ccamp G. Xie
Internet-Draft W. Sun
Intended status: Standards Track Shanghai Jiao Tong University
Expires: August 26, 2007 G. Zhang
China Academy of Telecommunication
Research,MII.
J. Han
IXIA
X. Wei
Fiberhome
J. Gao
Huawei
February 22, 2007
Label Switched Path (LSP) Dynamical Provisioning Performance Metrics in
Generalized MPLS Networks
draft-xie-ccamp-lsp-dppm-00.txt
Status of this Memo
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Copyright (C) The IETF Trust (2007).
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Abstract
Generalized Multi-Protocol Label Switching (GMPLS) is one of the most
promising candidate technologies for the future data transmission
network. The GMPLS has been developed to control and cooperate
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. Dynamic provisioning ability of these
physically diverse devices differs from each other drastically. At
the same time, the need for dynamically provisioned connections is
increasing because optical networks are being deployed in metro area.
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 LSP provisioning performance in GMPLS networks,
specifically the dynamical LSP setup/release performance. These
metrics can depict the features of the GMPLS network in LSP dynamic
provisioning.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Conventions Used in This Document . . . . . . . . . . . . . . 6
3. Overview of Performance Metrics . . . . . . . . . . . . . . . 7
4. A Singleton Definition for Unidirectional LSP Setup Delay . . 8
4.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 8
4.3. Metric Parameters . . . . . . . . . . . . . . . . . . . . 8
4.4. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 9
4.5. Definition . . . . . . . . . . . . . . . . . . . . . . . . 9
4.6. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 9
4.7. Methodologies . . . . . . . . . . . . . . . . . . . . . . 10
5. A Definition for Samples of Unidirectional LSP Setup Delay . . 11
5.1. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 11
5.2. Metric Parameters . . . . . . . . . . . . . . . . . . . . 11
5.3. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 11
5.4. Definition . . . . . . . . . . . . . . . . . . . . . . . . 11
5.5. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 12
5.6. Methodologies . . . . . . . . . . . . . . . . . . . . . . 12
6. A Singleton Definition for 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
7. A Definition for Samples of Bidirectional LSP Setup Delay . . 17
7.1. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 17
7.2. Metric Parameters . . . . . . . . . . . . . . . . . . . . 17
7.3. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 17
7.4. Definition . . . . . . . . . . . . . . . . . . . . . . . . 17
7.5. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 18
7.6. Methodologies . . . . . . . . . . . . . . . . . . . . . . 18
8. A Singleton Definition for LSP Graceful Release Delay . . . . 19
8.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 19
8.2. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 19
8.3. Metric Parameters . . . . . . . . . . . . . . . . . . . . 19
8.4. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 19
8.5. Definition . . . . . . . . . . . . . . . . . . . . . . . . 19
8.6. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 20
8.7. Methodologies . . . . . . . . . . . . . . . . . . . . . . 21
9. A Definition for Samples of LSP Graceful Release Delay . . . . 23
9.1. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 23
9.2. Metric Parameters . . . . . . . . . . . . . . . . . . . . 23
9.3. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 23
9.4. Definition . . . . . . . . . . . . . . . . . . . . . . . . 23
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9.5. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 24
9.6. Methodologies . . . . . . . . . . . . . . . . . . . . . . 24
10. Some Statistics Definitions for Metrics to Report . . . . . . 25
10.1. The Minimum of Metric . . . . . . . . . . . . . . . . . . 25
10.2. The Median of Metric . . . . . . . . . . . . . . . . . . . 25
10.3. The percentile of Metric . . . . . . . . . . . . . . . . . 25
10.4. The failure probability . . . . . . . . . . . . . . . . . 25
11. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 26
12. Security Considerations . . . . . . . . . . . . . . . . . . . 27
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 28
14. Normative References . . . . . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30
Intellectual Property and Copyright Statements . . . . . . . . . . 32
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1. Introduction
Generalized Multi-Protocol Label Switching (GMPLS) is one of the most
promising candidate technologies for the future data transmission
network. The GMPLS has been developed to control and cooperate
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. Dynamic provisioning ability of these
physically diverse devices differs from each other drastically.
