2.4.14 Packet Sampling (psamp)

NOTE: This charter is a snapshot of the 61st IETF Meeting in Washington, DC USA. It may now be out-of-date.

Last Modified: 2004-09-22


Andy Bierman <abierman@cisco.com>
Juergen Quittek <quittek@netlab.nec.de>

Operations and Management Area Director(s):

Bert Wijnen <bwijnen@lucent.com>
David Kessens <david.kessens@nokia.com>

Operations and Management Area Advisor:

David Kessens <david.kessens@nokia.com>

Mailing Lists:

General Discussion: psamp@ops.ietf.org
To Subscribe: psamp-request@ops.ietf.org
In Body: subscribe
Archive: https://ops.ietf.org/lists/psamp/

Description of Working Group:

The Packet Sampling working group is chartered to define a standard
set of capabilities for network elements to sample subsets of packets
by statistical and other methods. The capabilities should be simple
enough that they can be implemented ubiquitously at maximal line
rate. They should be rich enough to support a range of existing and
emerging measurement-based applications, and other IETF working groups
where appropriate.

The focus of the WG will be to (i) specify a set of selection
operations by which packets are sampled (ii) specify the information
that is to be made available for reporting on sampled packets; (iii)
describe protocols by which information on sampled packets is reported
to applications; (iv) describe protocols by which packet selection and
reporting configured.

Packet reports must be communicable in a timely manner, to
applications either on-board of off-board the sampling network
element. The streams of packet reports produced by a packet sampling
must (i) allow consistent interpretation, independent of the
particular network element that produced them; (ii) be self-defining,
in that their interpretation does not require additional information
to be supplied by the network element; (iii) allow robustness of
interpretation with respect to missing reports or part of reports;

Network elements shall support multiple parallel packet samplers, each
with independently configurable packet selectors, reports, report
streams, and export. Network elements must allow easy and secure
reconfiguration of these packet samplers by on-board or external

Export of a report stream across a network must be congestion avoiding
in compliance with RFC 2914. Unreliable transport is permitted because
the requirements at the exporter for reliable transport (state
maintenance, addressibilty, acknowledgment processing, buffering
unacknowledged data) would prevent ubiquitous deployment. Congestion
avoidance with unreliable export is to be accomplished by the
following measures, which shall be mandatory to implement and use. The
maximum export rate of a report stream must be configurable at the
exporter. A report stream must contain sufficient information for
transmission loss to be detected a collector. Then the collector must
run a congestion control algorithm to compute a new sending rate, and
reconfigure the exporter with this rate. In order to maintain report
collection during periods of congestion, PSAMP report streams may
claim more than a fair share of link bandwidth, provided the number of
report streams in competition with fair sharing traffic is limited.

Selection of the content of packet reports will be cognizant of
privacy and anonymity issues while being responsive to the needs of
measurement applications, and in accordance with RFC 2804.

Re-use of existing protocols will be encouraged provided the protocol
capabilities are compatible with PSAMP requirements.

Specifically, the PSAMP WG will perform the following tasks, in
accordance with the principles stated above:

1. Selectors for packet sampling. Define the set of primitive packet
  selection operations for network elements, the parameters by which
  they may be configured, and the ways in which they can be combined.

2. Packet Information. Specify extent of packet that is to be made
  available for reporting. Target for inclusion the packet's IP
  header, some subsequent bytes of the packet, and encapsulating
  headers if present. Full packet capture of arbitrary packet
  streams is explicitly out of scope. Specify variants for IPv4 and
  IPv6, extent of IP packet available under encapsulation methods,
  and under packet encryption.

3. Sampled packet reports. Define the format of the report that is
  constructed by the network element for each sampled packet for
  communication to applications. The format shall be sufficiently
  rich as to allow inclusion in the packet report of (i) IP packet
  information as specified in paragraph 2 above; (ii) encapsulating
  packet headers as specified in paragraph 2 above; (iii) interface
  or channel identifiers associated with transit of the packet across
  the network element; (iv) quantities computable from packet content
  and router state, (v) quantities computed during the selection
  operation. All reported quantities must reflect the router state
  and configuration encountered by the packet in the network element.

4. Report Streams. Define a format for a stream of packet reports, to
  include: (i) the format of packet reports in the stream; (ii) the
  packet reports themselves; (iii) configuration parameters of the
  selectors of the packets reported on; (iv) configuration parameters
  and state information of the network element; (v) quantities that
  enable collectors and applications to infer of attained packet
  sampling rates, detect loss during samping, report loss in
  transmission, and correct for information missing from the packet
  report stream; (vi) indication of the inherent accuracy
  of the reported quantities, e.g., of timestamps.

5. Multiple Report Streams. Define requirements for multiple parallel
  packet samplers in one network element, including the allowed
  degradation of packet reporting when packets are selected by
  multiple packet samplers.

6. Configuration and Management. Define a packet sampler MIB to reside
  at the network element, including parameters for packet selection,
  packet report and stream format, and export. Select or define a
  communication protocol to configure/read this MIB.

7. Presentation, Export, and Transport of Packet Reports. Define
  interface for presentation of reports to on-board applications.
  Select unreliable transport protocol for remote export. Determine
  rate control algorithms for export.

