draft-ietf-ccamp-gmpls-recovery-terminology-06.txt   rfc4427.txt 
CCAMP Working Group CCAMP GMPLS P&R Design Team Network Working Group E. Mannie, Ed.
Internet Draft Request for Comments: 4427 Perceval
Category: Informational Eric Mannie (Editor) Category: Informational D. Papadimitriou, Ed.
Expiration Date: October 2005 Dimitri Papadimitriou (Editor) Alcatel
March 2006
April 2005
Recovery (Protection and Restoration) Terminology Recovery (Protection and Restoration) Terminology
for Generalized Multi-Protocol Label Switching (GMPLS) for Generalized Multi-Protocol Label Switching (GMPLS)
draft-ietf-ccamp-gmpls-recovery-terminology-06.txt Status of This Memo
Status of this Memo
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). All Rights Reserved. Copyright (C) The Internet Society (2006).
Abstract Abstract
This document defines a common terminology for Generalized Multi- This document defines a common terminology for Generalized Multi-
Protocol Label Switching (GMPLS) based recovery mechanisms (i.e. Protocol Label Switching (GMPLS)-based recovery mechanisms (i.e.,
protection and restoration). The terminology is independent of the protection and restoration). The terminology is independent of the
underlying transport technologies covered by GMPLS. underlying transport technologies covered by GMPLS.
E.Mannie, D.Papadimitriou et al. - Informational 1
Table of Contents Table of Contents
Status of this Memo .............................................. 1 1. Introduction ....................................................3
Abstract ......................................................... 1 2. Contributors ....................................................4
Table of Contents ................................................ 2 3. Conventions Used in this Document ...............................5
1. Contributors .................................................. 3 4. Recovery Terminology Common to Protection and Restoration .......5
2. Introduction .................................................. 3 4.1. Working and Recovery LSP/Span ..............................6
3. Conventions used in this document ............................. 4 4.2. Traffic Types ..............................................6
4. Recovery Terminology Common to Protection and Restoration ..... 4 4.3. LSP/Span Protection and Restoration ........................6
4.1 Working and Recovery LSP/Span ................................ 5 4.4. Recovery Scope .............................................7
4.2 Traffic Types ................................................ 5 4.5. Recovery Domain ............................................8
4.3 LSP/Span Protection and Restoration .......................... 6 4.6. Recovery Types .............................................8
4.4 Recovery Scope ............................................... 7 4.7. Bridge Types ..............................................10
4.5 Recovery Domain .............................................. 7 4.8. Selector Types ............................................10
4.6 Recovery Types ............................................... 7 4.9. Recovery GMPLS Nodes ......................................11
4.7 Bridge Types ................................................. 9 4.10. Switch-over Mechanism ....................................11
4.8 Selector Types ............................................... 9 4.11. Reversion operations .....................................11
4.9 Recovery GMPLS Nodes ........................................ 10 4.12. Failure Reporting ........................................12
4.10 Switch-over Mechanism ...................................... 10 4.13. External commands ........................................12
4.11 Reversion operations ....................................... 10 4.14. Unidirectional versus Bi-Directional Recovery Switching ..13
4.12 Failure Reporting .......................................... 11 4.15. Full versus Partial Span Recovery Switching ..............14
4.13 External commands .......................................... 11 4.16. Recovery Schemes Related Time and Durations ..............14
4.14 Unidirectional versus Bi-Directional Recovery Switching .... 12 4.17. Impairment ...............................................15
4.15 Full versus Partial Span Recovery Switching ................ 12 4.18. Recovery Ratio ...........................................15
4.16 Recovery Schemes Related Time and Durations ................ 13 4.19. Hitless Protection Switch-over ...........................15
4.17 Impairment ................................................. 14 4.20. Network Survivability ....................................15
4.18 Recovery Ratio ............................................. 14 4.21. Survivable Network .......................................16
4.19 Hitless Protection Switch-over ............................. 14 4.22. Escalation ...............................................16
4.20 Network Survivability ...................................... 14 5. Recovery Phases ................................................16
4.21 Survivable Network ......................................... 14 5.1. Entities Involved During Recovery .........................17
4.22 Escalation ................................................. 14 6. Protection Schemes .............................................17
5. Recovery Phases .............................................. 14 6.1. 1+1 Protection ............................................18
5.1 Entities Involved During Recovery ........................... 15 6.2. 1:N (N >= 1) Protection ...................................18
6. Protection Schemes ........................................... 16 6.3. M:N (M, N > 1, N >= M) Protection .........................18
6.1 1+1 Protection .............................................. 16 6.4. Notes on Protection Schemes ...............................19
6.2 1:N (N >= 1) Protection ..................................... 16 7. Restoration Schemes ............................................19
6.3 M:N (M, N > 1, N >= M) Protection ........................... 16 7.1. Pre-Planned LSP Restoration ...............................19
6.4 Notes on Protection Schemes ................................. 17 7.1.1. Shared-Mesh Restoration ............................19
7. Restoration Schemes .......................................... 17 7.2. LSP Restoration ...........................................20
7.1 Pre-planned LSP Restoration ................................. 17 7.2.1. Hard LSP Restoration ...............................20
7.1.1 Shared-Mesh Restoration ................................... 18 7.2.2. Soft LSP Restoration ...............................20
7.2 LSP Restoration ............................................. 18 8. Security Considerations ........................................20
7.2.1 Hard LSP Restoration ...................................... 18 9. References .....................................................20
7.2.2 Soft LSP Restoration ...................................... 18 9.1. Normative References ......................................20
8. Security Considerations ...................................... 18 9.2. Informative References ....................................20
9. IANA Considerations .......................................... 18 10. Acknowledgements ..............................................21
10. References .................................................. 18
10.1 Normative References ....................................... 18
10.2 Informative References ..................................... 19
11. Acknowledgments ............................................. 20
12. Editor's Address ............................................ 20
Intellectual Property Statement ................................. 21
E.Mannie, D.Papadimitriou et al.- Expires October 2005 2
Disclaimer of Validity .......................................... 21
Copyright Statement ............................................. 21
1. Contributors
This document is the result of the CCAMP Working Group Protection
and Restoration design team joint effort. The following are the
authors that contributed to the present document:
Deborah Brungard (AT&T)
Rm. D1-3C22 - 200 S. Laurel Ave.