As more and more applications are seeking to use GMPLS 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 draft intends to define
performance metrics that can be used to depict the dynamic LSP
provisioning performance of GMPLS networks.
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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, to depict the dynamic LSP provisioning performance of a
GMPLS network, we define 3 performance metrics: unidirectional LSP
setup delay, bidirectional LSP setup delay, and LSP graceful release
delay. The latency of the LSP setup/release signal is similar to the
Round-trip Delay in IP networks. So we refer 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.
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4. A Singleton Definition for Unidirectional LSP Setup Delay
This part defines a metric for unidirectional Label Switched Path
setup delay across a GMPLS network.
4.1. Motivation
Unidirectional Label Switched Path setup delay is useful for several
reasons:
o LSP setup delay is an important metric that depicts 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.
o The minimum value of this metric provides an indication of the
delay that will likely be experienced when the LSP traversed 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 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 different impact on to applications.
Erratic variation in LSP setup delay makes it difficult to support
applications that has stringent setup delay requirement.
The measurement of unidirectional LSP setup delay instead of
bidirectional LSP setup delay is motivated by the following factors:
o Some applications may only use unidirectional LSPs rather than
bidirectional ones. For example, content delivery services in
multicast method (IPTV) only use unidirectional LSPs.
4.2. Metric Name
Unidirectional LSP setup delay
4.3. Metric Parameters
o ID0, the ingress LSR ID
o ID1, the egress LSR ID
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o T, a time
4.4. Metric Units
The value of unidirectional LSP setup delay is either a real number,
or an undefined (informally, infinite) number of seconds.
4.5. Definition
The unidirectional LSP setup delay from the ingress node to the
egress node [RFC3945] at T is dT means that ingress node sent the
first bit of a PATH message packet to egress node at wire-time T, and
that the ingress node received the last bit of responding RESV
message packet from egress node at wire-time T+dT in the
unidirectional LSP setup case.
The unidirectional LSP setup delay from the ingress node to the
egress node at T is undefined (informally, infinite), means that
ingress node sent the first bit of PATH message packet to egress node
at wire-time T and that ingress node did not receive the
corresponding RESV message within a reasonable period of time.
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 could be used. But the GMPLS network
accommodates many kinds of devices. For example, some photonic
cross-connects (PXCs) have to move the micro mirrors. This
physical motion may take several milliseconds. But the common
electronic switches finish the nodal process within several
microseconds. So the unidirectional LSP setup delay varies
drastically from a network to another. In practice, the upper
bound should be chose carefully.
o If ingress node sent out the PATH message to set up LSP, but never
receive corresponding RESV message, unidirectional LSP setup delay
is deemed to be infinite.
o If ingress node sent out the PATH message to set up LSP but
receive PathErr message, unidirectional LSP setup delay is also
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deemed to be infinite. There are many possible reasons for this
case. For example, the PATH message has invalid parameters or the
network has not enough resource 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 resource 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 in 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
the 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 (informally, infinite). Note that the
'reasonable' threshold of is a parameter of the methodology.
o If the corresponding response message is PathErr, the
unidirectional LSP setup delay is deemed to be undefined
(informally, infinite).
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5. A Definition for Samples of Unidirectional LSP Setup Delay
In the previous part, we define the singleton metric of
unidirectional LSP setup delay. Now we define how to get one
particular sample of unidirectional LSP setup delay. Sampling is to
select a particular potion of singleton values of the given
parameters. Like the [RFC2330], we use Poisson sampling as an
example.
5.1. Metric Name
Unidirectional LSP setup delay sample
5.2. 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 seconds
o Td, the 'reasonable' threshold
5.3. Metric Units
A sequence of pairs; the elements of each pair are:
o T, a time, and
o dT, either a real number or an undefined number of seconds.
The values of T in the sequence are monotonically increasing. Note
that T would be a valid parameter to unidirectional LSP setup delay
sample, and that dT would be a valid value of unidirectional LSP
setup delay.
