Re: comments on draft-ietf-psamp-framework-03.txt - 2

[Ganesh Sadasivan <gsadasiv@cisco.com>]

Here is the comments on rest of the doc.

Thanks
Ganesh

7 Export Process

  7.1 Collector Destination

  When exporting to a remote collector, the collector is identified
  by IP address and port number.

G: Transport protocol and transport port # (in case there are multiple
transport protocols)

  7.2 Local Export

  The report stream may be directly exported to on-board measurement
  based applications, for example those that form composite
  statistics from more than one packet. Local export may be presented
  through an interface direct to the higher level applications, i.e.,
  through an API, rather than employing the transport used for
  off-board export.

G: You can mention that local export mechanism is outside the scope of
PSAMP.

Duffield (Ed.)       draft-ietf-psamp-framework-03.txt         [Page 15]

Internet-Draft          Passive Packet Measurement             June 2003


  A possible example of local export could be that packets selected
  by the PSAMP measurement process serve as the input for the IPFIX
  protocol, which then forms flow records out of the stream of
  selected packets. Note that IPFIX being still developed; this is
  given only as a possible example.

  7.3  Reliable vs. Unreliable Transport

  The export of the report stream does not require reliable
  export. On the contrary, retransmission of lost measurement packets
  consumes additional network resources and requires maintenance of
  state by the export process. As such, the export process would have
  to be able to receive and process acknowledgments, and to store
  unacknowledged data. Furthermore, the entity that hosts the export
  process may not possess its own network address (for example an
  embedded measurement subsystem in an interface) at which to receive
  acknowledgments.

G: Is the above statement valid? Every export process needs a network 
address
and the reverse communication in the form of ACKs  can be expected on this
IP address if a congestion-aware (or congestion-responsive) traffic is
employed for export.

These requirements would be a significant
  impediment to having ubiquitous support PSAMP.

  Instead, it is proposed that the export process support unreliable
  export.  Sequence numbers on the measurement packets would indicate
  when loss has occurred, and the analysis of the collected
  measurement data can account for this loss.  In some sense, packet
  loss becomes another form of sampling (albeit a less desirable, and
  less controlled, form of sampling).

  7.4 Limiting Delay in Exporting Measurement Packets
 
  The export process may queue the report stream in order to export
  multiple reports in a single measurement packet. Any consequent
  delay MUST still allow for timely availability of packet reports

G: Can MUST be changed to "SHOULD" there could be undesirable events in
an exporter which can cause more delay. Or the recomedation should be to
drop the reports if > delay.




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