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draft psamp WG charter
thanks for your comments on the previous draft charter. Here's a new
version intended to take account of the discussion. Please send any
feedback to the list.
Packet Sampling (psamp)
This draft: 05/21/2002
Description of Working Group:
The Packet Sampling working group is chartered to define a standard
set of capabilities for network elements to sample packets. 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 standard shall encompass (i) selection operations by which packets
are sampled; (ii) the formation of reports on the sampled packets;
(iii) the timely communication of packet reports to applications, either
on-board or off-board the network element.
Resulting streams of packet reports produced by a network element 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 several 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
Network elements and collectors must together be able to ensure that
transmission of packet reports across a network path is aware of and
responsive to congestion on that path.
Selection of the content of packet reports shall balance the
requirements of privacy and anonymity with the needs of measurement
Re-use of existing protocols will be encouraged provided the protocol
capabilities are compatible with PSAMP requirements.
Specifically, the tasks of the PSAMP WG will be the following:
1. Selectors for packet sampling. Define the set of primitive packet
selection operations for network elements, and the ways in which
they can be combined.
2. Sampled packet reports. Define the format of the report that is
constructed by the network element for each sampled packet. The
format shall be sufficiently rich as to allow inclusion in the
packet report of (i) the packet's IP header and some subsequent
bytes of the packet, or subsets thereof; (ii) encapsulating packet
headers, e.g., of MPLS; (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.
3. 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 report loss in transmission, and correct for
information missing from the packet report stream.
4. 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.
5. 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.
6. Presentation, Export, and Transport of Packet Reports. Define
interface for presentation of reports to on-board applications.
Select transport protocol for remote export that is compatible with
PSAMP goals. Determine requirements on measurement device and
collector for use of selected transport protocol, while being aware
of and responsive to network congestion.
August 2002: Framework document
Novemeber 2002: Packet selector function document
February 2003: Report format and report stream format document
May 2003: Export and requirements for collectors document
August 2003: MIB document
A Framework for Passive Packet Measurement
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