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draft minutes of Minneapolis session
Dear all,
Below please find a draft of the minutes of the Minneapolis session.
Thanks to Dave Plonka for taking them.
Please check them an send comments if you disagree or if you miss
something.
Thanks,
Juergen
=======================================
Minutes of the PSAMP session at IETF 58
Tuesday November 11, 9:00 h - 11:30 h
=======================================
Minutes taken by Dave Plonka and Juergen Quittek
===============
Session summary
===============
The WG documents on the PSAMP framework and on packet selection
are now consistent with respect to each other and both are
quite mature. For both documents the editors will send the
list of remaining open issue to the mailing list soon. After
the next update (planned for mid of December) both documents
can enter WG last call together. The protocol and information
model documents are available as first versions. They describe
how the (upcoming) IPFIX protocol is used for exporting packet
samples. They depend on the corresponding IPFIX documents that
are expected to be completed by May 2004. The PSAMP MIB
definition progressed slowly, because it depends on the packet
selection document. The WG discussed how to integrate an
individual I-D describing hash functions for packet selection
in detail. the WG hesitated to have this as an additional WG
document. It rather should be integrated into the packet
selection document.
=============================
Presentations and discussions
=============================
Andy Bierman on the WG Status
=============================
Andy reported on the status of the WG documents.
The sampling framework document and the packet selection
document are quite mature and should enter WG last call soon.
The report format and report stream format document
(PSAMP protocol) is waiting for progress of the IPFIX protocol.
The export protocol and requirements for collectors document
(PSAMP information model) is waiting for progress of the IPFIX
info model.
Nick Duffield on the PSAMP framework
====================================
Nick discussed open issues on the framework document.
The term 'sampling' was misunderstood by several reader.
Therefore it was replaced by 'packet selection'.
The framework description was extended to better cover
encrypted packets. The description of exporting packet
reports now discusses compliancy to and coexistence with IPFIX.
The term 'emulated selection' will be replaced by
'approximative selection'. The term 'measurement packets'
will be replaced by 'export packet'.
An issue of discussion is the reporting of the sequence counter.
Suggestion is to report it regularly, but not with every
packet report. The issue will be put on the mailing list.
Support of encryption of packet reports will be changed to
be REQUIRED.
Reporting sequence numbers is considered to enable
re-normalization of measured bytes.
He discussed export requirements including confidentiality
and timeliness. Is there a need to request that a delay
SHOULD not exceed 1 second?
Q: [Andy] why not make it configurable?
Q: [Nick] why would an implementation not want to export ASAP?
A: [Andy] there may be resource issues
A: [Maurizio Molina] implementer may wish to group packets for
export
There is the general feeling that the export protocol for
PSAMP is waiting on IPFIX.
A: [Andy] coupling with IPFIX is not just to reuse documents,
but also implementation code
A: [?] reminder that SCTP is already RFC defined, PR-SCTP is
in IEST queue packet selection
Tanja Zseby on packet selection
===============================
Tanja presented progress on the packet selection document.
Terminology is now almost consistent with the framework
document. After recent discussions only small changes are
required here. Packet selectors could be part of IPFIX or
other metering process. A still open issues is the set of
methods for flow state sampling. Further open issues of the
document include: Should we include some examples for flow
state sampling or just leave it open to vendor-specified
parameters based on the info model? Is there a better term
for hash-based sampling than "emulation" or "approximation"?
A: [Juergen] re: the flow state sampling, since the known
current methods are experimental, perhaps we should just
say they are vendor-specified (ie. w/o examples)
A: [Maurizio] perhaps it would help to have one
example (such as sample and hold)
Benoit Claise on the PSAMP protocol
===================================
Benoit discussed the initial version of the PSAMP protocol
document describing how the IPFIX protocol is used for
exporting packet records. The IPFIX documents only speak
about 'flow records'. These will be used as 'packet records'
in PSAMP. The information model of IPFIX and PSAMP overlap.
The PSAMP information model can be defined as extension of
the IPFIX information model.
