Internet Engineering Task Force                           Takumi Kimura
INTERNET-DRAFT                                            NTT
Expires in: April 2004                                    Jerry Perser
                                                          Spirent
                                                          October 2003


          Benchmarking Terminology for Protection Performance

                 <draft-kimura-protection-term-02.txt>


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC 2026.

   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-Drafts.

   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
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.


Abstract

   This document addresses common terminology and metrics for the
   performance benchmarking of sub-IP layer protection technologies:
   Automatic Protection Switching (APS) for SONET/SDH, Fast Reroute for
   Multi-Protocol Label Switching (MPLS), and Resilient Packet Ring
   (RPR) standardized in IEEE.  The benchmarks describe the performance
   based on the effects in the IP-layer to avoid dependence on a
   specific sub-IP layer protection technology.


Table of Contents

    1. Introduction  ..............................................  2
    2. Existing definitions  ......................................  3



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    3. Term definitions  ..........................................  3
      3.1 Path
        3.1.1 Path  ...............................................  3
        3.1.2 Working Path  .......................................  4
        3.1.3 Ordinary Path  ......................................  4
        3.1.4 Recovery Path  ......................................  5
        3.1.5 Recovery Span  ......................................  5
      3.2 Protection
        3.2.1 Path Failure  .......................................  6
        3.2.2 Failure Detection  ..................................  6
        3.2.3 Switch Over  ........................................  7
        3.2.4 Protection Switching  ...............................  7
        3.2.5 Protection-Capable Node  ............................  8
        3.2.6 Protection System  ..................................  8
      3.3 Reference Model for Protection Benchmarking
        3.3.1 Pseudo-Failure Equipment  ...........................  9
        3.3.2 Trigger for Failure Protection  .....................  9
        3.3.3 Reference Model for Protection Benchmarking  ........ 10
      3.4 Metrics
        3.4.1 Errored Packet  ..................................... 11
        3.4.2 Lost Packet  ........................................ 12
        3.4.3 Sequence-Error Period  .............................. 12
        3.4.4 Loss Period  ........................................ 13
        3.4.5 Base Latency  ....................................... 13
        3.4.6 Additive Latency  ................................... 14
        3.4.7 Induced Latency  .................................... 14
        3.4.8 Unstable-latency Period  ............................ 15
        3.4.9 Recovery Time  ...................................... 15
    4. Security Considerations  ................................... 16
    5. Acknowledgements  .......................................... 16
    6. References  ................................................ 17
    7. Authors' Addresses  ........................................ 17
    8. Full Copyright Statement  .................................. 17


1. Introduction

   Reliability is needed in today's IP networks, because the Internet
   has already become an important communication infrastructure, and
   quality-sensitive applications are being used on it.  Protection
   technologies have been implemented in sub-IP layers improve IP-layer
   reliability.  Automatic Protection Switching (APS) is for SONET/SDH,
   Fast Reroute is for Multi-Protocol Label Switching (MPLS), and
   Resilient Packet Ring (RPR) is standardized in IEEE.  The recovery
   time in the IP-layer is different from that in sub-IP layers because
   of the recognition mechanism for when interfaces go up and down and
   the buffering effect of IP routers.  Protection performance
   benchmarks and methodologies for testing them are required to allow



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   an objective comparison of implementations.

   These benchmark definitions are based on the effects in the IP layer,
   so that they can be developed independent of protection technologies
   and that we can compare different protection technologies.


2.  Existing definitions

   This document draws on existing terminology defined in other BMWG
   work.  Examples include, but are not limited to:

        Latency                   [RFC 1242, section 3.8]
        Frame Loss Rate           [RFC 1242, section 3.6]
        Throughput                [RFC 1242, section 3.17]
        Device Under Test (DUT)   [RFC 2285, section 3.1.1]
        System Under Test (SUT)   [RFC 2285, section 3.1.2]
        Out-of-sequence Packet    [Ref.[4], section 3.3.1]
        Out-of-order Packet       [Ref.[4], section 3.3.2]
        Duplicate Packet          [Ref.[4], section 3.3.3]

   This document adopts the definition format in Section 2 of RFC 1242.

   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.


3. Term definitions

3.1 Path

3.1.1 Path

    Definition:
        A sequence of nodes, <R1, ..., Rn>, with the following
        properties:
        - R1 is the ingress node and forwards IP packets, which are
        entered into DUT/SUT, to R2 as sub-IP frames.
        - Ri is a node which forwards data frames to R[i+1] for all i,
        1<i<n, based on information in the sub-IP layer.
        - Rn is the egress node and it passes sub-IP frames to its IP
        layer for forwarding.

