Internet DRAFT - draft-ietf-ccamp-dpm
draft-ietf-ccamp-dpm
Network Working Group W. Sun, Ed.
Internet-Draft SJTU
Intended status: Standards Track G. Zhang, Ed.
Expires: March 5, 2013 CATR
September 1, 2012
Label Switched Path (LSP) Data Path Delay Metrics in Generalized MPLS/
MPLS-TE Networks
draft-ietf-ccamp-dpm-08.txt
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 LSP users or
applications that control their use as indication that data path has
become usable. The existence of the inconsistency between the
signaling messages and cross connection programing, 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 way in which LSPs are used and to make applications or
tools that depend on and use LSPs more robust. This document defines
a series of performance metrics to evaluate the connectivity of data
path in the signaling process.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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This Internet-Draft will expire on March 5, 2013.
Copyright Notice
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Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Conventions Used in This Document . . . . . . . . . . . . . . 6
3. Overview of Performance Metrics . . . . . . . . . . . . . . . 7
4. Terms used in this document . . . . . . . . . . . . . . . . . 8
5. A singleton Definition for RRFD . . . . . . . . . . . . . . . 9
5.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 9
5.2. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 9
5.3. Metric Parameters . . . . . . . . . . . . . . . . . . . . 9
5.4. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 9
5.5. Definition . . . . . . . . . . . . . . . . . . . . . . . . 9
5.6. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 10
5.7. Methodologies . . . . . . . . . . . . . . . . . . . . . . 11
6. A singleton Definition for RSRD . . . . . . . . . . . . . . . 12
6.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 12
6.2. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 12
6.3. Metric Parameters . . . . . . . . . . . . . . . . . . . . 12
6.4. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 12
6.5. Definition . . . . . . . . . . . . . . . . . . . . . . . . 13
6.6. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 13
6.7. Methodologies . . . . . . . . . . . . . . . . . . . . . . 14
7. A singleton Definition for PRFD . . . . . . . . . . . . . . . 15
7.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 15
7.2. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 15
7.3. Metric Parameters . . . . . . . . . . . . . . . . . . . . 15
7.4. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 15
7.5. Definition . . . . . . . . . . . . . . . . . . . . . . . . 15
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7.6. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 16
7.7. Methodologies . . . . . . . . . . . . . . . . . . . . . . 17
8. A singleton Definition for PSFD . . . . . . . . . . . . . . . 18
8.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 18
8.2. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 18
8.3. Metric Parameters . . . . . . . . . . . . . . . . . . . . 18
8.4. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 18
8.5. Definition . . . . . . . . . . . . . . . . . . . . . . . . 18
8.6. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 19
8.7. Methodologies . . . . . . . . . . . . . . . . . . . . . . 20
9. A singleton Definition for PSRD . . . . . . . . . . . . . . . 21
9.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 21
9.2. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 21
9.3. Metric Parameters . . . . . . . . . . . . . . . . . . . . 21
9.4. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 21
9.5. Definition . . . . . . . . . . . . . . . . . . . . . . . . 21
9.6. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 22
9.7. Methodologies . . . . . . . . . . . . . . . . . . . . . . 23
10. A Definition for Samples of Data Path Delay . . . . . . . . . 24
10.1. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 24
10.2. Metric Parameters . . . . . . . . . . . . . . . . . . . . 24
10.3. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 24
10.4. Definition . . . . . . . . . . . . . . . . . . . . . . . . 24
10.5. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 25
10.6. Methodologies . . . . . . . . . . . . . . . . . . . . . . 25
10.7. Typical testing cases . . . . . . . . . . . . . . . . . . 25
10.7.1. With No LSP in the Network . . . . . . . . . . . . . 25
10.7.2. With a Number of LSPs in the Network . . . . . . . . 25
11. Some Statistics Definitions for Metrics to Report . . . . . . 27
11.1. The Minimum of Metric . . . . . . . . . . . . . . . . . . 27
11.2. The Median of Metric . . . . . . . . . . . . . . . . . . . 27
11.3. The percentile of Metric . . . . . . . . . . . . . . . . . 27
11.4. The Failure Probability . . . . . . . . . . . . . . . . . 27
11.4.1. Failure Count . . . . . . . . . . . . . . . . . . . . 28
11.4.2. Failure Ratio . . . . . . . . . . . . . . . . . . . . 28
12. Security Considerations . . . . . . . . . . . . . . . . . . . 29
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 31
15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 32
15.1. Normative References . . . . . . . . . . . . . . . . . . . 32
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15.2. Informative References . . . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33
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1. Introduction
Label Switched Paths (LSPs) are established, controlled, and
allocated for use by management tools or directly by the components
that use them. In this document we call such management tools and
the components that use LSPs "applications". Such applications may
be Network Management Stations (NMSs), hardware or software
components that forward data onto virtual links, programs or tools
that use dedicated links, or any other user of an LSP.