5.4. Definition
Given T0, Tf, and lambda, we 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 at this time. The value of the sample is the sequence
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made up of the resulting <time, unidirectional LSP setup delay>
pairs. If there are no such pairs, the sequence is of length zero
and the sample is said to be empty.
5.5. Discussion
The parameter lambda should be carefully chosen. If the rate is too
large, too frequent LSP setup/release procedure results 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 could not completely reflect the
dynamic provisioning performance of the GMPLS network. The
appropriate lambda value depends on the given network.
5.6. 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 as the methodology for the singleton unidirectional
LSP setup delay, and obtain the value of unidirectional LSP setup
delay
o Release the LSP, and wait for the next Poisson arrival process
Note that: it is possible that before the previous LSP release
procedure completes, the next Poisson arrival process has arrived and
the LSP setup procedure has been initiated. If there is resource
contention between the two LSPs, the LSP setup may fail.
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6. A Singleton Definition for Bidirectional LSP Setup Delay
Bidirectional optical LSPs (or lightpaths) are seen as a requirement
for most optical networking service. GMPLS allows establishment of
bi-directional symmetric LSPs (not of asymmetric LSPs). A symmetric
bidirectional LSP has the same traffic engineering requirements
including fate sharing, protection and restoration, LSRs, and
resource requirements (e.g., delay and delay variance) in either
direction.
Compared with the approach of establishing a bidirectional LSP using
two unidirectional LSP, the bidirectional LSP has the following
advantages:
o Reduces the setup delay to one ingress-egress round trip time plus
processing time in the nodes en-route;
o Reduces the signal overhead in the control plane;
o Allows suggesting a label by an upstream node to reduce the setup
delay.
This part defines a metric for bidirectional LSP setup delay across a
GMPLS network.
6.1. Motivation
Bidirectional Label Switched Path setup delay is useful for several
reasons:
o LSP setup delay is an important metric that depicts 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
applications scheduling.
o The minimum value of this metric provides an indication of the
delay that will likely be experienced when the LSP traversed 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 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.
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o LSP setup delay variance has different impact on to applications.
Erratic variation in LSP setup delay makes it difficult to support
applications that has stringent setup delay requirement.
The measurement of 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
network while the LSPs are unidirectional in nature in the MPLS
network. For most applications, the communication is
bidirectional. So bidirectional LSP delay is necessary and more
reasonable than unidirectional LSP delay.
6.2. Metric Name
Bidirectional LSP setup delay
6.3. Metric Parameters
o ID0, the ingress LSR ID
o ID1, the egress LSR ID
o T, a time
6.4. Metric Units
The value of bidirectional LSP setup delay is either a real number,
or an undefined (informally, infinite) number of seconds.
6.5. Definition
For a real number dT, the bidirectional LSP setup delay from ingress
node to egress node at T is dT, means that ingress node sent out the
first bit of a PATH message including an Upstream Label [RFC3473]
heading for egress node at wire-time T, egress node received that
packet, then immediately sent a RESV message packet back to ingress
node, and that ingress node received the last bit of that packet at
wire-time T+dT.
The bidirectional LSP setup delay from ingress node to egress node at
T is undefined (informally, infinite), means that ingress node sent
the first bit of PATH message to egress node at wire-time T and that
(either egress node did not receive the packet, egress node did not
send corresponding RESV message packet in response, or) ingress node
did not receive that response packet.
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6.6. Discussion
The following issues are likely to come up in practice:
o The accuracy of 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 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 could be used. But the GMPLS network
accommodates many kinds of devices. For example, some photonic
cross-connects (PXCs) have to move the micro mirrors. This
physical motion may take several milliseconds. But the common
electronic switches finish the nodal process within several
microseconds. So the bidirectional LSP setup delay varies
drastically from a 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 will also
increase obviously. Thus, in practice, the upper bound should be
chosen carefully.
o If the ingress node sent out the PATH message to set up the LSP,
but never receive the corresponding RESV message, bidirectional
LSP setup delay is deemed to be infinite.
o If the ingress node sent out the PATH message to set up the LSP,
but receive PathErr message, bidirectional LSP setup delay is also
deemed to be infinite. There are many possible reasons for this
case. For example, the PATH message has invalid parameters or the
network has not enough resource to set up the requested LSP.