    Discussion:
        The term "path" is used as the sub-IP layer path in this
        document, unlike an IP path in RFC 2026.  For example, the
        SONET/SDH path and the label-switched path for MPLS.  A path may



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        be regarded as being equivalent to one IP link between two IP
        nodes, i.e., R1 and Rn.  The two IP nodes may have multiple
        paths between them for redundancy.  A packet will travel on only
        one path between the nodes.  Packets belonging to a microflow
        (RFC 2474) will transverse one or more paths.  The path is
        unidirectional.

    Measurement units:
        n/a

    Issues:
        "A bidirectional path", which transmits traffic in both
        directions along the same nodes, consists of two unidirectional
        paths.  Therefore, the two unidirectional paths belonging to
        "one bidirectional path" will be treated independently when
        benchmarking for " a bidirectional path".

    See Also:


3.1.2 Working Path

    Definition:
        The current path that the DUT/SUT is using to forward packets.

    Discussion:
        An ordinary path (3.1.3) is a working path before failure
        protection, while a recovery path (3.1.4) becomes a working path
        after failure protection.

    Measurement units:
        n/a

    Issues:

    See Also:
        Path (3.1.1)
        Ordinary Path (3.1.3)
        Recovery Path (3.1.4)


3.1.3 Ordinary Path

    Definition:
        A path which is a working path before failure protection.

    Discussion:




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    Measurement units:
        n/a

    Issues:

    See Also:
        Path (3.1.1)
        Working Path (3.1.2)
        Path Failure (3.2.1)


3.1.4 Recovery Path

    Definition:
        A path which is prepared for the eventuality of ordinary path
        failure, and used to forward packets as a working path after
        failure protection.

    Discussion:
        There are various types of recovery paths: a dedicated recovery
        path (1+1), which has 100% redundancy for a specific ordinary
        path, a shared recovery path (1:N), which is dedicated to the
        protection of N specific ordinary paths, and an associated
        shared recovery path (M:N) for which a specific set of recovery
        paths (N) protects a specific set of ordinary paths (M).

    Measurement units:
        n/a

    Issues:

    See Also:
        Path (3.1.1)
        Working Path (3.1.2)
        Ordinary Path (3.1.3)
        Path Failure (3.2.1)


3.1.5 Recovery Span

    Definition:
        A section of an ordinary path that includes a failure link or
        node and is changed to other link(s) and node(s) for protection.

    Discussion:
        There are two types of recovery spans: a full recovery span,
        which is a recovery span prepared between the ingress and egress
        nodes of DUT/SUT, and a partial recovery span, which is a



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        recovery span prepared for only parts of an ordinary path
        between ingress and egress nodes of DUT/SUT.  For a full
        recovery span, the whole of an ordinary path is changed to a
        recovery span for protection, and the ordinary and recovery
        paths do not overlap.  For a partial recovery span, only a part
        of an ordinary path is changed to a recovery span for
        protection, and parts of the ordinary and recovery paths may
        overlap (as in ring restorations).

    Measurement units:
        n/a

    Issues:

    See Also:
        Ordinary Path (3.1.3)
        Recovery Path (3.1.4)
        Path Failure (3.2.1)


3.2 Protection

3.2.1 Path Failure

    Definition:
        A condition that prevents packets from being forwarded on an
        ordinary path as a working path, caused by fault(s) with link(s)
        or node(s) in a sub-IP layer.

    Discussion:

    Measurement units:
        n/a

    Issues:

    See Also:
        Working Path (3.1.2)
        Ordinary Path (3.1.3)


3.2.2 Failure Detection

    Definition:
        The operation of identifying working-path failure which is
        caused by fault(s) with link(s) or node(s) in a sub-IP layer.

    Discussion:



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    Measurement units:
        n/a

    Issues:

    See Also:
        Working Path (3.1.2)
        Ordinary Path (3.1.3)
        Path Failure (3.2.1)


3.2.3 Switch Over

    Definition:
        The operation that changes a working path from an ordinary path
        to a recovery path.

    Discussion:
        Switch over does not always replace an entire ordinary path with
        other link(s) and node(s) for a partial recovery span.  This
        operation can be instituted automatically or manually in cases
        of failure.

