| Rfc | 5814 |
|---|
| Title | Label Switched Path (LSP) Dynamic Provisioning Performance Metrics
in Generalized MPLS Networks |
|---|
| Author | W. Sun, Ed., G. Zhang, Ed. |
|---|
| Date | March
2010 |
|---|
| Format: | TXT, HTML |
|---|
| Status: | PROPOSED STANDARD |
|---|
|
Internet Engineering Task Force (IETF) W. Sun, Ed.
Request for Comments: 5814 SJTU
Category: Standards Track G. Zhang, Ed.
ISSN: 2070-1721 CATR
March 2010
Label Switched Path (LSP) Dynamic Provisioning Performance Metrics
in Generalized MPLS Networks
Abstract
Generalized Multi-Protocol Label Switching (GMPLS) is one of the most
promising candidate technologies for a future data transmission
network. GMPLS has been developed to control and operate different
kinds of network elements, such as conventional routers, switches,
Dense Wavelength Division Multiplexing (DWDM) systems, Add-Drop
Multiplexers (ADMs), photonic cross-connects (PXCs), optical cross-
connects (OXCs), etc. These physically diverse devices differ
drastically from one another in dynamic provisioning ability. At the
same time, the need for dynamically provisioned connections is
increasing because optical networks are being deployed in metro
areas. As different applications have varied requirements in the
provisioning performance of optical networks, it is imperative to
define standardized metrics and procedures such that the performance
of networks and application needs can be mapped to each other.
This document provides a series of performance metrics to evaluate
the dynamic Label Switched Path (LSP) provisioning performance in
GMPLS networks, specifically the dynamic LSP setup/release
performance. These metrics can be used to characterize the features
of GMPLS networks in LSP dynamic provisioning.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc5814.
Copyright Notice
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Table of Contents
1. Introduction ....................................................6
2. Conventions Used in This Document ...............................6
3. Overview of Performance Metrics .................................6
4. A Singleton Definition for Single Unidirectional LSP
Setup Delay .....................................................7
4.1. Motivation .................................................7
4.2. Metric Name ................................................7
4.3. Metric Parameters ..........................................8
4.4. Metric Units ...............................................8
4.5. Definition .................................................8
4.6. Discussion .................................................8
4.7. Methodologies ..............................................9
4.8. Metric Reporting ...........................................9
5. A Singleton Definition for Multiple Unidirectional LSPs
Setup Delay ....................................................10
5.1. Motivation ................................................10
5.2. Metric Name ...............................................10
5.3. Metric Parameters .........................................10
5.4. Metric Units ..............................................10
5.5. Definition ................................................11
5.6. Discussion ................................................11
5.7. Methodologies .............................................12
5.8. Metric Reporting ..........................................13
6. A Singleton Definition for Single Bidirectional LSP
Setup Delay ....................................................13
6.1. Motivation ................................................13
6.2. Metric Name ...............................................14
6.3. Metric Parameters .........................................14
6.4. Metric Units ..............................................14
6.5. Definition ................................................14
6.6. Discussion ................................................15
6.7. Methodologies .............................................15
6.8. Metric Reporting ..........................................16
7. A Singleton Definition for Multiple Bidirectional LSPs
Setup Delay ....................................................16
7.1. Motivation ................................................16
7.2. Metric Name ...............................................16
7.3. Metric Parameters .........................................17
7.4. Metric Units ..............................................17
7.5. Definition ................................................17
7.6. Discussion ................................................18
7.7. Methodologies .............................................19
7.8. Metric Reporting ..........................................19
8. A Singleton Definition for LSP Graceful Release Delay ..........20
8.1. Motivation ................................................20
8.2. Metric Name ...............................................20
8.3. Metric Parameters .........................................20
8.4. Metric Units ..............................................20
8.5. Definition ................................................20
8.6. Discussion ................................................22
8.7. Methodologies .............................................22
8.8. Metric Reporting ..........................................23
9. A Definition for Samples of Single Unidirectional LSP
Setup Delay ....................................................24
9.1. Metric Name ...............................................24
9.2. Metric Parameters .........................................24
9.3. Metric Units ..............................................24
9.4. Definition ................................................24
9.5. Discussion ................................................25
9.6. Methodologies .............................................25
9.7. Typical Testing Cases .....................................26
9.7.1. With No LSP in the Network .........................26
9.7.2. With a Number of LSPs in the Network ...............26
9.8. Metric Reporting ..........................................26
10. A Definition for Samples of Multiple Unidirectional
LSPs Setup Delay ..............................................26
10.1. Metric Name ..............................................27
10.2. Metric Parameters ........................................27
10.3. Metric Units .............................................27
10.4. Definition ...............................................27
10.5. Discussion ...............................................28
10.6. Methodologies ............................................28
10.7. Typical Testing Cases ....................................29
10.7.1. With No LSP in the Network ........................29
10.7.2. With a Number of LSPs in the Network ..............29
10.8. Metric Reporting .........................................29
11. A Definition for Samples of Single Bidirectional LSP
Setup Delay ...................................................30
11.1. Metric Name ..............................................30
11.2. Metric Parameters ........................................30
11.3. Metric Units .............................................30
11.4. Definition ...............................................30
11.5. Discussion ...............................................31
11.6. Methodologies ............................................31
11.7. Typical Testing Cases ....................................32
11.7.1. With No LSP in the Network ........................32
11.7.2. With a Number of LSPs in the Network ..............32
11.8. Metric Reporting .........................................32
12. A Definition for Samples of Multiple Bidirectional
LSPs Setup Delay ..............................................32
12.1. Metric Name ..............................................33
12.2. Metric Parameters ........................................33
12.3. Metric Units .............................................33
12.4. Definition ...............................................33
12.5. Discussion ...............................................34
12.6. Methodologies ............................................34
12.7. Typical Testing Cases ....................................35
12.7.1. With No LSP in the Network ........................35
12.7.2. With a Number of LSPs in the Network ..............35
12.8. Metric Reporting .........................................35
13. A Definition for Samples of LSP Graceful Release Delay ........35
13.1. Metric Name ..............................................36
13.2. Metric Parameters ........................................36
13.3. Metric Units .............................................36
13.4. Definition ...............................................36
13.5. Discussion ...............................................36
13.6. Methodologies ............................................37
13.7. Metric Reporting .........................................37
14. Some Statistics Definitions for Metrics to Report .............37
14.1. The Minimum of Metric ....................................37
14.2. The Median of Metric .....................................37
14.3. The Maximum of Metric ....................................38
14.4. The Percentile of Metric .................................38
14.5. Failure Statistics of Metric .............................38
14.5.1. Failure Count .....................................39
14.5.2. Failure Ratio .....................................39
15. Discussion ....................................................39
16. Security Considerations .......................................40
17. Acknowledgments ...............................................41
18. References ....................................................41
18.1. Normative References .....................................41
18.2. Informative References ...................................42
Appendix A. Authors' Addresses ...................................43
1. Introduction
Generalized Multi-Protocol Label Switching (GMPLS) is one of the most
promising control plane solutions for future transport and service
network. GMPLS has been developed to control and operate different
kinds of network elements, such as conventional routers, switches,
Dense Wavelength Division Multiplexing (DWDM) systems, Add-Drop
Multiplexors (ADMs), photonic cross-connects (PXCs), optical cross-
connects (OXCs), etc. These physically diverse devices differ
drastically from one another in dynamic provisioning ability.