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 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 in 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
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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 bidirectional LSP setup delay is
deemed to be undefined (informally, infinite). Note that the
'reasonable' threshold is a parameter of the methodology.
o If the corresponding response message is PathErr, the
bidirectional LSP setup delay is deemed to be undefined
(informally, infinite).
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7. A Definition for Samples of Bidirectional LSP Setup Delay
In the previous part, we define the singleton metric of bidirectional
LSP setup delay. Now we define how to get one particular sample of
bidirectional LSP setup delay. We also use Poisson sampling as an
example.
7.1. Metric Name
Bidirectional LSP setup delay sample
7.2. 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 seconds
o Td, the 'reasonable' threshold
7.3. Metric Units
A sequence of pairs; the elements of each pair are:
o T, a time, and
o dT, either a real number or an undefined number of seconds.
The values of T in the sequence are monotonical increasing. Note
that T would be a valid parameter to bidirectional LSP setup delay
sample, and that dT would be a valid value of bidirectional LSP setup
delay.
7.4. Definition
Given T0, Tf, and lambda, we 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 at this time. The value of the sample is the sequence
made up of the resulting <time, bidirectional LSP setup delay> pairs.
If there are no such pairs, the sequence is of length zero and the
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sample is said to be empty.
7.5. Discussion
The parameter lambda should be carefully chosen. If the rate is too
large, too frequent LSP setup/release procedure results in high load
in the control plane, which will in turn increase unidirectional LSP
setup delay. On the other hand if the rate is too small, the sample
could not completely reflect the dynamic provisioning performance of
the GMPLS network. The appropriate lambda value depends on the given
network.
7.6. Methodologies
Generally the methodology would proceed as follows:
o Setup the LSP to be deleted
o The selection of specific times, using the specified Poisson
arrival process, and
o Release the LSP as the methodology for the singleton LSP graceful
release delay, and obtain the value of LSP graceful release delay
o Setup the LSP, and restart the Poisson arrival process, wait for
the next Poisson arrival process
Note that: it is possible that before the previous LSP release
procedure completes, the next Poisson arrival process has arrived and
the LSP setup procedure has been initiated. If there is resource
contention between these two LSPs, the LSP setup may fail.
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8. A Singleton Definition for LSP Graceful Release Delay
There are two different kinds of LSP release mechanisms in the GMPLS
network: graceful release and forceful release. As a matter of fact,
the forceful release employs PathErr message to tear down the LSP.
Memo in current version has not taken 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 tear down time can not be ignored
o The LSP graceful release procedure is more reasonable for GMPLS
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
8.4. Metric Units
The value of LSP graceful release delay is either a real number, or
an undefined (informally, infinite) number of seconds.
8.5. Definition
There are two different LSP graceful release procedures, one is
initiated by the ingress node, and another is initiated by egress
node. The two procedures are depicted in the [RFC3473]. We define
the graceful LSP release delay for these two procedures separately.
For a real number dT, the LSP graceful release delay from ingress
node to egress node at T is dT, means that ingress node sent the
first bit of a PATH message including Admin Status Object with
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setting the Reflect (R) and Delete (D) bits to egress node at wire-
time T, that egress node received that packet, then immediately sent
a RESV message including Admin Status Object with the Delete (D) bit
set back to ingress node. The ingress node sends out PathTear
downstream to remove the LSP, and egress node received the last bit
of PathTear packet at wire-time T+dT.
The LSP graceful release delay from ingress node to egress node at T
is undefined (informally, infinite), means that ingress node sent the
first bit of PATH message to egress node at wire-time T and that
(either egress node did not receive the PATH packet, egress node did
not send corresponding RESV message packet in response, ingress node
did not receive that RESV packet, or) the egress did not receive the
PathTear.