A: [Plonka] timeliness of export needs to be mentioned in
PSAMP protocol and the other drafts (such as requirements)
need to take into consideration that if you choose an
existing transport like IPFIX, that it might impose limits
on the timeliness
A: [Andy] doubts that its reasonable to demand some explicit
export time, especially as little as one second, perhaps
it should just be user configurable [presumably within
the implementation limits]
A: [Benoit] IPFIX does have a timeout, to get timely reporting
A: [Dave Plonka] in IPFIX, there is currently no explicit bound
on the time from flow timeout until export
A: [Nick] motivation for 1 second "time limit", we want to
specify a maximum, so that its not uncontrolled
A: [Benoit] you can piggyback this on IPFIX
Benoit Claise on the PSAMP information model
============================================
Benoit presented the initial draft of the PSAMP information
model. It is defined as extension of the IPFIX information
model and adds a data type of a variable length byte array
and it adds several information elements. It needs to be
synchronized with the packet selection document.
Q: [Nick] Do you have fields defined for all the sampling
types, such as hash-based?
A: [Benoit/Juergen] not yet, yes - that needs to be added.
This document is still in a premature state.
Juergen Quittek [on behalf of Thomas] on the PSAMP MIB
======================================================
Very small changes were committed to the PSAMP MIB since
the document depends on the packet selection document that
was submitted just before the cut-off date leaving no time
to reflect it in the PSAMP MIB. Committed changes concerned
the support of multiple receivers of packet samples. We need
to determine which portions are mandatory and which optional.
A: [Andy/Juergen] regarding the existing drafts, suggest
perhaps 4 weeks time to deal with existing open issues,
and take them to last call
A: [Juergen] document editors should take the open issues to
mailing list, try to get them addressed in 4 weeks, to
enter last call in december, perhaps to wrap-up in January.
Maurizio Molina about hash functions
====================================
So far, the WG documents to not precisely describe hash
functions. The presented individual I-D suggests to do so
and defines some hash functions that have already been tested.
A: [Andy] re: specification of hash function, I'm relunctant
to add more RFCs to the initial PSAMP effort. If this
document were an informational RFC (resulting from an
individual draft) that would be sufficient.
A: [Nevil Brownlee] re: hash functions - they're hard to get
right, it would be better for PSAMP to settle on a short
list (of no more than 3), and concurs with Andy's suggestion
for new hash algorithms to be individual drafts specified
outside PSAMP.
A: [Nick] there is a benefit from PSAMP implementations
using the same hash functions, for consistency there is
a trade-off between strength and complexity when trying
to identify the "best" hash functions for PSAMP.
A: [Andy] if hash functions need to be in their own draft
so that they can be easily edited, that probably means
that they're not mature enought to be part of PSAMP yet.
He suggest taking the discussion to the mailing list.
A: [Andy] PSAMP could publish detailed functional requirements
of a candidate hash function, rather than specifying a
specific one with pseudo-code.
A: [Nick] trying to avoid different vendors using different
hash functions - because that's not that useful.
A: [Andy] OK, well then there needs to be some agreement
[on standard hash functions]
Emile Stephan about spacial metrics for IPPM
============================================
Emile suggests that one use of psamp is to determine the delay
and loss of individual packets [and thus would perhaps benefit
from IPPM defined spatial metrics for same].
Q: [Henk Uijterwaal] why can't you apply the existing IPPM
metrics (to points H1 to H2 in slide #3)?
A: [Emile] [something about it not being end-to-end]
Q: [Andy] Nick, do we have any requirement on time
syncronization?
A: [Nick] there is no such PSAMP requirement specified, but
we do say that when timestamps are supplied that the
accuracy is indicated.
Q: [Andy] [to Emile] are you suggestion some change to PSAMP
[to accomodate this potential application of PSAMP data]?
Q: [Nick] Does IPFIX address timestamp issues?
A: [Nevil] Yes, microsecond resolution is possible in export
data type, but the accuracy and resolution are not have to
be specified.
A: [Tanja] QoS monitoring is one of IPFIX' target applications,
and that would somewhat depend on timestamps.
==================
Session conclusion
==================
Andy asked authors to post their open issues to the mailing list.
Q: [Randy Bush] how are we doing on progress?
A: [Andy] plan for Jan. 10 for two main drafts to go to last call.
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