The introduction of a control plane into optical circuit switching
networks provides the basis for automating the provisioning of
connections and drastically reduces connection provision delay. As
more and more services and applications are seeking to use GMPLS-
controlled networks as their underlying transport network, and
increasingly in a dynamic way, the need is growing for measuring and
characterizing the performance of LSP provisioning in GMPLS networks,
such that requirement from applications and the provisioning
capability of the network can be mapped to each other.
This document defines performance metrics and methodologies that can
be used to characterize the dynamic LSP provisioning performance of
GMPLS networks, more specifically, performance of the signaling
protocol. The metrics defined in this document can be used to
characterize the average performance of GMPLS implementations.
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].
3. Overview of Performance Metrics
In this memo, to characterize the dynamic LSP provisioning
performance of a GMPLS network, we define three performance metrics:
unidirectional LSP setup delay, bidirectional LSP setup delay, and
LSP graceful release delay. The latency of the LSP setup/release
signal is conceptually similar to the Round-trip Delay in IP
networks. This enables us to refer to the structures and notions
introduced and discussed in the IP Performance Metrics (IPPM)
Framework documents, [RFC2330] [RFC2679] [RFC2681]. The reader is
assumed to be familiar with the notions in those documents.
Note that data-path-related metrics, for example, the time between
the reception of a Resv message by the ingress node and when the
forward data path becomes operational, are defined in another
document [CCAMP-DPM]. It is desirable that both measurements are
performed to complement each other.
4. A Singleton Definition for Single Unidirectional LSP Setup Delay
This section defines a metric for single unidirectional Label
Switched Path setup delay across a GMPLS network.
4.1. Motivation
Single unidirectional Label Switched Path setup delay is useful for
several reasons:
o Single LSP setup delay is an important metric that characterizes
the provisioning performance of a GMPLS network. Longer LSP setup
delay will most likely incur higher overhead for the requesting
application, especially when the LSP duration itself is comparable
to the LSP setup delay.
o The minimum value of this metric provides an indication of the
delay that will likely be experienced when the LSP traverses the
shortest route at the lightest load in the control plane. As the
delay itself consists of several components, such as link
propagation delay and nodal processing delay, this metric also
reflects the status of the control plane. For example, for LSPs
traversing the same route, longer setup delays may suggest
congestion in the control channel or high control element load.
For this reason, this metric is useful for testing and diagnostic
purposes.
o The observed variance in a sample of LSP setup delay metric values
variance may serve as an early indicator on the feasibility of
support of applications that have stringent setup delay
requirements.
The measurement of single unidirectional LSP setup delay instead of
bidirectional LSP setup delay is motivated by the following factors:
o Some applications may use only unidirectional LSPs rather than
bidirectional ones. For example, content delivery services with
multicasting may use only unidirectional LSPs.
4.2. Metric Name
Single unidirectional LSP setup delay
4.3. Metric Parameters
o ID0, the ingress Label Switching Router (LSR) ID
o ID1, the egress LSR ID
o T, a time when the setup is attempted
4.4. Metric Units
The value of single unidirectional LSP setup delay is either a real
number of milliseconds or undefined.
4.5. Definition
The single unidirectional LSP setup delay from ingress node ID0 to
egress node ID1 [RFC3945] at T is dT means that ingress node ID0
sends the first bit of a Path message packet to egress node ID1 at
wire-time T, and that ingress node ID0 received the last bit of
responding Resv message packet from egress node ID1 at wire-time
T+dT.
The single unidirectional LSP setup delay from ingress node ID0 to
egress node ID1 at T is undefined means that ingress node ID0 sends
the first bit of Path message packet to egress node ID1 at wire-time
T and that ingress node ID0 does not receive the corresponding Resv
message within a reasonable period of time.
The undefined value of this metric indicates an event of Single
Unidirectional LSP Setup Failure and would be used to report a count
or a percentage of Single Unidirectional LSP Setup failures. See
Section 14.5 for definitions of LSP setup/release failures.
4.6. Discussion
The following issues are likely to come up in practice:
o The accuracy of unidirectional LSP setup delay at time T depends
on the clock resolution in the ingress node; but synchronization
between the ingress node and egress node is not required since
unidirectional LSP setup uses two-way signaling.
o A given methodology will have to include a way to determine
whether a latency value is infinite or whether it is merely very
large. Simple upper bounds MAY be used, but GMPLS networks may
accommodate many kinds of devices. For example, some photonic
cross-connects (PXCs) have to move micro mirrors. This physical
motion may take several milliseconds, but the common electronic
switches can finish the nodal processing within several
microseconds. So the unidirectional LSP setup delay varies
drastically from one network to another. In practice, the upper
bound SHOULD be chosen carefully.
o If the ingress node sends out the Path message to set up an LSP,
but never receives the corresponding Resv message, the
unidirectional LSP setup delay MUST be set to undefined.
o If the ingress node sends out the Path message to set up an LSP
but receives a PathErr message, the unidirectional LSP setup delay
MUST be set to undefined. There are many possible reasons for
this case; for example, the Path message has invalid parameters or
the network does not have enough resources to set up the requested
LSP, etc.
4.7. Methodologies
Generally, the methodology would proceed as follows:
o Make sure that the network has enough resources to set up the
requested LSP.
o At the ingress node, form the Path message according to the LSP
requirements. A timestamp (T1) may be stored locally on the
ingress node when the Path message packet is sent towards the
egress node.
o If the corresponding Resv message arrives within a reasonable
period of time, take the timestamp (T2) as soon as possible upon
receipt of the message. By subtracting the two timestamps, an
estimate of unidirectional LSP setup delay (T2-T1) can be
computed.
o If the corresponding Resv message fails to arrive within a
reasonable period of time, the unidirectional LSP setup delay is
deemed to be undefined. Note that the "reasonable" threshold is a
parameter of the methodology.
o If the corresponding response is a PathErr message, the
unidirectional LSP setup delay is deemed to be undefined.
4.8. Metric Reporting
The metric result (either a real number or undefined) MUST be
reported together with the selected upper bound. The route that the
LSP traverses MUST also be reported. The route MAY be collected via
use of the record route object, see [RFC3209], or via the management
plane. The collection of routes via the management plane is out of
scope of this document.
5. A Singleton Definition for Multiple Unidirectional LSPs Setup Delay
This section defines a metric for multiple unidirectional Label
Switched Paths setup delay across a GMPLS network.
5.1. Motivation
Multiple unidirectional Label Switched Paths setup delay is useful
for several reasons:
o Carriers may require that a large number of LSPs be set up during
a short time period. This request may arise, e.g., as a
consequence to interruptions on established LSPs or other network
failures.
o The time needed to set up a large number of LSPs during a short
time period cannot be deduced from single LSP setup delay.
5.2. Metric Name
Multiple unidirectional LSPs setup delay
5.3. Metric Parameters
o ID0, the ingress LSR ID
o ID1, the egress LSR ID
o Lambda_m, a rate in reciprocal milliseconds
o X, the number of LSPs to set up
o T, a time when the first setup is attempted
5.4. Metric Units
The value of multiple unidirectional LSPs setup delay is either a
real number of milliseconds or undefined
5.5. Definition
Given Lambda_m and X, the multiple unidirectional LSPs setup delay
from the ingress node to the egress node [RFC3945] at T is dT means:
o ingress node ID0 sends the first bit of the first Path message
packet to egress node ID1 at wire-time T;
o all subsequent (X-1) Path messages are sent according to the
specified Poisson process with arrival rate Lambda_m;
o ingress node ID0 receives all corresponding Resv message packets
from egress node ID1; and
o ingress node ID0 receives the last Resv message packet at wire-
time T+dT.
