Network Working Group                         S. Poretsky
 Internet Draft                                NextPoint Networks
 Expires: August 2008
 Intended Status: Informational
                                               S. Poretsky
                                               Reef Point Systems                R. Papneja
                                               Isocore

                                               J. Karthik
                                               Cisco Systems

                                               S. Vapiwala
                                               Cisco Systems

                                               November 2007

                                               February 25, 2008

         Benchmarking Terminology for Protection Performance
             <draft-ietf-bmwg-protection-term-03.txt

             <draft-ietf-bmwg-protection-term-04.txt >

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   Copyright (C) The IETF Trust (2007). (2008).

Abstract
  This document provides common terminology and metrics for benchmarking
  the performance of sub-IP layer protection mechanisms. The performance
  benchmarks are measured at the IP-Layer, so avoid dependence on
  specific sub-IP protection mechanisms. The benchmarks and terminology
  can be applied in methodology documents for different sub-IP layer
  protection mechanisms such as Automatic Protection Switching (APS),
  Virtual Router Redundancy Protocol (VRRP), Stateful High Availability
  (HA), and Multi-Protocol Label Switching Fast Reroute (MPLS-FRR).

                          Protection Performance
 Table of Contents
        1. Introduction..............................................3
        2. Existing definitions......................................4 definitions......................................6
        3. Test Considerations.......................................5 Considerations.......................................7
           3.1. Path.................................................5 Paths................................................7
              3.1.1. Path............................................5 Path............................................7
              3.1.2. Working Path....................................6 Path....................................8
              3.1.3. Primary Path....................................6 Path....................................8
              3.1.4. Protected Primary Path..........................6 Path..........................8
              3.1.5. Backup Path.....................................7 Path.....................................9
              3.1.6. Standby Backup Path.............................8 Path.............................10
              3.1.7. Dynamic Backup Path.............................8 Path.............................10
              3.1.8. Disjoint Paths..................................8 Paths..................................10
              3.1.9. Point of Local repair (PLR).....................11
              3.1.10. Shared Risk Link Group (SRLG)...................9 (SRLG)..................11
           3.2. Protection...........................................9
              3.2.1. Protection Switching System.....................9
              3.2.2. Mechanisms................................12
              3.2.1. Link Protection.................................10
              3.2.3. Protection.................................12
              3.2.2. Node Protection.................................10
              3.2.4. Protection.................................12
              3.2.3. Path Protection.................................10
              3.2.5. Protection.................................12
              3.2.4. Backup Span.....................................11
              3.2.6 Span.....................................13
              3.2.5. Local Link Protection...........................13
              3.2.6. Redundant Node Protection.......................14
              3.2.7  State Control Interface.........................14
              3.2.8. Protected Interface.............................11 Interface.............................15
           3.3. Protection Switching.................................12 Switching.................................15
              3.3.1. Failover Event..................................12 Protection Switching System.....................15
              3.3.2. Failure Detection...............................12 Failover Event..................................15
              3.3.3. Failover........................................13 Failure Detection...............................16
              3.3.4. Restoration.....................................13 Failover........................................17
              3.3.5. Reversion.......................................14 Restoration.....................................17
              3.3.6. Reversion.......................................18
           3.4. Nodes................................................14 Nodes................................................18
              3.4.1. Protection-Switching Node.......................14 Node.......................18
              3.4.2. Non-Protection Switching Node...................14 Node...................19
              3.4.3. Failover Node...................................15 Headend Node....................................19
              3.4.4. Merge Node......................................15 Backup Node.....................................19
              3.4.5. Point of Local repair (PLR).....................16 Merge Node......................................20
              3.4.6. Head-end Failover Node..........................16 Primary Node....................................20
              3.4.7. Standby Node....................................21
           3.5. Benchmarks...........................................17 Benchmarks...........................................21
              3.5.1. Failover Packet Loss............................17 Loss............................21
              3.5.2. Reversion Packet Loss...........................17 Loss...........................22
              3.5.3. Failover Time...................................18 Time...................................22
              3.5.4. Reversion Time..................................18 Time..................................23
              3.5.5. Additive Backup Latency.........................19 Latency.........................23
           3.6 Failover Time Calculation Methods.....................19 Methods.....................24
              3.6.1 Time-Based Loss Method...........................19 Method...........................24
              3.6.2 Packet-Loss Based Method.........................20 Method.........................25
              3.6.3 Timestamp-Based Method...........................21 Method...........................25
        4. Acknowledgments...........................................22 Acknowledgments...........................................26
        5. IANA Considerations.......................................22 Considerations.......................................26
        6. Security Considerations...................................22 Considerations...................................26
        7. References................................................22 References................................................26
        8. Author's Address..........................................23 Address..........................................27
                          Protection Performance

1. Introduction

   The IP network layer provides route convergence to protect data
   traffic against planned and unplanned failures in the internet.
   Fast convergence times are critical to maintain reliable network
   connectivity and performance.  Technologies that function at sub-IP
   layers can be enabled to provide further protection of IP
   traffic by providing the failure recovery at the sub-IP layers so
   that the outage is not observed at the IP-layer.  Such Sub-IP
   Protection technologies
   includes include High Availability (HA) stateful failover.
   failover, Virtual Router Redundancy Protocol (VRRP), Automatic Link
   Protection (APS) for SONET/SDH, Resilient Packet Ring (RPR) for
   Ethernet, and Fast Reroute for Multi-Protocol Label Switching
   (MPLS-FRR) [8].

