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Versions: 00 01 draft-ietf-ccamp-dpm

Network Working Group                                        W. Sun, Ed.
Internet-Draft                                                      SJTU
Intended status: Standards Track                           G. Zhang, Ed.
Expires: December 26, 2009                                          CATR
                                                           June 24, 2009


 Label Switched Path (LSP) Data Path Delay Metric in Generalized MPLS/
                            MPLS-TE Networks
                       draft-sun-ccamp-dpm-00.txt

Status of this Memo

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   This Internet-Draft will expire on December 26, 2009.

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Abstract

   When setting up a label switched path (LSP) in Generalized MPLS and
   MPLS/TE networks, the completion of the signaling process does not
   necessarily mean that the cross connection along the LSP have been
   programmed accordingly and in a timely manner.  Meanwhile, the
   completion of signaling process may be used by applications as
   indication that data path has become usable.  The existence of this
   delay and the possible failure of cross connection programming, if
   not properly treated, will result in data loss or even application
   failure.  Characterization of this performance can thus help
   designers to improve the application model and to build more robust
   applications.  This document defines a series of performance metrics
   to evaluate the availability of data path in the signaling process.



Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4

   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  5

   3.  Overview of Performance Metrics  . . . . . . . . . . . . . . .  6

   4.  Terms used in this document  . . . . . . . . . . . . . . . . .  7

   5.  A singleton Definition for RRFD  . . . . . . . . . . . . . . .  8
     5.1.  Motivation . . . . . . . . . . . . . . . . . . . . . . . .  8
     5.2.  Metric Name  . . . . . . . . . . . . . . . . . . . . . . .  8
     5.3.  Metric Parameters  . . . . . . . . . . . . . . . . . . . .  8
     5.4.  Metric Units . . . . . . . . . . . . . . . . . . . . . . .  8
     5.5.  Definition . . . . . . . . . . . . . . . . . . . . . . . .  9
     5.6.  Discussion . . . . . . . . . . . . . . . . . . . . . . . .  9
     5.7.  Methodologies  . . . . . . . . . . . . . . . . . . . . . . 10

   6.  A singleton Definition for RSRD  . . . . . . . . . . . . . . . 11
     6.1.  Motivation . . . . . . . . . . . . . . . . . . . . . . . . 11
     6.2.  Metric Name  . . . . . . . . . . . . . . . . . . . . . . . 11
     6.3.  Metric Parameters  . . . . . . . . . . . . . . . . . . . . 11
     6.4.  Metric Units . . . . . . . . . . . . . . . . . . . . . . . 11
     6.5.  Definition . . . . . . . . . . . . . . . . . . . . . . . . 12
     6.6.  Discussion . . . . . . . . . . . . . . . . . . . . . . . . 12
     6.7.  Methodologies  . . . . . . . . . . . . . . . . . . . . . . 13

   7.  A singleton Definition for PRFD  . . . . . . . . . . . . . . . 14
     7.1.  Motivation . . . . . . . . . . . . . . . . . . . . . . . . 14
     7.2.  Metric Name  . . . . . . . . . . . . . . . . . . . . . . . 14



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     7.3.  Metric Parameters  . . . . . . . . . . . . . . . . . . . . 14
     7.4.  Metric Units . . . . . . . . . . . . . . . . . . . . . . . 14
     7.5.  Definition . . . . . . . . . . . . . . . . . . . . . . . . 14
     7.6.  Discussion . . . . . . . . . . . . . . . . . . . . . . . . 15
     7.7.  Methodologies  . . . . . . . . . . . . . . . . . . . . . . 15

   8.  A Definition for Samples of Data Path Delay  . . . . . . . . . 17
     8.1.  Metric Name  . . . . . . . . . . . . . . . . . . . . . . . 17
     8.2.  Metric Parameters  . . . . . . . . . . . . . . . . . . . . 17
     8.3.  Metric Units . . . . . . . . . . . . . . . . . . . . . . . 17
     8.4.  Definition . . . . . . . . . . . . . . . . . . . . . . . . 17
     8.5.  Discussion . . . . . . . . . . . . . . . . . . . . . . . . 18
     8.6.  Methodologies  . . . . . . . . . . . . . . . . . . . . . . 18
     8.7.  Typical testing cases  . . . . . . . . . . . . . . . . . . 18
       8.7.1.  With No LSP in the Network . . . . . . . . . . . . . . 18
         8.7.1.1.  Motivation . . . . . . . . . . . . . . . . . . . . 18
         8.7.1.2.  Methodologies  . . . . . . . . . . . . . . . . . . 18
       8.7.2.  With a Number of LSPs in the Network . . . . . . . . . 19
         8.7.2.1.  Motivation . . . . . . . . . . . . . . . . . . . . 19
         8.7.2.2.  Methodologies  . . . . . . . . . . . . . . . . . . 19