If the multiple unidirectional LSPs setup delay at T is "undefined",
this means that:
o ingress node ID0 sends all the Path messages toward egress node
ID1,
o the first bit of the first Path message packet is sent at wire-
time T, and
o ingress node ID0 does not receive one or more of the corresponding
Resv messages within a reasonable period of time.
The undefined value of this metric indicates an event of Multiple
Unidirectional LSP Setup Failure and would be used to report a count
or a percentage of Multiple Unidirectional LSP Setup failures. See
Section 14.5 for definitions of LSP setup/release failures.
5.6. Discussion
The following issues are likely to come up in practice:
o The accuracy of multiple unidirectional LSPs setup delay at time T
depends on the clock resolution in the ingress node; but
synchronization between the ingress node and egress node is not
required since unidirectional LSP setup uses two-way signaling.
o A given methodology will have to include a way to determine
whether a latency value is infinite or whether it is merely very
large. Simple upper bounds MAY be used, but GMPLS networks may
accommodate many kinds of devices. For example, some photonic
cross-connects (PXCs) have to move micro mirrors. This physical
motion may take several milliseconds, but electronic switches can
finish the nodal processing within several microseconds. So the
multiple unidirectional LSP setup delay varies drastically from
one network to another. In practice, the upper bound SHOULD be
chosen carefully.
o If the ingress node sends out the multiple Path messages to set up
the LSPs, but never receives one or more of the corresponding Resv
messages, multiple unidirectional LSP setup delay MUST be set to
undefined.
o If the ingress node sends out the Path messages to set up the LSPs
but receives one or more PathErr messages, multiple unidirectional
LSPs setup delay MUST be set to undefined. There are many
possible reasons for this case. For example, one of the Path
messages has invalid parameters or the network does not have
enough resources to set up the requested LSPs, etc.
o The arrival rate of the Poisson process Lambda_m SHOULD be chosen
carefully such that on the one hand, the control plane is not
overburdened. On the other hand, the arrival rate is large enough
to meet the requirements of applications or services.
o It is important that all the LSPs MUST traverse the same route.
If there are multiple routes between the ingress node ID0 and
egress node ID1, Explicit Route Objects (EROs), or an alternate
method, e.g., static configuration, MUST be used to ensure that
all LSPs traverse the same route.
5.7. Methodologies
Generally, the methodology would proceed as follows:
o Make sure that the network has enough resources to set up the
requested LSPs.
o At the ingress node, form the Path messages according to the LSPs'
requirements.
o At the ingress node, select the time for each of the Path messages
according to the specified Poisson process.
o At the ingress node, send out the Path messages according to the
selected time.
o Store a timestamp (T1) locally on the ingress node when the first
Path message packet is sent towards the egress node.
o If all of the corresponding Resv messages arrive within a
reasonable period of time, take the final timestamp (T2) as soon
as possible upon the receipt of all the messages. By subtracting
the two timestamps, an estimate of multiple unidirectional LSPs
setup delay (T2-T1) can be computed.
o If one or more of the corresponding Resv messages fail to arrive
within a reasonable period of time, the multiple unidirectional
LSPs setup delay is deemed to be undefined. Note that the
"reasonable" threshold is a parameter of the methodology.
o If one or more of the corresponding responses are PathErr
messages, the multiple unidirectional LSPs setup delay is deemed
to be undefined.
5.8. Metric Reporting
The metric result (either a real number or undefined) MUST be
reported together with the selected upper bound. The route that the
LSPs traverse MUST also be reported. The route MAY be collected via
use of the record route object, see [RFC3209], or via the management
plane. The collection of routes via the management plane is out of
scope of this document.
6. A Singleton Definition for Single Bidirectional LSP Setup Delay
GMPLS allows establishment of bidirectional symmetric LSPs (not of
asymmetric LSPs). This section defines a metric for single
bidirectional LSP setup delay across a GMPLS network.
6.1. Motivation
Single bidirectional Label Switched Path setup delay is useful for
several reasons:
o LSP setup delay is an important metric that characterizes the
provisioning performance of a GMPLS network. Longer LSP setup
delay will incur higher overhead for the requesting application,
especially when the LSP duration is comparable to the LSP setup
delay. Thus, measuring the setup delay is important for
application scheduling.
o The minimum value of this metric provides an indication of the
delay that will likely be experienced when the LSP traverses the
shortest route at the lightest load in the control plane. As the
delay itself consists of several components, such as link
propagation delay and nodal processing delay, this metric also
reflects the status of the control plane. For example, for LSPs
traversing the same route, longer setup delays may suggest
congestion in the control channel or high control element load.
For this reason, this metric is useful for testing and diagnostic
purposes.
o LSP setup delay variance has a different impact on applications.
Erratic variation in LSP setup delay makes it difficult to support
applications that have stringent setup delay requirement.
The measurement of single bidirectional LSP setup delay instead of
unidirectional LSP setup delay is motivated by the following factors:
o Bidirectional LSPs are seen as a requirement for many GMPLS
networks. Its provisioning performance is important to
applications that generate bidirectional traffic.
6.2. Metric Name
Single bidirectional LSP setup delay
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
The value of single bidirectional LSP setup delay is either a real
number of milliseconds or undefined
6.5. Definition
For a real number dT, the single bidirectional LSP setup delay from
ingress node ID0 to egress node ID1 at T is dT means that ingress
node ID0 sends out the first bit of a Path message including an
Upstream Label [RFC3473] heading for egress node ID1 at wire-time T,
egress node ID1 receives that packet, then immediately sends a Resv
message packet back to ingress node ID0, and that ingress node ID0
receives the last bit of the Resv message packet at wire-time T+dT.
If the single bidirectional LSP setup delay from ingress node ID0 to
egress node ID1 at T is "undefined", this means that ingress node ID0
sends the first bit of a Path message to egress node ID1 at wire-time
T and that ingress node ID0 does not receive that response packet
within a reasonable period of time.
The undefined value of this metric indicates an event of Single
Bidirectional LSP Setup Failure and would be used to report a count
or a percentage of Single Bidirectional LSP Setup failures. See
Section 14.5 for definitions of LSP setup/release failures.
6.6. Discussion
The following issues are likely to come up in practice:
o The accuracy of single bidirectional LSP setup delay depends on
the clock resolution in the ingress node; but synchronization
between the ingress node and egress node is not required since
single bidirectional LSP setup uses two-way signaling.
o A given methodology will have to include a way to determine
whether a latency value is infinite or whether it is merely very
large. Simple upper bounds MAY be used, but GMPLS networks may
accommodate many kinds of devices. For example, some photonic
cross-connects (PXCs) have to move micro mirrors. This physical
motion may take several milliseconds, but electronic switches can
finish the nodal processing within several microseconds. So the
bidirectional LSP setup delay varies drastically from one network
to another. In the process of bidirectional LSP setup, if the
downstream node overrides the label suggested by the upstream
node, the setup delay may also increase. Thus, in practice, the
upper bound SHOULD be chosen carefully.
o If the ingress node sends out the Path message to set up the LSP,
but never receives the corresponding Resv message, single
bidirectional LSP setup delay MUST be set to undefined.
o If the ingress node sends out the Path message to set up the LSP,
but receives a PathErr message, single bidirectional LSP setup
delay MUST be set to undefined. There are many possible reasons
for this case. For example, the Path message has invalid
parameters or the network does not have enough resources to set up
the requested LSP.