   Benchmarking terminology have been defined for IP-layer route
   convergence [7].  New terminology and methodologies specific
   to benchmarking sub-IP layer protection mechanisms are required.
   This will enable different implementations of the same
   protection mechanisms to be benchmarked and evaluated. In
   addition, different protection mechanisms can be benchmarked and
   evaluated.  The metrics for benchmarking the performance of sub-IP
   protection mechanisms are measured at the IP layer, so that the
   results are always measured in reference to IP and independent of
   the specific protection mechanism being used. The purpose of this
   document is to provide a single terminology for benchmarking sub-IP
   protection mechanisms.  It is intended that there can exist unique
   methodology documents for each sub-IP protection mechanism. The
   sequence of events is as follows:

   1. Failover Event - Primary Path fails
   2. Failure Detection-  Failover Event is detected
   3. Failover - Backup Path becomes the Working Path due to Failover
                 Event
   4. Restoration - Primary Path recovers from a Failover Event
   5. Reversion (optional) - Primary Path becomes the Working Path

   These terms are further defined in this document.  Figure  Figures 1 shows
   the
   through 5 show fundamental model models that is to MAY be used in
   benchmarking sub-IP
   protection Sub-IP Protection mechanisms.  A  Sub-IP Protection
   mechanisms MUST use a Protection Switching System that consists
   of a minimum of two Protection-Switching Nodes Nodes, an Ingress Node
   known as the Headend Node and an Egress Node known as the Merge
   Node.  The protection MAY be provided with either a Primary
   Path and a Backup
   Path. Path, as shown in Figures 1 through 4, or a
   Primary Node and Standby Node, as shown in Figure 5.

   A Protection Switching System may provide link protection, node
   protection, path protection, local link protection, and high
   availability, as shown in Figures 1 through 5 respectively.
   A Failover Event occurs along the Primary Path.  A Tester is
   set outside the two nodes as it sends and receives IP traffic along Path or at the Working Path. Primary
                          Protection Performance

   Node.  The Working Path is the Primary Path prior to the Failover
   Event and the Backup Path after the Failover Event.
   If Reversion is supported then the Working Path  A Tester is
   set outside the Primary Path
   after Restoration (Failure Recovery) of two paths or nodes as it sends and receives IP
   traffic along the Primary Working Path.  The tester MUST record the IP
   packet sequence numbers, departure time, and arrival time so that
   the metrics of Failover Time, Additive Latency, Packet Reordering,
   Duplicate Packets, and Reversion Time can be measured.  The Tester
   may be a single device or a test system.

                          Protection Performance

                                  +-----------+
             +--------------------|  Tester   |<-------------------+
             |                    +-----------+                    |
             | IP Traffic               |  If Reversion is
   supported then the Working Path is the Primary Path after
   Restoration (Failure Recovery) of the Primary Path.

   Link Protection, as shown in Figure 1, provides protection
   when a Failover      IP Traffic |
             |                          | Event                    |
             | occurs on the link between two nodes along
   the Primary     |                          |
             |    +--------+  Path      v            +--------+    |
             |    |        |------------------------>|        |    |
             +--->| Path.  Node 1 | Protection, as shown in Figure 2,
   provides protection when a Failover Event occurs at a Node along
   the Primary Path.  Path Protection, as shown in Figure 3,
   provides protection for link or node failures for multiple hops
   along the Primary Path.  Local Link Protection, as shown in
   Figure 4, provides Sub-IP Protection of a link between two nodes,
   without a Backup Node.  An example of such a Sub-IP Protection
   mechanism is SONET APS.  High Availability Protection, as shown
   in Figure 5, provides protection of a Primary Node with a
   redundant Standby Node.  State Control is provided between the
   Primary and Standby Nodes.  Failure of the Primary Node is
   detected at the Sub-IP layer to force traffic to switch to
   the Standby Node, which has state maintained for zero or minimal
   packet loss.

                      +-----------+
       +--------------|  Tester   |<-----------------------+
       |              +-----------+                        |
       | IP Traffic        | Failover           IP Traffic |
       |                   |  Event                        |
       |                   |                               |
       |     ------------  |                 ----------    |
       +--->|  Ingress/  | V                | Egress/  |---+
            |Headend Node|------------------|Merge Node|  Primary
             ------------                    ----------    Path
                |                                ^
                |         ---------              |  Backup
                +--------| Backup  |-------------+   Path
                         |  Node   |
                          ---------

   Figure 1. System Under Test (SUT) for Sub-IP Link Protection
                          Protection Performance

                            +-----------+
       +--------------------|  Tester   |<-----------------+
       |                    +-----------+                  |
       | IP Traffic               | Failover    IP Traffic |
       |                          | Event                  |
       |                          V                        |
       |     ------------      --------      ----------    |
       +--->|  Ingress/  |    |MidPoint|    | Egress/  |---+
            |Headend Node|----|  Node  |----|Merge Node|  Primary
             ------------      --------      ----------    Path
                |                                ^
                |         ---------              |  Backup
                +--------| Backup  |-------------+   Path
                         |  Node   |
                          ---------

   Figure 2. System Under Test (SUT) for Sub-IP Node Protection

                               +-----------+
    +---------------------------|  Tester   |<----------------------+
    |                           +-----------+                       |
    | IP Traffic                      | Failover         IP Traffic |
    |                                 | Event                       |
    |                Primary Path     |                             |
    |     ------------      --------  |  --------     ----------    |
    +--->|  Ingress/  |    |MidPoint| V |Midpoint|   | Egress/  |---+
         |Headend Node|----|  Node  |---|  Node  |---|Merge Node|
          ------------      --------     --------     ----------
                |                                         ^
                |         ---------      --------         | Backup
                +--------| Backup  |----| Backup |--------+  Path
                         |  Node   |    |  Node  |
                          ---------      --------