   9.  Some Statistics Definitions for Metrics to Report  . . . . . . 20
     9.1.  The Minimum of Metric  . . . . . . . . . . . . . . . . . . 20
     9.2.  The Median of Metric . . . . . . . . . . . . . . . . . . . 20
     9.3.  The percentile of Metric . . . . . . . . . . . . . . . . . 20
     9.4.  The Failure Probability  . . . . . . . . . . . . . . . . . 20

   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 21

   11. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 22

   12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23

   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 24
     13.1. Normative References . . . . . . . . . . . . . . . . . . . 24
     13.2. Informative References . . . . . . . . . . . . . . . . . . 24

   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25













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1.  Introduction

   Ideally, the completion of the signaling process means that the
   signaled label switched path (LSP) is available and is ready to carry
   traffic.  However, in actual implementations, vendors may choose to
   program the cross connection in a pipelined manner, so that the
   overall LSP provisioning delay can be reduced.  In such situations,
   the data path may not be available instantly after the signaling
   process completes.  Implementation deficiency may also cause the
   inconsistency in between the signaling process and data path
   provisioning.  For example, if the data plane failed to program the
   cross connection accordingly but does not manage to report this to
   the control plane, the signaling process may complete successfully
   while the corresponding data path will never become functional at
   all.

   On the other hand, the completion of the signaling process may be
   used in many cases as indication of data path availability.  For
   example, when invoking through User Network Interface (UNI), a client
   device or an application may use the reception of the correct RESV
   message as indication that data path is fully functional and start to
   transmit traffic.  This will results in data loss or even application
   failure.

   Although RSVP(-TE) specifications have suggested that the cross
   connections are programmed before signaling messages are propagated
   upstream, it is still worthwhile to verify the conformance of an
   implementation and measure the delay, when necessary.

   This document defines a series of performance metrics to evaluate the
   availability of data path when the signaling process completes.  The
   metrics defined in this document complements the control plane
   metrics defined in [I-D.ietf-ccamp-lsp-dppm].  They can be used to
   verify the conformance of implementations against related
   specifications, as elaborated in
   [I-D.shiomoto-ccamp-switch-programming].  They also can be used to
   build more robust applications.














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2.  Conventions Used in This Document

   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 [RFC2119].














































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3.  Overview of Performance Metrics

   In this memo, we define three performance metrics to characterize the
   performance of data path provisioning with GMPLS/MPLS-TE signaling.
   These metrics complement the metrics defined in
   [I-D.ietf-ccamp-lsp-dppm], in the sense that the completion of the
   signaling process for a Label Switched Path (LSP) and the programming
   of cross connections along the LSP may not be consistent.  The
   performance metrics in [I-D.ietf-ccamp-lsp-dppm] characterize the
   performance of LSP provisioning from the pure signaling point of
   view, while the metric in this document takes into account the
   validity of the data path.

   The three metrics are:

   o  RRFD - the delay between RESV message received by ingress node and
      forward data path becomes available.

   o  RSRD - the delay between RESV message sent by egress node and
      reverse data path becomes available.

   o  PRFD - the delay between PATH message received by egress node and
      forward data path becomes available.

   As in [I-D.ietf-ccamp-lsp-dppm], we continue to use the structures
   and notions introduced and discussed in the IPPM Framework document,
   [RFC2330] [RFC2679] [RFC2681].  The reader is assumed to be familiar
   with the notions in those documents.  The readers are assumed to be
   familiar with the definitions in [I-D.ietf-ccamp-lsp-dppm] as well.






