6.7. Methodologies
Generally, the methodology would proceed as follows:
o Make sure that the network has enough resources to set up the
requested LSP.
o At the ingress node, form the Path message (including the Upstream
Label or suggested label) according to the LSP requirements. A
timestamp (T1) may be stored locally on the ingress node when the
Path message packet is sent towards the egress node.
o If the corresponding Resv message arrives within a reasonable
period of time, take the final timestamp (T2) as soon as possible
upon the receipt of the message. By subtracting the two
timestamps, an estimate of bidirectional LSP setup delay (T2-T1)
can be computed.
o If the corresponding Resv message fails to arrive within a
reasonable period of time, the single bidirectional LSP setup
delay is deemed to be undefined. Note that the "reasonable"
threshold is a parameter of the methodology.
o If the corresponding response is a PathErr message, the single
bidirectional LSP setup delay is deemed to be undefined.
6.8. Metric Reporting
The metric result (either a real number or undefined) MUST be
reported together with the selected upper bound. The route that the
LSP traverses MUST also be reported. The route MAY be collected via
use of the record route object, see [RFC3209], or via the management
plane. The collection of routes via the management plane is out of
scope of this document.
7. A Singleton Definition for Multiple Bidirectional LSPs Setup Delay
This section defines a metric for multiple bidirectional LSPs setup
delay across a GMPLS network.
7.1. Motivation
Multiple bidirectional LSPs setup delay is useful for several
reasons:
o Upon traffic interruption caused by network failure or network
upgrade, carriers may require a large number of LSPs be set up
during a short time period.
o The time needed to set up a large number of LSPs during a short
time period cannot be deduced by single LSP setup delay.
7.2. Metric Name
Multiple bidirectional LSPs setup delay
7.3. Metric Parameters
o ID0, the ingress LSR ID
o ID1, the egress LSR ID
o Lambda_m, a rate in reciprocal milliseconds
o X, the number of LSPs to set up
o T, a time when the first setup is attempted
7.4. Metric Units
The value of multiple bidirectional LSPs setup delay is either a real
number of milliseconds or undefined
7.5. Definition
Given Lambda_m and X, for a real number dT, the multiple
bidirectional LSPs setup delay from ingress node to egress node at T
is dT, means that:
o Ingress node ID0 sends the first bit of the first Path message
heading for egress node ID1 at wire-time T;
o All subsequent (X-1) Path messages are sent according to the
specified Poisson process with arrival rate Lambda_m;
o Ingress node ID1 receives all corresponding Resv message packets
from egress node ID1; and
o Ingress node ID0 receives the last Resv message packet at wire-
time T+dT.
If the multiple bidirectional LSPs setup delay from ingress node to
egress node at T is "undefined", this means that the ingress node
sends all the Path messages to the egress node and that the ingress
node fails to receive one or more of the response Resv messages
within a reasonable period of time.
The undefined value of this metric indicates an event of Multiple
Bidirectional LSP Setup Failure and would be used to report a count
or a percentage of Multiple Bidirectional LSP Setup failures. See
Section 14.5 for definitions of LSP setup/release failures.
7.6. Discussion
The following issues are likely to come up in practice:
o The accuracy of multiple bidirectional LSPs setup delay depends on
the clock resolution in the ingress node; but synchronization
between the ingress node and egress node is not required since
bidirectional LSP setup uses two-way signaling.
o A given methodology will have to include a way to determine
whether a latency value is infinite or whether it is merely very
large. Simple upper bounds MAY be used, but GMPLS networks may
accommodate many kinds of devices. For example, some photonic
cross-connects (PXCs) have to move micro mirrors. This physical
motion may take several milliseconds, but electronic switches can
finish the nodal process within several microseconds. So the
multiple bidirectional LSPs setup delay varies drastically from a
network to another. In the process of multiple bidirectional LSPs
setup, if the downstream node overrides the label suggested by the
upstream node, the setup delay may also increase. Thus, in
practice, the upper bound SHOULD be chosen carefully.
o If the ingress node sends out the Path messages to set up the
LSPs, but never receives all the corresponding Resv messages, the
multiple bidirectional LSPs setup delay MUST be set to undefined.
o If the ingress node sends out the Path messages to set up the
LSPs, but receives one or more responding PathErr messages, the
multiple bidirectional LSPs setup delay MUST be set to undefined.
There are many possible reasons for this case. For example, one
or more of the Path messages have invalid parameters or the
network does not have enough resources to set up the requested
LSPs.
o The arrival rate of the Poisson process Lambda_m SHOULD be
carefully chosen such that on the one hand, the control plane is
not overburdened. On the other hand, the arrival rate is large
enough to meet the requirements of applications or services.
o It is important that all the LSPs MUST traverse the same route.
If there are multiple routes between the ingress node ID0 and
egress node ID1, EROs, or an alternate method, e.g., static
configuration, MUST be used to ensure that all LSPs traverse the
same route.
7.7. Methodologies
Generally, the methodology would proceed as follows:
o Make sure that the network has enough resources to set up the
requested LSPs.
o At the ingress node, form the Path messages (including the
Upstream Label or suggested label) according to the LSPs'
requirements.
o At the ingress node, select the time for each of the Path messages
according to the specified Poisson process.
o At the ingress node, send out the Path messages according to the
selected time.
o Store a timestamp (T1) locally in the ingress node when the first
Path message packet is sent towards the egress node.
o If all of the corresponding Resv messages arrive within a
reasonable period of time, take the final timestamp (T2) as soon
as possible upon the receipt of all the messages. By subtracting
the two timestamps, an estimate of multiple bidirectional LSPs
setup delay (T2-T1) can be computed.
o If one or more of the corresponding Resv messages fail to arrive
within a reasonable period of time, the multiple bidirectional
LSPs setup delay is deemed to be undefined. Note that the
"reasonable" threshold is a parameter of the methodology.
o If one or more of the corresponding responses are PathErr
messages, the multiple bidirectional LSPs setup delay is deemed to
be undefined.
7.8. Metric Reporting
The metric result (either a real number or undefined) MUST be
reported together with the selected upper bound. The route that the
LSPs traverse MUST also be reported. The route MAY be collected via
use of the record route object, see [RFC3209], or via the management
plane. The collection of routes via the management plane is out of
scope of this document.
8. A Singleton Definition for LSP Graceful Release Delay
There are two different kinds of LSP release mechanisms in GMPLS
networks: graceful release and forceful release. This document does
not take forceful LSP release procedure into account.
8.1. Motivation
LSP graceful release delay is useful for several reasons:
o The LSP graceful release delay is part of the total cost of
dynamic LSP provisioning. For some short duration applications,
the LSP release time cannot be ignored.
o The LSP graceful release procedure is more preferred in a GMPLS
controlled network, particularly the optical networks. Since it
doesn't trigger restoration/protection, it is "alarm-free
connection deletion" in [RFC4208].
8.2. Metric Name
LSP graceful release delay
8.3. Metric Parameters
o ID0, the ingress LSR ID
o ID1, the egress LSR ID
o T, a time when the release is attempted
8.4. Metric Units
The value of LSP graceful release delay is either a real number of
milliseconds or undefined
8.5. Definition
There are two different LSP graceful release procedures: one is
initiated by the ingress node, and another is initiated by the egress
node. The two procedures are depicted in [RFC3473]. We define the
graceful LSP release delay for these two procedures separately.
