Subject: Non-member submission from [Sukrit Dasgupta <[email-masked]>]

From: "Adrian Farrel" <[email-masked]>
Date: Tue, 7 Aug 2007 17:58:21 +0100

----- Original Message ----- 

> To: [email-masked]
> Cc: JP Vasseur <[email-masked]>,
> Jaudelice Cavalcante de Oliveira <[email-masked]>,
> [email-masked]
> From: Sukrit Dasgupta <[email-masked]>
> Subject: Comments/Feedback on 
> draft-dasgupta-ccamp-path-comp-analysis-00.txt
> Date: Tue, 7 Aug 2007 11:54:20 -0400
>
> Hi Dimitri,
>
> With respect to our discussion on the floor at CCAMP, it would be
> great to get your comments/feedback on draft-dasgupta-ccamp-path-comp-
> analysis-00.txt/pdf. This would help to further proceed with the draft.
>
> Thanks,
> Sukrit

---

From: dimitri papadimitriou <[email-masked]>
Date: Sat, 11 Aug 2007 18:03:09 +0200

hi

here are my comments on this document:

Need to distinguish the different crankback methodologies when carrying
out comparisons (source, per domain/area, etc.)

Section 3 needs way better refined definitions before drawing 
conclusions - as examplest that section states:

"With the PD or PCE approach, the signaling of a TE LSP my fail because 
of lack of synchronization between the Traffic Engineering Database 
(TED) used by the computing entity and the actual link reservation state."

fair but why then the following is observed (Section 5.3)

"Figures 2e and 3e shows the distribution of the total number of 
signaling failures experienced by the TE LSPs during setup.  About 38% 
and 55% of TE LSPs for MESH-CORE and SYM-CORE, respectively, experience 
a signaling failures with per-domain path computation when link failures 
take place in the network. In contrast, only about 3% of the TE LSPs 
experience signaling failures with the PCE method.  It should be noted 
that the signaling failures experienced with the PCE correspond only to 
the TEDs being out of date."

from

"As discussed in the previous sections, signaling failures occur either 
due to an outdated TED or when a path cannot be found from theselected 
entry border router."

one can deduce that the delta is resulting from

"With the PD approach, another situation leading to a signaling failure 
is when the selected exit domain router does not have any path obeying 
the set of constraints toward a downstream exit node or the TE LSP
destination."

why the TED is not populated with that information for PD path 
computation purposes such to have comparable working assumptions ? (in 
other terms why only the BRPC method benefits from this advantage ?) 
comparisons shall be done with identical TED otherwise you don't need 
experiments by definition having less critical information leeds to such 
results

the observation is thus not that BRPC is better than PD computation but 
that BOTH techniques needs to have certain information about links 
inter-connecting domains to decrease the blocking/failure probability.

thanks,
-d.

Adrian Farrel wrote:
> .