    Measurement units:
        n/a

    Issues:

    See Also:
        Working Path (3.1.2)
        Ordinary Path (3.1.3)
        Recovery Path (3.1.4)
        Recovery Span (3.1.5)
        Path Failure (3.2.1)


3.2.4 Protection Switching

    Definition:
        The operation of the detection of working-path failure(s) and
        switch-over response to the detection of failure(s).

    Discussion:
        A protection-switching scheme includes both the mechanisms for
        failure detection and switch over.

    Measurement units:
        n/a



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    Issues:

    See Also:
        Working Path (3.1.2)
        Ordinary Path (3.1.3)
        Recovery Path (3.1.4)
        Recovery Span (3.1.5)
        Path Failure (3.2.1)
        Failure Detection (3.2.2)
        Switch Over (3.2.3)


3.2.5 Protection-Capable Node

    Definition:
        A node that includes functional elements to perform protection
        switching.

    Discussion:
        Both end nodes of a recovery span for an ordinary path must be
        protection-capable nodes.

    Measurement units:
        n/a

    Issues:

    See Also:
        Ordinary Path (3.1.3)
        Recovery Path (3.1.4)
        Recovery Span (3.1.5)
        Protection Switching (3.2.4)


3.2.6 Protection System

    Definition:
        A system which consists of two or more protection-capable nodes
        connected to each other by link(s) and node(s) constructing
        ordinary paths and recovery paths.

    Discussion:
        When a working-path failure occurs, the system detects the
        failure and switches the working path from the failed ordinary
        path to the recovery path.  Some technologies for this are in
        sub-IP layers, i.e., MPLS-based recovery and SONET/SDH-based
        recovery.




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    Measurement units:
        n/a

    Issues:

    See Also:
        Working Path (3.1.2)
        Ordinary Path (3.1.3)
        Recovery Path (3.1.4)
        Recovery Span (3.1.5)
        Path Failure (3.2.1)
        Failure Detection (3.2.2)
        Switch Over (3.2.3)
        Protection Switching (3.2.4)
        Protection-Capable Node (3.2.5)


3.3 Reference Model for Protection Benchmarking

3.3.1 Pseudo-Failure Equipment

    Definition:
        Equipment which emulate a path failure after receiving a
        trigger-signal from test equipment.

    Discussion:
        Pseudo-failure equipment is used in benchmarking protection
        systems, since it provides more reliable and reproducible
        testing than actual path failure.

    Measurement units:
        n/a

    Issues:
        The time from receiving a signal to producing a failure
        condition may be a potential source of measurement error, if the
        time is used as the start time of the metrics.

    See Also:
        Path Failure (3.2.1)
        Trigger for Failure Protection (3.3.2)


3.3.2 Trigger for Failure Protection

    Definition:
        A signal which is sent from test equipment to make a piece of
        pseudo-failure equipment create a pseudo-failure in an ordinary



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        path.

    Discussion:

    Measurement units:
        n/a

    Issues:

    See Also:
        Working Path (3.1.2)
        Ordinary Path (3.1.3)
        Path Failure (3.2.1)
        Pseudo-Failure Equipment (3.3.1)


3.3.3 Reference Model for Protection Benchmarking

    Definition:
        A fundamental model that is used in benchmarking protection
        systems.  A System Under Test (SUT) consists of two protection-
        capable nodes connected by both an ordinary path and a recovery
        path.  Pseudo-failure equipment is placed at a point along the
        ordinary path.  Test equipment is set outside the two nodes and
        generates IP traffic.  The test equipment also sends the
        triggers for protection that cause the piece of pseudo-failure
        equipment to simulate path failures.


                              +----------------+
            +-----------------| Test Equipment |<------------------+
            |                 +----------------+                   |
            |                          | Trigger                  |
            |                          |   for Protection         |
            |              Ordinary    v                          |
            |    +--------+  Path +---------+       +--------+    |
            |    |        |-------| Failure |------>|        |    |
            +--->| Node 1 |       +---------+       | Node 2 |----+
                 |        |- - - - - - - - - - - - >|        |
                 +--------+      Recovery Path      +--------+

                 |                                           |
                 +-------------------------------------------+
                              System Under Test (SUT)

                                    Figure 1





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    Discussion:
        A reference model for protection benchmarking is shown in fig.1.
        A SUT consists of two protection-capable nodes connected by both
        an ordinary path and a recovery path.  The ordinary path has
        pseudo-failure equipment.  Test equipment, which is placed
        outside the two nodes, continuously sends IP packets that
        include sequence numbers and time stamps to one of the nodes and
        receives packets from the other node.  After the test equipment
        has sent a trigger for protection to the pseudo-failure
        equipment, the system detects the failure and switches from the
        failed ordinary path to the recovery path.  The test equipment
        records the sequence numbers and time stamps in the IP packets
        as well as the packet-reception times, during the time it takes
        protection switching to detect and finish responding to a
        failure.

