Network Working Group                                          A. Morton
Internet-Draft                                                 AT&T Labs
Intended status: Standards Track                           June 24, 2012
Expires: Informational                         December 26, 21, 2012
Expires: June 24, 2013

                   Rate Measurement Problem Statement
                    draft-ietf-ippm-rate-problem-00
                    draft-ietf-ippm-rate-problem-01

Abstract

   There is a rate measurement scenario which has wide-spread attention
   of users Internet access subscribers and seemingly all industry participants, players,
   including regulators.  This memo presents an access rate-measurement
   problem statement for IP Performance Metrics.  Key test protocol
   aspects require the ability to control packet size on the tested path
   and enable asymmetrical packet size testing in a controller-responder
   architecture.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on December 26, 2012. June 24, 2013.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Purpose and Scope  . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Active Rate Measurement  . . . . . . . . . . . . . . . . . . . . 4  5
   4.  Measurement Method Categories  . . . . . . . . . . . . . . . . .  6
   5.  Test Protocol Control & Generation Requirements  . . . . . . . . 7  8
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . . 7  8
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . . 8  9
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8  9
   9.  Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . 8  9
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8  9
     10.1.  Normative References  . . . . . . . . . . . . . . . . . . . 8  9
     10.2.  Informative References  . . . . . . . . . . . . . . . . . . 9 10
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9 10

1.  Introduction

   There are many possible rate measurement scenarios.  This memo
   describes one rate measurement problem and presents a rate-
   measurement problem statement for IP Performance Metrics (IPPM).

   The access-rate scenario or use case has wide-spread attention of
   users
   Internet access subscribers and seemingly all Internet industry participants,
   players, including regulators.
   It  This problem is being approached with
   many different measurement methods.

2.  Purpose and Scope

   The scope and purpose of this memo is to define the measurement
   problem statement for test protocols conducting access rate
   measurement on production networks.  Relevant test protocols include
   [RFC4656] and [RFC5357]), but the problem is stated in a general way
   so that it can be addressed by any existing test protocol.  This memo
   discusses possibilities for methods of measurement, but does not
   specify exact methods which would normally be part of the solution,
   not the problem.

   We characterize this the access rate measurement scenario as follows:

   o  The Access portion of the network is the focus of this effort. problem
      statement.  The user typically subscribes to a service with bi-directional bi-
      directional access partly described by rates in bits per second.

   o  Rates at the edge of the network are several orders of magnitude
      less than aggregation and core portions.

   o  Asymmetrical ingress and egress rates are prevalent.

   o  Extremely large scale of access services requires low complexity
      devices participating at the user end of the path.

   Today, the majority of widely deployed access services achieve rates
   less than 100 Mbit/s, and this is the rate-regime order of magnitude for which a
   solution is sought now.

   This problem statement assumes that the most-likely bottleneck device
   or link is adjacent to the remote (user-end) measurement device, or
   is within one or two router/switch hops of the remote measurement
   device.

   Other use cases for rate measurement involve situations where the
   packet switching and transport facilities are leased by one operator
   from another and the actual capacity available cannot be directly
   determined (e.g., from device interface utilization).  These
   scenarios could include mobile backhaul, Ethernet Service access
   networks, and/or extensions of a layer 2 or layer 3 networks.  The
   results of rate measurements in such cases could be employed to
   select alternate routing, investigate whether capacity meets some
   previous agreement, and/or adapting adapt the rate of certain traffic sources if a
   capacity bottleneck is found via the rate measurement.  In the case
   of aggregated leased networks, available capacity may also be
   asymmetric.  In these cases, the tester is assumed to have a sender
   and receiver location under their control.  We refer to this scenario
   below as the aggregated leased network case.

   Only active measurement methods will be addressed here, consistent
   with the IPPM working group's current charter.  Active measurements
   require synthetic traffic dedicated to testing, and do not use user
   traffic.

   The actual path used by traffic may influence the rate measurement
   results for some forms of access, as it may differ between user and
   test traffic.

   o  This issue requires further study to list traffic if the likely causes for
      this behavior. test traffic has different characteristics,
   primarily in terms of the packets themselves (the Type-P described in
   [RFC2330]).

   There are several aspects of Type-P where user traffic may be
   examined and directed to special treatment that may affect
   transmission rates.  The possibilities include include:

   o  Packet length

   o  IP address assignment,
      transport addresses used

   o  Transport protocol used (where TCP packets may be routed
      differently from UDP). UDP)

   o  Transport Protocol port numbers used

   This issue requires further discussion when specific solutions/
   methods of measurement are proposed, but for this problem statement
   it is sufficient to Identify the problem and indicate that the
   solution may require an extremely close emulation of user traffic, in
   terms of the factors above.

   Although the user may have multiple instances of network access
   available to them, the primary intent problem scope is to measure one form
   of access at a time.  It is plausible that a solution for the single
   access problem will be applicable to simultaneous measurement of
   multiple access instances, but discussion of this is beyond the
   current scope.