   Figure 3. System Under Test (SUT) for Sub-IP Path Protection

                                  +-----------+
             +--------------------|  Tester   |<-------------------+
             |                    +-----------+                    |
             | IP Traffic               | Failover      IP Traffic |
             |                          | Event                    |
             |              Primary     |                          |
             |    +--------+  Path      v            +--------+    |
             |    |        |------------------------>|        |    | Node 2
             +--->| Ingress|                         | Egress |----+
                  |  Node  |- - - - - - - - - - - - >|  Node  |
                  +--------+      Backup Path        +--------+
                  ^                                           ^
                  |            IP-Layer Forwarding            |
                  +-------------------------------------------+

   Figure 1. 4. System Under Test (SUT) for Sub-IP Local Link Protection
                          Protection Performance

                         +-----------+
       +-----------------|  Tester   |<--------------------+
       |                 +-----------+                     |
       | IP Traffic            | Failover       IP Traffic |
       |                       | Event                     |
       |                       V                           |
       |     ---------      --------      ----------       |
       +--->| Ingress |    |Primary |    | Egress/  |------+
            |   Node  |----|  Node  |----|Merge Node|  Primary
             ---------      --------      ----------    Path
                |        State |Control       ^
                |    Interface |(Optional)    |
                |          ---------          |
                +---------| Standby |---------+
                          |  Node   |
                           ---------

Figure 5. System Under Test (SUT) for Sub-IP Redundant Node Protection Mechanisms

2. Existing definitions
   This document uses existing terminology defined in other BMWG
   work.  Examples include, but are not limited to:

          Latency                   [Ref.[2], section 3.8]
          Frame Loss Rate           [Ref.[2], section 3.6]
          Throughput                [Ref.[2], section 3.17]
          Device Under Test (DUT)   [Ref.[3], section 3.1.1]
          System Under Test (SUT)   [Ref.[3], section 3.1.2]
          Out-of-order Packet       [Ref.[4], section 3.3.2]
          Duplicate Packet          [Ref.[4], section 3.3.3]
          Forwarding Delay          [Ref.[4], section 3.2.4]
          Jitter                    [Ref.[4], section 3.2.5]
          Packet Loss               [Ref.[7], Section 3.5]
          Packet Reordering         [Ref.[10], section 3.3]

   This document has the following frequently used acronyms:
      DUT  Device Under Test
      SUT  System Under Test

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

   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 BCP 14, RFC 2119 [5].
   RFC 2119 defines the use of these key words to help make the
   intent of standards track documents as clear as possible.  While this
   document uses these keywords, this document is not a standards track
   document.

                          Protection Performance

3. Test Considerations

  3.1. Path Paths

    3.1.1 Path

    Definition:
       A unidirectional sequence of nodes, <R1, ..., Rn>, and links
      <L12,... L(n-1)n> with the following properties:

       a. R1 is the ingress node and forwards IP packets, which input
       into DUT/SUT, to R2 as sub-IP frames over link L12.

       b. Ri is a node which forwards data frames to R[i+1] over Link
       Li[i+1] for all i, 1<i<n, based on information in the sub-IP
       layer.

       c. Rn is the egress node and it outputs sub-IP frames from
       DUT/SUT as IP packets.

    Discussion:
       The path is defined in the sub-IP layer in this document, unlike
       an IP path in RFC 2026 [1].   One path may 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 for protection.  A
       packet will travel on only one path between the nodes.  Packets
       belonging to a microflow [9] will traverse one or more paths.
       The path is unidirectional.  Example paths are the SONET/SDH
       path and the label switched path for MPLS.

    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:
       Working Path
       Primary Path
       Backup Path
                          Protection Performance

    3.1.2. Working Path

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

    Discussion:
       A Primary Path is the Working Path before occurrence of a
       Failover Event.  A Backup Path becomes the Working Path after
       a Failover Event.

    Measurement units:
       n/a

    Issues:

    See Also:
       Path
       Primary Path
       Backup Path

   3.1.3.  Primary Path

       Definition:
       The preferred path for forwarding traffic between two or
       more nodes.

       Discussion:
       The Primary Path is the Path that traffic traverses
       prior to a Failover Event.

       Measurement units:
          n/a

        Issues:
          None

        See Also:
          Path
          Failover Event

    3.1.4.  Protected Primary Path

       Definition:
       A Primary Path that is protected with a Backup Path.

       Discussion:
       A Protected Primary Path MUST include at least one Protection
       Switching Node.

                          Protection Performance

       Measurement units:
          n/a

       Issues: None

       See Also:
          Path
          Primary Path

    3.1.5.  Backup Path

       Definition:
       A path that exists to carry data traffic only if a Failover
       Event occurs on a Primary Path.

       Discussion:
       The Backup Path SHALL be the Working Path upon a Failover Event.
       A Path MAY have one or more Backup Paths.  A Backup Path MAY
       protect one or more Primary Paths.  There are various types of
       Backup Paths:

          a. dedicated recovery Backup Path (1+1), which has 100%
          redundancy for a specific ordinary path,

          b. shared Backup Path (1:N), which is dedicated to the
          protection for more than one specific Primary Path

          c. associated shared Backup Path (M:N) for which a specific
          set of Backup Paths protects a specific set of more than one
          Primary Path.