Ideally, the completion of the signaling process means that the
signaled LSP 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 ready for
use 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
fails 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 connectivity. For
example, when invoking through User Network Interface (UNI)
[RFC4208], 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 result 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
connectivity of data path during the signaling process. The metrics
defined in this document complement the control plane metrics defined
in [RFC5814]. These metrics can be used to verify the conformance of
implementations against related specifications, as elaborated in
[RFC6383]. 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 five performance metrics to characterize the
performance of data path provisioning with GMPLS/MPLS-TE signaling.
These metrics complement the metrics defined in [RFC5814], 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 [RFC5814]
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 five metrics are:
o RRFD - the delay between RESV message received by ingress node and
forward data path becomes ready for use.
o RSRD - the delay between RESV message sent by egress node and
reverse data path becomes ready for use.
o PRFD - the delay between PATH message received by egress node and
forward data path becomes ready for use.
o PSFD - the delay between PATH message sent by ingress and forward
data path becomes ready for use.
o PSRD - the delay between PATH message sent by ingress and reverse
data path becomes ready for use.
As in [RFC5814], 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 [RFC5814] 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 bidirectional LSP.
o Reverse data path - the data path from the egress node to the
ingress node in a bidirectional LSP.
o Data path delay - the time needed to complete the data path
configuration, in relation to the signaling process. Five types
of data path delay are defined in this document, namely RRFD,
RSRD, PRFD, PSFD and PSRD. Data path delay used in this document
must be distinguished from the transmission delay along the data
path, i.e., the time needed to transmit traffic from one side of
the data path to the other.
o Error free signal - data plane specific indication of connectivity
of the data path. For example, for packet switching capable
interfaces, the reception of the first error free packet from one
side of the LSP to the other may 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.
o Ingress/egress node - in this memo, an ingress/egress node means a
measurement endpoint with both control plane and data plane
features. Typically, the control plane part on an ingress/egress
node interact with the control plane of the network under test.
The data plane part of an ingress/egress node will generate data
path signals and send the signal to the data plane of the network
under test, or receive data path signals from the network under
test.
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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 [RFC6383], 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 [RFC6383], the data path may not be
ready for use 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 connectivity. 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 = RESV Received, Forward Data path
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 of milli-seconds or undefined.
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
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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 may use a
rate based method to verify the connectivity 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 such intervals 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 The accuracy of this metric is also dependent on the physical
layer serialization/de-serialization of the test signal for
certain data path technologies. For instance, for an LSP between
a pair of low speed Ethernet interfaces, the time needed to
serialize/deserialize a large frame may not be negligible. In
this case, it is RECOMMENDED that the ingress node uses small
frames. The average length of the frame MAY be reported.
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 ready for use before a RESV
message reaches the ingress node. In such cases, RRFD can be a
negative value. It is RECOMMENDED that PRFD measurement is
carried out to further characterize the forward data path delay
when a negative RRFD value is observed.
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o If error free signal is received by the egress node before PATH
message is sent on the ingress node, an error MUST be reported and
the measurement SHOULD terminate.
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, i.e., a threshold, RRFD MUST be treated as undefined.
The value of the threshold MUST be reported.
o If the LSP setup fails, the metric value 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 measurement.
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 [RFC6383], 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
bidirectional LSP.
6.1. Motivation
RSRD is useful for several reasons:
o For the reasons described in [RFC6383], the data path may not be
ready for use 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 connectivity. 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 = RESV sent, Reverse Data path
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 of milli-seconds or undefined.
