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Minutes of the PSAMP session at IETF 64
Thursday November 10, 13:00 h - 15:00 h
Minutes taken by Tanja Zseby, Ralf Wolter
and Thomas Dietz
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Packet Sampling Session
Chair: Juergen Quittek
0. Session Summary
1. Agenda bashing, WG Status, IPFIX documents status (Juergen Quittek)
2. New results of hash function evaluation (Nick Duffield)
3. PSAMP protocol (Benoit Claise)
4. PSAMP information model (Paul Aitken)
5. PSAMP MIB (Thomas Dietz)
6. Use of IPFIX for Export of Per-Packet Information (Elisa Boschi)
7. IPFIX inplementation guidelines (Elisa Boschi)
8. Path-coupled meter configuration (Juergen Quittek)
9. Passive measurement and IPPM composition of metrics (Emile Stephan)
10. Wrap up
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Discussed Internet drafts
Packet Sampling (PSAMP) Protocol Specifications
http://www.ietf.org/internet-drafts/draft-ietf-psamp-protocol-02.txt
Information Model for Packet Sampling Exports
http://www.ietf.org/internet-drafts/draft-ietf-psamp-info-03.txt
Definitions of Managed Objects for Packet Sampling
http://www.ietf.org/internet-drafts/draft-ietf-psamp-mib-05.txt
Use of IPFIX for Export of Per-Packet Information
http://www.ietf.org/internet-drafts/draft-boschi-export-perpktinfo-01.txt
IPFIX Implementation Guidelines
http://www.ietf.org/internet-drafts/draft-boschi-ipfix-implementation-guidelines-00.txt
Framework for Metering NSLP
http://www.ietf.org/internet-drafts/draft-fessi-nsis-m-nslp-framework-02.txt
NSLP for Metering Configuration Signaling
http://www.ietf.org/internet-drafts/draft-dressler-nsis-metering-nslp-03.txt
IPFIX templates for common ISP usages
http://www.ietf.org/internet-drafts/draft-stephan-isp-templates-01.txt
IP Performance Metrics (IPPM) for spatial and multicast
http://www.ietf.org/internet-drafts/draft-stephan-ippm-multimetrics-02.txt
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0. Session summary
The first two PSAMP deliverables are under review by the AD.
The remaining three documents have made very good progress
and open issues were discussed - some even solved - at the
meeting. WG last call for all three documents is expected
to be before the next IETF meeting.
In the second part of the session several contributions were
discussed that are related to PSAMP and IPFIX, but not covered
by the respective charters. Discussed items included IPFIX
protocol implementation guidelines, efficient export of packet
reports, path-coupled configuration of meters, and BCP for
IPFIX templates. The work on these items (and on three further
items discussed at earlier IPFIX and PSAMP meetings) will be
continued by individual contributors.
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1. Agenda bashing, WG Status, IPFIX documents status (Juergen)
Juergen explained that the IPFIX documents have been submitted to the IESG
for publication as RFC. They are currently reviewed by area director David
Kessens. Now, the PSAMP documents can also progress quickly.
As there is no IPFIX session at this IETF meeting, there are some IPFIX-related
issues on the PSAMP agenda.
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2. New results of hash function evaluation (Nick Duffield)
The test discussed so far for selecting a standard hash functions by the PSAMP
WG are documented in http://www.research.att.com/~duffield/pubs/31-085A.pdf.
Nick showed results of a new study. Hash functions for packet selection use
parts of the IP packet as input that that doe not change while the packet is
forwarded. The output is a hash value per packet. Requirements for the hash
functions include representative sampling, uniformity and independence.
Tests were performed for hash functions BOB, CRC32, IPSX, MMH with traces from
NEC and MAWI. For the tests, the lowest lowest sampling rate was 1 in 1000.
Concerning uniformity, BOB is closest and more consistent than CRC32, MMH and
IPSX are not close to uniformity. Concerning independence, only BOB appears
close in all tests (20 byte input), CRC matches BOB performance with 24 bytes
input compared to 20 bytes. Concerning execution speed, IPSX is fastest,
followed by BOB and CRC32. If the uniformity is not important, IPSX could be
useful. In general. BOB is the best function and the one recommended in the
PSAMP packet selection draft.
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3. PSAMP protocol (Benoit Claise)
http://www.ietf.org/internet-drafts/draft-ietf-psamp-protocol-02.txt
Benoit introduced the new design of the PSAMP protocol that is based on
requirements in the PSAMP framework draft and the PSAMP packet selection draft.