   A key consideration is whether active measurements will be conducted
   with user traffic present (In-Service Testing), testing), or not present (Out-
   of-Service Testing), testing), such as during pre-service testing or
   maintenance that interrupts service temporarily.  Out-of-Service
   testing includes activities described as "service commissioning",
   "service activation", and "planned maintenance".  Both In-Service and
   Out-of-Service Testing testing are within the scope of this problem.

   It is a non-goal to solve the measurement protocol specification
   problem in this memo.

   It is a non-goal to standardize methods of measurement in this memo.
   However, the problem statement will mandate that support for one or
   more categories of rate measurement methods and adequate control
   features for the methods in the test protocol.

3.  Active Rate Measurement

   This section lists features of active measurement methods needed to
   measure access rates in production networks.

   Test coordination between Source source and Destination destination devices through
   control messages and other basic capabilities described in the
   methods of IPPM RFCs [RFC2679][RFC2680] are taken as given (these
   could be listed later, if desired).

   Most forms of active testing intrude on user performance to some
   degree.  One key tenet of IPPM methods is to minimize test traffic
   effects on user traffic in the production network.  Section 5 of
   [RFC2680] lists the problems with high measurement traffic rates, and
   the most relevant for rate measurement is the tendency for
   measurement traffic to skew the results, followed by the possibility
   to introduce
   of introducing congestion on the access link.  Obviously, categories
   of rate measurement methods that use less active test traffic than
   others with similar accuracy SHALL be preferred for In-Service
   Testing.
   testing.

   On the other hand, Out-of-Service Tests tests where the test path shares no
   links with In-Service user traffic have none of the congestion or
   skew concerns, but these tests must address other practical concerns
   such as conducting measurements within a reasonable time from the
   tester's point of view.  Out-of-Service Tests tests where some part of the
   test path is shared with In-Service traffic MUST respect the In-Service In-
   Service constraints.

   The **intended metrics to be measured** have strong influence over
   the categories of measurement methods required.  For example, using
   the terminology of [RFC5136], a it may be possible to measure a Path
   Capacity Metric while In-Service if the level of background (user)
   traffic can be assessed and included in the reported result.

   The measurement *architecture* MAY be either of one-way (e.g.,
   [RFC4656]) or two-way (e.g., [RFC5357]), but the scale and complexity
   aspects of end-user or aggregated access measurement clearly favor
   two-way (with low-complexity user-end device and round-trip results
   collection, as found in [RFC5357]).  However, the asymmetric rates of
   many access services mean that the measurement system MUST be able to
   assess
   evaluate performance in each direction of transmission.  In the two-way two-
   way architecture, it is expected that both end devices MUST include
   the ability to launch test streams and collect the results of
   measurements in both (one-way) directions of transmission (this
   requirement is consistent with previous protocol specifications, and
   it is not a unique problem for rate measurements).

   The following paragraphs describe features for the roles of test
   packet SENDER, RECEIVER, and results REPORTER.

   SENDER:

   Ability to generate

   Generate streams of test packets with various characteristics as
   desired (see Section 4).  The SENDER may be located at the user end
   of the access path, or may be located elsewhere in the production
   network, such as at one end of an aggregated leased network segment.

   RECEIVER:

   Ability to collect

   Collect streams of test packets with various characteristics (as
   described above), and make the measurements necessary to support rate
   measurement at the other end of an end-user access or aggregated
   leased network segment.

   REPORTER:

   Ability to use

   Use information from test packets and local processes to measure
   delivered packet rates.

4.  Measurement Method Categories

   The design of rate measurement methods can be divided into two
   phases: test stream design and measurement (SENDER and RECEIVER), and
   a follow-up phase for analysis of the measurement to produce results
   (REPORTER).  The measurement protocol that addresses this problem
   MUST only serve the test stream generation and measurement functions.

   For the purposes of this problem statement, we categorize the many
   possibilities for rate measurement stream generation as follows;

   1.  Packet pairs, with fixed intra-pair packet spacing and fixed or
       random time intervals between pairs in a test stream.

   2.  Multiple streams of packet pairs, with a range of intra-pair
       spacing and inter-pair intervals.

   3.  One or more packet ensembles in a test stream, using a fixed
       ensemble size in packets and one or more fixed intra-ensemble
       packet spacings (including zero). zero spacing).

   4.  One or more packet chirps, where intra-packet spacing typically
       decreases between adjacent packets in the same chirp and each
       pair of packets represents a rate for testing purposes.

   For all categories, the test protocol MUST support:

   1.  Variable payload lengths among packet streams

   2.  Variable length (in packets) among packet streams or ensembles

   3.  Variable IP header markings among packet streams

   4.  Choice of UDP transport and variable port numbers, OR, choice of
       TCP transport and variable port numbers for two-way architectures
       only, OR BOTH.