Middletown, NJ 07748, USA
EMail: dbrungard@att.com
Sudheer Dharanikota
EMail: sudheer@ieee.org
Jonathan P. Lang (Sonos)
506 Chapala Street
Santa Barbara, CA 93101, USA
EMail: jplang@ieee.org
Guangzhi Li (AT&T)
180 Park Avenue,
Florham Park, NJ 07932, USA
EMail: gli@research.att.com
Eric Mannie
EMail: eric_mannie@hotmail.com
Dimitri Papadimitriou (Alcatel)
Francis Wellesplein, 1
B-2018 Antwerpen, Belgium
EMail: dimitri.papadimitriou@alcatel.be
Bala Rajagopalan (Intel Broadband Wireless Division)
2111 NE 25th Ave.
Hillsboro, OR 97124, USA
EMail: bala.rajagopalan@intel.com
Yakov Rekhter (Juniper)
1194 N. Mathilda Avenue
Sunnyvale, CA 94089, USA
EMail: yakov@juniper.net
2. Introduction 1. Introduction
This document defines a common terminology for Generalized Multi- This document defines a common terminology for Generalized Multi-
Protocol Label Switching (GMPLS) based recovery mechanisms (i.e. Protocol Label Switching (GMPLS)-based recovery mechanisms (i.e.,
protection and restoration). protection and restoration).
E.Mannie, D.Papadimitriou et al.- Expires October 2005 3
The terminology proposed in this document is independent of the The terminology proposed in this document is independent of the
underlying transport technologies and borrows from the G.808.1 ITU-T underlying transport technologies and borrows from the G.808.1 ITU-T
Recommendation [G.808.1] and from the G.841 ITU-T Recommendation Recommendation [G.808.1] and from the G.841 ITU-T Recommendation
[G.841]. The restoration terminology and concepts have been gathered [G.841]. The restoration terminology and concepts have been gathered
from numerous sources including IETF drafts. from numerous sources including IETF documents.
In the context of this document, the term "recovery" denotes both In the context of this document, the term "recovery" denotes both
protection and restoration. The specific terms "protection" and protection and restoration. The specific terms "protection" and
"restoration" will only be used when differentiation is required. "restoration" will only be used when differentiation is required.
This document focuses on the terminology for the recovery of Label This document focuses on the terminology for the recovery of Label
Switched Paths (LSPs) controlled by a GMPLS control plane. The Switched Paths (LSPs) controlled by a GMPLS control plane. The
proposed terminology applies to end-to-end, segment, and span (i.e. proposed terminology applies to end-to-end, segment, and span (i.e.,
link) recovery. Note that the terminology for recovery of the link) recovery. Note that the terminology for recovery of the
control plane itself is not in the scope of this document. control plane itself is not in the scope of this document.
Protection and restoration of switched LSPs under tight time Protection and restoration of switched LSPs under tight time
constraints is a challenging problem. This is particularly relevant constraints is a challenging problem. This is particularly relevant
to optical networks that consist of Time Division Multiplex (TDM) to optical networks that consist of Time Division Multiplex (TDM)
and/or all-optical (photonic) cross-connects referred to as GMPLS and/or all-optical (photonic) cross-connects referred to as GMPLS
nodes (or simply nodes, or even sometimes "Label Switching Routers, nodes (or simply nodes, or even sometimes "Label Switching Routers,
or LSRs") connected in a general topology [RFC3945]. or LSRs") connected in a general topology [RFC3945].
Recovery typically involves the activation of a recovery (or Recovery typically involves the activation of a recovery (or
alternate) LSP when a failure is encountered in the working LSP. alternate) LSP when a failure is encountered in the working LSP.
A working or recovery LSP is characterized by an ingress interface, A working or recovery LSP is characterized by an ingress interface,
an egress interface, and a set of intermediate nodes and spans an egress interface, and a set of intermediate nodes and spans
through which the LSP is routed. The working and recovery LSPs are through which the LSP is routed. The working and recovery LSPs are
typically resource disjoint (e.g. node and/or span disjoint). This typically resource disjoint (e.g., node and/or span disjoint). This
ensures that a single failure will not affect both the working and ensures that a single failure will not affect both the working and
recovery LSPs. recovery LSPs.
A bi-directional span between neighboring nodes is usually realized A bi-directional span between neighboring nodes is usually realized
as a pair of unidirectional spans. The end-to-end path for a bi- as a pair of unidirectional spans. Therefore, the end-to-end path
directional LSP therefore consists of a series of bi-directional for a bi-directional LSP consists of a series of bi-directional
segments (i.e. Sub-Network Connections, or SNCs, in the ITU-T segments (i.e., Sub-Network Connections, or SNCs, in the ITU-T
terminology) between the source and destination nodes, traversing terminology) between the source and destination nodes, traversing
intermediate nodes. intermediate nodes.
3. Conventions used in this document: 2. Contributors
This document is the result of a joint effort by the CCAMP Working
Group Protection and Restoration design team. The following are the
authors that contributed to the present document:
Deborah Brungard (AT&T)
Rm. D1-3C22 - 200 S. Laurel Ave.