    Measurement units:
        n/a

    Issues:

    See Also:
        Working Path (3.1.2)
        Ordinary Path (3.1.3)
        Recovery Path (3.1.4)
        Path Failure (3.2.1)
        Failure Detection (3.2.2)
        Switch Over (3.2.3)
        Protection Switching (3.2.4)
        Protection-Capable Node (3.2.5)
        Pseudo-Failure Equipment (3.3.1)
        Trigger for Failure Protection (3.3.2)


3.4 Metrics

        Performance metrics for protection benchmarking will include
        Lost Packets (related to Frame Loss Rate in RFC 1242) including
        Errored Packets, Out-of-order Packets (Ref.[4]), Duplicate
        Packets (Ref.[4]), Induced Latency, and Recovery Time.


3.4.1 Errored Packet

    Definition:
        A received packet that fails at least one error detection scheme
        in a sub-IP (FCS) or IP layer (IP checksum).




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    Discussion:
        Packets may have these errors due to failure or protection
        switching in a sub-IP layer.  Such packets with one or more
        errors are equivalent to lost packets in upper-layers, because
        the errors are detected in IP or lower layers.

    Measurement units:
        Packet count

    Issues:

    See Also:
        Lost Packet (3.4.2)


3.4.2 Lost Packet

    Definition:
        A packet which either has one or more errors or dropped from the
        buffer in a DUT/SUT node.

    Discussion:
        The input traffic rate SHOULD be less than or equal to the
        Throughput (RFC 1242) which is the smallest of two Throughputs
        for paths before and after protection switching.  This metric is
        related to the Frame Loss Rate defined in RFC 1242 but we are
        interested in the number of lost packets during testing.

    Measurement units:
        Packet count

    Issues:
        Lost packets cannot be directly observed because they cannot be
        received by test equipment.

    See Also:
        Throughput (RFC 1242)
        Frame Loss Rate (RFC 1242)
        Errored Packet (3.4.1)


3.4.3 Sequence-Error Period

    Definition:
        The time duration between the first time and the last time when
        Out-of-sequence Packets (Ref.[4]) are observed at the end of
        DUT/SUT during whole testing.




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    Discussion:
        Observation of out-of-sequence packets can track all of the lost
        packets, which include errored packets, out-of-order packets,
        and duplicate packets.

    Measurement units:
        Seconds

    Issues:

    See Also:
        Out-of-sequence Packet (Ref.[4])
        Errored Packet (3.4.1)
        Lost Packet (3.4.2)
        Out-of-order Packet (Ref.[4])
        Duplicate Packet (Ref.[4])


3.4.4 Loss Period

    Definition:
        The time duration calculated by dt/(Ns-Nr) if Ns > Nr, or 0 if
        Ns<=Nr, where dt is a constant inter-packet time with which the
        test equipment sends packets.  Ns is the number of packets sent
        from the test equipment and Nr is the number of packets received
        by the test equipment.

    Discussion:
        Each test packet does not need to have its sequence number in it
        to measure this metric.

    Measurement units:
        Seconds

    Issues:

    See Also:
        Lost Packet (3.4.2)


3.4.5 Base Latency

    Definition:
        Latency during no network changes: no path failures, no route
        changes, and no traffic overload.

    Discussion:
        Base latencies before path failure and after protection



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        switching are the latencies in an ordinary path and in a
        recovery path respectively.  If a recovery path takes more hops
        than an ordinary path, the base latency is increased by
        protection switching.  Base latency in the duration between path
        failure and protection switching cannot be determined under the
        above definition, because the working path is changed in this
        duration.  In this case, base latency is defined as the base
        latency before path failure.  So, base latency changes during
        testing.

    Measurement units:
        Seconds

    Issues:

    See Also:
        Ordinary Path (3.1.3)
        Recovery Path (3.1.4)
        Latency (RFC 1242)


3.4.6 Additive Latency

    Definition:
        Difference in base latencies in recovery path compared to the
        ordinary path.

    Discussion:
        If a recovery path takes more hops than an ordinary path, the
        latency is increased by protection switching.

