[EMAIL PROTECTED] wrote:
Dean,
See my comments in-line.
Igor
As for COPS, its application environment is somewhat similar
to that of PCE but has some problems (if used for PCE applciation)
due to much optimization around its specifics such as:
1) The PEP (client) is the one required to initiate the
connection with a PDP (server). Whereas for PCE
application, either PCE (server) or PCC may initiate
the connection.
IB>> Why would a PCE want to initiate a connection with a PCC?
more generally i am not sure to understand why "PC" elements would
initiate connections ... are they not meant to "compute" paths ?
2) There requires a synchronization between PEP and PDP for
the policy application with states maintained on both places.
For PCE application, the PCE server is only required to
perform a one-time service for each LSP, without the need
maintain any subsequent states.
IB>> Even if all this is true, why is it a big deal?
there is also a need to discuss what are these states and what they
represent in the context of this application (PCE) before claiming that
they are impacting one implementation and not the other
3) It requires some work to support a PDP functions as a PEP
and communicates with another PDP. PCEP supports this model
fully.
IB>> Functions of PDP and PEP are orthogonal and surely could be
physically co-located
indeed
4) COPS is a server-client protocol, but with code point
heavily dedicated for a specific application. It does not
serve general purpose if any, and to support PCE application,
there would be a large number of extensions, thus defeating
the purpose of reusage.
IB>> PCIM is designed to be easily expanded for application (read PCE)
specific needs
Igor
As a result, I'd favor PECP as a PCE-specific protocol; it is much
cleaner and also light-weighted.
there is very little material/argumentation as part of this e-mail that
allows to come to such conclusion
by the way i would like to ask what is meant here by "cleaner" ? and how
it is possible to come to the conclusion that PCEP is lightweighted by
the argumentation provided here above ?
Dean
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Dean Cheng (dcheng)
Sent: Monday, October 03, 2005 3:30 PM
To: Adrian Farrel; [EMAIL PROTECTED]
Subject: RE: [Pce] Choosing the PCE protocol
Hi,
I don't think HTTP is a good candidate for the PCE application
and here are some weakness one could think of, if it used for
PCE application:
1) The HTTP is specifically designed for communications between
web server and its client, or applications in that nature.
Although it is possible to add extensions to support PCE
application, it would require a considerable amount of work.
That is not worth of the effort given the much smaller and
narrower application scope of PCE.
2) The payload of HTTP messages (both request and response)
is in form of byte stream, which is unstructured comparing
to the PCEP proposal, where the content is structured
with objects.
For the PCE application, the object based format is more
efficient in terms of processing.
3) The HTTP does not have unsolicited messages such as Notification
message and Error message that are defined by PCEP.
4) PCE architecture allows a PCE functions as a server but also as
a client communicating with another PCE server. In both cases,
the same protocol is used. PCEP supports this scenario. There
requires some work to make HTTP behavior as such.
Dean
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Adrian Farrel
Sent: Thursday, September 29, 2005 7:27 AM
To: [EMAIL PROTECTED]
Subject: [Pce] Choosing the PCE protocol
Hi,
Three candidate protocols have been brought to my attention for us to
consider. These are (in no specific order):
- HTTP
- PCECP (as draft-vasseur-pce-pcep-02.txt)
- COPS
I would like to close the nomination period, and move on to
select our
protocol.
The best approach will be if supporters of the candidate protocols
indicate (briefly) why their proposed protocol is suitable. It would
also be helpful if they were frank about what the weaknesses of their
proposal are.
And please - this is not an election, it is an interview process.
Thanks,
Adrian
PS The reason why JP is keeping quite on this is that he is an author
of draft-vasseur-pce-pcep-02.txt and so (quite rightly) is not
occupying the chair during this discussion.
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