The paths chosen by Generalized MPLS (GMPLS) Traffic Engineering (TE)
Label Switched Paths (LSPs) can be constrained using the Explicit
Route (ERO) object and related sub-objects. Standard ERO sub-objects
can specify the Autonomous System (AS), LSR Node Ids, Numbered or
unnumbered TE links, downstream and upstream labels, and PCE path
keys thus restricting which resources are to be used by a TE-LSP.
The Explicit Label Control (ELC) in the explicit route object (ERO)
allows both terminating an LSP on a particular outgoing port and
label of an egress node, as well as restricting which label to use on
any hop along the path determined by the route. However, currently,
its not allowed to specify more than 2 labels (downstream and
upstream label), and it is not possible to specify, for a given
section or segment of a TE-LSP path, a set of labels to restrict
which label to be allocated from a Set of candidate labels.
This memo provides extensions to the RSVP-TE and PCEP protocols to
support Label Sets in the form of ERO sub-objects, being applicable
to ERO and ERO-like (IRO, RRO, XRO) sub-objects, extending the ELC
concept to a set of candidate labels.