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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 connectivity
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 The accuracy of this metric is also dependent on the physical
layer serialization/de-serialization of the test signal for
certain data path technologies. For instance, for an LSP between
a pair of low speed Ethernet interfaces, the time needed to
serialize/deserialize a large frame may not be negligible. In
this case, it is RECOMMENDED that the egress node uses small
frames. The average length of the frame MAY be reported.
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, i.e., a threshold, RSRD MUST be treated as undefined.
The value of the threshold MUST be reported.
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o If error free signal is received before PATH message is sent on
the ingress node, an error MUST be reported and the measurement
SHOULD terminate.
o If the LSP setup fails, the metric value MUST NOT be counted.
6.7. 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 ingress node before PATH message is sent, report
an error and terminate the measurement.
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
ready for use 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 = PATH received, Forward Data path
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 of milli-seconds or undefined.
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 connectivity
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 The accuracy of this metric is also dependent on the physical
layer serialization/de-serialization of the test signal for
certain data path technologies. For instance, for an LSP between
a pair of low speed Ethernet interfaces, the time needed to
serialize/deserialize a large frame may not be negligible. In
this case, it is RECOMMENDED that the ingress node uses small
frames. The average length of the frame MAY 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, the metric value 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.
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7.7. 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 measurement.
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 singleton Definition for PSFD
This part defines a metric for forward data path delay when an LSP is
setup.
As described in [RFC6383], 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 from the PATH message sent by the ingress
node, till the completion of the cross connection programming along
the LSP forward data path.
8.1. Motivation
PSFD is useful for the following reasons:
o For the reasons described in [RFC6383], the data path setup delay
may not be consistent with the control plane LSP setup delay. The
data path setup delay metric is more precise for LSP setup
performance measurement.
o The completion of the signaling process may be used by application
designers as indication of data path connectivity. The difference
between the control plane setup delay and data path delay, and the
potential failure of cross connection programming, if not properly
treated, will result in data loss or application failure. This
metric can thus help designers to improve the application model.
8.2. Metric Name
PSFD = Path Sent, Forward Data path
8.3. Metric Parameters
o ID0, the ingress LSR ID
o ID1, the egress LSR ID
o T, a time when the setup is attempted
8.4. Metric Units
Either a real number of milli-seconds or undefined.
8.5. Definition
For a real number dT, PSFD from ingress node ID0 to egress node ID1
at T is dT means that ingress node ID0 sends the first bit of a PATH
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message to 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.
8.6. Discussion
The following issues are likely to come up in practice:
o The accuracy of PSFD 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 this metric is also dependent on how the error
free signal is received and may differ significantly when the
underlying data plane technology is different. For instance, for
an LSP between a pair of Ethernet interfaces, the ingress node may
use a rate based method to verify the connectivity 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 this metric 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 The accuracy of this metric is also dependent on the physical
layer serialization/de-serialization of the test signal for
certain data path technologies. For instance, for an LSP between
a pair of low speed Ethernet interfaces, the time needed to
serialize/deserialize a large frame may not be negligible. In
this case, it is RECOMMENDED that the ingress node uses small
frames. The average length of the frame MAY 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, the metric value MUST NOT be counted.
o If the PATH message is sent by the ingress node, but no error free
signal is received by the egress node within a reasonable period
of time, i.e., a threshold, the metric value MUST be treated as
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undefined. The value of the threshold MUST be reported.
8.7. 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 measurement.
o At the ingress node, form the PATH message according to the LSP
requirements and send the message towards the egress node. A
timestamp (T1) may be stored locally in the ingress node when the
PATH message packet is sent towards the egress node.
o When an error free signal is observed on the egress node, take the
time stamp (T2) as soon as possible. An estimate of PSFD (T2-T1)
can be computed.
o If the LSP setup fails, this metric is not counted.
o If no error free signal is received within a reasonable period of
time by the egress node, PSFD is deemed to be undefined.
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9. A singleton Definition for PSRD
This part defines a metric for reverse data path delay when an LSP is
setup.
This metric defines the time from the ingress node sends the PATH
message, till the completion of the cross connection programming
along the LSP reverse data path. This metric MAY be used together
with PSFD to characterize the data path delay of a bidirectional LSP.