For a real number dT, if the LSP graceful release delay from ingress
node ID0 to egress node ID1 at T is dT, this means that ingress node
ID0 sends the first bit of a Path message including an Admin Status
Object with the Reflect (R) and Delete (D) bits set to the egress
node at wire-time T, that egress node ID1 receives that packet, then
immediately sends a Resv message including an Admin Status Object
with the Delete (D) bit set back to the ingress node. Ingress node
ID0 sends the PathTear message downstream to remove the LSP, and
egress node ID1 receives the last bit of PathTear packet at wire-time
T+dT.
Also, as an option, upon receipt of the Path message including an
Admin Status Object with the Reflect (R) and Delete (D) bits set,
egress node ID1 may respond with a PathErr message with the
Path_State_Removed flag set.
The LSP graceful release delay from ingress node ID0 to egress node
ID1 at T is undefined means that ingress node ID0 sends the first bit
of Path message to egress node ID1 at wire-time T and that (either
the egress node does not receive the Path packet, the egress node
does not send a corresponding Resv message packet in response, or the
ingress node does not receive that Resv packet, and) egress node ID1
does not receive the PathTear message within a reasonable period of
time.
If the LSP graceful release delay from egress node ID1 to ingress
node ID0 at T is dT, this means that egress node ID1 sends the first
bit of a Resv message including an Admin Status Object with the
Reflect (R) and Delete (D) bits set to the ingress node at wire-time
T. Ingress node ID0 sends a PathTear message downstream to remove
the LSP, and egress node ID1 receives the last bit of PathTear packet
at wire-time T+dT.
If the LSP graceful release delay from egress node ID1 to ingress
node ID0 at T is "undefined", this means that egress node ID1 sends
the first bit of Resv message including an Admin Status Object with
the Reflect (R) and Delete (D) bits set to the ingress node ID0 at
wire-time T and that (either the ingress node does not receive the
Resv packet or the ingress node does not send PathTear message packet
in response, and) egress node ID1 does not receive the PathTear
message within a reasonable period of time.
The undefined value of this metric indicates an event of LSP Graceful
Release Failure and would be used to report a count or a percentage
of LSP Graceful Release failures. See Section 14.5 for definitions
of LSP setup/release failures.
8.6. Discussion
The following issues are likely to come up in practice:
o In the first (second) circumstance, the accuracy of LSP graceful
release delay at time T depends on the clock resolution in the
ingress (egress) node. In the first circumstance, synchronization
between the ingress node and egress node is required, but it is
not in the second circumstance.
o A given methodology has to include a way to determine whether a
latency value is infinite or whether it is merely very large.
Simple upper bounds MAY be used, but the upper bound SHOULD be
chosen carefully in practice.
o In the first circumstance, if the ingress node sends out Path
message including an Admin Status Object with the Reflect (R) and
Delete (D) bits set to initiate LSP graceful release, but the
egress node never receives the corresponding PathTear message, LSP
graceful release delay MUST be set to undefined.
o In the second circumstance, if the egress node sends out the Resv
message including an Admin Status Object with the Reflect (R) and
Delete (D) bits set to initiate LSP graceful release, but never
receives the corresponding PathTear message, LSP graceful release
delay MUST be set to undefined.
8.7. Methodologies
In the first circumstance, the methodology may proceed as follows:
o Make sure the LSP to be deleted is set up;
o At the ingress node, form the Path message including an Admin
Status Object with the Reflect (R) and Delete (D) bits set. A
timestamp (T1) may be stored locally on the ingress node when the
Path message packet is sent towards the egress node.
o Upon receiving the Path message including an Admin Status Object
with the Reflect (R) and Delete (D) bits set, the egress node
sends a Resv message including an Admin Status Object with the
Delete (D) and Reflect (R) bits set. Alternatively, the egress
node sends a PathErr message with the Path_State_Removed flag set
upstream.
o When the ingress node receives the Resv message or the PathErr
message, it sends a PathTear message to remove the LSP.
o The egress node takes a timestamp (T2) once it receives the last
bit of the PathTear message. The LSP graceful release delay is
then (T2-T1).
o If the ingress node sends the Path message downstream, but the
egress node fails to receive the PathTear message within a
reasonable period of time, the LSP graceful release delay is
deemed to be undefined. Note that the "reasonable" threshold is a
parameter of the methodology.
In the second circumstance, the methodology would proceed as follows:
o Make sure the LSP to be deleted is set up;
o On the egress node, form the Resv message including an Admin
Status Object with the Reflect (R) and Delete (D) bits set. A
timestamp may be stored locally on the egress node when the Resv
message packet is sent towards the ingress node.
o Upon receiving the Admin Status Object with the Reflect (R) and
Delete (D) bits set in the Resv message, the ingress node sends a
PathTear message downstream to remove the LSP.
o The egress node takes a timestamp (T2) once it receives the last
bit of the PathTear message. The LSP graceful release delay is
then (T2-T1).
o If the egress node sends the Resv message upstream, but it fails
to receive the PathTear message within a reasonable period of
time, the LSP graceful release delay is deemed to be undefined.
Note that the "reasonable" threshold is a parameter of the
methodology.
8.8. Metric Reporting
The metric result (either a real number or undefined) MUST be
reported together with the selected upper bound and the procedure
used (e.g., either from the ingress node to the egress node or from
the egress node to the ingress node; see Section 8.5 for more
details). The route that the LSP traverses MUST also be reported.
The route MAY be collected via use of the record route object, see
[RFC3209], or via the management plane. The collection of routes via
the management plane is out of scope of this document.
9. A Definition for Samples of Single Unidirectional LSP Setup Delay
In Section 4, we defined the singleton metric of single
unidirectional LSP setup delay. Now we define how to get one
particular sample of single unidirectional LSP setup delay. Sampling
means to take a number of distinct instances of a skeleton metric
under a given set of parameters. As in [RFC2330], we use Poisson
sampling as an example.
9.1. Metric Name
Single unidirectional LSP setup delay sample
9.2. 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 milliseconds
o Th, LSP holding time
o Td, the maximum waiting time for successful setup
9.3. 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 milliseconds or undefined
9.4. 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 unidirectional LSP setup
delay sample. The value of the sample is the sequence made up of the
resulting <time, LSP setup delay> pairs. If there are no such pairs,
the sequence is of length zero and the sample is said to be empty.
9.5. Discussion
The parameter Lambda should be carefully chosen. If the rate is too
high, too frequent LSP setup/release procedure will result in high
overhead in the control plane. In turn, the high overhead will
increase unidirectional LSP setup delay. On the other hand, if the
rate is too low, the sample might not completely reflect the dynamic
provisioning performance of the GMPLS network. The appropriate
Lambda value depends on the given network.
The parameters Td should be carefully chosen. Different switching
technologies may vary significantly in performing a cross-connect
operation. At the same time, the time needed in setting up an LSP
under different traffic may also vary significantly.
In the case of active measurement, the parameters Th should be
carefully chosen. The combination of Lambda and Th reflects the load
of the network. The selection of Th should take into account that
the network has sufficient resources to perform subsequent tests.
The value of Th MAY be constant during one sampling process for
simplicity considerations.
Note that for online or passive measurements, the arrival rate and
LSP holding time are determined by actual traffic; hence, in this
case, Lambda and Th are not input parameters.
It is important that, in obtaining a sample, all the LSPs MUST
traverse the same route. If there are multiple routes between the
ingress node ID0 and egress node ID1, EROs, or an alternate method,
e.g., static configuration, MUST be used to ensure that all LSPs
traverse the same route.