Middletown, NJ 07748, USA
EMail: dbrungard@att.com
Sudheer Dharanikota
EMail: sudheer@ieee.org
Jonathan P. Lang (Sonos)
506 Chapala Street
Santa Barbara, CA 93101, USA
EMail: jplang@ieee.org
Guangzhi Li (AT&T)
180 Park Avenue,
Florham Park, NJ 07932, USA
EMail: gli@research.att.com
Eric Mannie
Perceval
Rue Tenbosch, 9
1000 Brussels
Belgium
Phone: +32-2-6409194
EMail: eric.mannie@perceval.net
Dimitri Papadimitriou (Alcatel)
Francis Wellesplein, 1
B-2018 Antwerpen, Belgium
EMail: dimitri.papadimitriou@alcatel.be
Bala Rajagopalan
Microsoft India Development Center
Hyderabad, India
EMail: balar@microsoft.com
Yakov Rekhter (Juniper)
1194 N. Mathilda Avenue
Sunnyvale, CA 94089, USA
EMail: yakov@juniper.net
3. Conventions Used in this Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
this document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
4. Recovery Terminology Common to Protection and Restoration 4. Recovery Terminology Common to Protection and Restoration
This section defines the following general terms common to both This section defines the following general terms common to both
protection and restoration (i.e. recovery). In addition, most of protection and restoration (i.e., recovery). In addition, most of
these terms apply to end-to-end, segment and span LSP recovery. Note these terms apply to end-to-end, segment, and span LSP recovery.
Note that span recovery does not protect the nodes at each end of the
E.Mannie, D.Papadimitriou et al.- Expires October 2005 4
that span recovery does not protect the nodes at each end of the
span, otherwise end-to-end or segment LSP recovery should be used. span, otherwise end-to-end or segment LSP recovery should be used.
The terminology and the definitions have been originally taken from The terminology and the definitions were originally taken from
[G.808.1]. However, for generalization, the following language that [G.808.1]. However, for generalization, the following language,
is not directly related to recovery has been adapted to GMPLS and which is not directly related to recovery, has been adapted to GMPLS
the common IETF terminology: and the common IETF terminology:
An LSP is used as a generic term to designate either an SNC (Sub- An LSP is used as a generic term to designate either an SNC (Sub-
Network Connection) or an NC (Network Connection) in ITU-T Network Connection) or an NC (Network Connection) in ITU-T
terminology. The ITU-T uses the term transport entity to designate terminology. The ITU-T uses the term transport entity to designate
either a link, an SNC or an NC. The term "Traffic" is used instead either a link, an SNC, or an NC. The term "Traffic" is used instead
of "Traffic Signal". The term protection or restoration "scheme" is of "Traffic Signal". The term protection or restoration "scheme" is
used instead of protection or restoration "architecture". used instead of protection or restoration "architecture".
The reader is invited to read [G.841] and [G.808.1] for references The reader is invited to read [G.841] and [G.808.1] for references to
to SDH protection and Generic Protection Switching terminology, SDH protection and Generic Protection Switching terminology,
respectively. Note that restoration is not in the scope of respectively. Note that restoration is not in the scope of
[G.808.1]. [G.808.1].
4.1 Working and Recovery LSP/Span 4.1. Working and Recovery LSP/Span
A working LSP/span is an LSP/span transporting "normal" user A working LSP/span is an LSP/span transporting "normal" user traffic.
traffic. A recovery LSP/span is an LSP/span used to transport A recovery LSP/span is an LSP/span used to transport "normal" user
"normal" user traffic when the working LSP/span fails. Additionally, traffic when the working LSP/span fails. Additionally, the recovery
the recovery LSP/span may transport "extra" user traffic (i.e. pre- LSP/span may transport "extra" user traffic (i.e., pre-emptable
emptable traffic) when normal traffic is carried over the working traffic) when normal traffic is carried over the working LSP/span.
LSP/span.
4.2 Traffic Types 4.2. Traffic Types
The different types of traffic that can be transported over an The different types of traffic that can be transported over an
LSP/span in the context of this document are defined hereafter: LSP/span, in the context of this document, are defined hereafter:
A. Normal traffic: A. Normal traffic:
User traffic that may be protected by two alternative LSPs/spans User traffic that may be protected by two alternative LSPs/spans (the
(the working and recovery LSPs/spans). working and recovery LSPs/spans).
B. Extra traffic: B. Extra traffic:
User traffic carried over recovery resources (e.g. a recovery User traffic carried over recovery resources (e.g., a recovery
LSP/span) when these resources are not being used for the recovery LSP/span) when these resources are not being used for the recovery of
of normal traffic; i.e. when the recovery resources are in standby normal traffic (i.e., when the recovery resources are in standby
mode. When the recovery resources are required to recover normal mode). When the recovery resources are required to recover normal
traffic from the failed working LSP/span, the extra traffic is pre- traffic from the failed working LSP/span, the extra traffic is pre-
empted. Extra traffic is not protected by definition, but may be empted. Extra traffic is not protected by definition, but may be
restored. Moreover, extra traffic does not need to commence or be restored. Moreover, extra traffic does not need to commence or be
terminated at the ends of the LSPs/spans that it uses. terminated at the ends of the LSPs/spans that it uses.
C. Null traffic: C. Null traffic:
E.Mannie, D.Papadimitriou et al.- Expires October 2005 5 Traffic carried over the recovery LSP/span if it is not used to carry
Traffic carried over the recovery LSP/span if it is not used to normal or extra traffic. Null traffic can be any kind of traffic
carry normal or extra traffic. Null traffic can be any kind of that conforms to the signal structure of the specific layer, and it
traffic that conforms to the signal structure of the specific layer, is ignored (not selected) at the egress of the recovery LSP/span.
and it is ignored (not selected) at the egress of the recovery
LSP/span.