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4.  Terms used in this document

   o  Forward data path - the data path from the ingress to the egress.
      Instances of forward data path include the data path of a uni-
      directional LSP and data path from the ingress node to the egress
      node in a bi-directional LSP.

   o  Reverse data path - the data path from the egress to the ingress
      in a bi-directional LSP.

   o  Error free signal - data plane specific indication of availability
      of the data path.  For example, for packet switched interfaces,
      the reception of the first error free packet from one side of the
      LSP to the other can be used as the error free signal.  For SDH/
      SONET cross connects, the disappearance of alarm can be used as
      the error free signal.  Through out this document, we will use the
      "error free signal" as a general term.  An implementations must
      choose a proper data path signal that is specific to the data path
      technology being tested.
































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5.  A singleton Definition for RRFD

   This part defines a metric for forward data path delay when an LSP is
   setup.

   As described in [I-D.shiomoto-ccamp-switch-programming], the
   completion of the RSVP-TE signaling process does not necessarily mean
   that the cross connections along the LSP being setup are in place and
   ready to carry traffic.  This metric defines the time difference
   between the reception of RESV message by the ingress node and the
   completion of the cross connection programming along the forward data
   path.

5.1.  Motivation

   RRFD is useful for several reasons:

   o  For the reasons described in
      [I-D.shiomoto-ccamp-switch-programming], the data path may not be
      available instantly after the completion of the RSVP-TE signaling
      process.  The delay itself is part of the implementation
      performance.

   o  The completion of the signaling process may be used by application
      designers as indication of data path availability.  The existence
      of this delay and the potential failure of cross connection
      programming, if not properly treated, will result in data loss or
      application failure.  The typical value of this delay can thus
      help designers to improve the application model.

5.2.  Metric Name

   RRFD

5.3.  Metric Parameters

   o  ID0, the ingress LSR ID

   o  ID1, the egress LSR ID

   o  T, a time when the setup is attempted

5.4.  Metric Units

   Either a real number or an undefined number of milli-seconds.






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5.5.  Definition

   For a real number dT, RRFD from ingress node ID0 to egress node ID1
   at T is dT, means that ingress node ID0 send a PATH message to egress
   node ID1 and the last bit of the corresponding RESV message is
   received by ingress node ID0 at T, and an error free signal is
   received by egress node ID1 by using a data plane specific test
   pattern at T+dT.

5.6.  Discussion

   The following issues are likely to come up in practice:

   o  The accuracy of RRFD depends on the clock resolution of both the
      ingress node and egress node.  Clock synchronization between the
      ingress node and egress node is required.

   o  The accuracy of RRFD is also dependent on how the error free
      signal is received and may differ significantly when the underline
      data plane technology is different.  For instance, for an LSP
      between a pair of Ethernet interfaces, the ingress node (sometimes
      the tester) may use a rate based method to verify the availability
      of the data path and use the reception of the first error free
      frame as the error free signal.  In this case, the interval
      between two successive frames has a significant impact on
      accuracy.  It is RECOMMENDED that the ingress node uses small
      intervals, under the condition that the injected traffic does not
      exceed the capacity of the forward data path.  The value of the
      interval MUST be reported.

   o  The accuracy of RRFD is also dependent on the time needed to
      propagate the error free signal from the ingress node to the
      egress node.  A typical value of propagating the error free signal
      from the ingress node to the egress node under the same
      measurement setup MAY be reported.  The methodology to obtain such
      values is outside the scope of this document.

   o  It is possible that under some implementations, a node may program
      the cross connection before it sends PATH message further
      downstream and the data path may be available before a RESV
      message reaches the ingress node.  In such cases, RRFD can be a
      negetive value.  It is RECOMMENDED that PRFD measurement is
      carried out to further characterize the forward data path delay
      when a negetive RRFD value is observed.

   o  If error free signal is received by the egress node before PATH
      message is sent, an error MUST be reported and the measurement
      SHOULD terminate.



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   o  If the corresponding RESV message is received, but no error free
      signal is received by the egress node within a reasonable period
      of time, RRFD MUST be treated as undefined.  The value of the
      threshold MUST be reported.

   o  If the LSP setup fails, RRFD MUST NOT be counted.

