The MPLS WG Archive

[sven.van_den_bosch@alcatel.be]

Hi,

I would like to clarify two questions regarding the hierarchy draft that is
currently on last call:

1. Dynamic recomputation of the path of the FA-LSP

If I understand correctly, the path information regarding the FA-LSP is
made available to other nodes by means of the PATH TLV. This information
may be used by other nodes for their own path computations. They could for
instance take it into account when computing a backup path. Then if the
FA-LSP changes path, primary and backup path of the client LSPs may no
longer be disjoint.

My proposal would be to foresee the possibility to restrict the
reroutability of the FA-LSP and advertise this in the PATH-TLV. In this
way, nodes that use this information would know whether it is subject to
change or not.

2. Automatic setup of FA-LSP

The draft says "Otherwise (if no existing FA-LSP is found), the LSR sets up
a new FA-LSP.  That is, it initiates a new LSP setup just for the FA-LSP."
I would like to clarify what happens when two FA-LSPs exist that, when
concatenated, can replace the new FA-LSP that is proposed to be set up in
the quoted text.

I would propose to say that the LSR may set up a new FA-LSP or
alternatively, it may replace the hop by a sequence of hops for which FAs
are available.

Would this make sense?

Sven.