9.1. Motivation
PSRD is useful for the following reasons:
o For the reasons described in [RFC6383], the data path setup delay
may not be consistent with the control plane LSP setup delay. The
data path setup delay metric is more precise for LSP setup
performance measurement.
o The completion of the signaling process may be used by application
designers as indication of data path connectivity. The difference
between the control plane setup delay and data path delay, and the
potential failure of cross connection programming, if not properly
treated, will result in data loss or application failure. This
metric can thus help designers to improve the application model.
9.2. Metric Name
PSRD = Path Sent, Reverse Data path
9.3. Metric Parameters
o ID0, the ingress LSR ID
o ID1, the egress LSR ID
o T, a time when the setup is attempted
9.4. Metric Units
Either a real number of milli-seconds or undefined.
9.5. Definition
For a real number dT, PSRD from ingress node ID0 to egress node ID1
at T is dT means that ingress node ID0 sends the first bit of a PATH
message to egress node ID1 at T, and an error free signal is received
through the reverse data path by the ingress node ID0 using a data
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plane specific test pattern at T+dT.
9.6. Discussion
The following issues are likely to come up in practice:
o The accuracy of PSRD depends on the clock resolution of the
ingress node. And clock synchronization between the ingress node
and egress node is not required.
o The accuracy of this metric is also dependent on how the error
free signal is received and may differ significantly when the
underlying data plane technology is different. For instance, for
an LSP between a pair of Ethernet interfaces, the egress node may
use a rate based method to verify the connectivity 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 egress 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 this metric 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 The accuracy of this metric is also dependent on the physical
layer serialization/de-serialization of the test signal for
certain data path technologies. For instance, for an LSP between
a pair of low speed Ethernet interfaces, the time needed to
serialize/deserialize a large frame may not be negligible. In
this case, it is RECOMMENDED that the egress node uses small
frames. The average length of the frame MAY 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, this metric value MUST NOT be counted.
o If the PATH message is sent by the ingress node, but no error free
signal is received by the ingress node within a reasonable period
of time, i.e., a threshold, the metric value MUST be treated as
undefined. The value of the threshold MUST be reported.
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9.7. 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 measurement.
o At the ingress node, form the PATH message according to the LSP
requirements and send the message towards the egress node. A
timestamp (T1) may be stored locally in the ingress node when the
PATH message packet is sent towards the egress node.
o When an error free signal is observed on the ingress node, take
the time stamp (T2) as soon as possible. An estimate of PSFD
(T2-T1) can be computed.
o If the LSP setup fails, this metric is not counted.
o If no error free signal is received within a reasonable period of
time by the ingress node, the metric value is deemed to be
undefined.
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10. A Definition for Samples of Data Path Delay
In Section 5, Section 6, Section 7, Section 8 and Section 9, 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 portion of singleton values of the given parameters. Like
in [RFC2330], we use Poisson sampling as an example.
10.1. Metric Name
Type <X> Data path delay sample, where X is either RRFD, RSRD, PRFD,
PSFD and PSRD.
10.2. 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
10.3. 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 of milli-seconds or undefined
10.4. 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.
10.5. 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 (see [RFC5814]).
o The parameter Ts should be carefully chosen and MUST be reported
along with the LSP forward/reverse data path delay sample.
10.6. 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
10.7. Typical testing cases
10.7.1. With No LSP in the Network
10.7.1.1. 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.
10.7.1.2. Methodologies
Make sure that there is no LSP in the network, and proceed with the
methodologies described in Section 10.6.
10.7.2. With a Number of LSPs in the Network
10.7.2.1. Motivation
Data path delay with a number of LSPs in the network is important
because it reflects the performance of an operational network with
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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.
10.7.2.2. 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 10.6.
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11. 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.
11.1. 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.
11.2. 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.
The Median SHOULD be set to undefined if all the dT values are
undefined, or if the sample is empty.When the number of defined
values in the given sample is small, the metric median may not be
typical and SHOULD be used carefully.
11.3. The percentile of Metric
The "empirical distribution function" (EDF) of a set of scalar
measurements is a function F(x) which for any x gives the fractional
proportion of the total measurements that were <= x.