       A Backup Path may be signaled or unsignaled.  The Backup Path
       MUST be created prior to the Failover Event.  A new Path
       computed after the Failover Event is simply Convergence [7]
       to a new Primary Path.

       Measurement units:
          n/a

       Issues:

       See Also:
          Path
          Working Path
          Primary Path
                          Protection Performance

     3.1.6.  Standby Backup Path

        Definition:
        A Backup Path that is established prior to a Failover Event
        to protect a Primary Path.

        Discussion:
        The Standby Backup Path and Dynamic Backup Path provide
        protection, but are established at different times.

        Measurement units: n/a

        Issues: None

        See Also:
           Path
           Working
           Backup Path
           Primary Path
           Failover Event

     3.1.7. Dynamic Backup Path

        Definition:
        A Backup Path that is established upon occurrence of a
        Failover Event.

        Discussion:
        The Standby Backup Path and Dynamic Backup Path provide
        protection, but are established at different times.

        Measurement units: n/a

        Issues: None

        See Also:
            Backup Path
             Working Path
             Primary
            Standby Backup Path
            Failover Event

     3.1.8. Disjoint Paths

        Definition:
        A pair of paths is considered disjoint if they do not
        share a common link.

        Discussions:
        Paths that protect a segment of a path may merge beyond the
        segment being protected and are considered disjoint if they
        do not use a link from the set of links in the protected
        segment. A path is node disjoint if it does not share a
        common node other than the ingress and egress.

                          Protection Performance

        Measurement units: n/a

        Issues: None

        See Also:
           Path
           Primary Path
           SRLG

     3.1.9. Point of Local Repair (PLR)
         Definition:
         A node along the Primary Path that uses a Backup Path to
         protect another node or link.

         Discussion:
         Based on the functionality of the PLR, its role is defined
         based on the type of method used.  If the one-to-one backup
         method is used, the PLR is responsible for computing a
         separate Backup Path for each Primary Path.  In the case
         the facility backup method is used, the PLR creates a
         single Backup Path that can be used to protect multiple
         Primary Paths.  Any node from the ingress node to the
         penultimate egress node MAY be a PLR.  If the PLR is at
         the ingress, the Backup Path is a Disjoint Path from the
         ingress to egress.

         Measurement units: n/a

         Issues: None

         See Also:
             Primary Path
             Backup Path
             Failover

     3.1.10. Shared Risk Link Group (SRLG)
         Definition:
          SRLG is a set of links which share a physical resource.

         Discussion:
          SRLG is considered the set of links to be avoided when
          the primary and secondary paths are considered disjoint.
          The SRLG will fail as a group if the shared resource fails.

         Measurement units: n/a

         Issues: None

         See Also:
             Path
             Primary Path
                          Protection Performance

   3.2. Protection
     3.2.1. Link Protection Switching System
         Definition:
           A DUT/SUT Backup Path that is capable signaled to at least one Backup Node
           to protect for failure of Failure Detection interfaces and Failover
          from links along a
           Primary Path.

         Discussion:
           Link Protection may or may not protect the entire Primary
           Path.  Link protection is shown in Figure 1.

         Measurement units: n/a

         Issues: None

         See Also:
             Primary Path
             Backup Path

     3.2.2. Node Protection
         Definition:
           A Backup Path that is signaled to at least one Backup Node
           to protect for failure of interfaces, links, and nodes
           along a Primary Path.

         Discussion:
           Node Protection may or may not protect the entire Primary
           Path.  Node Protection also provides Link Protection.
           Node Protection is shown in Figure 2.

         Measurement units: n/a

         Issues: None

         See Also:
             Link Protection

     3.2.3. Path Protection
        Definition:
        A Backup Path when a Failover Event
          occurs. that is signaled to at least one Backup Node
        to provide protection along the entire Primary Path.

        Discussion:
          The
        Path Protection provides Node Protection and Link Protection
        for every node and link along the Primary Path.  A Backup
        Path providing Path Protection Switching System MUST have a the same ingress
        node as the Primary Path.  Path
          and Protection is shown in
        Figure 3.

        Measurement units: n/a

        Issues: None
                          Protection Performance

        See Also:
             Primary Path
             Backup Path
             Node Protection
             Link protection

     3.2.4. Backup Span

        Definition:
        The number of hops used by a Backup Path.

        Discussion:
        The Backup Path MAY Span is an integer obtained by counting the
        number of nodes along the Backup path

        Measurement units:
             number of nodes

        Issues:
             None

        See Also:
             Primary Path
             Backup Path

     3.2.5. Local Link Protection

        Definition:
        A Backup Path that is a redundant path between two nodes
        which does not use a Backup Node.

        Discussion:
        Local Link Protection MUST be provided as a Standby Backup Path or
        between two nodes along the Primary Path without the use
        of a dynamic Backup Path.  The Node.  Local Link Protection is provided by
        Protection Switching System includes the mechanisms for both Failure
          Detection and Failover. Systems such as SONET APS.  Local
        Link Protection is shown in Figure 4.

        Measurement units: n/a None

        Issues: None

        See Also:
             Primary Path
        Backup Path
             Failover path
        Headend
                          Protection Performance

     3.2.2.  Link

     3.2.6. Redundant Node Protection

        Definition:
        A Backup Path that is signaled to protect for failure
           of interfaces and links along Protection Switching System with a Primary Node
        protected by a Standby Node along the Primary Path.