4.3 LSP/Span Protection and Restoration 4.3. LSP/Span Protection and Restoration
The following subtle distinction is generally made between the terms The following subtle distinction is generally made between the terms
"protection" and "restoration", even though these terms are often "protection" and "restoration", even though these terms are often
used interchangeably [RFC3386]. used interchangeably [RFC3386].
The distinction between protection and restoration is made based on The distinction between protection and restoration is made based on
the resource allocation done during the recovery LSP/span the resource allocation done during the recovery LSP/span
establishment. The distinction between different types of establishment. The distinction between different types of
restoration is made based on the level of route computation, restoration is made based on the level of route computation,
signaling and resource allocation done during the restoration signaling, and resource allocation during the restoration LSP/span
LSP/span establishment. establishment.
A. LSP/Span Protection A. LSP/Span Protection
LSP/span protection denotes the paradigm whereby one or more LSP/span protection denotes the paradigm whereby one or more
dedicated protection LSP(s)/span(s) is/are fully established to dedicated protection LSP(s)/span(s) is/are fully established to
protect one or more working LSP(s)/span(s). protect one or more working LSP(s)/span(s).
For a protection LSP, this implies that route computation took For a protection LSP, this implies that route computation took place,
place, that the LSP was fully signaled all the way and that its that the LSP was fully signaled all the way, and that its resources
resources were fully selected (i.e. allocated) and cross-connected were fully selected (i.e., allocated) and cross-connected between the
between the ingress and egress nodes. ingress and egress nodes.
For a protection span, this implies that the span has been selected For a protection span, this implies that the span has been selected
and reserved for protection. and reserved for protection.
Indeed, it means that no signaling takes place to establish the Indeed, it means that no signaling takes place to establish the
protection LSP/span when a failure occurs. However, various other protection LSP/span when a failure occurs. However, various other
kinds of signaling may take place between the ingress and egress kinds of signaling may take place between the ingress and egress
nodes for fault notification, to synchronize their use of the nodes for fault notification, to synchronize their use of the
protection LSP/span, for reversion, etc. protection LSP/span, for reversion, etc.
B. LSP/Span Restoration B. LSP/Span Restoration
LSP/span restoration denotes the paradigm whereby some restoration LSP/span restoration denotes the paradigm whereby some restoration
resources may be pre-computed, signaled and selected a priori, but resources may be pre-computed, signaled, and selected a priori, but
not cross-connected to restore a working LSP/span. The complete not cross-connected to restore a working LSP/span. The complete
establishment of the restoration LSP/span occurs only after a establishment of the restoration LSP/span occurs only after a failure
failure of the working LSP/span, and requires some additional of the working LSP/span, and requires some additional signaling.
signaling.
Both protection and restoration require signaling. Signaling to Both protection and restoration require signaling. Signaling to
establish the recovery resources and signaling associated with the establish the recovery resources and signaling associated with the
use of the recovery LSP(s)/span(s) are needed. use of the recovery LSP(s)/span(s) are needed.
E.Mannie, D.Papadimitriou et al.- Expires October 2005 6 4.4. Recovery Scope
4.4 Recovery Scope
Recovery can be applied at various levels throughout the network. An Recovery can be applied at various levels throughout the network. An
LSP may be subject to local (span), segment, and/or end-to-end LSP may be subject to local (span), segment, and/or end-to-end
recovery. recovery.
Local (span) recovery refers to the recovery of an LSP over a link Local (span) recovery refers to the recovery of an LSP over a link
between two nodes. between two nodes.
End-to-end recovery refers to the recovery of an entire LSP from its End-to-end recovery refers to the recovery of an entire LSP from its
source (ingress node end-point) to its destination (egress node end- source (ingress node end-point) to its destination (egress node end-
point). point).
Segment recovery refers to the recovery over a portion of the Segment recovery refers to the recovery over a portion of the network
network of a segment LSP (i.e. an SNC in the ITU-T terminology) of of a segment LSP (i.e., an SNC in the ITU-T terminology) of an end-
an end-to-end LSP. Such recovery protects against span and/or node to-end LSP. Such recovery protects against span and/or node failure
failure over a particular portion of the network traversed by an over a particular portion of the network that is traversed by an
end-to-end LSP. end-to-end LSP.
4.5 Recovery Domain 4.5. Recovery Domain
A recovery domain is defined as a set of nodes and spans over which A recovery domain is defined as a set of nodes and spans, over which
one or more recovery schemes are provided. A recovery domain served one or more recovery schemes are provided. A recovery domain served
by one single recovery scheme is referred to as a "single recovery by one single recovery scheme is referred to as a "single recovery
domain", while a recovery domain served by multiple recovery schemes domain", while a recovery domain served by multiple recovery schemes
is referred to as a "multi recovery domain". is referred to as a "multi recovery domain".
The recovery operation is contained within the recovery domain. A The recovery operation is contained within the recovery domain. A
GMPLS recovery domain must be entirely contained within a GMPLS GMPLS recovery domain must be entirely contained within a GMPLS
domain. A GMPLS domain (defined as a set of nodes and spans domain. A GMPLS domain (defined as a set of nodes and spans
controlled by GMPLS) may contain multiple recovery domains. controlled by GMPLS) may contain multiple recovery domains.