The LSP graceful release delay from egress node to ingress node at T
is dT, means that egress node sent the first bit of a RESV message
including Admin Status Object with setting the Reflect (R) and Delete
(D) bits to ingress node at wire-time T, that ingress node received
the packet, then immediately sent a PathTear message downstream to
egress node. The ingress node sends out PathTear downstream to
remove the LSP, and egress node received the last bit of PathTear
packet at wire-time T+dT.
The LSP graceful release delay from egress node to ingress node at T
is undefined (informally, infinite), means that egress node sent the
first bit of RESV message including Admin Status Object with setting
the Reflect (R) and Delete (D) bits to ingress node at wire-time T
and that (either ingress node did not receive the RESV packet,
ingress node did not send PathTear message packet in response or) the
egress did not receive the PathTear.
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 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 could be used. But the upper bound should be
chosen carefully in practice;
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o In the first circumstance, if ingress node sent out PATH message
including Admin Status Object with the Reflect (R) and Delete (D)
bits set to initiate LSP graceful release, but never receive
corresponding RESV message, LSP graceful release delay is deemed
to be infinite. In the second circumstance, if egress node sent
out RESV message including Admin Status Object with the Reflect
(R) and Delete (D) bits set to initiate LSP graceful release, but
never receive corresponding PathTear message, LSP graceful release
delay is deemed to be infinite;
o It is possible that some node(s) along an LSP will not support the
Admin Status Object. In the case of a non-supporting intermediate
node(s), the object will pass through the node(s) unmodified and
normal processing can continue. In the case of a non-supporting
ingress/egress node, the Admin Status Object will not be reflected
back in the RESV Message. To support the case of a non-supporting
ingress/egress node, the ingress (egress in the second
circumstance) SHOULD only wait a configurable period of time for
the updated Admin Status Object in a RESV message. Once the
period of time has elapsed, the ingress (egress in the second
circumstance) node sends out a PathTear message to delete LSP.
8.7. Methodologies
In the first circumstance, the methodology would proceed as follows:
o Make sure the LSP to be deleted is set up;
o At the egress node, form the RESV message including Admin Status
Object with the Reflect (R) and Delete (D) bits set. A timestamp
(T1) may be stored locally in the egress node when the PATH
message packet is sent towards the ingress node;
o Intermediate nodes process the Admin Status Object as described in
[RFC2330], and forward the PATH message to 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 When the egress node receive the Admin Status Object with the
Delete (D) bit set in the RESV message, the ingress node sends a
PathTear message to remove the LSP;
o When the egress node receives the PathTear message, take a
timestamp (T2) as soon as possible. The LSP graceful release
delay (T2-T1) is this timestamp minus the initial one.
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In the second circumstance, the methodology would proceed as follows:
o Make sure the LSP to be deleted is set up;
o At the initiator node (egress node in this case), form the RESV
message including Admin Status Object with the Reflect (R) and
Delete (D) bits set. A timestamp may be stored locally in the
initiator node when the PATH message packet is sent towards the
terminator node;
o Intermediate nodes process the Admin Status Object as described in
[RFC2330], and forward the PATH message to the terminator node;
o Upon receiving the Admin Status Object with the Reflect (R) and
Delete (D) bits set in the RESV message, the terminator node sends
a PathTear message downstream to remove the LSP;
o When the initiator node receives the PathTear message, take a
timestamp as soon as possible. The LSP graceful release delay is
this timestamp minus the initial one.
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9. A Definition for Samples of LSP Graceful Release Delay
In the previous part, we define 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.
9.1. Metric Name
LSP graceful release 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 reciprocal seconds
o Td, the 'reasonable' threshold
9.3. Metric Units
A sequence of pairs; the elements of each pair are:
o T, a time, and
o dT, either a real number or an undefined number of seconds.
The values of T in the sequence are monotonical increasing. Note
that T would be a valid parameter to LSP graceful release delay
sample and that dT would be a valid value of LSP graceful release
delay.
