Subject: [Pce] Concurrent Optimization and More

From: <[email-masked]>
Date: Thu, 19 Jun 2008 07:24:36 +0100

Hi,
 
I have three basic questions (but I might the correct place in RFCs or
drafts for that...);
 
1. How does the protocol for computing a single path works in a
hierarchical network (more than one level of PCE's)?
2. What the draft for the concurrent optimization referred to: only
inside of a sub-domain or also an inter-domain optimization which
requires communication between the PCE's?
3. Can we assume that the node's demands are splittable (i.e., can be
simultaneously satisfied by more than one path)?
 
Many thanks,
 
David Amzallag
BT

_______________________________________________
Pce mailing list
[email-masked]
https://www.ietf.org/mailman/listinfo/pce

---

From: "Daniel King" <[email-masked]>
Date: Thu, 19 Jun 2008 10:50:25 +0100

Hi David, 

So far this requirement has been out of scope for the current work. There is
growing momentum in the application of PCE to multi-layer networks, ASON,
and "domain-paths." So this topic will require further thought and
discussion.

>>2. What the draft for the concurrent optimization referred to: only inside
of a sub-domain or also an inter-domain optimization which requires
communication between the PCE's?

As above. The pce-global-concurrent-optimization draft focuses on single
domain optimisation, specifically the PCC-PCE communication needs and
protocol extensions to support the concurrent optimisation. Although, the
authors do mention that a Global Concurrent Optimization (GCO) is applicable
to a Virtual Network Topology (VNT) and multi-layer traffic engineering for
new deployments. 

I may need some further clarity on this question. Do you mean that there may
be more than one possible solution to a path computation, or that the
solution to the computation may be a set of "parallel" paths with some
assumption of load sharing (e.g. inverse multiplexing)?

The answer to the first question is yes and is already done, although some
work might be required to allow the PCE to supply a choice of paths to the
PCC.

The answer to the second question is also yes, but (very simple) protocol
extensions will be needed to handle this case.

Other relevant drafts you may find interesting for this topic include:

A Path Computation Element (PCE)-Based Architecture 

http://www.ietf.org/rfc/rfc4655.txt

A Framework for Inter-Domain Multiprotocol Label Switching Traffic
Engineering

http://www.ietf.org/rfc/rfc4726.txt

A Per-Domain Path Computation Method for Establishing Inter-Domain Traffic
Engineering (TE) Label Switched Paths (LSPs)

http://www.ietf.org/rfc/rfc5152.txt

Evaluation of existing GMPLS Protocols against Multi Layer and Multi Region
Networks (MLN/MRN)

http://www.ietf.org/internet-drafts/draft-ietf-ccamp-gmpls-mln-eval-05.txt

A Backward Recursive PCE-based Computation (BRPC) Procedure To Compute
Shortest Constrained Inter-domain Traffic Engineering Label Switched Paths

http://www.ietf.org/internet-drafts/draft-ietf-pce-brpc-09.txt

Br, Dan

From: [email-masked] [mailto:[email-masked]] On Behalf Of
[email-masked]
Sent: 19 June 2008 07:25
To: [email-masked]
Subject: [Pce] Concurrent Optimization and More

Hi,

1. How does the protocol for computing a single path works in a hierarchical
network (more than one level of PCE's)?
2. What the draft for the concurrent optimization referred to: only inside
of a sub-domain or also an inter-domain optimization which requires
communication between the PCE's?

Many thanks,

David Amzallag

BT

---

From: <[email-masked]>
Date: Fri, 20 Jun 2008 08:26:27 +0100

Dan,
 
Many thanks for your fast reply. Are you familiar with any "real-time"
implementation of few of the PCE ideas? Anyone that implements the
distributed approach?
 
Warm regards,
 
David Amzallag,
BT

________________________________

From: Daniel King [mailto:[email-masked]] 
Sent: 19 June 2008 12:50
To: [email-masked]
Subject: RE: [Pce] Concurrent Optimization and More

Hi David, 

So far this requirement has been out of scope for the current work.
There is growing momentum in the application of PCE to multi-layer
networks, ASON, and "domain-paths." So this topic will require further
thought and discussion.

As above. The pce-global-concurrent-optimization draft focuses on single
domain optimisation, specifically the PCC-PCE communication needs and
protocol extensions to support the concurrent optimisation. Although,
the authors do mention that a Global Concurrent Optimization (GCO) is
applicable to a Virtual Network Topology (VNT) and multi-layer traffic
engineering for new deployments. 

I may need some further clarity on this question. Do you mean that there
may be more than one possible solution to a path computation, or that
the solution to the computation may be a set of "parallel" paths with
some assumption of load sharing (e.g. inverse multiplexing)?

The answer to the first question is yes and is already done, although
some work might be required to allow the PCE to supply a choice of paths
to the PCC.

The answer to the second question is also yes, but (very simple)
protocol extensions will be needed to handle this case.

A Per-Domain Path Computation Method for Establishing Inter-Domain
Traffic Engineering (TE) Label Switched Paths (LSPs)

Evaluation of existing GMPLS Protocols against Multi Layer and Multi
Region Networks (MLN/MRN)

http://www.ietf.org/internet-drafts/draft-ietf-ccamp-gmpls-mln-eval-05.t
xt

A Backward Recursive PCE-based Computation (BRPC) Procedure To Compute
Shortest Constrained Inter-domain Traffic Engineering Label Switched
Paths

Br, Dan

Hi,

Many thanks,

David Amzallag

BT

---

From: "Daniel King" <[email-masked]>
Date: Fri, 20 Jun 2008 09:15:42 +0100

Hi David, 

Aha ,"real-time". Well as we know real-time is relative. We talked
previously about the PCE GCO application. Performing a GCO, via an NMS on a
centralized PCE, on a complex network might require 6hrs of computation
time. This could be considered real-time and perhaps is an acceptable amount
of time to wait for a near-optimal solution. Another scenario might be
performing path computation for a local backup path after an existing backup
path fails. A local backup path solution could be required within a few
seconds and computed via a distributed PCE that has local network knowledge.
Both scenarios would require a real-time view (topology, services and
resources) of the network at the time of the path computation request.  The
mechanisms are in place to support these architectures and I am aware of
vendors implementing some of these ideas.

We should not mention specific vendors on the WG mailing list. I am
compiling a list of PCE vendors and implementers at:
www.pathcomputationelement.com. Any vendors not currently listed are welcome
to contact me and add their name and information.

Br, Dan. 

From: [email-masked] [mailto:[email-masked]] On Behalf Of
[email-masked]
Sent: 20 June 2008 08:26
To: [email-masked]
Subject: Re: [Pce] Concurrent Optimization and More

Dan,

Warm regards,

David Amzallag,

BT

  _____  

Hi David, 

Br, Dan

Hi,

Many thanks,

David Amzallag

BT