possible, except in some failure conditions, to
load spread end station traffic at the flow level across links to such
multiple edge TRILL switches and rapdily re-configure to accomodate
topology changes.


Active-Active Solution Requirements / Goals
-------------------------------------------

Requirements:

    Support TRILL ignorant end stations.
    Prevent, except as a transient condition during topology change:
        Loops.
	Packet duplications.
	Address flip-flop.
	Packet drop due to RPF check.

Goals, with most important goal first:

    Supported by existing silicon.
    Minimize nickname consumption.
    Minimize configuration. If confguration is required, ability to
        detect misconfiguration.

Other Factors:

    Changes to TRILL switches adjacent to the active-active end
        statations are more acceptable than changes to other TRILL
        switches in the campus.