        Discussion:
           Link
        Redundant Node Protection may or may not protect is provided by Protection
        Switching Systems such as VRRP and HA.  The protection
        mechanisms occur at Sub-IP layers to switch traffic from
        a Primary Node to Backup Node upon a Failover Event at
        the entire Primary
           Path. Node.  Traffic continues to traverse the
        Primary Path through the Standby Node.  The failover MAY
        be stateful, in which the state information MAY be
        exchanged in-band or over an out-of-band state control
        interface.  The Standby Node MAY be active or passive.
        Redundant Node Protection is shown in Figure 5.

        Measurement units: n/a None

        Issues: None

        See Also:
        Primary Path
        Primary Node
        Backup Path

     3.2.3. Node Protection

     3.2.7. State Control Interface

        Definition:
           A Backup Path that is signaled
        An out-of-band control interface used to protect for failure
           of interfaces, links and nodes along a exchange state
        information between the Primary Path. Node and Standby Node.

        Discussion:
        The State Control Interface MAY be used for Redundant Node
        Protection.  The State Control Interface MUST be out-of-band.
        It is possible to have Redundant Node Protection may in which
        there is no state control or may not protect state control is provided
        in-band.  The State Control Interface between the entire Primary
           Path.
        and Standby Node Protection also provides Link Protection. MAY be one or more hops.

        Measurement units: n/a None

        Issues: None

        See Also:
             Link Protection

     3.2.4.   Path
        Primary Node
        Standby Node
                          Protection Performance

     3.2.8. Protected Interface

        Definition:
        A Backup Path that provides protection for
        An interface along the entire Primary Path that is protected by
        a Backup Path.

        Discussion:
        Path
        A Protected Interface is an interface protected by a
        Protection Switching Systems that provides Link
        Protection, Node Protection and Protection, Path Protection, Local
        Link Protection
        for every node Protection, and link along the Primary Path.  A Backup
        Path providing Path Protection MUST have the same ingress
        node as the Primary Path. Redundant Node Protection.

        Measurement units: n/a None

        Issues: None
                          Protection Performance

        See Also:
           Primary Path
           Backup Path
             Node

   3.3. Protection
             Link protection

     3.2.5. Backup Span Switching

     3.3.1.  Protection Switching System

        Definition:
        The numbers
          A DUT/SUT that is capable of hop used by Failure Detection and Failover
          from a Backup Path.

        Discussion:

        Measurement units: number of nodes

        Issues: None

        See Also: Primary Path to a Backup Path

     3.2.6 Protected Interface

        Definition:
        An interface along the or Standby Node when a
          Failover Event occurs.

        Discussion:
          The Protection Switching System MUST have a Primary Path that is protected by
          and a Backup Path.  The Backup Path MAY be a Standby
          Backup Path

        Discussion: or a dynamic Backup Path.  The Protection
          Switching System includes the mechanisms for both Failure
          Detection and Failover.

        Measurement units: None n/a

        Issues: None

        See Also:
             Primary Path
             Backup Path
                          Protection Performance

   3.3. Protection Switching

     3.3.1.
             Failover

     3.3.2.  Failover Event

       Definition:
       The occurrence of a planned or unplanned action in the network
       that results in a change in the Path that data traffic traverses.

                          Protection Performance

       Discussion:
       Failover Events include, but are not limited to, link failure
       and router failure.  Routing changes are considered Convergence
       Events [7] and are not Failover Events.  This restricts
       Failover Events to sub-IP layers. Failover may be at the PLR or
       at the ingress. If the failover is at the ingress it is
       generally on the ingress it is
       generally on a disjoint path from the ingress to egress.

       Failover Events may results from failures such as link failure
       or router failure.  The change in path after Failover MAY have
       a Backup Span of one or more nodes.  Failover Events are
       distinguished from routing changes and Convergence Events [7]
       by the detection of the failure and subsequent protection
       switching at a sub-IP layer.  Failover occurs at a disjoint path from the ingress to egress. Point of
       Local Repair (PLR) or Primary Node.

       Measurement units:
          n/a

       Issues:

       See Also:
          Path
          Failure Detection
          Disjoint Path

     3.3.2.

     3.3.3.  Failure Detection

       Definition:
       The process to identify at a sub-IP layer a Failover Event
       at a Primary Node or along the Primary Path.

       Discussion:
       Failure Detection occurs at the Primary Node or ingress node
       of the Primary  Path.  Failure Detection occurs via a sub-IP
       mechanism such as detection of a link down event or timeout for
       receipt of a control packet. A failure may be completely
       isolated. A failure may affect a set of links which share a
       single SRLG (e.g. port with many sub-interfaces). A failure may
       affect multiple links that are not part of SRLG.

       Measurement units: n/a

       Issues:

       See Also:
         Primary Path
                          Protection Performance

     3.3.3.

     3.3.4.  Failover

        Definition:
        The process to switch data traffic from the Protected Primary
        Path to the Backup Path upon Failure Detection of a Failover
        Event.

        Discussion:
        Failover to a Backup Path provides Link Protection, Node
        Protection, or Path Protection.  Failover is complete when
        Packet Loss [7], Out-of-order Packets [4], and Duplicate
        Packets [4] are no longer observed.  Forwarding Delay [4]
        may continue to be observed.

        Measurement units:
            n/a

        Issues:

        See Also:
             Primary Path
             Backup Path
             Failover Event

     3.3.4.