Initial Internet-Draft: A Framework for Passive Packet Measurement

Goals and Milestones:

Done  Submit initial Framework document
Done  Submit initial Packet selector and packet information document
Done  Submit initial Report format and report stream format document
Done  Submit initial Export and requirements for collectors document
Done  Submit initial MIB document
May 03  Submit final Framework document
May 03  Submit final Packet selector and packet information document
Sep 03  Submit final Report format and report stream format document
Oct 03  Submit final Export and requirements for collectors document
Nov 03  Submit final MIB document


  • draft-ietf-psamp-framework-09.txt
  • draft-ietf-psamp-sample-tech-05.txt
  • draft-ietf-psamp-mib-03.txt
  • draft-ietf-psamp-info-02.txt

    No Request For Comments

    Current Meeting Report

    Minutes of the PSAMP BOF session at IETF 61
    Friday November 12, 9:00 h - 11:30 h

    Packet Sampling Working Group
    Chairs: Andy Bierman <abierman@cisco.com>, Juergen Quittek <quittek@netlab.nec.de>

    Minutes taken by Dave Plonka and Ralf Wolter

    0. Session Summary
    1. PSAMP WG Status
    2. Update of Sampling Framework
    3. Update od Packet Selection
    4. Discussion of open PSAMP protocol issues
    5. Discussion of open PSAMP Information Model issues
    6. PSAMP MIB
    7. Wrap up

    Discussed Internet drafts

    A Framework for Passive Packet Measurement http://www.ietf.org/internet-drafts/draft-ietf-psamp-framework-09.txt

    Sampling and Filtering Techniques for IP Packet Selection http://www.ietf.org/internet-drafts/draft-ietf-psamp-sample-tech-05.txt

    Packet Sampling (PSAMP) Protocol Specifications (expired) draft-ietf-psamp-protocol-01.txt

    Information Model for Packet Sampling Exports http://www.ietf.org/internet-drafts/draft-ietf-psamp-info-02.txt

    Definitions of Managed Objects for Packet Sampling http://www.ietf.org/internet-drafts/draft-ietf-psamp-mib-03.txt

    0. Session Summary

    The PSAMP WG finished last call of its first document, the PSAMP framework. A few editorial issues were still put on the list of actions items during the meeting. The document on packet selection is still in WG last call. The call was extended, because the number of reviews was performed until the session was not sufficient. After completing the packet selection document all required input for the PSAMP MIB is available and this document can be completed next. The remaining two document, the protocol and the information model specification, are on hold, because they depend on the IPFIX protocol and information model specifications, which are not finished yet. If work in the IPFIX WG progresses as expected, the two missing documents can be discussed at the next meeting and will enter WG last call shortly after that meeting.

    1. PSAMP WG Status (Juergen)

    The PSAMP framework document passed WG last call. It will be forwarded to the area directors soon. The packet selection document is quite mature. The deadline of WG last call on this document is past, but since there was no serious review to be observed yet, it remains in last call. Juergen requested that positive responses to the draft should be posted as well so that there is evidence that it has been reviewed.

    Protocol and info model document are waiting for progress of the corresponding IPFIX docuements. Work on the PSAMP MIB can go on when last call on the packedt selection document is closed. Then the PSAMP MIB can be completed soon.

    2. PSAMP Framework Document (Nick Duffield)


    Nick explained that there were only minor changes applied to the draft since the last version. The last call is closed and should be ready for WG last call.

    [Benoit Claise] On the low-level filter, we only kept logical AND [in the packet selection draft] and removed logical OR because it was too hard to model, so it should be removed from this doc as well.

    [Tanja Zseby] I agree and think this was just overlooked.

    Andy reminded participants who review docs to make it known (that they reviewed it) even if there are no negative issues/problems

    3. Sampling and Filtering Techniques (Tanja Zseby)


    Tanja explained that Mask/match was renamed to field match filter. Low level filter definition were substituted by a high level definition. There are further minor changes, e.g. the terminology section was updated. the Introduction and text on other PSAMP document was added as well as the AT&T IPR statement.

    Tanja requested that people read the document, and send feedback regardless of whether or not there are problems

    [Andy] Are there any volunteers willing to commit to reviewing this document in the next 2-3 weeks? I don't see a way to move forward unless there's reviews.

    Stewart Bryant offered to do so.

    4. PSAMP Protocol Specifications (Benoit Claise)

    draft-ietf-psamp-protocol-01.txt (expired)

    Benoit explained that there was no proegress on this document because it strongly depends on the IPFIX protocol document that is not yet finished. The draft is already expired. Benoit present a summary of recent progress with the IPFIX protocol document. For details about IPFIX, see BenoitÕs section in the minutes of the IETF 61 IPFIX session. After completing IPFIX WG last call, work on the PSAMP protocol draft will continue.

    [Andy] Is this a big delay in the PSAMP schedule
    [Dave Plonka (IPFIX chair)] PSAMP participants should/could review the IPFIX protocol document.
    [Juergen] When the IPFIX protocol is complete, there will be no big technical issues for the PSAMP protocol.

    5. PSAMP Information Model (no slides)


    JŸrgen listed of open PSAMP Information Model issues. The state is similar to the protocol document, but the draft was updated in July 2004 and is not yet expired. After completing IPFIX WG last call on the IPFIX info model, work on the PSAMP IM draft will continue. A new version should be available by the next meeting.

    6. PSAMP MIB (no slides)


    Also this draft was not not updated since July 2004. But the MIB is almost complete, except for some work on packet selection, due to updates in that area. After packet selection document finishes WG last call, the MIB could go to last call as well, currently targeted for December 04.

    7. Wrap up

    The meeting was adjourned. Following the meeting, Juergen invited those in the room to review the drafts documents now, since there was plenty of time left in the session's time slot.


    PSAMP Framework Document
    Sampling and Filtering Techniques
    PSAMP Protocol Specifications