9.6. Methodologies
o Select the times using the specified Poisson arrival process,
o Set up the LSP as the methodology for the singleton unidirectional
LSP setup delay, and obtain the value of unidirectional LSP setup
delay, and
o Release the LSP after Th, and wait for the next Poisson arrival
event.
Note: it is possible that before the previous LSP release procedure
completes, the next Poisson arrival event arrives and the LSP setup
procedure is initiated. If there is resource contention between the
two LSPs, the LSP setup may fail. Ways to avoid such contention are
outside the scope of this document.
9.7. Typical Testing Cases
9.7.1. With No LSP in the Network
9.7.1.1. Motivation
Single unidirectional LSP setup delay with no LSP in the network is
important because this reflects the inherent delay of a Resource
Reservation Protocol - Traffic Engineering (RSVP-TE) implementation.
The minimum value provides an indication of the delay that will
likely be experienced when an LSP traverses the shortest route with
the lightest load in the control plane.
9.7.1.2. Methodologies
Make sure that there is no LSP in the network and proceed with the
methodologies described in Section 9.6
9.7.2. With a Number of LSPs in the Network
9.7.2.1. Motivation
Single unidirectional LSP setup 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 vary. It can be used as
a scalability metric of an RSVP-TE implementation.
9.7.2.2. Methodologies
Set up the required number of LSPs, and wait until the network
reaches a stable state; then, proceed with the methodologies
described in Section 9.6.
9.8. Metric Reporting
The metric results including both real and undefined values MUST be
reported together with the total number of values. The context under
which the sample is obtained, including the selected parameters, the
route traversed by the LSPs, and the testing case used, MUST also be
reported.
10. A Definition for Samples of Multiple Unidirectional LSPs Setup
Delay
In Section 5, we defined the singleton metric of multiple
unidirectional LSPs setup delay. Now we define how to get one
particular sample of multiple unidirectional LSPs setup delay.
Sampling means to take a number of distinct instances of a skeleton
metric under a given set of parameters. As in [RFC2330], we use
Poisson sampling as an example.
10.1. Metric Name
Multiple unidirectional LSPs setup delay sample
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_m, a rate in the reciprocal milliseconds
o Lambda, a rate in the reciprocal milliseconds
o X, the number of LSPs to set up
o Th, LSP holding time
o Td, the maximum waiting time for successful multiple
unidirectional LSPs setup
10.3. Metric Units
A sequence of pairs; the elements of each pair are:
o T, a time when the first setup is attempted
o dT, either a real number of milliseconds or undefined
10.4. Definition
Given T0, Tf, and Lambda, compute a pseudo-random Poisson process
beginning at or before T0, with an 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 multiple unidirectional LSP
setup delay sample. The value of the sample is the sequence made up
of the resulting <time, setup delay> pairs. If there are no such
pairs, the sequence is of length zero and the sample is said to be
empty.
10.5. Discussion
The parameter Lambda is used as an arrival rate of "batch
unidirectional LSPs setup" operation. It regulates the interval in
between each batch operation. The parameter Lambda_m is used within
each batch operation, as described in Section 5
The parameters Lambda and Lambda_m should be carefully chosen. If
the rate is too high, overly frequent LSP setup/release procedure
will result in high overhead in the control plane. In turn, the high
overhead will increase unidirectional LSP setup delay. On the other
hand, if the rate is too low, the sample might not completely reflect
the dynamic provisioning performance of the GMPLS network. The
appropriate Lambda and Lambda_m value depends on the given network.
The parameters Td should be carefully chosen. Different switching
technologies may vary significantly in performing a cross-connect
operation. At the same time, the time needed in setting up an LSP
under different traffic may also vary significantly.
It is important that, in obtaining a sample, all the LSPs MUST
traverse the same route. If there are multiple routes between the
ingress node ID0 and egress node ID1, EROs, or an alternate method,
e.g., static configuration, MUST be used to ensure that all LSPs
traverse the same route.
10.6. Methodologies
o Select the times using the specified Poisson arrival process,
o Set up the LSP as the methodology for the singleton multiple
unidirectional LSPs setup delay, and obtain the value of multiple
unidirectional LSPs setup delay, and
o Release the LSP after Th, and wait for the next Poisson arrival
event.
Note: it is possible that before the previous LSP release procedure
completes, the next Poisson arrival event arrives and the LSP setup
procedure is initiated. If there is resource contention between the
two LSPs, the LSP setup may fail. Ways to avoid such contention are
outside the scope of this document.
10.7. Typical Testing Cases
10.7.1. With No LSP in the Network
10.7.1.1. Motivation
Multiple unidirectional LSPs setup delay with no LSP in the network
is important because this reflects the inherent delay of an RSVP-TE
implementation. The minimum value provides an indication of the
delay that will likely be experienced when LSPs traverse the shortest
route with the lightest load in the control plane.
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
Multiple unidirectional LSPs setup 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 can vary
significantly as the number of existing LSPs vary. It can be used as
a scalability metric of an RSVP-TE implementation.
10.7.2.2. Methodologies
Set up the required number of LSPs, and wait until the network
reaches a stable state; then, proceed with the methodologies
described in Section 10.6.
10.8. Metric Reporting
The metric results including both real and undefined values MUST be
reported together with the total number of values. The context under
which the sample is obtained, including the selected parameters, the
route traversed by the LSPs, and the testing case used, MUST also be
reported.
11. A Definition for Samples of Single Bidirectional LSP Setup Delay
In Section 6, we defined the singleton metric of single bidirectional
LSP setup delay. Now we define how to get one particular sample of
single bidirectional LSP setup delay. Sampling means to take a
number of distinct instances of a skeleton metric under a given set
of parameters. As in [RFC2330], we use Poisson sampling as an
example.
11.1. Metric Name
Single bidirectional LSP setup delay sample with no LSP in the
network
11.2. 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 milliseconds
o Th, LSP holding time
o Td, the maximum waiting time for successful setup
11.3. 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 milliseconds or undefined
11.4. Definition
Given T0, Tf, and Lambda, compute a pseudo-random Poisson process
beginning at or before T0, with an 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 bidirectional LSP setup delay
sample. The value of the sample is the sequence made up of the
resulting <time, LSP setup delay> pairs. If there are no such pairs,
the sequence is of length zero and the sample is said to be empty.
11.5. Discussion
The parameters Lambda should be carefully chosen. If the rate is too
high, overly frequent LSP setup/release procedure will result in high
overhead in the control plane. In turn, the high overhead will
increase bidirectional LSP setup delay. On the other hand, if the
rate is too low, the sample might not completely reflect the dynamic
provisioning performance of the GMPLS network. The appropriate
Lambda value depends on the given network.
The parameters Td should be carefully chosen. Different switching
technologies may vary significantly in performing a cross-connect
operation. At the same time, the time needed to set up an LSP under
different traffic may also vary significantly.
In the case of active measurement, the parameters Th should be
carefully chosen. The combination of Lambda and Th reflects the load
of the network. The selection of Th SHOULD take into account that
the network has sufficient resources to perform subsequent tests.
The value of Th MAY be constant during one sampling process for
simplicity considerations.
Note that for online or passive measurements, the arrival rate and
the LSP holding time are determined by actual traffic; hence, in this
case, Lambda and Th are not input parameters.
It is important that, in obtaining a sample, all the LSPs MUST
traverse the same route. If there are multiple routes between the
ingress node ID0 and egress node ID1, EROs, or an alternate method,
e.g., static configuration, MUST be used to ensure that all LSPs
traverse the same route.