4.6 Recovery Types 4.6. Recovery Types
The different recovery types can be classified depending on the The different recovery types can be classified depending on the
number of recovery LSPs/spans that are protecting a given number of number of recovery LSPs/spans that are protecting a given number of
working LSPs/spans. The definitions given hereafter are from the working LSPs/spans. The definitions given hereafter are from the
point of view of a working LSP/span that needs to be protected by a point of view of a working LSP/span that needs to be protected by a
recovery scheme. recovery scheme.
A. 1+1 type: dedicated protection A. 1+1 type: dedicated protection
One dedicated protection LSP/span protects exactly one working One dedicated protection LSP/span protects exactly one working
LSP/span and the normal traffic is permanently duplicated at the LSP/span, and the normal traffic is permanently duplicated at the
ingress node on both the working and protection LSPs/spans. No extra ingress node on both the working and protection LSPs/spans. No extra
traffic can be carried over the protection LSP/span. traffic can be carried over the protection LSP/span.
This type is applicable to LSP/span protection, but not to LSP/span This type is applicable to LSP/span protection, but not to LSP/span
restoration. restoration.
B. 0:1 type: unprotected B. 0:1 type: unprotected
E.Mannie, D.Papadimitriou et al.- Expires October 2005 7
No specific recovery LSP/span protects the working LSP/span. No specific recovery LSP/span protects the working LSP/span.
However, the working LSP/span can potentially be restored through However, the working LSP/span can potentially be restored through any
any alternate available route/span, with or without any pre-computed alternate available route/span, with or without any pre-computed
restoration route. Note that there are no resources pre-established restoration route. Note that no resources are pre-established for
for this recovery type. this recovery type.
This type is applicable to LSP/span restoration, but not to LSP/span This type is applicable to LSP/span restoration, but not to LSP/span
protection. Span restoration can be for instance achieved by moving protection. Span restoration can be achieved, for instance, by
all the LSPs transported over of a failed span to a dynamically moving all the LSPs transported over a failed span to a dynamically
selected span. selected span.
C. 1:1 type: dedicated recovery with extra traffic C. 1:1 type: dedicated recovery with extra traffic
One specific recovery LSP/span protects exactly one specific working One specific recovery LSP/span protects exactly one specific working
LSP/span but the normal traffic is transmitted only over one LSP LSP/span, but the normal traffic is transmitted over only one LSP
(working or recovery) at a time. Extra traffic can be transported (working or recovery) at a time. Extra traffic can be transported
using the recovery LSP/span resources. using the recovery LSP/span resources.
This type is applicable to LSP/span protection and LSP restoration, This type is applicable to LSP/span protection and LSP restoration,
but not to span restoration. but not to span restoration.
D. 1:N (N > 1) type: shared recovery with extra traffic D. 1:N (N > 1) type: shared recovery with extra traffic
A specific recovery LSP/span is dedicated to the protection of up to A specific recovery LSP/span is dedicated to the protection of up to
N working LSPs/spans. The set of working LSPs/spans is explicitly N working LSPs/spans. The set of working LSPs/spans is explicitly
identified. Extra traffic can be transported over the recovery identified. Extra traffic can be transported over the recovery
LSP/span. All these LSPs/spans must start and end at the same nodes. LSP/span. All these LSPs/spans must start and end at the same nodes.
Sometimes, the working LSPs/spans are assumed to be resource Sometimes, the working LSPs/spans are assumed to be resource disjoint
disjoint in the network so that they do not share any failure in the network so that they do not share any failure probability, but
probability, but this is not mandatory. Obviously, if more than one this is not mandatory. Obviously, if more than one working LSP/span
working LSP/span in the set of N are affected by some failure(s) at in the set of N are affected by some failure(s) at the same time, the
the same time, the traffic on only one of these failed LSPs/spans traffic on only one of these failed LSPs/spans may be recovered over
may be recovered over the recovery LSP/span. Note that N can be the recovery LSP/span. Note that N can be arbitrarily large (i.e.,
arbitrarily large (i.e. infinite). The choice of N is a policy infinite). The choice of N is a policy decision.
decision.
This type is applicable to LSP/span protection and LSP restoration, This type is applicable to LSP/span protection and LSP restoration,
but not to span restoration. but not to span restoration.
Note: a shared recovery where each recovery resource can be shared Note: a shared recovery where each recovery resource can be shared by
by a maximum of X LSPs/spans is not defined as a recovery type but a maximum of X LSPs/spans is not defined as a recovery type but as a
as a recovery scheme. The choice of X is a network resource recovery scheme. The choice of X is a network resource management
management policy decision. policy decision.
E. M:N (M, N > 1, N >= M) type: E. M:N (M, N > 1, N >= M) type:
A set of M specific recovery LSPs/spans protects a set of up to N A set of M specific recovery LSPs/spans protects a set of up to N
specific working LSPs/spans. The two sets are explicitly identified. specific working LSPs/spans. The two sets are explicitly identified.
Extra traffic can be transported over the M recovery LSPs/spans when Extra traffic can be transported over the M recovery LSPs/spans when
available. All the LSPs/spans must start and end at the same nodes. available. All the LSPs/spans must start and end at the same nodes.
E.Mannie, D.Papadimitriou et al.- Expires October 2005 8 Sometimes, the working LSPs/spans are assumed to be resource disjoint
Sometimes, the working LSPs/spans are assumed to be resource in the network so that they do not share any failure probability, but
disjoint in the network so that they do not share any failure this is not mandatory. Obviously, if several working LSPs/spans in
probability, but this is not mandatory. Obviously, if several the set of N are concurrently affected by some failure(s), the
working LSPs/spans in the set of N are concurrently affected by some traffic on only M of these failed LSPs/spans may be recovered. Note
failure(s), the traffic on only M of these failed LSPs/spans may be that N can be arbitrarily large (i.e., infinite). The choice of N
recovered. Note that N can be arbitrarily large (i.e. infinite). The and M is a policy decision.
choice of N and M is a policy decision.