5.7.  Methodologies

   Generally the methodology would proceed as follows:

   o  Make sure that the network has enough resource to set up the
      requested LSP.

   o  Start the data path measurement and/or monitoring procedures on
      the ingress node and egress node.  If error free signal is
      received by the egress node before PATH message is sent, report an
      error and terminate the mmeasurement.

   o  At the ingress node, form the PATH message according to the LSP
      requirements and send the message towards the egress node.

   o  Upon receiving the last bit of the corresponding RESV message,
      take the time stamp (T1) on the ingress node as soon as possible.

   o  When an error free signal is observed on the egress node, take the
      time stamp (T2) as soon as possible.  An estimate of RRFD (T2 -
      T1) can be computed.

   o  If the corresponding RESV message arrives, but no error free
      signal is received within a reasonable period of time by the
      ingress node, RRFD is deemed to be undefined.

   o  If the LSP setup fails, RRFD is not counted.

















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6.   A singleton Definition for RSRD

   This part defines a metric for reverse data path delay when an LSP is
   setup.

   As described in [I-D.shiomoto-ccamp-switch-programming], the
   completion of the RSVP-TE signaling process does not necessarily mean
   that the cross connections along the LSP being setup are in place and
   ready to carry traffic.  This metric defines the time difference
   between the completion of the signaling process and the completion of
   the cross connection programming along the reverse data path.  This
   metric MAY be used together with RRFD to characterize the data path
   delay of a bi-directional LSP.

6.1.  Motivation

   RSRD is useful for several reasons:

   o  For the reasons described in
      [I-D.shiomoto-ccamp-switch-programming], the data path may not be
      available instantly after the completion of the RSVP-TE signaling
      process.  The delay itself is part of the implementation
      performance.

   o  The completion of the signaling process may be used by application
      designers as indication of data path availability.  The existence
      of this delay and the possible failure of cross connection
      programming, if not properly treated, will result in data loss or
      application failure.  The typical value of this delay can thus
      help designers to improve the application model.

6.2.  Metric Name

   RSRD

6.3.  Metric Parameters

   o  ID0, the ingress LSR ID

   o  ID1, the egress LSR ID

   o  T, a time when the setup is attempted

6.4.  Metric Units

   Either a real number or an undefined number of milli-seconds.





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6.5.  Definition

   For a real number dT, RSRD from ingress node ID0 to egress node ID1
   at T is dT, means that ingress node ID0 send a PATH message to egress
   node ID1 and the last bit of the corresponding RESV message is sent
   by egress node ID1 at T, and an error free signal is received by the
   ingress node ID0 using a data plane specific test pattern at T+dT.

6.6.  Discussion

   The following issues are likely to come up in practice:

   o  The accuracy of RSRD depends on the clock resolution of both the
      ingress node and egress node.  And clock synchronization between
      the ingress node and egress node is required.

   o  The accuracy of RSRD is also dependent on how the error free
      signal is received and may differ significantly when the underline
      data plane technology is different.  For instance, for an LSP
      between a pair of Ethernet interfaces, the egress node (sometimes
      the tester) may use a rate based method to verify the availability
      of the data path and use the reception of the first error free
      frame as the error free signal.  In this case, the interval
      between two successive frames has a significant impact on
      accuracy.  It is RECOMMENDED that in this case the egress node
      uses small intervals, under the condition that the injected
      traffic does not exceed the capacity of the reverse data path.
      The value of the interval MUST be reported.

   o  The accuracy of RSRD is also dependent on the time needed to
      propagate the error free signal from the egress node to the
      ingress node.  A typical value of propagating the error free
      signal from the egress node to the ingress node under the same
      measurement setup MAY be reported.  The methodology to obtain such
      values is outside the scope of this document.

   o  If the corresponding RESV message is sent, but no error free
      signal is received by the ingress node within a reasonable period
      of time, RSRD MUST be treated as undefined.  The value of the
      threshold MUST be reported.

   o  If error free signal is received before PATH message is sent, an
      error MUST be reported and the measurement SHOULD terminate.

   o  If the LSP setup fails, RSRD MUST NOT be counted.