Given a percentage X, the X-th percentile of Metric means the
smallest value of x for which F(x) >= X. In computing the percentile,
undefined values MUST NOT be included.
See [RFC2330] for further details.
11.4. The Failure Probability
Given the samples of the performance metric, we now offer two
statistics of failure events of these samples to report. The two
statistics can be applied to both forward data path and reverse data
path. For example, when a sample of RRFD has been obtained the
forward data path failure statistics can be obtained, while when a
sample of RSRD can be used to calculate the reverse data path failure
statistics. Detailed definitions of the Failure Count and Failure
Ratio are given below.
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11.4.1. Failure Count
Failure Count is defined as the number of the undefined value of the
corresponding performance metric in a sample. The value of Failure
Count is an integer.
11.4.2. Failure Ratio
Failure Ratio is the percentage of the number of failure events to
the total number of requests in a sample. Here an failure event
means that the signaling completes with no error, while no error free
signal is observed. The calculation for Failure Ratio is defined as
follows:
Failure Ratio = Number of undefined value/(Number of valid metric
values + Number of undefined value) * 100%.
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12. Security Considerations
In the control plane, since the measurement endpoints must be
conformant to signaling specifications and behave as normal signaling
endpoints, it will not incur other security issues than normal LSP
provisioning. However, 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.
In the data plane, the measurement endpoint MUST use a signal that is
consistent with what is specified in the control plane. For example,
in a packet switched case, the traffic injected into the data plane
MUST NOT exceed the specified rate in the corresponding LSP setup
request. In a wavelength switched case, the measurement endpoint
MUST use the specified or negotiated lambda with appropriate power.
The security considerations pertaining to the original RSVP protocol
[RFC2205] and its TE extensions [RFC3209] also remain relevant.
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13. IANA Considerations
This document makes no requests for IANA action.
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14. Acknowledgements
We wish to thank Adrian Farrel, Lou Berger and Al Morton for their
comments and help. We also wish to thank the reviews done by Klaas
Wierenga and Alexey Melnikov.
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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15. References
15.1. 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.
15.2. Informative References
[RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
"Framework for IP Performance Metrics", RFC 2330,
May 1998.
[RFC4208] Swallow, G., Drake, J., Ishimatsu, H., and Y. Rekhter,
"Generalized Multiprotocol Label Switching (GMPLS) User-
Network Interface (UNI): Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Support for the Overlay
Model", RFC 4208, October 2005.
[RFC5814] Sun, W. and G. Zhang, "Label Switched Path (LSP) Dynamic
Provisioning Performance Metrics in Generalized MPLS
Networks", RFC 5814, March 2010.
[RFC6383] Shiomoto, K. and A. Farrel, "Advice on When It Is Safe to
Start Sending Data on Label Switched Paths Established
Using RSVP-TE", RFC 6383, September 2011.
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Authors' Addresses
Weiqiang Sun, Editor
Shanghai Jiao Tong University
800 Dongchuan Road
Shanghai 200240
China
Phone: +86 21 3420 5359
Email: sun.weiqiang@gmail.com
Guoying Zhang, Editor
China Academy of Telecommunication Research, MIIT, China.
No.52 Hua Yuan Bei Lu,Haidian District
Beijing 100083
China
Phone: +86 1062300103
EMail: zhangguoying@catr.cn
Jianhua Gao
Huawei Technologies Co., LTD.
China
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
Huawei Technologies
Santa Clara, CA 95050
Reston, VA 20190
USA
Phone: +1 571 926 8593
Email: rajiv.papneja@huawei.com
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Contributors
Bin Gu
IXIA
Oriental Kenzo Plaza 8M, 48 Dongzhimen Wai Street, Dongcheng District
Beijing 200240
China
Phone: +86 13611590766
Email: BGu@ixiacom.com
Xueqin Wei
Fiberhome Telecommunication Technology Co., Ltd.
Wuhan
China
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: tm-otani@kddi.com
Ruiquan Jing
China Telecom Beijing Research Institute
118 Xizhimenwai Avenue
Beijing 100035
China
Phone: +86-10-58552000
Email: jingrq@ctbri.com.cn
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