This type is applicable to LSP/span protection and LSP restoration, This type is applicable to LSP/span protection and LSP restoration,
but not to span restoration. but not to span restoration.
4.7 Bridge Types 4.7. Bridge Types
A bridge is the function that connects the normal traffic and extra A bridge is the function that connects the normal traffic and extra
traffic to the working and recovery LSP/span. traffic to the working and recovery LSP/span.
A. Permanent bridge A. Permanent bridge
Under a 1+1 type, the bridge connects the normal traffic to both the Under a 1+1 type, the bridge connects the normal traffic to both the
working and protection LSPs/spans. This type of bridge is not working and protection LSPs/spans. This type of bridge is not
applicable to restoration types. There is of course no extra traffic applicable to restoration types. There is, of course, no extra
connected to the recovery LSP/span. traffic connected to the recovery LSP/span.
B. Broadcast bridge B. Broadcast bridge
For 1:N and M:N types, the bridge permanently connects the normal For 1:N and M:N types, the bridge permanently connects the normal
traffic to the working LSP/span. In the event of recovery switching, traffic to the working LSP/span. In the event of recovery switching,
the normal traffic is additionally connected to the recovery the normal traffic is additionally connected to the recovery
LSP/span. Extra traffic is either not connected or connected to the LSP/span. Extra traffic is either not connected or connected to the
recovery LSP/span. recovery LSP/span.
C. Selector bridge C. Selector bridge
For 1:N and M:N types, the bridge connects the normal traffic to For 1:N and M:N types, the bridge connects the normal traffic to
either the working or the recovery LSP/span. Extra traffic is either either the working or the recovery LSP/span. Extra traffic is either
not connected or connected to the recovery LSP/span. not connected or connected to the recovery LSP/span.
4.8 Selector Types 4.8. Selector Types
A selector is the function that extracts the normal traffic either A selector is the function that extracts the normal traffic from
from the working or the recovery LSP/span. Extra traffic is either either the working or the recovery LSP/span. Extra traffic is either
extracted from the recovery LSP/span, or is not extracted. extracted from the recovery LSP/span, or is not extracted.
A. Selective selector A. Selective selector
Is a selector that extracts the normal traffic from either the Is a selector that extracts the normal traffic from either the
working LSP/span output or the recovery LSP/span output. working LSP/span output or the recovery LSP/span output.
B. Merging selector B. Merging selector
For 1:N and M:N protection types, the selector permanently extracts For 1:N and M:N protection types, the selector permanently extracts
the normal traffic from both the working and recovery LSP/span the normal traffic from both the working and recovery LSP/span
E.Mannie, D.Papadimitriou et al.- Expires October 2005 9
outputs. This alternative works only in combination with a selector outputs. This alternative works only in combination with a selector
bridge. bridge.
4.9 Recovery GMPLS Nodes 4.9. Recovery GMPLS Nodes
This section defines the GMPLS nodes involved during recovery. This section defines the GMPLS nodes involved during recovery.
A. Ingress GMPLS node of an end-to-end LSP/segment LSP/span A. Ingress GMPLS node of an end-to-end LSP/segment LSP/span
The ingress node of an end-to-end LSP/segment LSP/span is where the The ingress node of an end-to-end LSP/segment LSP/span is where the
normal traffic may be bridged to the recovery end-to-end LSP/segment normal traffic may be bridged to the recovery end-to-end LSP/segment
LSP/span. Also known as source node in the ITU-T terminology. LSP/span. Also known as source node in the ITU-T terminology.
B. Egress GMPLS node of an end-to-end LSP/segment LSP/span B. Egress GMPLS node of an end-to-end LSP/segment LSP/span
skipping to change at line 504 skipping to change at page 11, line 28
normal traffic may be selected from either the working or the normal traffic may be selected from either the working or the
recovery end-to-end LSP/segment LSP/span. Also known as sink node in recovery end-to-end LSP/segment LSP/span. Also known as sink node in
the ITU-T terminology. the ITU-T terminology.
C. Intermediate GMPLS node of an end-to-end LSP/segment LSP C. Intermediate GMPLS node of an end-to-end LSP/segment LSP
A node along either the working or recovery end-to-end LSP/segment A node along either the working or recovery end-to-end LSP/segment
LSP route between the corresponding ingress and egress nodes. Also LSP route between the corresponding ingress and egress nodes. Also
known as intermediate node in the ITU-T terminology. known as intermediate node in the ITU-T terminology.
4.10 Switch-over Mechanism 4.10. Switch-over Mechanism
A switch-over is an action that can be performed at both the bridge A switch-over is an action that can be performed at both the bridge
and the selector. This action is as follows: and the selector. This action is as follows:
A. For the selector: A. For the selector:
The action of selecting normal traffic from the recovery LSP/span The action of selecting normal traffic from the recovery LSP/span
rather than from the working LSP/span. rather than from the working LSP/span.
B. For the bridge: B. For the bridge:
In case of permanent connection to the working LSP/span, the action In case of permanent connection to the working LSP/span, the action
of connecting or disconnecting the normal traffic to the recovery of connecting or disconnecting the normal traffic to or from the
LSP/span. In case of non-permanent connection to the working recovery LSP/span. In case of non-permanent connection to the
LSP/span, the action of connecting the normal traffic to the working LSP/span, the action of connecting the normal traffic to the
recovery LSP/span. recovery LSP/span.
