Network Working Group                                        S. Shalunov
Internet Draft                                                 Internet2
Expiration Date: January 2002                              B. Teitelbaum
                               Advanced Network & Services and Internet2
                                                               July 2001

           A One-way Active Measurement Protocol Requirements

1. Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at

   The list of Internet-Draft shadow directories can be accessed at

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

2. Abstract

   With growing availability of good time sources to network nodes, it
   becomes increasingly possible to measure one-way IP performance
   metrics with high precision.  To do so in an interoperable manner, a
   common protocol for such measurements is required.  This document
   specifies requirements for a one-way active measurement protocol
   (OWAMP) standard.  The protocol can measure one-way delay, as well as
   unidirectional characteristics such as one-way loss and others.

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3. Motivations and Goals

   The IETF IP Performance Metrics (IPPM) working group has proposed
   draft standard metrics for one-way packet delay [RFC2679] and loss
   [RFC 2680] across Internet paths.  Although there are now several
   measurement platforms that implement the collection of these metrics
   ([CQOS], [BRIX], [RIPE], [SURVEYOR]), there is not currently a
   standard for interoperability.

   With the increasingly wide availability of affordable global
   positioning system (GPS) and CDMA based time sources, hosts
   increasingly have available to them very accurate time
   sources--either directly or through their proximity to NTP primary
   (stratum 1) time servers.  By standardizing a technique for
   collecting IPPM one-way active measurements, we hope to create an
   environment where these metrics may be collected across a far broader
   mesh of Internet paths than is currently possible.  One particularly
   compelling vision is of widespread deployment of open one-way active
   measurement beacons that would make measurements of one-way delay as
   commonplace as measurements of round-trip time are today using ICMP-
   based tools like ping.

   To support interoperability between alternative OWDP implementations
   and make possible a world where "one-way ping" could become
   commonplace, a standard is required that specifies how test streams
   are initiated, how test packets are exchanged, and how test results
   are retrieved. Detailed functional requirements are given in the
   subsequent section.

4. Functional Requirements

   The protocol(s) should provide ability to measure, record, and
   distribute the results of measurements of one-way singleton network
   characteristics such as characteristics defined in [RFC2679] and

   It should be possible to measure arbitrary one-way singleton
   characteristics (e.g., loss, average delay, mean delay, jitter, 90th
   percentile of delay, etc.).  Since RFC2679 and RFC2680 standardize on
   Poisson streams of test packets, Poisson streams at least should be

   Non-singleton characteristics (such as those related to trains of
   packets, back-to-back tuples, and so forth) and application traffic
   simulation aren't areas that the protocol(s) need to address.

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4.1. Keeping All Data for Post-processing

   To facilitate the broadest possible use of obtained measurement
   results, the protocol(s) should not necessitate any required post-
   processing.  All data obtained during a measurement session should be
   available after it is finished if desired by endpoint so that various
   characteristics can be computed from the raw data using arbitrary

4.2. Result Distribution

   A means to distribute measurement results (between hosts
   participating in a measurement session and beyond) should be
   provided.  Since there can exist a wide variety of scenarios as to
   where the final data destination should be, these should be invoked
   separately from measurement requests (e.g., receiver should not have
   to automatically send measurement results to the sender, since it may
   be the receiver or a third host that are the ultimate data

   At the same time, ability to transfer results directly to their
   destination (without need for potentially large intermediate
   transfers) should be provided.

4.3. Protocol Separation

   Since measurement session setup and the actual measurement session
   (i) are different tasks; (ii) require different levels of
   functionality, flexibility, and implementation effort; (iii) may need
   to run over different transport protocols, there should exist
   different protocols for conducting the actual measurement session on
   one side and for session setup/teardown/confirmation/retrieval on the
   other.  These protocols are further referred to as OWDP-Test and
   OWDP-Control, respectively.

   It should be possible to use devices that only support OWDP-Test but
   not OWDP-Control to conduct measurement sessions (such devices will
   necessarily need to support one form of session setup protocol or the
   other, but it doesn't have to be known to external parties).

   OWDP-Control would thus become a common protocol for different
   domains, which may or may not use it for session setup internally.

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4.4. Test Protocol

   The test protocol needs to be implemented on all measurement nodes
   and should therefore have the following characteristics:

   +  Be lightweight and easy to implement.

   +  Be suitable for implementation on a wide range of measurement

   +  Since the protocol needs to be able to measure individual packet
      delivery time and has to run on various machines, it needs to
      support UDP as transport protocol.