11.6. Methodologies
o Select the times using the specified Poisson arrival process,
o Set up the LSP as the methodology for the singleton bidirectional
LSP setup delay, and obtain the value of bidirectional LSP setup
delay, and
o Release the LSP after Th, and wait for the next Poisson arrival
event.
Note: it is possible that before the previous LSP release procedure
completes, the next Poisson arrival event arrives and the LSP setup
procedure is initiated. If there is resource contention between the
two LSPs, the LSP setup may fail. Ways to avoid such contention are
outside the scope of this document.
11.7. Typical Testing Cases
11.7.1. With No LSP in the Network
11.7.1.1. Motivation
Single bidirectional LSP setup delay with no LSP in the network is
important because this reflects the inherent delay of an RSVP-TE
implementation. The minimum value provides an indication of the
delay that will likely be experienced when an LSP traverses the
shortest route with the lightest load in the control plane.
11.7.1.2. Methodologies
Make sure that there is no LSP in the network and proceed with the
methodologies described in Section 11.6.
11.7.2. With a Number of LSPs in the Network
11.7.2.1. Motivation
Single bidirectional LSP setup 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 can vary
significantly as the number of existing LSPs varies. It can be used
as a scalability metric of an RSVP-TE implementation.
11.7.2.2. Methodologies
Set up the required number of LSPs and wait until the network reaches
a stable state; then, proceed with the methodologies described in
Section 11.6.
11.8. Metric Reporting
The metric results including both real and undefined values MUST be
reported together with the total number of values. The context under
which the sample is obtained, including the selected parameters, the
route traversed by the LSPs, and the testing case used, MUST also be
reported.
12. A Definition for Samples of Multiple Bidirectional LSPs Setup Delay
In Section 7, we defined the singleton metric of multiple
bidirectional LSPs setup delay. Now we define how to get one
particular sample of multiple bidirectional LSP setup delay.
Sampling means to take a number of distinct instances of a skeleton
metric under a given set of parameters. As in [RFC2330], we use
Poisson sampling as an example.
12.1. Metric Name
Multiple bidirectional LSPs setup delay sample
12.2. Metric Parameters
o ID0, the ingress LSR ID
o ID1, the egress LSR ID
o T0, a time
o Tf, a time
o Lambda_m, a rate in the reciprocal milliseconds
o Lambda, a rate in the reciprocal milliseconds
o X, the number of LSPs to set up
o Th, LSP holding time
o Td, the maximum waiting time for successful multiple
unidirectional LSPs setup
12.3. Metric Units
A sequence of pairs; the elements of each pair are:
o T, a time when the first setup is attempted
o dT, either a real number of milliseconds or undefined
12.4. Definition
Given T0, Tf, and Lambda, compute a pseudo-random Poisson process
beginning at or before T0, with an 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 multiple unidirectional LSP
setup delay sample. The value of the sample is the sequence made up
of the resulting <time, setup delay> pairs. If there are no such
pairs, the sequence is of length zero and the sample is said to be
empty.
12.5. Discussion
The parameter Lambda is used as an arrival rate of "batch
bidirectional LSPs setup" operation. It regulates the interval in
between each batch operation. The parameter Lambda_m is used within
each batch operation, as described in Section 7.
The parameters Lambda and Lambda_m should be carefully chosen. If
the rate is too high, overly frequent LSP setup/release procedure
will result in high overhead in the control plane. In turn, the high
overhead will increase unidirectional LSP setup delay. On the other
hand, if the rate is too low, the sample might not completely reflect
the dynamic provisioning performance of the GMPLS network. The
appropriate Lambda and Lambda_m values depend on the given network.
The parameters Td should be carefully chosen. Different switching
technologies may vary significantly in performing a cross-connect
operation. At the same time, the time needed to set up an LSP under
different traffic may also vary significantly.
It is important that, in obtaining a sample, all the LSPs MUST
traverse the same route. If there are multiple routes between the
ingress node ID0 and egress node ID1, EROs, or an alternate method,
e.g., static configuration, MUST be used to ensure that all LSPs
traverse the same route.
12.6. Methodologies
o Select the times using the specified Poisson arrival process,
o Set up the LSP as the methodology for the singleton multiple
bidirectional LSPs setup delay, and obtain the value of multiple
unidirectional LSPs setup delay, and
o Release the LSP after Th, and wait for the next Poisson arrival
event.
Note: it is possible that before the previous LSP release procedure
completes, the next Poisson arrival event arrives and the LSP setup
procedure is initiated. If there is resource contention between the
two LSPs, the LSP setup may fail. Ways to avoid such contention are
outside the scope of this document.
12.7. Typical Testing Cases
12.7.1. With No LSP in the Network
12.7.1.1. Motivation
Multiple bidirectional LSPs setup delay with no LSP in the network is
important because this reflects the inherent delay of an RSVP-TE
implementation. The minimum value provides an indication of the
delay that will likely be experienced when an LSPs traverse the
shortest route with the lightest load in the control plane.
12.7.1.2. Methodologies
Make sure that there is no LSP in the network and proceed with the
methodologies described in Section 10.6.
12.7.2. With a Number of LSPs in the Network
12.7.2.1. Motivation
Multiple bidirectional LSPs setup 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 vary. It may be used as
a scalability metric of an RSVP-TE implementation.
12.7.2.2. Methodologies
Set up the required number of LSPs, and wait until the network
reaches a stable state; then, proceed with the methodologies
described in Section 12.6.
12.8. Metric Reporting
The metric results including both real and undefined values MUST be
reported together with the total number of values. The context under
which the sample is obtained, including the selected parameters, the
route traversed by the LSPs, and the testing case used, MUST also be
reported.
13. A Definition for Samples of LSP Graceful Release Delay
In Section 8, we defined the singleton metric of LSP graceful release
delay. Now we define how to get one particular sample of LSP
graceful release delay. We also use Poisson sampling as an example.
13.1. Metric Name
LSP graceful release delay sample
13.2. 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 reciprocal milliseconds
o Td, the maximum waiting time for successful LSP release
13.3. Metric Units
A sequence of pairs; the elements of each pair are:
o T, a time, and
o dT, either a real number of milliseconds or undefined
13.4. Definition
Given T0, Tf, and Lambda, we compute a pseudo-random Poisson process
beginning at or before T0, with an 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 LSP graceful release delay
sample. The value of the sample is the sequence made up of the
resulting <time, LSP graceful delay> pairs. If there are no such
pairs, the sequence is of length zero and the sample is said to be
empty.
13.5. Discussion
The parameter Lambda should be carefully chosen. If the rate is too
large, overly frequent LSP setup/release procedure will result in
high overhead in the control plane. In turn, the high overhead will
increase unidirectional LSP setup delay. On the other hand, if the
rate is too small, the sample might not completely reflect the
dynamic provisioning performance of the GMPLS network. The
appropriate Lambda value depends on the given network.
It is important that, in obtaining a sample, all the LSPs MUST
traverse the same route. If there are multiple routes between the
ingress node ID0 and egress node ID1, EROs, or an alternate method,
e.g., static configuration, MUST be used to ensure that all LSPs
traverse the same route.
13.6. Methodologies
Generally, the methodology would proceed as follows:
o Set up the LSP to be deleted
o Select the times using the specified Poisson arrival process,
o Release the LSP as the methodology for the singleton LSP graceful
release delay, and obtain the value of LSP graceful release delay,
and
o Set up the LSP, and restart the Poisson arrival process, wait for
the next Poisson arrival event.
