Subject: [Idr] PCE Text within draft-wu-idr-te-pm-bgp-03

From: "Daniel King" <[email-masked]>
Date: Wed, 1 Jan 2014 23:01:47 -0000

Hi Authors, 

Useful I-D, and nice to see H-PCE Architecture (RFC6805) being discussed in
use cases. 

My comment is a suggested text update for Section 3.1 (MPLS-TE with PCE):

For inter-AS path computation the Hierarchical PCE (H-PCE) [RFC6805] may be
used to compute the optimal sequence of domains. Within the H-PCE
architecture, the child PCE communicates domain connectivity information to
the parent PCE, and the parent PCE will use this information to compute a
multi-domain path based on the optimal TE links between domains for the
end-to-end path. 

The following figure demonstrates how a child PCE may obtain TE performance
information beyond that contained in the LINK_STATE attributes
[I.D-ietf-idr-ls-distribution] using the mechanism described in this
document.

<< 

Also an FYI, we (PCE WG) adopted the H-PCE extensions document
(http://tools.ietf.org/html/draft-ietf-pce-hierarchy-extensions). So if you
are discussing configuration examples, you may also want to reference this
document as well.  

Br, Dan.

---

From: Qin Wu <[email-masked]>
Date: Mon, 6 Jan 2014 04:07:33 +0000

Hi, Dan:

From: Idr [mailto:[email-masked]] On Behalf Of Daniel King
Sent: Thursday, January 02, 2014 7:02 AM
To: [email-masked]
Subject: [Idr] PCE Text within draft-wu-idr-te-pm-bgp-03

Hi Authors,

Useful I-D, and nice to see H-PCE Architecture (RFC6805) being discussed in use cases.

My comment is a suggested text update for Section 3.1 (MPLS-TE with PCE):

For inter-AS path computation the Hierarchical PCE (H-PCE) [RFC6805] may be used to compute the optimal sequence of domains. Within the H-PCE architecture, the child PCE communicates domain connectivity information to the parent PCE, and the parent PCE will use this information to compute a multi-domain path based on the optimal TE links between domains for the end-to-end path.

The following figure demonstrates how a child PCE may obtain TE performance information beyond that contained in the LINK_STATE attributes [I.D-ietf-idr-ls-distribution] using the mechanism described in this document.

[Qin]: Your proposed change looks good except you say "demonstrates how a child PCE may obtain TE performance", I think in H-PCE case, it is parent PCE who need to build TED based on domain connectivity information, i.e., inter-AS TE performance information. Child PCE provide that information. Intra-domain information can not be provided to parent PCE based on RFC6805 since providing intr-domain infor would violate the confidentiality and scaling principles(See 4.4 of RFC6805).
For intra-domain path computation, parent PCE still need to rely on child PCE for per-domain path calculation.

Besides H-PCE case, I think there are other cases where one external PCE can gather information from other Ass. In those case,  providing intra-domain info from one AS to the PCE in another AS will not
violate the confidentiality and scaling principles provided by RFC6805.
<<

Also an FYI, we (PCE WG) adopted the H-PCE extensions document (http://tools.ietf.org/html/draft-ietf-pce-hierarchy-extensions). So if you are discussing configuration examples, you may also want to reference this document as well.

[Qin]: I can add this reference in your proposed change.

Br, Dan.

---

From: "Daniel King" <[email-masked]>
Date: Mon, 6 Jan 2014 07:18:30 -0000

Hi Qin, 

The scaling and confidentially especially relates to the internal topologies
of the Child domains. I would agree that having the Parent PCE compute both
the intra-domain and inter-domain path would be bad. 

A variety of methods exist to provide the parent PCE the inter-domain
information. Using BGP-LS as a northbound distribution mechanism, there
would be a BGP speaker in each domain that sends the necessary information
to a BGP speaker in the parent domain. This may be the Child PCE
disseminating inter-domain adjacency information to the Parent PCE, but
using policy to ensure that information is restricted to inter-domain
connectivity.

Or. 

A Parent PCE may also simply participate in the IGP of a domain in order to
learn about connected domains, and/or learn inter-domain connectivity from a
BGP Route Reflector (filtering), or indeed using PCEP Notifications but this
may upset some in the PCE Working Group. What knowledge is provided to the
Parent PCE may be dependent on who is "responsible" for the Parent PCE and
domains, single provider or multiple providers. 

Finally, the Parent PCE may also only simply send a proposed sequence of
domains to the ingress domain Child PCE so that the end-to-end domain path
can be constructed using Per Domain or Backwards Recursive Path Computation
could be used, instead of H-PCE path computation.

Either way, your suggested text update is fine and all of these permutations
of how the Parent PCE may learn inter-domain information will have to be
considered for the H-PCE extension work.

Br, Dan. 

From: Qin Wu [mailto:[email-masked]] 
Sent: 06 January 2014 04:08
To: Daniel King; [email-masked]
Subject: RE: [Idr] PCE Text within draft-wu-idr-te-pm-bgp-03

Hi, Dan:

From: Idr [mailto:[email-masked]] On Behalf Of Daniel King
Sent: Thursday, January 02, 2014 7:02 AM
To: [email-masked] <mailto:[email-masked]> 
Subject: [Idr] PCE Text within draft-wu-idr-te-pm-bgp-03

Hi Authors, 

My comment is a suggested text update for Section 3.1 (MPLS-TE with PCE):

[Qin]: Your proposed change looks good except you say "demonstrates how a
child PCE may obtain TE performance", I think in H-PCE case, it is parent
PCE who need to build TED based on domain connectivity information, i.e.,
inter-AS TE performance information. Child PCE provide that information.
Intra-domain information can not be provided to parent PCE based on RFC6805
since providing intr-domain infor would violate the confidentiality and
scaling principles(See 4.4 of RFC6805).

For intra-domain path computation, parent PCE still need to rely on child
PCE for per-domain path calculation. 

Besides H-PCE case, I think there are other cases where one external PCE can
gather information from other Ass. In those case,  providing intra-domain
info from one AS to the PCE in another AS will not

<< 

Br, Dan.