    Measurement units:
        Seconds

    Issues:

    See Also:
        Ordinary Path (3.1.3)
        Recovery Path (3.1.4)
        Latency (RFC 1242)
        Base Latency (3.4.5)


3.4.7 Induced Latency

    Definition:
        Difference in measured latency during testing compared to the
        base latency.



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    Discussion:
        This latency may be induced by buffering in nodes during
        protection switching and it may vary with time.

    Measurement units:
        Seconds

    Issues:
        It is necessary to write a timestamp in every packet to measure
        this metric.

    See Also:
        Ordinary Path (3.1.3)
        Recovery Path (3.1.4)
        Latency (RFC 1242)
        Base Latency (3.4.5)


3.4.8 Unstable-latency Period

    Definition:
        The time duration between the first time and the last time when
        test packets injected with a constant period dt are received
        with a time interval which is not equal to dt at the end of
        DUT/SUT during the entire test.

    Discussion:
        An observed inter-packet time T is set equal to dt, if dt - s <
        T < dt + s, where the measurement error is limited by the value
        s.  The test equipment measures inter-packet times received by
        it, because we do not need the value of induced latency itself.
        The observation of packet intervals can indirectly track induced
        latency,

    Measurement units:
        Seconds

    Issues:

    See Also:
        Ordinary Path (3.1.3)
        Recovery Path (3.1.4)
        Latency (RFC 1242)


3.4.9 Recovery Time

    Definition:



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        The time duration from an earlier start time of unstable-latency
        and sequence-error periods to a later end time of these periods.

    Discussion:
        Recovery time could be the sum of failure detection time,
        switch-over time, and the time taken for the system to be
        stabilized.  This is the time duration when protection switching
        in response to path failure has finished and stability is
        restored enabling packets to be forwarded normally, i.e.,
        abnormal and abnormally received packets (lost, errored, out-of-
        order, and duplicated) are no longer present, induced latency
        has decreased, and latency becomes stable.

        The Loss Period may be an alternative metric of the recovery
        time.  But this metric may be not so accurate.  If Loss Period
        is used as an alternative of the recovery time, it MUST be
        referred to as "Recovery Time by Loss Period"

    Measurement units:
        Seconds

    Issues:

    See Also:
        Ordinary Path (3.1.3)
        Recovery Path (3.1.4)
        Failure Detection (3.2.2)
        Switch Over (3.2.3)
        Protection Switching (3.2.4)
        Latency (RFC 1242)
        Errored Packet (3.4.1)
        Lost Packet (3.4.2)
        Out-of-order Packet (Ref.[4])
        Duplicate Packet (Ref.[4])
        Induced Latency (3.4.7)
        Sequence-Error Period (3.4.3)
        Loss Period (3.4.4)
        Unstable-latency Period (3.4.8)


4. Security Considerations

   This document only addresses terminology for the performance
   benchmarking of protection systems, and the information contained in
   this document shall have no effect on the security of the Internet.


5. Acknowledgements



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   The editors gratefully acknowledge the contribution of Al Morton in
   reviewing this document.


6. References

   [1]  Bradner, S., "The Internet Standards Process -- Revision 3",
        RFC 2026, October 1996.

   [2]  Bradner, S., Editor, "Benchmarking Terminology for
        Network Interconnection Devices", RFC 1242, July 1991.

   [3]  Mandeville, R., "Benchmarking Terminology for LAN
        Switching Devices", RFC 2285, February 1998.

   [4]  Perser, J., et al., "Terminology for Benchmarking Network-layer
        Traffic Control Mechanisms",
        Internet Draft, Work in Progress,
        draft-ietf-bmwg-dsmterm-07.txt, June 2003.

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

   [6]  Paxson, V., et al., "Framework for IP Performance Metrics",
        RFC 2026, May 1998.


7. Authors' Addresses

   Takumi Kimura
   NTT Service Integration Laboratories
   3-9-11 Midori-cho
   Musashino-shi, Tokyo 180-8585
   Japan
   Phone: +81 422 59 3026
   EMail: takumi.kimura@lab.ntt.co.jp

   Jerry Perser
   Spirent Communications
   26750 Agoura Road
   Calabasas, CA 91302
   USA
   Phone: + 1 818 676 2300
   EMail: jerry.perser@spirentcom.com


8. Full Copyright Statement




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   Copyright (C) The Internet Society (2003).  All Rights Reserved.

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Kimura & Perser            Expires April 2004                  [Page 18]