draft-peluso-flowselection-tech-00.txt

IPv6协议中flow_label的相关RFC

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                       Packet(s) coming in to Observation Point(s)
                         |                                   |
                         v                                   v
        +----------------+-------------------------+   +-----+-------+
        |          Metering Process on an          |   |             |
        |             Observation Point            |   |             |
        |                                          |   |             |
        |   packet header capturing                |   |             |
        |        |                                 |...| Metering    |
        |   timestamping                           |   | Process N   |
        |        |                                 |   |             |
        |   packet selection                       |   |             |
        |        |                                 |   |             |
        |   classification                         |   |             |
        |        |                                 |   |             |
        |   flow state dependent sampling (*)      |   |             |
        |        |                                 |   |             |
        |   aggregation                            |   |             |
        |        |                                 |   |             |
        |   flow recording (*)                     |   |             |
        |        |                                 |   |             |
        |        |        Timing out Flows         |   |             |
        |        |    Handle resource overloads    |   |             |
        +--------|---------------------------------+   +-----|-------+
                 |                                           |
         Flow Records (selected by Observation Domain)  Flow Records
                 |                                           |
                 +----------------------+--------------------+
                                        |
                 +----------------------|---------------+
                 | Exporting Process    v               |
                 |      +---------------+-----------+   |
                 |      |     flow selection (*)    |   |
                 |      +---------------+-----------+   |
                 |                      |               |
                 |      +---------------+-----------+   |
                 |      |        flow export        |   |
                 |      +---------------+-----------+   |
                 |                      |               |
                 +----------------------+---------------+
                                        |
                                        v
                         IPFIX export packet to Collector

      (*) indicates where flow selection can take place.

                                 Figure 1




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   As for the metering process, the flow selection consists in
   accounting only a subset of all the incoming packets collected at the
   observation point.  However, unlike the selection process realized
   before the packet classification is performed, the flow selection at
   the metering process is in charge of electing only those incoming
   packets which somehow satisfy certain conditions related to the flows
   state information available from the flow recording process.  This
   kind of selection is referred as a packet sampling technique, in
   accordance with [PSAMP-TECH] which introduces it as flow state
   dependent sampling.  The state of the stored flow records is thus
   considered during the packet selection, so that the process
   responsible for generating or updating flow records might result
   easily influenced by selectively accounting the packets which feed
   it.  Under this perspective, unlike the flow selection performed at
   the flow recording and exporting processes, flow selection operate at
   a very early stage to regard to the concept of flow, as it acts at
   packet level.  In this way, in fact, one can prevent that some
   observed/observable packets might enforce the flow recording process
   to account, for instance, not representative or not expected flow
   records.  Coming to the flow selection that might be provided in the
   flow recording and/or exporting processes, as above clarified, it is
   done at flow level, therefore, after that packets are classified in
   to the correspondent flows.  More exactly, the flow selection process
   can be carried out on the flow recording process by storing new flow
   records only in those cases in which enough resources are available
   at the monitoring device to maintain them or by discarding already
   accounted records which, under certain circumstances and at a certain
   point in time, might be retained not anymore representative.
   Finally, at the flow exporting process it might be required that not
   all of the stored flow records available to be exported can be
   actually send to the collectors.

   We can distinguish the following selection techniques:

   1.  based on flow record content (i.e. all reported flow
       characteristics);

   2.  based on flow record arrival time;

   3.  based on external events like the exhaustion of local resources.

5.1.  Flow selection on flow record content

   <Text for this section>







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5.2.  Flow selection on flow record arrival time

   <Text for this section>

5.3.  Flow selection on external events

   <Text for this section>


6.  Solutions for flow cache data structure

   The flow cache is the component of the flow monitoring system which
   in charge of storing flow records, i.e. the data structures devoted
   to contain values of predefined metrics related to every observed
   flow.  The effectiveness of the flow cache definitely affects the
   overall performance of the flow monitoring system.  This is the most
   challenging component, as it has to search for the flow records and
   update the related metrics within the packet interarrival time.
   Elements in the flow cache can be ordered according to a Least
   Recently Used (LRU) algorithm: as a packet arrives at the network
   interface it is classified, i.e. a flowID, is computed and assigned
   to it.  Solutions for the generation of flow IDs and search
   mechanisms for flow records within flow cache are described in
   [MoCD06].  In case a corresponding flow record, i.e. a record with
   that flowID, already exists in the linked list, then it is updated
   with packet-related data and moved to the top of the list.
   Otherwise, a new flow record is created and inserted on top of the
   list.  This ordering algorithm allows addressing two issues: first,
   timed out flows can be easily identified by scanning the list from
   the tail and checking for each record whether the difference between
   the last update time and the current time exceeds the timeout value.
   Second, it is intuitive that records related to living flows
   transporting a lot of traffic, the so-called elephant flows, are
   frequently moved to the head of the list.  Therefore, data about such
   flows can be found with high probability by scanning the LRU list
   from the head.