     3.3.5.  Restoration

        Definition:
        The act state of failover recovery in which the Primary Path
        recovers
        has recovered from a Failover Event, but is not yet
        forwarding packets because the Backup Path remains the
        Working Path.

        Discussion:
        Restoration MUST occur while the Backup Path is the
        Working Path.  The Backup Path is maintained as the
        Working Path during Restoration.  Restoration produces
        a Primary Path that is recovered from failure, but is
        not yet forwarding traffic.  Traffic is still being
        forwarded by the Backup Path functioning as the Working
        Path.

        Measurement units:
            n/a

        Issues:

        See Also:
            Primary Path
            Failover Event
            Failure Recovery
            Working Path
            Backup Path
                          Protection Performance

     3.3.5.

     3.3.6.  Reversion

        Definition:
        The act state of failover recovery in which the Primary Path becomes has
        become the Working Path so that it is forwarding packets.

        Discussion:
        Protection Switching Systems may or may not support Reversion.
        Reversion, if supported, MUST occur after Restoration.
        Packet forwarding on the Primary Path resulting from Reversion
        may occur either fully or partially over the Primary Path.  A
        potential problem with Reversion is the discontinuity in end to
        end delay when the Forwarding Delays [4] along the Primary Path
        and Backup Path are different, possibly causing Out of Order
        Packets [4], Duplicate Packets [4], and increased Jitter [4].

        Measurement units: n/a

        Issues: None

        See Also:
            Protection Switching System
            Working Path
            Primary Path

   3.4. Nodes

     3.4.1.  Protection-Switching Node

         Definition:
         A node that is capable to participate of participating in a Protection
         Switching System.

         Discussion:
         The Protection Switching Node MAY be an ingress or egress for
         a Primary Path or Backup Path, such as used for MPLS Fast
         Reroute configurations.  The Protection Switching Node MAY
         provide Redundant Node Protection as a Primary Node in a
         Redundant chassis configuration with a Standby Node, such as
         used for VRRP and HA configurations.

         Measurement units:
             n/a

         Issues:

         See Also:
             Protection Switching System
                          Protection Performance

     3.4.2.  Non-Protection Switching Node

         Definition:
         A node that is not capable of participating in a Protection
         Switching System, however it MAY exist along the Primary
         Path or Backup Path.

         Discussion:

         Measurement units:
             n/a

         Issues:

         See Also:
             Protection Switching System
             Primary Path
             Backup Path

     3.4.3.  Headend Node
        Definition:
        A node along the Primary Path that is capable of Failover.

        Discussion:
        The Headend Node can be any node along the Primary Path
        except the egress node of the Primary Path.  There can be
        multiple Failover Nodes along a Primary Path.  The Failover
        Node MUST be the ingress to the Backup Path.  The Failover
        Node MAY also be the ingress of the Primary Path. The Headend
        Failover Node is always a PLR.

        Measurement units: n/a

        Issues:

        See Also:
             Primary Path
             Point of Local Repair
             Failover

     3.4.4.  Backup Node
        Definition:
        A node along the Backup Path.

        Discussion:
        The Backup Node can be any node along the Backup Path.
        There MAY be one or more Backup Nodes along the Backup Path.
        A Backup Node MAY be the ingress, mid-point, or egress of
        the Backup Path.

         Measurement units:
             n/a

         Issues:

         See Also:
             Protection Switching System

     3.4.2.  Non-Protection Switching Node

         Definition:
         A node  If the Backup Path has only one Backup
        Node, then that Backup Node is not capable the ingress and egress of participating in a Protection
         Switching System, however it MAY exist along the Primary
         Path or
        Backup Path.

                          Protection Performance

         Discussion:

        Measurement units: n/a

        Issues:

        See Also:
             Protection Switching System
             Primary Path
             Backup Path

     3.4.3.  Failover

       3.4.5.  Merge Node
         Definition:
             A node Node along the Primary Path that is capable of Failover. primary path where backup path terminates.

         Discussion:
             The Failover Merge Node can be any node along the Primary Path
             except the egress ingress node of the Primary Path.  There can be
             multiple Failover Merge Nodes along a Primary Path.  A Merge Node
             can be the egress node for a single or multiple Backup
             Paths.  The Failover Merge Node MUST be the ingress egress to the Backup
             Path.  The Failover Merge Node MAY also be the ingress egress of the
             Primary Path. Path or point of local repair (PLR).

         Measurement units:
             n/a

         Issues:

         See Also:
             Primary Path
             Backup Path
             PLR
             Failover

     3.4.4.  Merge

     3.4.6. Primary Node

        Definition:
        A Node node along the primary path where backup path terminates. Primary Path that is capable of Failover to a
        redundant Standby Node.

        Discussion:
        The Merge Primary Node can MAY be any used for Protection Switching Systems
        that provide Redundant Node Protection, such as VRRP and HA

        Measurement units: n/a

        Issues:

        See Also:
             Protection Switching System
             Redundant Node Protection
             Standby Node
                          Protection Performance

     3.4.7.  Standby Node

        Definition:
        A redundant node to a Primary Node that forwards traffic along
        the Primary Path
             except the ingress node upon Failure Detection of the Primary Path.  There can Node.

        Discussion:
        The Standby Node MUST be
             multiple Merge Nodes used for Protection Switching
        Systems that provide Redundant Node Protection, such as VRRP
        and HA.  The Standby Node MUST provide protection along a the
        same Primary Path.  A Merge  If the failover is to a Disjoint Path then
        it is a Backup Node.  The Standby Node
             can MAY be the egress node configured
        for a single 1:1 or multiple Backup
             Paths. N:1 protection.

