Hi Authors/WG,
Some comments on draft-ietf-pce-stateful-pce-07.
Apologies for a long mail.
Major
- I noticed that the PCReq/PCRep encoding are removed from this
version, how should the passive stateful PCE behave now (with no
LSP object). In section 5.6.1 when a passive stateful PCE sends
PCRep message, PCC send PCRpt message to indicate is the path can
be setup or not. There is a need to link the PCRep with PCRpt in
case of passive stateful PCE. The LSP object added in PCReq/PCRep
in the previous version could do this. I wish there is some
discussion on the mailing list, so that the WG is aware of why the
changes were made.
- PCRpt/PCUpd Message: What is the way to know the source and
destination of the LSP in the current encoding esp when the LSP is
down or not yet setup? Also note that the ERO is a mandatory
object in PCRpt. Should it be existing when the path calculation
has not been initiated so far? ERO object is also mandatory in
PCUpd. IMO PCE may choose to tear down an LSP (say during handling
of a higher priority LSP), what should be in the ERO object then?
IMHO ENDPOINT object in PCRpt/PCUpd will make for much cleaner
design but "...an ERO with just the 'endpoints'" is also an
option. Either way some text in the document should explain that.
- PLSP-ID: it is constant for the life time of a PCEP session. IMO
its a better idea to make PLSP-ID unique NOT per PCEP session but
across PCEP session, i.e. if there are multiple stateful PCE and
re-delegation happens (after the earlier delegated PCE is down),
PLSP-ID will not change. IMO in case of PCE-Initiated LSP, it
would allow a new stateful PCE to take control over the orphan LSP
using the same PLSP-ID in a much simpler way.
Minor
- Abstract
Although PCEP explicitly makes no assumptions regarding the
information available to the PCE, it also makes no provisions
for synchronization or ...
Prefer if *synchronization* can be clarified, i.e. we explicitly
say LSP state synchronization, so as not to be confused with TED
sync.
- Terminology
State Timeout Interval: when a PCEP session is terminated, a
PCC waits for this time period before flushing LSP state
associated with that PCEP session and reverting to operator-
defined default parameters.
Can we change this to operator-defined default parameters or
procedures? By procedure I meant that on state timeout interval
expiry, PCC may rely on local CSPF computed path or ask a
passive/stateless PCE to re-compute based on the operator-
defined procedure.
- Sec 3.1.3. Protocol vs. Configuration
Security: opening up a configuration channel to a PCE would
allow a malicious PCE to take over a PCC.
Rest of the section compares the shortcoming of existing
configuration tools/protocols with stateful PCE; But this point
suggest opening up configurations of state directly at PCE. Am
not so sure about it.
- Sec 5.3. Capability Advertisement
If PCE advertise its stateful capability during IGP discovery,
do the PCC/PCE still need to follow the procedure laid out in
this section. This should be clarified in the draft.
If the PCEP Speakers support the extensions of this draft but
did not advertise this capability, then a PCErr with error-
type 19 (Invalid Operation), error-value 2 (Attempted LSP
Update Request if active stateful PCE capability was not
advertised)(see Section 8.4) will be generated and the PCEP
session will be terminated.
Also needed an error-value for attempting to send LSP State
report if stateful PCE capability was not advertised. Basically
a PCEP speaker which supports this extension but did not
advertise it, PCC anyhow chooses to send PCRpt message then the
another error value is needed.
- Sec 5.4. State Synchronization
The set of LSPs for which state is synchronized with a PCE is
determined by advertised stateful PCEP capabilities and PCC's
local configuration (see more details in Section 9.1).
How is the capability advertisement related to decision which
set of LSP are synchronized? IMO Capability advertisement
determines if the state synchronization as a whole is performed
or not, it doesn't determine a set (subset) of LSPs which are
synchronized.
A PCE SHOULD NOT send PCUpd messages to a PCC before State
Synchronization is complete. A PCC SHOULD NOT send PCReq
messages to a PCE before State Synchronization is complete.
Some text can be added to suggest how should the PCC/PCE react
if above happens? Error Message? Termination of PCEP session?