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6.7.  Methodologies

   Generally the methodology would proceed as follows:

   o  Make sure that the network has enough resource to set up the
      requested LSPs.

   o  Start the data path measurement and/or monitoring procedures on
      the ingress node and egress node.  If error free signal is
      received by the ingress node before PATH message is sent, report
      an error and terminate the mmeasurement.

   o  At the ingress node, form the PATH message according to the LSP
      requirements and send the message towards the egress node.

   o  Upon sending the last bit of the corresponding RESV message, take
      the time stamp (T1) on the egress node as soon as possible.

   o  When an error free signal is observed on the ingress node, take
      the time stamp (T2) as soon as possible.  An estimate of RSRD
      (T2-T1) can be computed.

   o  If the LSP setup fails, RSRD is not counted.

   o  If no error free signal is received within a reasonable period of
      time by the ingress node, RSRD is deemed to be undefined.

























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7.   A singleton Definition for PRFD

   This part defines a metric for forward data path delay when an LSP is
   setup.

   In an RSVP-TE implementation, when setting up an LSP, each node may
   choose to program the cross connection before it sends PATH message
   further downstream.  In this case, the forward data path may become
   available before the signaling process completes, ie. before the RESV
   reaches the ingress node.  This metric can be used to identify such
   implementation practice and give useful information to application
   designers.

7.1.  Motivation

   PRFD is useful for the following reasons:

   o  PRFD can be used to identify an RSVP-TE implementation practice,
      in which cross connections are programmed before PATH message is
      sent downtream.

   o  The value of PRFD may also help application designers to fine tune
      their application model.

7.2.  Metric Name

   PRFD

7.3.  Metric Parameters

   o  ID0, the ingress LSR ID

   o  ID1, the egress LSR ID

   o  T, a time when the setup is attempted

7.4.  Metric Units

   Either a real number or an undefined number of milli-seconds.

7.5.  Definition

   For a real number dT, PRFD from ingress node ID0 to egress node ID1
   at T is dT, means that ingress node ID0 send a PATH message to egress
   node ID1 and the last bit of the PATH message is received by egress
   node ID1 at T, and an error free signal is received by the egress
   node ID1 using a data plane specific test pattern at T+dT.




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7.6.  Discussion

   The following issues are likely to come up in practice:

   o  The accuracy of PRFD depends on the clock resolution of the egress
      node.  And clock synchronization between the ingress node and
      egress node is not required.

   o  The accuracy of PRFD is also dependent on how the error free
      signal is received and may differ significantly when the underline
      data plane technology is different.  For instance, for an LSP
      between a pair of Ethernet interfaces, the egress node (sometimes
      the tester) may use a rate based method to verify the availability
      of the data path and use the reception of the first error free
      frame as the error free signal.  In this case, the interval
      between two successive frames has a significant impact on
      accuracy.  It is RECOMMENDED that in this case the ingress node
      uses small intervals, under the condition that the injected
      traffic does not exceed the capacity of the forward data path.
      The value of the interval MUST be reported.

   o  The accuracy of PRFD is also dependent on the time needed to
      propagate the error free signal from the ingress node to the
      egress node.  A typical value of propagating the error free signal
      from the ingress node to the egress node under the same
      measurement setup MAY be reported.  The methodology to obtain such
      values is outside the scope of this document.

   o  If error free signal is received before PATH message is sent, an
      error MUST be reported and the measurement SHOULD terminate.

   o  If the LSP setup fails, PRFD MUST NOT be counted.

   o  This metric SHOULD be used together with RRFD.  It is RECOMMENDED
      that PRFD measurement is carried out after a negetive RRFD value
      has already been observed.

7.7.  Methodologies

   Generally the methodology would proceed as follows:

   o  Make sure that the network has enough resource to set up the
      requested LSPs.

   o  Start the data path measurement and/or monitoring procedures on
      the ingress node and egress node.  If error free signal is
      received by the egress node before PATH message is sent, report an
      error and terminate the mmeasurement.



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   o  At the ingress node, form the PATH message according to the LSP
      requirements and send the message towards the egress node.

   o  Upon receiving the last bit of the PATH message, take the time
      stamp (T1) on the egress node as soon as possible.

   o  When an error free signal is observed on the egress node, take the
      time stamp (T2) as soon as possible.  An estimate of PRFD (T2-T1)
      can be computed.

   o  If the LSP setup fails, PRFD is not counted.

   o  If no error free signal is received within a reasonable period of
      time by the egress node, PRFD is deemed to be undefined.





































