Hi, Dear Jon,
Thank you very much for the useful comments. Please see our reply inline
(looking for [AUTHORS]):
________________________________________
发件人: Jonathan Hardwick [[email protected]]
发送时间: 2013年7月9日 5:46
到: Zhangxian (Xian); [email protected]
Cc: [email protected]
主题: RE: [Pce] FW: New Version Notification for
draft-zhx-pce-stateful-lsp-sync-00.txt
Hi there
The incremental state synchronization mechanism looks like a potentially useful
optimization. I have a few questions for the draft authors.
The motivation of the incremental synchronization mechanism is to reduce the
time and bandwidth of the synchronization process. This is likely to be true
in scenarios where the LSP database is large and the number of changes since
the last successful synchronization is small. Conversely, if the LSP database
is small and the PCE has taken a long time to recover then it might actually be
quicker to perform a full mark-and-sweep synchronization.
[AUTHORS]: Agreed.
Is the intent of your draft that the PCC and PCE can choose whether to perform
an incremental or full synchronization based on how out of date the PCE's
database is? In which case, who makes the choice, using what criteria, and how
is that choice made known to the other party? Or is the intent that
incremental synchronization is always preferred if both parties support it?
[AUTHORS]: In the current version 'incremental synchronization' is always
preferred if both parties support it. Do you feel strongly if this needs
changing?
The incremental synchronization relies on the PCC replaying the necessary PCRpt
messages to the PCE to bring it up to date, including any that relate to
deleted LSPs. Do you have any guidelines on how many PCRpts the PCC should
cache and for how long? Have you considered a check-pointing mechanism where
the PCE occasionally confirms that is has a persistent copy of DB version x to
avoid this cache from growing too large?
[AUTHORS]: PCC needs to cache PCRpts of deleted LSPs only if there exist some
PCEP session to a stateful PCE a)which was previously up and LSP-DB
synchronized, but temporarily down; b)supported LSP-DB-Version TLV in PCRpts
(IDB flag was set in OPEN).
[AUTHORS]: Also, say the DB version when a LSP gets deleted is X, The DB
version at the time of last synchronization for a 'down' session be DBV(i)
where i=1 to N (N temporarily down sessions with above conditions satisfied),
Then you no longer need to cache PCRpts of a deleted LSPs if X <
MIN{DBV(i),(i=1...N)}
[AUTHORS]: Whenever a down session comes up and state is synchronized, the
above condition can be used to clear the cache. Since this is a local mechanism
of PCC, should it be a part of the specification?
You need to deal with the case where both PCE and PCC set the D flag and yet
the PCC's cache of PCRpts does not go back far enough to make an incremental
synchronization possible. In this case, a full synchronization is necessary
regardless of the D bits.
[AUTHORS]: One way to do this would be to have another flag in LSP object along
with SYNC to indicate if PCC report is for incremental state synchronization.
Best Regards,
Xian (on behalf of all authors)
Regards
Jon
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Zhangxian
(Xian)
Sent: 08 July 2013 10:59
To: [email protected]
Subject: [Pce] FW: New Version Notification for
draft-zhx-pce-stateful-lsp-sync-00.txt
Hi, Dear PCErs,
We have just upload a new draft specifying the need in PCEP to allow
incremental LSP state synchronization as well as PCE control over this process
for stateful PCE(s). It also proposes PCEP extensions to support the
requirements.
Any comments/feedback are appreciated.
Regards,
Xian ( on behalf of all authors)
________________________________________
发件人: [email protected] [[email protected]]
发送时间: 2013年7月7日 19:41
到: Zhangxian (Xian); Xiegang (A); Dhruv Dhody
主题: New Version Notification for draft-zhx-pce-stateful-lsp-sync-00.txt
A new version of I-D, draft-zhx-pce-stateful-lsp-sync-00.txt
has been successfully submitted by Xian Zhang and posted to the
IETF repository.
Filename: draft-zhx-pce-stateful-lsp-sync
Revision: 00
Title: LSP Synchronization for Stateful Path Computation Element (PCE)
Creation date: 2013-07-05
Group: Individual Submission
Number of pages: 7
URL:
http://www.ietf.org/internet-drafts/draft-zhx-pce-stateful-lsp-sync-00.txt
Status: http://datatracker.ietf.org/doc/draft-zhx-pce-stateful-lsp-sync
Htmlized: http://tools.ietf.org/html/draft-zhx-pce-stateful-lsp-sync-00
Abstract:
The Path Computation Element Communication Protocol (PCEP) provides
mechanisms for Path Computation Elements (PCEs) to perform path
computations in response to Path Computation Clients (PCCs) requests.
[Stateful-pcep] specifies a set of extensions to PCEP to enable
stateful control of MPLS-TE and GMPLS Label Switched Paths (LSPs) via
PCEP and maintaining of these LSPs at the stateful PCE. This
document describes the mechanisms for incremental LSP Database (LSP-
DB) synchronization as well as PCE control of the LSP-DB
synchronization process.
The IETF Secretariat
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