The solution uses the IPFIX protocol. The discussion was focusing on open
issues /as they have been numbered on the mailing list):
Open Issue #3 - How to deal with multiple IE's in a data record using
the same IE identifier?
A solution for this problem is not defined in the IPFIX documents.
At the interoperability testing event it was discuvered that different
implementations handle the issue differently.
Dave Plonka: a placeholder would be required to express for which information
elements the order is relevant and where not.
Dave Plonka: There are 2 solutions: Propose change to IPFIX Protocol or use
several IE's selctorId1, selectorId2, selectorId3,...
Juergen: Another alternative would be using arrays.
Benoit: IPFIX proto should clarify what to do.
Juergen: Currently it is an ambiguity in the IPFIX protocol specification.
Elisa: Implemention guidelines draft describes the problem, but does not
yet suggest a solution.
Emile: Does the template allow this?
Juergen: Yes.
Elisa Boschi: Has also a section in her draft and wanted to know
where to solve it.
Discussion to be continued on the mailing list
Open Issue #2 - Field Match and Router State Filtering
From the protocol's perspective, there are no differences between the field
match and router state fields. Proposal: merge both fields to simplify the
protocol.
Tanja: Currently, the packet selection draft separates them. Merging them
is OK. It will simplify the protocol.
Open Issue #9: Filtering is so far restricted to IPFIX IEs only.
It was agreed to remove the restriction and allow filtering on any IE.
Open Issue (not numbered): Terminology Metering Process (IPFIX) vs.
Measurement Process(PSAMP)
Terminology problem: When psamp started it wasn't clear that ipfix would be
chosen for export, the architecture is similar but still different. What IPFIX
calls "metering" is defined as "measurement" in PSAMP terminology.
Juergen: Let's use term "metering" for both. Shall we also drop terms
"selection process" and "reporting process"?
Tanja: Keep selection process as part of metering process (is in line with
IPFIX, because metering process can contain sampling/filtering). But
selection process should be kept.
Nick: I agree.
Juergen: The changes need to be applied also to the framework draft and the
packet selection draft that are currently in AD review.
Open Issue #7: Metering Process ID in Association ID
This concerns the IPFIX processes in the associations ID (section 7.1 and 7.2
of psamp-tech). The proposal is to remove "metering process ID" to avoid
confusion, as no one could think of a possible scenario.
Tanja: It was introduced to support multiple IPFIX proecesses sharing a
selector. But since no example was found swo far where this is demanded
and since it it can be done (but less efficient) without the associations
by having 2 selectors, it is OK to drop it.
Discussion to be concluded on the mailing list.
Open Issue #8: Send Selector Input Sequence Number in each Data Report
The selector input sequence number (counter 64) is part of every data record.
Proposal: Don't send in every packet, instead on an interval base or as
option records.
Andy Johnson: Just send the sequence number of the last selector.
Arguing with Nick about complexity, trade off etc.
Nick: The idea was to make it easier for the collector, for bandwidth reduction.
The proposal is ok.
Juergen: Use a combination of MAY/MUST provides maximum flexibility
Nick: "MUST be able" is fine.
Open Issue #11: Representation of Observation Point
How to represent the observation point? Should we have an observation point ID
or re-use any information element (such as interface, line card, router)?
Proposal: re-use any information element.
Juergen: Can we use the "scope" definition from ipfix?
Benoit: There was a reason why it wasn't possible.
Paul: It is not possible when using different elements.
Discussion to be contimnued on the mailing list.
Open Issue (not numbered): Chunk with too short lenght
How to encode "chunk" with a too short length? Padding wouldn't be recognized
by the collector. One solution would be using a new template for each length.
Proposal: The protocol draft should say that padding MUST NOT be used for
variable length IEs.
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4. PSAMP information model (Paul Aitken)
http://www.ietf.org/internet-drafts/draft-ietf-psamp-info-03.txt
For the new version, several IEs were 'cleaned up'. New IEs cover chunks of
packets. There is no need to distinguish filtering and sampling. It is
sufficient to use a single IE for all selections methods.
Open issue: The term 'layer 2' is not well defined.
Therefore IEs named 'layer 2 header' are ambiguous.
Pauls proposal: replace 'layer 2 header' with 'data link frame'.
Juergen: How would you implement this for it work for IP over ATM?
Please give hints to implementers for handling such cases.
Open Issue: What if the chunk is not long enough. Ta be solved by PSAMP
Protocol.