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8.  A Definition for Samples of Data Path Delay

   In Section Section 5, Section 6 and Section 7, we define the
   singleton metrics of data path delay.  Now we define how to get one
   particular sample of such delay.  Sampling is to select a particular
   potion of singleton values of the given parameters.  Like in
   [RFC2330], we use Poisson sampling as an example.

8.1.  Metric Name

   Type <X> Data path delay sample, where X is either RRFD, RSRD or
   PRFD.

8.2.  Metric Parameters

   o  ID0, the ingress LSR ID

   o  ID1, the egress LSR ID

   o  T0, a time

   o  Tf, a time

   o  Lambda, a rate in the reciprocal seconds

   o  Th, LSP holding time

   o  Td, the maximum waiting time for successful LSP setup

   o  Ts, the maximum waiting time for error free signal

8.3.  Metric Units

   A sequence of pairs; the elements of each pair are:

   o  T, a time when setup is attempted

   o  dT, either a real number or an undefined number of milli-seconds

8.4.  Definition

   Given T0, Tf, and lambda, compute a pseudo-random Poisson process
   beginning at or before T0, with average arrival rate lambda, and
   ending at or after Tf.  Those time values greater than or equal to T0
   and less than or equal to Tf are then selected.  At each of the times
   in this process, we obtain the value of data path delay sample of
   type <X> at this time.  The value of the sample is the sequence made
   up of the resulting <time, type <X> data path delay> pairs.  If there



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   are no such pairs, the sequence is of length zero and the sample is
   said to be empty.

8.5.  Discussion

   The following issues are likely to come up in practice:

   o  The parameters lambda, Th and Td should be carefully chosen, as
      explained in the discussions for LSP setup delay.

   o  The parameter Ts should be carefully chosen and MUST be reported
      along with the LSP forward/reverse data path delay sample.

   o  Note that for online or passive measurements, the holding time of
      an LSP is determined by actual traffic, hence in this case Th is
      not an input parameter.

8.6.  Methodologies

   Generally the methodology would proceed as follows:

   o  The selection of specific times, using the specified Poisson
      arrival process, and

   o  Set up the LSP and obtain the value of type <X> data path delay

   o  Release the LSP after Th, and wait for the next Poisson arrival
      process

8.7.  Typical testing cases

8.7.1.  With No LSP in the Network

8.7.1.1.  Motivation

   Data path delay with no LSP in the network is important because this
   reflects the inherent delay of a device implementation.  The minimum
   value provides an indication of the delay that will likely be
   experienced when an LSP data path is configured under light traffic
   load.

8.7.1.2.  Methodologies

   Make sure that there is no LSP in the network, and proceed with the
   methodologies described in Section 8.6.






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8.7.2.  With a Number of LSPs in the Network

8.7.2.1.  Motivation

   Data path delay with a number of LSPs in the network is important
   because it reflects the performance of an operational network with
   considerable load.  This delay may vary significantly as the number
   of existing LSPs varies.  It can be used as a scalability metric of a
   device implementation.

8.7.2.2.  Methodologies

   Setup the required number of LSPs, and wait until the network reaches
   a stable state, and then proceed with the methodologies described in
   Section 8.6.




































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9.  Some Statistics Definitions for Metrics to Report

   Given the samples of the performance metric, we now offer several
   statistics of these samples to report.  From these statistics, we can
   draw some useful conclusions of a GMPLS network.  The value of these
   metrics is either a real number, or an undefined number of
   milliseconds.  In the following discussion, we only consider the
   finite values.

9.1.  The Minimum of Metric

   The minimum of metric is the minimum of all the dT values in the
   sample.  In computing this, undefined values SHOULD be treated as
   infinitely large.  Note that this means that the minimum could thus
   be undefined if all the dT values are undefined.  In addition, the
   metric minimum SHOULD be set to undefined if the sample is empty.

9.2.  The Median of Metric

   Metric median is the median of the dT values in the given sample.  In
   computing the median, the undefined values MUST NOT be counted in.

9.3.  The percentile of Metric

   Given a metric and a percent X between 0% and 100%, the Xth
   percentile of all the dT values in the sample.  In addition, the
   percentile is undefined if the sample is empty.

