Packet Sampling (psamp)

Last Modified: 2008-02-25

Additional information is available at tools.ietf.org/wg/psamp

Chair(s):

  • Juergen Quittek <quittek@netlab.nec.de>

    Operations and Management Area Director(s):

  • Dan Romascanu <dromasca@avaya.com>
  • Ronald Bonica <rbonica@juniper.net>

    Operations and Management Area Advisor:

  • Dan Romascanu <dromasca@avaya.com>

    Mailing Lists:

    General Discussion: psamp@ietf.org
    To Subscribe: psamp-request@ietf.org
    In Body: (un)subscribe
    Archive: http://www.ietf.org/mail-archive/web/psamp/index.html

    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
    applications.

    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
    [draft-duffield-framework-papame]

    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
    Done  Submit final Framework document
    Done  Submit final Packet selector and packet information document
    Done  Submit final PSAMP protocol specification
    Mar 2008  Submit final PSAMP information model
    May 2008  Submit final MIB document

    Internet-Drafts:

    A Framework for Packet Selection and Reporting (91096 bytes)
    Sampling and Filtering Techniques for IP Packet Selection (112913 bytes)
    Packet Sampling (PSAMP) Protocol Specifications (103142 bytes)
    Information Model for Packet Sampling Exports (80955 bytes)

    No Request For Comments

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