Open issue: How to export very long packets?
Juergen: Please add comment to draft.
Juergen: Question to the editors.:how many additional revisions are required
before going last call?
Benoit: All issues were listed. We wait for feedback on the mailling list.
We expect to have new versions of the drafts by Christmas and to complete them
close to the next IETF meeting.
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5. PSAMP MIB (Thomas Dietz)
http://www.ietf.org/internet-drafts/draft-ietf-psamp-mib-05.txt
Thomas explained that he just applied a few changes to the document, because
already the previous version was quite mature. The modifications of the
information model presented by Paul were already conered. Still to be done
are diagrams and examples for clarification, better support for hash filtering,
and solving a few naming issues.
Benoit: I suggest having a link between records exported by IPFIX and get
the summary information via SNMP by re-using the selector ID from the
metering process. This would enable a collector to verify the configuration
etc. via SNMP.
Thomas: There is an issue with index number, so an extra element might be
required. In general: the link is required!
Juergen: The PSAMP charter will be fulfilled after submitting these documents.
The following presentations will show that further work related to IPFIX
and PSAMP exist. It is not clear how and where to proceed with them after
the IPFIX and PSAMP charters are fulfilled.
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6. Use of IPFIX for Export of Per-Packet Information (Elisa Boschi)
http://www.ietf.org/internet-drafts/draft-boschi-export-perpktinfo-01.txt
The draft was previously presented to IKPFIX. The idea is to reduce redundancy
and increase efficiency of the export. It doesn't require changes to IPFIX or
PSAMP protocols. Option and data templates define flow and packet attributes.
The draft is an individual submission, related to both IPFIX and PSAMP.
Emile: Are new IE in psamp or ipfix required?
Juergen: flow ID is already included, however a collector would need extensions.
How to continue with this work??
Andrew: The principle used by Elisa can be generalized for more efficient IPFIX
and PSAMP transmissions. As PSAMP is based on IPFIX, the best place for the
document seems to be the IPFIX WG, so that both protocols can use it.
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7. IPFIX inplementation guidelines (Elisa Boschi)
http://www.ietf.org/internet-drafts/draft-boschi-ipfix-implementation-guidelines-00.txt
New draft, takes suggestions from the interoperability testing event at the
last IETF meeting into account. It follows the protocol draft structure.
Benoit: Some issues should already be fixed in the IPFIX protocol, not just
in the implementation guidelines.
Andrew: Please clarify what is meant by actual and NAT src address.
Elisa: We are planning another interop event.
Juergen: Also PSAMP implementations will be welcome there.
Where to host this document?
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8. Path-coupled meter configuration (Juergen Quittek)
http://www.ietf.cnri.reston.va.us/internet-drafts/draft-fessi-nsis-m-nslp-framework-02.txt
http://www.ietf.org/internet-drafts/draft-dressler-nsis-metering-nslp-03.txt
Juergen explained that based on RSVP, the NSIS WG proposed the idea of signaling
functions with split layers. One approach is to collect all flows and find
issues by data mining -- requires massive infrastructure. An alternative is to
use active measurement -- leads to additional traffic generation. The idea of
the new proposal is sending signaling message along the data path (similar to
RSVP) and configure data collection per domain. Reviews and feedback are very
welcome, particularly on the sceanrios in the framework draft (accounting, QoS,
security). The NSLP draft is still evolving. Again hosting this work at the
IETF is an open issue. NSIS will re-charter in the near future, but there is
no decision on covering this work. The NSIS WG wants to get feedback from
IPFIX and PSAMP.
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9. Passive measurement and IPPM composition of metrics (Emile Stephan)
http://www.ietf.org/internet-drafts/draft-stephan-isp-templates-01.txt
http://www.ietf.org/internet-drafts/draft-stephan-ippm-multimetrics-02.txt
Emile gave an uppdate from the last IETF meeting where this work was presented
at the IPFIX session. He explained relationships between the composition of
metrics discussed in IPPM and the work in PSAMP and IPFIX. This work will
probably become an IPPM WG work item. But IPFIX/PSAMP IEs may be needed.
Question: how to move on with this? How can new IE be defined when the IPFIX is completed?
Juergen: number of IEs not fixed, can be extended requested by IANA
Bert Wijnen: I'm still reviewing the IPFIX documents, if expert review is
required for IEs, IESG will assign experts.
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10. Wrap up (Juergen)
Next step: Complete the three reamining WG documents at next IETF meeting
in Dallas.
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