4.11 Reversion operations 4.11. Reversion operations
A revertive recovery operation refers to a recovery switching A revertive recovery operation refers to a recovery switching
operation, where the traffic returns to (or remains on) the working operation, where the traffic returns to (or remains on) the working
LSP/span if the switch-over requests are terminated; i.e. when the LSP/span when the switch-over requests are terminated (i.e., when the
working LSP/span has recovered from the failure. working LSP/span has recovered from the failure).
E.Mannie, D.Papadimitriou et al.- Expires October 2005 10 Therefore, a non-revertive recovery switching operation is when the
Therefore a non-revertive recovery switching operation is when the traffic does not return to the working LSP/span when the switch-over
traffic does not return to the working LSP/span if the switch-over
requests are terminated. requests are terminated.
4.12 Failure Reporting 4.12. Failure Reporting
This section gives (for information) several signal types commonly This section gives (for information) several signal types commonly
used in transport planes to report a failure condition. Note that used in transport planes to report a failure condition. Note that
fault reporting may require additional signaling mechanisms. fault reporting may require additional signaling mechanisms.
A. Signal Degrade (SD): a signal indicating that the associated data A. Signal Degrade (SD): a signal indicating that the associated data
has degraded. has degraded.
B. Signal Fail (SF): a signal indicating that the associated data B. Signal Fail (SF): a signal indicating that the associated data has
has failed. failed.
C. Signal Degrade Group (SDG): a signal indicating that the C. Signal Degrade Group (SDG): a signal indicating that the
associated group data has degraded. associated group data has degraded.
D. Signal Fail Group (SFG): a signal indicating that the associated D. Signal Fail Group (SFG): a signal indicating that the associated
group has failed. group has failed.
Note: SDG and SFG definitions are under discussion at the ITU-T. Note: SDG and SFG definitions are under discussion at the ITU-T.
4.13 External commands 4.13. External commands
This section defines several external commands, typically issued by This section defines several external commands, typically issued by
an operator through the Network Management System (NMS)/Element an operator through the Network Management System (NMS)/Element
Management System (EMS), which can be used to influence or command Management System (EMS), that can be used to influence or command the
the recovery schemes. recovery schemes.
A. Lockout of recovery LSP/span: A. Lockout of recovery LSP/span:
A configuration action initiated externally that results in the A configuration action, initiated externally, that results in the
recovery LSP/span being temporarily unavailable to transport traffic recovery LSP/span being temporarily unavailable to transport traffic
(either normal or extra traffic). (either normal or extra traffic).
B. Lockout of normal traffic: B. Lockout of normal traffic:
A configuration action initiated externally that results in the A configuration action, initiated externally, that results in the
normal traffic being temporarily not allowed to be routed over its normal traffic being temporarily not allowed to be routed over its
recovery LSP/span. Note that in this case extra-traffic is still recovery LSP/span. Note that in this case extra-traffic is still
allowed on the recovery LSP/span. allowed on the recovery LSP/span.
C. Freeze: C. Freeze:
A configuration action initiated externally that prevents any A configuration action, initiated externally, that prevents any
switch-over action to be taken, and as such freezes the current switch-over action from being taken, and, as such, freezes the
state. current state.
D. Forced switch-over for normal traffic: D. Forced switch-over for normal traffic:
E.Mannie, D.Papadimitriou et al.- Expires October 2005 11 A switch-over action, initiated externally, that switches normal
A switch-over action initiated externally that switches normal
traffic to the recovery LSP/span, unless an equal or higher priority traffic to the recovery LSP/span, unless an equal or higher priority
switch-over command is in effect. switch-over command is in effect.
E. Manual switch-over for normal traffic: E. Manual switch-over for normal traffic:
A switch-over action initiated externally that switches normal A switch-over action, initiated externally, that switches normal
traffic to the recovery LSP/span, unless a fault condition exists on traffic to the recovery LSP/span, unless a fault condition exists on
other LSPs/spans (including the recovery LSP/span) or an equal or other LSPs/spans (including the recovery LSP/span) or an equal or
higher priority switch-over command is in effect. higher priority switch-over command is in effect.
F. Manual switch-over for recovery LSP/span: F. Manual switch-over for recovery LSP/span:
A switch-over action initiated externally that switches normal A switch-over action, initiated externally, that switches normal
traffic to the working LSP/span, unless a fault condition exists on traffic to the working LSP/span, unless a fault condition exists on
the working LSP/span or an equal or higher priority switch-over the working LSP/span or an equal or higher priority switch-over
command is in effect. command is in effect.
G. Clear: G. Clear:
An action initiated externally that clears the active external An action, initiated externally, that clears the active external
command. command.
4.14 Unidirectional versus Bi-Directional Recovery Switching 4.14. Unidirectional versus Bi-Directional Recovery Switching
A. Unidirectional recovery switching: A. Unidirectional recovery switching:
A recovery switching mode in which, for a unidirectional fault (i.e. A recovery switching mode in which, for a unidirectional fault (i.e.,
a fault affecting only one direction of transmission), only the a fault affecting only one direction of transmission), only the
normal traffic transported in the affected direction (of the LSP or normal traffic transported in the affected direction (of the LSP or
span) is switched to the recovery LSP/span. span) is switched to the recovery LSP/span.
B. Bi-directional recovery switching: B. Bi-directional recovery switching:
A recovery switching mode in which, for a unidirectional fault, the A recovery switching mode in which, for a unidirectional fault, the
normal traffic in both directions (of the LSP or span), including normal traffic in both directions (of the LSP or span), including the
the affected direction and the unaffected direction, are switched to affected direction and the unaffected direction, are switched to the
the recovery LSP/span. recovery LSP/span.