13.7. Metric Reporting
The metric results including both real and undefined values MUST be
reported together with the total number of values. The context under
which the sample is obtained, including the selected parameters, and
the route traversed by the LSPs MUST also be reported.
14. 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 of milliseconds or undefined. In the
following discussion, we only consider the finite values.
14.1. The Minimum of Metric
The minimum of the 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.
14.2. 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 included.
14.3. The Maximum of Metric
The maximum of the metric is the maximum of all the dT values in the
sample. In computing this, undefined values MUST NOT be included.
Note that this means that measurements that exceed the upper bound
are not reported in this statistic. This is an important
consideration when evaluating the maximum when the number of
undefined measurements is non-zero.
14.4. 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 the 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.
14.5. Failure Statistics of Metric
In the process of LSP setup/release, it may fail due to various
reasons. For example, setup/release may fail when the control plane
is overburdened or when there is resource shortage in one of the
intermediate nodes. Since the setup/release failure may have
significant impact on network operation, it is worthwhile to report
each failure cases, so that appropriate operations can be performed
to check the possible implementation, configuration or other
deficiencies.
Five types of failure events are defined in previous sections:
o Single Unidirectional LSP Setup Failure
o Multiple Unidirectional LSP Setup Failure
o Single Bidirectional LSP Setup Failure
o Multiple Bidirectional LSP Setup Failure
o LSP Graceful Release Failure
Given the samples of the performance metric, we now offer two
statistics of failure events of these samples to report.
14.5.1. Failure Count
Failure Count is defined as the number of the undefined value of the
corresponding performance metric (failure events) in a sample. The
value of Failure Count is an integer.
14.5.2. Failure Ratio
Failure Ratio is the percentage of the number of failure events to
the total number of requests in a sample. The calculation for
Failure Ratio is defined as follows:
X type failure ratio = Number of X type failure events/(Number of
valid X type metric values + Number of X type failure events) * 100%.
15. Discussion
It is worthwhile to point out that:
o The unidirectional/bidirectional LSP setup delay is one ingress-
egress round-trip time plus processing time. But in this
document, unidirectional/bidirectional LSP setup delay has not
taken the processing time in the end nodes (ingress and/or egress)
into account. The timestamp T2 is taken after the endpoint node
receives it. Actually, the last node has to take some time to
process local procedures. Similarly, in the LSP graceful release
delay, the memo has not considered the processing time in the end
node.
o This document assumes that the correct procedures for installing
the data plane are followed as described in [RFC3209], [RFC3471],
and [RFC3473]. That is, by the time the egress receives and
processes a Path message, it is safe for the egress to transmit
data on the reverse path, and by the time the ingress receives and
processes a Resv message it is safe for the ingress to transmit
data on the forward path. See [CCAMP-SWITCH] for detailed
explanations. This document does not include any verification
that the implementations of the control plane software are
conformant, although such tests MAY be constructed with the use of
suitable signal generation test equipment. In [CCAMP-DPM], we
defined a series of metrics to do such verifications. However, it
is RECOMMENDED that both the measurements defined in this document
and the measurements defined in [CCAMP-DPM] are performed to
complement each other.
o Note that, in implementing the tests described in this document, a
tester should be sure to measure the time taken for the control
plane messages including the processing of those messages by the
nodes under test.
o Bidirectional LSPs may be set up using three-way signaling, where
the initiating node will send a ResvConf message downstream upon
receiving the Resv message. The ResvConf message is used to
notify the terminate node that it can transfer data upstream.
Actually, both directions should be ready to transfer data when
the Resv message is received by the initiating node. Therefore,
the bidirectional LSP setup delay defined in this document does
not take the confirmation procedure into account.
16. Security Considerations
Samples of the metrics can be obtained in either active or passive
manners.
In active measurement, ingress nodes inject probing messages into 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.
When samples of the metrics are collected in a passive manner, e.g.,
by monitoring the operations on real-life LSPs, the implementation of
the monitoring and reporting mechanism must be careful so that they
will not be used to attack the control plane. A typical
implementation may use the Management Information Base (MIB) to
collect/store the metrics and access to the MIB is limited to the
Network Management Systems (NMSs). In this case, passive monitoring
will not incur other security issues than implementing the MIBs and
NMSs. If an implementation chooses to expose the performance data to
other applications, then it must take into account the possible
security issues it may face. For example, when exposing the
performance data through Simple Network Management Protocol (SNMP),
certain authentication methods should be used to ensure that the
entity maintaining the performance data are not subject to
unauthorized readings and modifications. Rate limiting on the
performance query may also be desirable to reduce the risk that the
entity maintaining the performance data are overwhelmed by too many
query requests. It is RECOMMENDED that implementers consider the
security features as provided by the SNMPv3 framework (see [RFC3410],
section 8), including full support for the SNMPv3 cryptographic
mechanisms (for authentication and privacy).
Additionally, the security considerations pertaining to the original
RSVP protocol [RFC2205] and its TE extensions [RFC3209] also remain
relevant.
17. Acknowledgments
We wish to thank Dan Li, Fang Liu (Christine), Zafar Ali, Monique
Morrow, Adrian Farrel, Deborah Brungard, Lou Berger, Thomas D. Nadeau
for their comments and help. Lou Berger and Adrian Farrel have made
text contributions to this document.
We wish to thank experts from IPPM and BMWG -- Reinhard Schrage, Al
Morton, and Henk Uijterwaal -- for reviewing this document. Reinhard
Schrage has made text contributions to this document.
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 National Natural Science Foundation of China (NSFC) and
863 program of China.
18. References
18.1. 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.
[RFC3471] Berger, L., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description",
RFC 3471, January 2003.
[RFC3473] Berger, L., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation
Protocol-Traffic Engineering (RSVP-TE) Extensions",
RFC 3473, January 2003.
[RFC3945] Mannie, E., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945,
October 2004.
[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.
18.2. Informative References
[CCAMP-DPM] Sun, W., Zhang, G., Gao, J., Xie, G., Papneja, R.,
Gu, B., Wei, X., Otani, T., and R. Jing, "Label
Switched Path (LSP) Data Path Delay Metric in
Generalized MPLS/ MPLS-TE Networks", Work
in Progress, December 2009.
[CCAMP-SWITCH] Shiomoto, K. and A. Farrel, "Advice on When It is
Safe to Start Sending Data on Label Switched Paths
Established Using RSVP-TE", Work in Progress,
October 2009.
[RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
"Framework for IP Performance Metrics", RFC 2330,
May 1998.
[RFC3410] Case, J., Mundy, R., Partain, D., and B. Stewart,
"Introduction and Applicability Statements for
Internet-Standard Management Framework", RFC 3410,
December 2002.
Appendix A. Authors' Addresses
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
Isocore
12359 Sunrise Valley Drive, STE 100
Reston, VA 20190
USA
Phone: +1 703 860 9273
EMail: rpapneja@isocore.com
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: otani@kddilabs.jp
Ruiquan Jing
China Telecom Beijing Research Institute
118 Xizhimenwai Avenue
Beijing 100035
China
Phone: +86-10-58552000
EMail: jingrq@ctbri.com.cn
Editors' Addresses
Weiqiang Sun (editor)
Shanghai Jiao Tong University
800 Dongchuan Road
Shanghai 200240
China
Phone: +86 21 3420 5359
EMail: sunwq@mit.edu
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@mail.ritt.com.cn