%% You should probably cite draft-ietf-pce-hierarchy-extensions instead of this I-D.
@techreport{zhang-pce-hierarchy-extensions-04,
    number =    {draft-zhang-pce-hierarchy-extensions-04},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-zhang-pce-hierarchy-extensions/04/},
    author =    {Fatai Zhang and Quintin Zhao and Oscar Gonzalez de Dios and Ramon Casellas and Daniel King},
    title =     {{Extensions to Path Computation Element Communication Protocol (PCEP) for Hierarchical Path Computation Elements (PCE)}},
    pagetotal = 14,
    year =      2013,
    month =     jul,
    day =       14,
    abstract =  {The Hierarchical Path Computation Element (H-PCE) architecture, defined in the companion framework document {[}RFC6805{]}, provides a mechanism to allow the optimum sequence of domains to be selected, and the optimum end-to-end path to be derived through the use of a hierarchical relationship between domains. This document defines the Path Computation Element Protocol (PCEP) extensions for the purpose of implementing Hierarchical PCE procedures which are described in the aforementioned document. These extensions are experimental and published for examination, discussion, implementation, and evaluation.},
}