9.4. Definition
Given T0, Tf, and lambda, we 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 LSP graceful release delay
sample at this time. The value of the sample is the sequence made up
of the resulting <time, LSP graceful release delay> pairs. If there
are no such pairs, the sequence is of length zero and the sample is
said to be empty.
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9.5. Discussion
The parameter lambda should be carefully chosen. If the rate is too
large, too frequent LSP setup/release procedure results 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 could not completely reflect the
dynamic provisioning performance of the GMPLS network. The
appropriate lambda value depends on the given network.
9.6. Methodologies
Generally the methodology would proceed as follows:
o Setup the LSP to be deleted
o The selection of specific times, using the specified Poisson
arrival process, and
o Release the LSP as the methodology for the singleton LSP graceful
release delay, and obtain the value of LSP graceful release delay
o Setup the LSP, and restart the Poisson arrival process, wait for
the next Poisson arrival process
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10. 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 (informally,
infinite) number of seconds. In the following discussion, we only
consider the finite values.
10.1. The Minimum of Metric
The minimum of metric is the minimum of all the dT values in the
sample. In computing this, undefined values are treated as
infinitely large. Note that this means that the minimum could thus
be undefined (informally, infinite) if all the dT values are
undefined. In addition, the metric minimum is undefined if the
sample is empty.
10.2. The Median of Metric
Metric median is the median of the dT values in the given sample. In
computing the median, the undefined values are not counted in.
10.3. The percentile of Metric
Given a metric and a percent X between 0% and 100%, the Xth
percentile of all the dT values in the sample. In addition, the
unidirectional LSP setup delay percentile is undefined if the sample
is empty.
Example: suppose we take a sample and the results are: Stream1 = <
<T1, 100 msec>, <T2, 110 msec>, <T3, undefined>, <T4, 90 msec>, <T5,
500 msec> >
Then the 50th percentile would be 110 msec, since 90 msec and 100
msec are smaller, and 110 and 500 msec are larger (undefined values
are not counted in).
10.4. The failure probability
In the process of LSP setup/release, it may fail for some reason.
The failure probability is the ratio of the failure times to the
total times.
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11. 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 the draft,
unidirectional/bidirectional LSP setup delay has not taken the
processing time in the end nodes (ingress or/and 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 procedure. Similarly, in the LSP graceful release
delay, the memo has not considered the processing time in the
endpoint node.
o All these metrics are defined from the point of control plane's
view. In fact, the control plane and data plane are not always
synchronized. In some cases, the LSPs have been set up in the
control plane. But the data can not be forwarded immediately.
The unidirectional/bidirectional LSP setup delay in the data plane
is longer than in the control plane.
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12. Security Considerations
The security considerations pertaining to the original RSVP protocol
[RFC2205] and its TE extensions [RFC3209] remain relevant.
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13. Acknowledgements
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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14. 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.
[RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
"Framework for IP Performance Metrics", RFC 2330,
May 1998.
[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.
[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.
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Authors' Addresses
Guowu Xie
Shanghai Jiao Tong University
800 Dongchuan Road
Shanghai 200240
CN
Phone: +86 21 3420 4596
Email: blithe@sjtu.edu.cn
Weiqiang Sun
Shanghai Jiao Tong University
800 Dongchuan Road
Shanghai 200240
CN
Phone: +86 21 3420 5359
Email: sunwq@sjtu.edu.cn
Guoying Zhang
China Academy of Telecommunication Research,MII.
Beijing 200240
CN
Phone: +86 1068094272
Email: zhangguoying@mail.ritt.com.cn
Jianghui Han
IXIA
Oriental Kenzo Plaza 8M,48 Dongzhimen Wai Street,Dongcheng District
Beijing 200240
CN
Phone: +86 13801156004
Email: JHan@ixiacom.com
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Xueqing Wei
Fiberhome Telecommunicaiton Technology Co.,Ltd.
Wuhan
CN
Phone: +86 13871127882
Email: xqwei@fiberhome.com.cn
Jianhua Gao
Huawei Technologies Co., LTD.
CN
Phone: +86 755 28973237
Email: gjhhit@huawei.com
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