Subject: RE: [Pce] Fwd: Internet Draft for Publication <draft-ash-pce-architecture-00.txt>

From: "Ash, Gerald R \(Jerry\), ALABS" <[email-masked]>
Date: Wed, 6 Oct 2004 08:34:20 -0500

Hi Eiji,

Thanks for your comments:

> The architecture draft well clarifies what PCE is.
> I have several comments on the draft as follows. 
> 
> 1. LSP information in TED. 
> 
> It would be useful to clarify information in TED. 
> 
> I understand that section 1 describes the definition of TED 
> and that TED is made by using IGP-TE or by other means. 
> Information in TED includes not only contents that can be built 
> from the distribution of IGP-TE, but LSP information as described in
> section 6.8. However, LSP information, which is not able to 
> be collected by IGP, is not clarified in the draft.

LSP information from sources other than the IGP is discussed in Section
6.7.  The scope of such information could be large.  Do you have
suggestions as to which information should be clarified?  

> I suggest that contents of LSP information, such as LSP routes, the
> reserved bandwidth, and measured traffic volume passing 
> through the LSP, be clarified. 
> 
> There are two reasons to add the LSP information. One is because the
LSP
> information is required to perform re-optimization for MPLS
> LSPs. LSP re-optimization is described in Sections 4.4 and 7. I
suggest
> that LSP information including measured traffic volume and LSP routes
> should be added in TED for LSP re-optimization. Otherwise, 
> LSP re-optimization is not effectively performed according to traffic
> fluctuation.
> 
> The other reason is because LSP information is needed to reconfigure
> virtual network topology (VNT). Lower-region LSPs such as optical
paths
> form a network topology, which is used for routing of higher-region
> traffic such as IP traffic.  The network topology formed by
lower-region
> LSPs is called a virtual network topology (VNT).

Sounds reasonable in general.  However, several LSP attributes are
listed in Section 6.6 -- what additional attributes, if any, are needed?
 
> I also suggest that more description be added on how LSP information
> might be collected and how this information could be synchronized with
> the conventional TED.

Collection of LSP information is discussed in several places and
synchronization is discussed in Section 6.7 -- anything specific to
suggest be added?

> TED information comes from different sources  such as OSPF-TE,
NetFlow, 
> SNMP, GTEP, XML etc. or TED information is obtained by making another
> new protocols or by extending IGP, PCC-PCE communication protocol.
> Therefore, there is an issue whether TED information is
> managed with a single database or multiple database. Several methods
for
> TED synchronization can be considered. 
>  
> a) Different TED database. One database often accesses the other 
> database for TED synchronization. 
> b) The same database. The database often is updated when LSP 
> information is changed. 
> 
> Method b would be better in terms of accuracy of TED synchronization.
> In terms of node processing load, more discussions are needed.

The tradeoffs of a) and b) are discussed in Section 6.7 on
synchronization, and elsewhere in the document.  Distributed and
centralized PCE architecture alternatives are identified and allowed
within the architecture -- no judgment is made on which is preferred.
Do you have any specific additions you would like to suggest (if so in
which Section)?
 
> 2. TED synchronization
> 
> As described above, TED synchronization is important. 
> I suggest that "TED synchronization: speed with which synchronization
is
> achieved, and the impact of the synchronization process on the data
> flows in the network." be added as evaluation metric in section 7. 

OK.  These would augment the last item in Section 7 regarding
synchronization:
"- Ability to maintain accurate synchronization between TED and network
topology and resource states."

Thanks,
Jerry

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---

From: Eiji Oki <[email-masked]>
Date: Fri, 08 Oct 2004 13:15:29 +0900

Hi Jerry, 

Thank you for your comments. 
Please see inlines. 

> suggestions as to which information should be clarified?  

I think that it would be better to include LSP routes, 
the reserved bandwidth, and measured traffic volume passing 
through the LSP, which are not included in IGP-TE information.

> listed in Section 6.6 -- what additional attributes, if any, are needed?

Yes, several attributes are listed. However, it seems to be fixed values
that are determined when an LSP is established. 

I suggest that changeable values according to traffic situation, LSP
routes and measured traffic volume passing through the LSP.

> within the architecture -- no judgment is made on which is preferred.

Yes, I agree with you.

> topology and resource states."

I would like to mean "quick" synchronization in evaluation metric.

Thank you.
Eiji