   5.  Variable number of packets-pairs, ensembles, or streams used in a
       test session

   The items above are additional variables that the test protocol MUST
   be able to
   communicate. identify and control.

   The test protocol SHALL support test packet ensemble generation
   (category 3), as this appears to minimize the demands on measurement
   accuracy.  Other stream generation categories are OPTIONAL.

   >>>>>>

   Note: For measurement systems employing TCP Transport protocol, the
   ability to generate specific stream characteristics requires a sender
   with the ability to establish and prime the connection such that the
   desired stream characteristics are allowed.  See Mathis' work in
   progress for more background [draft-mathis-ippm-model-based-metrics].

   The general requirement statements needed to describe an "open-loop"
   TCP sender require some additional discussion.

   It may also be useful to specify a control for Bulk Transfer Capacity
   measurement with fully-specified TCP senders and receivers, as
   envisioned in [RFC3148], but this would be a brute-force assessment
   which does not follow the conservative tenets of IPPM measurement.

   >>>>>>

   Measurements for each test packet transferred between SENDER and
   RECEIVER MUST be compliant with the singleton measurement methods
   described in IPPM RFCs [RFC2679][RFC2680] (these could be listed
   later, if desired).  The time-stamp information or loss/arrival
   status for each packet MUST be available for communication to the
   protocol entity that collects results.

5.  Test Protocol Control & Generation Requirements

   Essentially, the test protocol MUST support the measurement features
   described in the sections above.  This requires:

   1.  Communicating all test variables to the Sender and Receiver

   2.  Results collection in a one-way architecture

   3.  Remote device control for both one-way and two-way architectures

   4.  Asymmetric and/or pseudo-one-way test capability in a two-way
       measurement architecture

   The ability to control packet size on the tested path and enable
   asymmetrical packet size testing in a two-way architecture are
   REQUIRED.

   The test protocol SHOULD enable measurement of the [RFC5136] Capacity
   metric, either Out-of-Service, In-Service, or both.  Other [RFC5136]
   metrics are OPTIONAL.

6.  Security Considerations

   The security considerations that apply to any active measurement of
   live networks are relevant here as well.  See [RFC4656] and
   [RFC5357].

   There may be a serious issue if a proprietary Service Level Agreement
   involved with the access network segment provider were somehow leaked
   in the process of rate measurement.  To address this, test protocols
   SHOULD NOT convey this information in a way that could be discovered
   by unauthorized parties.

7.  IANA Considerations

   This memo makes no requests of IANA.

8.  Acknowledgements

   Dave McDysan provided comments and text for the aggregated leased use
   case.  Yaakov Stein suggested many considerations to address,
   including the in-service In-Service vs. out-of-service Out-of-Service distinction and its
   implication on test traffic limits. limits and protocols.

9.  Appendix

   This Appendix is intended was proposed to briefly summarize previous rate
   measurement experience.  (There is a large body of research on rate
   measurement, so there is a question of what to include and what to
   omit.)
   omit.  Suggestions are welcome.)

10.  References

10.1.  Normative References

   [RFC1305]  Mills, D., "Network Time Protocol (Version 3)
              Specification, Implementation", RFC 1305, March 1992.

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

   [RFC2330]  Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
              "Framework for IP Performance Metrics", RFC 2330,
              May 1998.

   [RFC2679]  Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
              Delay Metric for IPPM", RFC 2679, September 1999.

   [RFC2680]  Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
              Packet Loss Metric for IPPM", RFC 2680, September 1999.

   [RFC4656]  Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.

              Zekauskas, "A One-way Active Measurement Protocol
              (OWAMP)", RFC 4656, September 2006.

   [RFC5357]  Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
              Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
              RFC 5357, October 2008.

   [RFC5618]  Morton, A. and K. Hedayat, "Mixed Security Mode for the
              Two-Way Active Measurement Protocol (TWAMP)", RFC 5618,
              August 2009.

   [RFC5938]  Morton, A. and M. Chiba, "Individual Session Control
              Feature for the Two-Way Active Measurement Protocol
              (TWAMP)", RFC 5938, August 2010.

   [RFC6038]  Morton, A. and L. Ciavattone, "Two-Way Active Measurement
              Protocol (TWAMP) Reflect Octets and Symmetrical Size
              Features", RFC 6038, October 2010.

10.2.  Informative References

   [RFC3148]  Mathis, M. and M. Allman, "A Framework for Defining
              Empirical Bulk Transfer Capacity Metrics", RFC 3148,
              July 2001.

   [RFC5136]  Chimento, P. and J. Ishac, "Defining Network Capacity",
              RFC 5136, February 2008.

Author's Address

   Al Morton
   AT&T Labs
   200 Laurel Avenue South
   Middletown,, NJ  07748
   USA

   Phone: +1 732 420 1571
   Fax:   +1 732 368 1192
   Email: acmorton@att.com
   URI:   http://home.comcast.net/~acmacm/