On 02/26/2013 12:18 AM, Zhangxian (Xian) wrote:
Hi, Dear Adrian,
I am confused by the explanation you provided below.
My question originated from the definition of an active PCE provided in
section 17(copied in below).
________________________________________
发件人: Adrian Farrel [[email protected]]
In the second case you would be suggesting an option I personally don't consider
is allowable. That is, a PCE cannot, IMHO, provision paths. It can only issue
recommendations for rerouting of LSPs that have been delegated to it.
Thus you have drawn out an important distinction between an NMS and an Active
PCE. That is, the NMS can provision new LSP and has control over existing LSPs.
The Active PCE cannot provision new LSPs and can only suggest changes to
existing LSPs. I have added a little text about this to Section 19.
Adrian
Dear Xian, Adrian, all,
Sorry for chiming in, this was one of the points discussed in Atlanta
and, IMHO, the taxonomy that I feel comfortable with after discussing
with some involved authors
a) Stateless PCE
b) Stateful PCE [LSPDB]
b.1) Passive stateful PCE [ ~LSPDB for the purposes of path
computation ]
b.2) Active stateful PCE [can affect state of delegated LSPs...]
b.2.1) Active stateful PCE without instantiation capabilities
b.2.2) Active stateful PCE with instantiation capabilities [...
and can instantiate new LSPs. Instantiated LSPs are automatically
delegated]
It seems to me that there is no agreement regarding whether b.2.2 should
be a function of a PCE. If I remember correctly, it has been mentioned
that this is (at least for now) out of charter
Adrian (correct me if wrong!) has stated his personal preference to
_not_ include such function. Oscar, Ina, Jan, Cyril, Ed. etc. have also
discussed about this ( I cannot comment on their preferences). Arguments
given against is that this should be a function of an NMS, a VNTM, a
provisioning manager, etc. On the other hand, accepting it to be a
function of the PCE seems to build on top of the existing PCEP to define
what otherwise would be an undefined interface ?
I don't have a strong opinion, but instantiation of LSPs being a
function of an NMS does not necessarily exclude a PCE from being able to
do so. An NMS could use a (to be defined) PCE northbound interface and
the active stateful with instantiation capabilities can use the PCEP
session to instantiate such LSPs.
Comments or thoughts? Given that Ina, Ed, Xian are leading the work on
stateful PCE and that there are a couple of drafts discussion
instantiation of LSPs (i.e. PCCreate) both in MPLS and GMPLS networks,
it would be interesting to know the wg opinion about this. It would be
great it we could gather arguments for and against.
Thanks and best regards
R,
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