A PCE implementing a limit on the resources a single PCC can
occupy, MUST send a PCErr message with error-type 19 (invalid
operation) and error-value 4 (indicating resource limit
exceeded) in response to the PCRpt message triggering this
condition in the synchronization phase and MUST terminate the
session.
By resource do you mean a limit on number of LSPs that a given
PCC can synchronize?
- Sec 6.1. The PCRpt Message
<path>::= <ERO><attribute-list>[<RRO>]
Please add some description on when RRO should be used. How it
works along ERO etc?
- Sec 7.2. SRP Object
The SRP (Stateful PCE Request Parameters) object MUST be
carried within PCUpd messages and MAY be carried within PCRpt,
PCNtf and PCErr messages.
PCNtf? Well then the extension of PCNtf is needed to support
carrying of SRP object.
- Sec 7.3.2. Symbolic Path Name TLV
The SYMBOLIC-PATH-NAME TLV MAY appear as a TLV in both the LSP
Object and the LSPA Object.
What is the purpose of this TLV inside the LSPA object? (Also
mentioned in section 7.4)
Editorial
- Terminology
This document uses the following terms defined in [RFC4090]:
MPLS TE Fast Reroute (FRR), FRR One-to-One Backup, FRR
Facility Backup.
Should be removed as they are not used in the document anymore.
Delegation
OLD
For intra-domain LSPs, this PCC SHOULD be the PCC of the LSP
head end.
NEW
For intra-domain LSPs, this PCC SHOULD be the LSP head end.
LSP State Report
OLD
an operation to send LSP state (Operational / Admin Status,
LSP attributes configured and set by a PCE, etc.) from a PCC
to a PCE.
NEW
an operation to send LSP state (Operational / Admin Status,
LSP attributes configured at PCC and updated by a PCE, etc.)
from a PCC to a PCE.
- Sec 3.1.3. Protocol vs. Configuration
OLD
Efficient State Synchronization: configuration channels may
be heavyweight and unidirectional, therefore efficient state
synchronization between a PCE and a PCE may be a problem.
NEW
Efficient State Synchronization: configuration channels may
be heavyweight and unidirectional, therefore efficient state
synchronization between a PCC and a PCE may be a problem.
- Sec 5.1. LSP State Ownership
OLD
An active stateful PCE may have control of a PCC's LSPs be
delegated to it, but the LSP state ownership is retained by
the PCC.
NEW
An active stateful PCE may have control of a PCC's LSPs that
are delegated to it, but the LSP state ownership is retained
by the PCC.
- Sec 7.3. LSP Object
The figure shows operational bits of 2 bit length, it should
be three!
Dhruv
On Wed, Oct 9, 2013 at 12:12 PM, <[email protected]> wrote:
>
> A New Internet-Draft is available from the on-line Internet-Drafts
> directories.
> This draft is a work item of the Path Computation Element Working Group
> of the IETF.
>
> Title : PCEP Extensions for Stateful PCE
> Author(s) : Edward Crabbe
> Jan Medved
> Ina Minei
> Robert Varga
> Filename : draft-ietf-pce-stateful-pce-07.txt
> Pages : 47
> Date : 2013-10-08
>
> 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.
>
> Although PCEP explicitly makes no assumptions regarding the
> information available to the PCE, it also makes no provisions for
> synchronization or PCE control of timing and sequence of path
> computations within and across PCEP sessions. This document
> describes a set of extensions to PCEP to enable stateful control of
> MPLS-TE and GMPLS LSPs via PCEP.
>
>
>
> The IETF datatracker status page for this draft is:
> https://datatracker.ietf.org/doc/draft-ietf-pce-stateful-pce
>
> There's also a htmlized version available at:
> http://tools.ietf.org/html/draft-ietf-pce-stateful-pce-07
>
> A diff from the previous version is available at:
> http://www.ietf.org/rfcdiff?url2=draft-ietf-pce-stateful-pce-07
>
>
> Please note that it may take a couple of minutes from the time of
> submission
> until the htmlized version and diff are available at tools.ietf.org.
>
> Internet-Drafts are also available by anonymous FTP at:
> ftp://ftp.ietf.org/internet-drafts/
>
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