        The communication between the Primary Node and Standby Node
        MAY be in-band or across an out-of-band State Control
        interface.  The Merge Standby Node MUST MAY be geographically dispersed
        from the egress to Primary Node.  When geographically dispersed, the Backup
             Path.
        number of hops of separation may increase failover time.

        The Merge Standby Node MAY also be the egress of the
             Primary Path passive or point active.  The Passive Standby
        Node is not offered traffic and does not forward traffic until
        Failure Detection of local repair (PLR).

         Measurement units:
             n/a
                          Protection Performance

         Issues:

         See Also: the Primary Path
             Backup Path
             PLR
             Failover

     3.4.5. Point Node.  Upon Failure Detection
        of Local Repair (PLR)

         Definition:
         A node along the Primary Path that uses a Backup Path Node, traffic offered to
         protect another node or link.

         Discussion:
         Based on the functionality of the PLR, its role is defined
         based on the type of method used.  If the one-to-one backup
         method is used, the PLR is responsible for computing a
         separate Backup Path for each Primary Path.  In the case
         the facility backup method Node is used, the PLR creates a
         single Backup Path that can be used
        instead offered to protect multiple
         Primary Paths.

         Measurement units: n/a

         Issues:

         See Also:
             Primary Path
             Backup Path
             Failover

     3.4.6.  Head-end Failover the Passive Standby Node.  The Active
        Standby Node

        Definition:
        A node is offered traffic and forwards traffic along the
        Primary Path that is capable of Failover.

        Discussion:
        The Head-end Failover while the Primary Node is also active.  Upon
        Failure Detection of the ingress node Primary Node, traffic offered to the Backup
        Path. The Head-end Failover
        Primary Node is always a PLR switched to the Active Standby Node.

        Measurement units: n/a

        Issues:

        See Also:
             Primary Path
             Point of Local Repair
             Failover
                          Protection Performance Node
             State Control Interface

     3.5.  Benchmarks
      3.5.1.  Failover Packet Loss
        Definition:
        The amount of packet loss produced by a Failover Event until
        Failover completes, where the measurement begins when the last
        unimpaired packet is received by the Tester on the Protected
        Primary Path and ends when the first unimpaired packet is
        received by the Tester on the Backup Path.

                          Protection Performance

        Discussion:
        Packet loss can be observed as a reduction of forwarded
        traffic from the maximum forwarding rate.  Failover Packet
        Loss includes packets that were lost, reordered, or delayed.
        Failover Packet Loss MAY reach 100% of the offered load.

        Measurement units:
          Number of Packets

        Issues:  None

        See Also:
           Failover Event
           Failover

      3.5.2.   Reversion Packet Loss

        Definition:
        The amount of packet loss produced by Reversion, where the
        measurement begins when the last unimpaired packet is received
        by the Tester on the Backup Path and ends when the first
        unimpaired packet is received by the Tester on the Protected
        Primary Path .

        Discussion:
        Packet loss can be observed as a reduction of forwarded
        traffic from the maximum forwarding rate.  Reversion Packet
        Loss includes packets that were lost, reordered, or delayed.
        Reversion Packet Loss MAY reach 100% of the offered load.

         Measurement units: Number of Packets

         Issues:  None

         See Also:
           Reversion
                          Protection Performance

      3.5.3. Failover Time

        Definition:
         The amount of time it takes for Failover to successfully
         complete.

        Discussion:
        Failover Time can be calculated using the Time-Based Loss
        Method (TBLM), Packet-Loss Based Method (PLBM), or
        Timestamp-Based Method (TBM).  It is RECOMMENDED that the
        TBM is used.

                          Protection Performance

        Measurement units:
           milliseconds

        Issues: None

        See Also:
           Failover
           Failover Time
           Time-Based Loss Method (TBLM)
           Packet-Loss Based Method (PLBM)
           Timestamp-Based Method (TBM)

      3.5.4.  Reversion Time

        Definition:
        The amount of time it takes for Reversion to complete so
        that the Primary Path is restored as the Working Path.

        Discussion:
        Reversion Time can be calculated using the Time-Based Loss
        Method (TBLM), Packet-Loss Based Method (PLBM), or
        Timestamp-Based Method (TBM).  It is RECOMMENDED that the
        TBM is used.

        Measurement units:
           milliseconds

        Issues: None

        See Also:
           Reversion
           Primary Path
           Working Path
           Reversion Packet Loss
           Time-Based Loss Method (TBLM)
           Packet-Loss Based Method (PLBM)
           Timestamp-Based Method (TBM)
                          Protection Performance

      3.5.5.  Additive Backup Delay

        Definition:
        The amount of increased Forwarding Delay [4] resulting
        from data traffic traversing the Backup Path instead of
        the Primary Path.

        Discussion:
        Additive Backup Delay is calculated using Equation 1 as
        shown below:

        (Equation 1)
        Additive Backup Delay =
                  Forwarding Delay(Backup Path) -
                  Forwarding Delay(Primary Path).

                          Protection Performance

        Measurement units:
           milliseconds

        Issues:
        Additive Backup Latency MAY be a negative result.
        This is theoretically possible, but could be indicative
        of a sub-optimum network configuration .

