WG Review: Packet Sampling (psamp)

[Steve Coya <[e-mail]>]

A new IETF working group has been proposed in the Operations &
Management Area. The IESG has not made any determination as yet. 

The following Description was submitted, and is provided for
informational purposes only:

Packet Sampling (psamp)
-----------------------

 Current Status: Proposed Working Group

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 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 are configured.

Packet reports must be communicable in a timely manner, to
applications either on-board or 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 by 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.

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. 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. 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.

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>