Questions on draft-ietf-mpls-bundle-00

["Atkinson, Stephen" <steve.atkinson@netplane.com>]

I've been reading the draft-ietf-mpls-bundle-00 spec and have a couple
questions.

Basically I'm trying to focus on why signaling unnumbered components using
Explicit Indication by Interface ID is different from all other cases. This
being the
only case which specifies an interface (component) for each direction of a
bi-directional LSP.

Bundling section 3.3.2 (Explicit Indication) requires that the upstream node
specify
the component interface to use in each direction when setting up
bi-directional
LSPs using unnumbered components.

Bundling section 3.3.1 (Implicit Indication) doesn't have this requirement.
Apparently
when signaling using "Implicit Indication" (for a bi-directional LSP) the
reverse direction
can be inferred. Is this true? If so is this behavior specified anywhere?

Also, when signaling a bi-directional LSP using numbered components the
reverse direction component can apparently be inferred using Implicit
Indication or 
Explicit Indication by Interface ID. Is this true? 

Assuming the statements above are correct. Why must a bi-directional LSP
being setup using
Explicit Indication and unnumbered components, specify a component for each
direction, while
each of the following only requires specifying a single component (or
interface)?

   - unnumbered component signaled implicitly
   - numbered component signaled implicitly
   - numbered component signaled explicitly
   - unnumbered interface (not bundling) signaled implicitly or explicitly
   - numbered interface (not bundling) signaled implicitly or explicitly


Thanks,
steve atkinson