[Pce] Comments on draft-ietf-pce-disco-proto-igp

Hi, all

I recently read the draft draft-ietf-pce-disco-proto-igp again, here are some comments。

When IGP is used as a PCED protocol, the capabilities of pce will be advertised periodicly along with other lsa/lsp information. In my opinion, unless the PCE's capabilities change,  there is no need for the PCC to receive and handle the information again. Furthermore, if most of the routers in a domain will always have no request to a PCE, there is also no need for them to maintain the information. 

My concern to PCE-DEST-DOMAINS sub-TLV is that we can't anticipate how many destination domains a PCE can  computate path towards, as a result,the length of space taken by this capality in the message can't be controlled. So I think if the PCC send a request to a PCE which can't compute the path for the reason of the destination domain, the PCE can tell the PCC in the PCrep message the right PCE. One additional quesion: is it suitable for the PCE to have such ability to know exactly the destination domain it can compute towards?

Some functions specified in the PATH-CAMP-CAP sub-TLV are also defined in the PCEP,  a clear division should be made. 

Cheers,

Zhang Renhai