scope:

The following functions are out of scope for this document:

• Determination of the destination domain (Section 4.5 of [RFC6805]):

◦ via a collection of reachability information from child domains,

◦ via requests to the child PCEs to discover if they contain the destination node, or

◦ via any other methods.

• Parent Traffic Engineering Database (TED) methods (Section 4.4 of [RFC6805]), although suitable mechanisms include:

◦ YANG-based management interfaces.

◦ BGP - Link State (BGP-LS) [RFC7752].

◦ Future extensions to PCEP (for example, see [PCEP-LS]).

• Learning of domain connectivity and border node addresses. Methods to achieve this function include:

◦ YANG-based management interfaces.

◦ BGP-LS [RFC7752].

◦ Future extensions to PCEP (for example, see [PCEP-LS].

• Stateful PCE operations. (Refer to [STATEFUL-HPCE].)

• Applicability of the H-PCE model to large multi-domain environments.

◦ The hierarchical relationship model is described in [RFC6805]. It is applicable to environments with small groups of domains where visibility from the ingress Label Switching Routers (LSRs) is limited. As highlighted in [RFC7399], applying the H-PCE model to very large groups of domains, such as the Internet, is not considered feasible or desirable.