   Example: suppose we take a sample and the results are: Stream1 =
   <<T1, 100 msec>, <T2, 110 msec>, <T3, undefined>, <T4, 90 msec>,
   <T5,500 msec>>.  Then the 50th percentile would be 110 msec, since 90
   msec and 100 msec are smaller, and 110 and 500 msec are larger
   (undefined values are not counted in).

9.4.  The Failure Probability

   In the process of LSP setup/release, it may fail for some reason.
   The failure probability is the ratio of the unsuccessful times to the
   total times.












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10.  Security Considerations

   The measurement parameters must be carefully selected so that the
   measurements inject trivial amounts of additional traffic into the
   networks they measure.  If they inject "too much" traffic, they can
   skew the results of the measurement, and in extreme cases cause
   congestion and denial of service.

   The security considerations pertaining to the original RSVP protocol
   [RFC2205] and its TE extensions [RFC3209] also remain relevant.









































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11.  IANA Considerations

   This document makes no requests for IANA action.
















































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12.  Acknowledgements

   We wish to thank Adrian Farrel and Lou Berger for their comments and
   helps.

   This document contains ideas as well as text that have appeared in
   existing IETF documents.  The authors wish to thank G. Almes, S.
   Kalidindi and M. Zekauskas.

   We also wish to thank Weisheng Hu, Yaohui Jin and Wei Guo in the
   state key laboratory of advanced optical communication systems and
   networks for the valuable comments.  We also wish to thank the
   support from NSFC and 863 program of China.






































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13.  References

13.1.  Normative References

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

   [RFC2205]  Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
              Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
              Functional Specification", RFC 2205, September 1997.

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

   [RFC2681]  Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip
              Delay Metric for IPPM", RFC 2681, September 1999.

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, December 2001.

13.2.  Informative References

   [I-D.ietf-ccamp-lsp-dppm]
              Sun, W., Zhang, G., Gao, J., Xie, G., Papneja, R., Gu, B.,
              Wei, X., Otani, T., and R. Jing, "Label Switched Path
              (LSP) Dynamic Provisioning Performance Metrics in
              Generalized MPLS Networks", draft-ietf-ccamp-lsp-dppm-05
              (work in progress), March 2009.

   [I-D.shiomoto-ccamp-switch-programming]
              Shiomoto, K. and A. Farrel, "Advice on When It is Safe to
              Start Sending Data on Label Switched Paths  Established
              Using RSVP-TE", draft-shiomoto-ccamp-switch-programming-00
              (work in progress), February 2009.

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












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Authors' Addresses

   Weiqiang Sun
   Shanghai Jiao Tong University
   800 Dongchuan Road
   Shanghai  200240
   CN

   Phone: +86 21 3420 5359
   Email: sunwq@mit.edu


   Guoying Zhang
   China Academy of Telecommunication Research,MII.
   Beijing  200240
   CN

   Phone: +86 1068094272
   Email: zhangguoying@mail.ritt.com.cn


   Jianhua Gao
   Huawei Technologies Co., LTD.
   CN

   Phone: +86 755 28973237
   Email: gjhhit@huawei.com


   Guowu Xie
   University of California, Riverside
   900 University Ave.
   Riverside, CA 92521
   USA

   Phone: +1 951 237 8825
   Email: xieg@cs.ucr.edu


   Rajiv Papneja
   Isocore
   12359 Sunrise Valley Drive, STE 100
   Reston, VA  20190
   USA

   Phone: +1 703 860 9273
   Email: rpapneja@isocore.com




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   Bin Gu
   IXIA
   Oriental Kenzo Plaza 8M,48 Dongzhimen Wai Street,Dongcheng District
   Beijing  200240
   CN

   Phone: +86 13611590766
   Email: BGu@ixiacom.com


   Xueqin Wei
   Fiberhome Telecommunicaiton Technology Co.,Ltd.
   Wuhan
   CN

   Phone: +86 13871127882
   Email: xqwei@fiberhome.com.cn


   Tomohiro Otani
   KDDI R&D Laboratories, Inc.
   2-1-15 Ohara Kamifukuoka Saitama
   356-8502
   Japan

   Phone: +81-49-278-7357
   Email: otani@kddilabs.jp


   Ruiquan Jing
   China Telecom Beijing Research Institute
   118 Xizhimenwai Avenue
   Beijing  100035
   CN

   Phone: +86-10-58552000
   Email: jingrq@ctbri.com.cn














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