7.  Information model for flow selection configuration

   This section aims at describing the representative parameters of the
   above presented flow selection techniques.  To this regard, this
   section provides the basis for an information model to adopt in order
   to configure the flow selection process at an IPFIX device.







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8.  IANA Considerations

   This document makes no request of IANA.


9.  Security Considerations

   <Text for this section>


10.  Acknowledgements

   <Text for this section>


11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

11.2.  Informative References

   [DuLT01a]  Duffield, N., Lund, C., and M. Thorup, "Charging from
              Sampled Network Usage", ACM Internet Measurement Workshop
              IMW 2001, San Francisco, USA, November 2001.

   [DuLT01b]  Duffield, N., Lund, C., and M. Thorup, "Properties and
              Prediction of Flow Statistics from Sampled Packet
              Streams", ACM SIGCOMM Internet Measurement Workshop 2002,
              November 2002.

   [DuLT01c]  Duffield, N., Lund, C., and M. Thorup, "Learn More, sample
              less: control of volume and variance in network
              measurement", IEEE Transactions on Information Theory,
              May 2005.

   [DuLT01d]  Duffield, N., Lund, C., and M. Thorup, "Flow Sampling
              under Hard Resource Constraints", ACM IFIP Conference on
              Measurement and Modeling of Computer Systems SIGMETRICS,
              June 2004.

   [EsVa01]   Estan, C. and G,. Varghese, "New Directions in Traffic
              Measurement and Accounting: Focusing on the Elephants,
              Ignoring the Mice", ACM SIGCOMM Internet Measurement
              Workshop 2001, San Francisco (CA), November 2001.




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   [FeGL98]   Feldmann, A., Rexford, J., and R. Caceres, "Efficient
              Policies for Carrying Web Traffic over Flow-Switched
              Networks", IEEE/ACM Transaction on Networking,
              December 1998.

   [IPFIX-ARCH]
              Sadasivan, G., Bownlee, N., Claise, B., and J. Quittek,
              "Architecture for IP Flow Information Export", Internet
              Draft draft-ietf-ipfix-architecture-12.txt, work in
              progress, September 2006.

   [IPFIX-INFO]
              Quittek, J., Bryant, S., Claise, B., Aitken, P., and J.
              Meyer, "Information Model for IP Flow Information Export",
              Internet Draft draft-ietf-ipfix-info-15.txt, work in
              progress, February 2007.

   [KuXW04]   Kumar, K., Xu, J., Wang, J., Spatschek, O., and L. Li,
              "Space-code bloom filter for efficient per-flow traffic
              measurement", INFOCOM 2004 Twenty-third AnnualJoint
              Conference of the IEEE Computer and Communications
              Societies, March 2004.

   [MoCD06]   Molina, M., Chiosi, A., D'Antonio, S., and G. Ventre,
              "Design principles and algorithms for effective high-speed
              IP flow monitoring", September 2006.

   [Moli03a]  Molina, M., "A scalable and efficient methodology for flow
              monitoring in the Internet", International Teletraffic
              Congress (ITC-18), Berlin, September 2003.

   [PSAMP-TECH]
              Zseby, T., Molina, M., Raspall, F., Duffield, N., and S.
              Niccolini, "Sampling and Filtering techniques for IP
              Packet Selection", Internet
              Draft draft-ietf-psamp-sample-tech-10.txt, work in
              progress, June 2007.














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Authors' Addresses

   Lorenzo Peluso
   Fraunhofer Institute FOKUS
   Kaiserin-Augusta-Allee 31
   Berlin  10589
   Germany

   Phone: [phone]
   Email: [e-mail]


   Tanja Zseby
   Fraunhofer Institute FOKUS
   Kaiserin-Augusta-Allee 31
   Berlin  10589
   Germany

   Phone: [phone]
   Email: [e-mail]


   Salvatore D'Antonio
   CINI Consortium/ITeM Laboratory
   Monte S.Angelo, Via Cinthia
   Napoli  80126
   Italy

   Phone: [phone]
   Email: [e-mail]





















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