   +  It should be possible to use varying packet sizes and network
      services, as negotiated using OWDP-Control.

   +  To be a lowest common denominator, OWDP-Test packet format should
      only include universally meaningful fields, and minimum number of

   +  It should be possible to make packets generated by OWDP-Test as
      small as possible, to be able to accurately measure paths where
      packet-splitting technologies such as ATM are used.

4.5. Control Protocol

   Control protocol needs to provide abilities to:

   +  authenticate peers to each other using a common authentication
      method that doesn't require building any new authentication
      infrastructure, such as user ID and a shared secret;

   +  schedule zero or more OWDP-Test sessions (which do not have to be
      between the peers of OWDP-Control conversation);

   +  start sessions simultaneously or at a pre-scheduled per-session

   +  retrieve OWDP-Test session results (of OWDP-Test sessions
      scheduled in the current and other OWDP-Control sessions);

   +  confirm graceful completion of session or abort them prematurely
      (for both sides).

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   The OWDP-Control design should not preclude the ability to record
   extended periods of losses.  It should provide peers with the ability
   to always distinguish between network and peer failures.

5. Scalability

   While some measurement architecture designs have inherent scalability
   problems (e.g., a full mesh of always-on measurements among N
   measurement nodes requires O(N^2) total resources, such as storage
   space and link capacity), OWDP itself should not exaggerate the
   problem or make it impossible (where it is in principle possible) to
   design other architectures that are free of scalability deficiencies.

6. Security Considerations

6.1. Being Hard to Detect

   The design of the protocol should make it possible to run sessions
   that would make it very difficult for any intermediate party to make
   results appear better than they would be if no interference was

6.2. Secrecy/Confidentiality

   It should be possible to make it infeasible for any outside party
   without knowledge of shared secret being used to learn what
   information is exchanged using OWDP-Control by inspecting OWDP-
   Control stream or by actively modifying it.

   (It is recognized that some information will inevitably leak from the
   mere fact of communication and from presence and timing of concurrent
   and subsequent OWDP-Test traffic.)

6.3. Authentication

   It should be possible to authenticate peers to each other using a
   user ID and a shared secret.  It should be infeasible for any
   external party without knowledge of the shared secret to obtain any
   information about it by observing, initiating, or modifying protocol

   It should also be infeasible for such party to use any information
   obtained by observing, modifying or initiating protocol transactions

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   to impersonate (other) valid users.

6.4. Integrity

   Facility to authenticate each message of the control protocol and
   their exact sequence and attribution to a given session has to be
   provided, so that any interference during a conversation (other than
   detention of some messages) can be detected.

   Facility to authenticate each message of the test protocol and its
   attribution to a specific session has to be provided, so that
   modifications of OWDP-Test messages can be detected.

   Facility to do the latter in such a way that timestamps themselves
   aren't encrypted and security properties are only valid for an
   attacker that cannot observe valid traffic between OWDP-Test sender
   and receiver has to be provided.

6.5. Modes of Operation

   Since the protocol(s) will be used in widely varying circumstances
   using widely varying equipment, it is necessary to have more than one
   mode of operation security-wise.

   A mode that is completely "open" (an unauthenticated mode) should be
   provided, where no security mechanisms are used.

   A mode where all security mechanisms are enabled and security
   objectives are realized to fullest extent possible (an encrypted
   mode) should be provided.

   Since timestamp encryption takes certain time, which may be hard to
   predict on some devices (with a time-sharing OS), a mode similar to
   encrypted mode, but where timestamps aren't encrypted, should be
   provided.  In said mode, all security properties of encrypted mode
   that can be retained without timestamp encryption should be present.

7. IANA Considerations

   Relevant IANA considerations will be placed into the protocol
   specification document itself, and not into the requirements

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8. References

   [BRIX] Brix 1000 Verifier,

   [CQOS] CQOS Home Page,

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

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

   [RIPE] RIPE NCC Test-Traffic Measurements home,

   [SURVEYOR] Surveyor Home Page,

9. Authors' Addresses

   Stanislav Shalunov
   200 Business Park Drive
   Armonk, NY  10504

   Phone: +1 914 765 1182

   Benjamin Teitelbaum
   Advanced Network & Services
   200 Business Park Drive
   Armonk, NY 10504

   Phone: +1 914 765 1118

   Expiration date: January 2002

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