        See Also:
           Primary Path
           Backup Path
           Primary Path Latency
           Backup Path Latency

     3.6 Failover Time Calculation Methods

     3.6.1 Time-Based Loss Method (TBLM)

      Definition:
      The method to calculate Failover Time (or Reversion Time) using a
      time scale on the Tester to measure the interval of Failover
      Packet Loss.

      Discussion:
      The Tester MUST provide statistics which show the duration of
      failure on a time scale to granularity of milliseconds based on
      occurrence of packet loss on a time scale.  This is indicated by
      the duration of non-zero packet loss.  The TBLM includes failure
      detection time and time for data traffic to begin traversing the
      Backup Path.  Failover Time and Reversion Time are calculated
      using the TBLM as shown in Equation 2:

                          Protection Performance

      (Equation 2)
          (Equation 2a)
          TBLM Failover Time = Time(Failover) - Time(Failover Event)

          (Equation 2b)
          TBLM Reversion Time = Time(Reversion) - Time(Restoration)

      Measurement units:
         milliseconds

      Issues:
         None

      See Also:
         Failover
         Packet-Loss Based Method
                          Protection Performance

     3.6.2 Packet-Loss Based Method (PLBM)

      Definition:
      The method used to calculate Failover Time (or Reversion Time)
      from the amount of Failover Packet Loss.

      Discussion:
      PLBM includes failure detection time and time for data traffic to
      begin traversing the Backup Path.  Failover Time can be
      calculated using PLBM from the amount Failover Packet Loss as
      shown below in Equation 3:

      (Equation 3)
           (Equation 3a)
           PLBM Failover Time =
              Number of packets lost /
                       (Offered Load rate * 1000)

           (Equation 3b)
           PLBM Restoration Time =
              Number of packets lost /
                       (Offered Load rate * 1000)

           Units are packets/(packets/second) = seconds

      Measurement units:
         milliseconds

      Issues:
         None

      See Also:
         Failover
         Time-Based Loss Method
                          Protection Performance

     3.6.3 Timestamp-Based Method (TBM)

      Definition:
      The method to calculate Failover Time (or Reversion Time)
      using a time scale to quantify the interval between
      unimpaired packets arriving in the test stream.

      Discussion:
      The purpose of this method is to quantify the duration of
      failure or reversion on a time scale with granularity of
      milliseconds based on the observation of unimpaired packets,
      using Equation 2 with the difference being that the time
      values are obtained from the timestamp in the packet payload
      rather than from the Tester.

      Unimpaired packets are normal packets that are not lost,
      reordered, or duplicated.  A reordered packet is defined in
                          Protection Performance

      [10, section 3.3].  A duplicate packet is defined in
      [4, section 3.3.3].  A lost packet is defined in
      [7, Section 3.5].  Unimpaired packets may be detected by checking
      a sequence number in the payload, where the sequence number equals
      the next expected number for an unimpaired packet.  A sequence gap
      or sequence reversal indicates impaired packets.

      For calculating Failover Time, the TBM includes failure
      detection time and time for data traffic to begin traversing the
      Backup Path.  For calculating Reversion Time, the TBM includes
      Reversion Time and time for data traffic to begin traversing the
      Primary Path.

      Measurement units:
         milliseconds

      Issues: None

      See Also:
         Failover
         Failover Time
         Reversion
         Reversion Time
                          Protection Performance

4. Acknowledgements
     We would like thank the BMWG and particularly Al Morton and Curtis
     Villamizar for their reviews, comments, and contributions to this
     work.

5. IANA Considerations
     This document requires no IANA considerations.

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

7. References
7.1. Normative 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] Poretsky, S., et al., "Terminology for Benchmarking
         Network-layer Traffic Control Mechanisms", RFC 4689,
         November 2006.

                          Protection Performance

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

     [6] Paxson, V., et al., "Framework for IP Performance Metrics",
         RFC 2330, May 1998.

     [7] Poretsky, S., Imhoff, B., "Benchmarking Terminology for IGP
         Convergence", draft-ietf-bmwg-igp-dataplane-conv-term-13, draft-ietf-bmwg-igp-dataplane-conv-term-15,
         work in progress, July 2007. February 2008.

     [8] Pan., P. et al, "Fast Reroute Extensions to RSVP-TE for LSP
         Paths", RFC 4090, May 2005.

     [9] Nichols, K., et al, "Definition of the Differentiated
         Services Field (DS Field) in the IPv4 and IPv6 Headers",
         RFC 2474, December 1998.

     [10] Morton, A., et al, "Packet Reordering Metrics", RFC 4737,
          November 2006.

7.2. Informative References
     None
                          Protection Performance

8.  Author's Address

   Scott Poretsky
   Reef Point Systems
   8 New England Executive Park
   Burlington,
   NextPoint Networks
   3 Federal Street
   Billerica, MA 01803 01821
   USA
   Phone: + 1 508 439 9008
   EMail: sporetsky@reefpoint.com sporetsky@nextpointnetworks.com

   Rajiv Papneja
   Isocore
   12359 Sunrise Valley Drive
   Reston, VA 22102
   USA
   Phone: 1 703 860 9273
   Email: rpapneja@isocore.com

   Jay Karthik
   Cisco Systems
   300 Beaver Brook Road
   Boxborough, MA 01719
   USA
   Phone: +1 978 936 0533
   Email: jkarthik@cisco.com
                          Protection Performance

   Samir Vapiwala
   Cisco System
   300 Beaver Brook Road
   Boxborough, MA 01719
   USA
   Phone: +1 978 936 1484
   Email: svapiwal@cisco.com

Full Copyright Statement

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                          Protection Performance

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