Subject: [Pce] some question about domain sequence in PCE-based architecture

From: [email-masked]
Date: Thu, 7 May 2009 15:35:37 +0800

Hi Pcer，

It is necessary to know the sequence of domains when BRPC (RFC5441) is 
used to compute the TE-LSP across multi-domains, and the same question 
exists in path-key scheme (RFC550). 

As we know, there are different ways to solve this problem. The first one 
is administratively predetermined, and this method seems too inefficient 
to find the optimal end-to-end TE-LSPs once there are a lot of domains. 
The second one, utilize the BGP routing tables to find the sequence if PCE 
function is inserted in ASBR; but what if the equipments do not know what
’s BGP in optical domains? The third solution, thanks to Farrel’s work, 
is the concept of a hierarchical PCE architecture to coordinate PCEs in 
peer domains to derive an optimal end-to-end path, which fits well with 
the ASON routing architecture.

How about a uniform solution applicable to both the data and optical 
environment? Is it well to add a simplified update message in PCEP? The 
update object body consists of routing prefix/domain number/PCE address, 
just as fellow. Every PCE that has the ability to compute the TE-LSP 
towards neighbor domain announces the update message to each other, then 
it stores one or more PCE sequences according to domain accounts. The PCE 
lookups the end-point object if a path computing request comes, and find 
the PCE sequences(one or more) responsible for this TE-LSP computing. 

It is easy to get the PCE sequences under the help of this method, and 
even if there are several hundreds of domains, it will converge quickly 
also. 

What are your opinions? Is it suitable to put forward this proposal in PCE 
group? Any comments?
 
          Best regards 

                 Fei Zhang

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