4.15 Full versus Partial Span Recovery Switching 4.15. Full versus Partial Span Recovery Switching
Bulk LSP recovery is initiated upon reception on either span failure Bulk LSP recovery is initiated upon reception of either span failure
notification or bulk failure notification of the S LSPs carried by notification or bulk failure notification of the S LSPs carried by
this span. In either case, the corresponding recovery switching this span. In either case, the corresponding recovery switching
actions are performed at the LSP level such that the ratio between actions are performed at the LSP level, such that the ratio between
the number of recovery switching messages and the number of the number of recovery switching messages and the number of recovered
recovered LSP (in one given direction) is minimized. If this ratio LSP (in one given direction) is minimized. If this ratio equals 1,
equals 1, one refers to full span recovery, otherwise, if this ratio one refers to full span recovery; otherwise, if this ratio is greater
is greater than 1 one refers to partial span recovery. than 1, one refers to partial span recovery.
A. Full Span Recovery A. Full Span Recovery
E.Mannie, D.Papadimitriou et al.- Expires October 2005 12
All the S LSP carried over a given span are recovered under span All the S LSP carried over a given span are recovered under span
failure condition. Full span recovery is also referred to as "bulk failure condition. Full span recovery is also referred to as "bulk
recovery". recovery".
B. Partial Span Recovery B. Partial Span Recovery
Only a subset s of the S LSP carried over a given span are recovered Only a subset s of the S LSP carried over a given span is recovered
under span failure condition. Both selection criteria of the under span failure condition. Both selection criteria of the
entities belonging to this subset and the decision concerning the entities belonging to this subset, and the decision concerning the
recovery of the remaining (S - s) LSP are based on local policy. recovery of the remaining (S - s) LSP, are based on local policy.
4.16 Recovery Schemes Related Time and Durations 4.16. Recovery Schemes Related Time and Durations
This section gives several typical timing definitions that are of This section gives several typical timing definitions that are of
importance for recovery schemes. importance for recovery schemes.
A. Detection time: A. Detection time:
The time between the occurrence of the fault or degradation and its The time between the occurrence of the fault or degradation and its
detection. Note that this is a rather theoretical time since in detection. Note that this is a rather theoretical time because, in
practice this is difficult to measure. practice, this is difficult to measure.
B. Correlation time: B. Correlation time:
The time between the detection of the fault or degradation and the The time between the detection of the fault or degradation and the
reporting of the signal fail or degrade. This time is typically used reporting of the signal fail or degrade. This time is typically used
in correlating related failures or degradations. in correlating related failures or degradations.
C. Notification time: C. Notification time:
The time between the reporting of the signal fail or degrade and the The time between the reporting of the signal fail or degrade and the
reception of the indication of this event by the entities that reception of the indication of this event by the entities that decide
decide on the recovery switching operation(s). on the recovery switching operation(s).
D. Recovery Switching time: D. Recovery Switching time:
The time between the initialization of the recovery switching The time between the initialization of the recovery switching
operation and the moment the normal traffic is selected from the operation and the moment the normal traffic is selected from the
recovery LSP/span. recovery LSP/span.
E. Total Recovery time: E. Total Recovery time:
The total recovery time is defined as the sum of the detection, the The total recovery time is defined as the sum of the detection, the
correlation, the notification and the recovery switching time. correlation, the notification, and the recovery switching time.
F. Wait To Restore time: F. Wait To Restore time:
A period of time that must elapse from a recovered fault before an A period of time that must elapse after a recovered fault before an
LSP/span can be used again to transport the normal traffic and/or to LSP/span can be used again to transport the normal traffic and/or to
select the normal traffic from. select the normal traffic from.
E.Mannie, D.Papadimitriou et al.- Expires October 2005 13
Note: the hold-off time is defined as the time between the reporting Note: the hold-off time is defined as the time between the reporting
of signal fail or degrade, and the initialization of the recovery of signal fail or degrade, and the initialization of the recovery
switching operation. This is useful when multiple layers of recovery switching operation. This is useful when multiple layers of recovery
are being used. are being used.
4.17 Impairment 4.17. Impairment
A defect or performance degradation, which may lead to SF or SD A defect or performance degradation, which may lead to SF or SD
trigger. trigger.
4.18 Recovery Ratio 4.18. Recovery Ratio
The quotient of the actually recovery bandwidth divided by the The quotient of the actual recovery bandwidth divided by the traffic
traffic bandwidth which is intended to be protected. bandwidth that is intended to be protected.
4.19 Hitless Protection Switch-over 4.19. Hitless Protection Switch-over
Protection switch-over, which does not cause data loss, data Protection switch-over, which does not cause data loss, data
duplication, data disorder, or bit errors upon recovery switching duplication, data disorder, or bit errors upon recovery switching
action. action.
4.20 Network Survivability 4.20. Network Survivability
The set of capabilities that allow a network to restore affected The set of capabilities that allows a network to restore affected
traffic in the event of a failure. The degree of survivability is traffic in the event of a failure. The degree of survivability is
determined by the network's capability to survive single and determined by the network's capability to survive single and multiple
multiple failures. failures.
4.21 Survivable Network 4.21. Survivable Network
A network that is capable of restoring traffic in the event of a A network that is capable of restoring traffic in the event of a
failure. failure.
4.22 Escalation 4.22. Escalation
A network survivability action caused by the impossibility of the A network survivability action caused by the impossibility of the
survivability function in lower layers. survivability function in lower layers.
5. Recovery Phases 5. Recovery Phases
It is commonly accepted that recovery implies that the following It is commonly accepted that recovery implies that the following
generic operations need to be performed when an LSP/span or a node generic operations need to be performed when an LSP/span or a node
failure occurs: failure occurs:
- Phase 1: Failure Detection - Phase 1: Failure Detection
The action of detecting the impairment (defect of performance The action of detecting the impairment (defect of performance
degradation) as a defect condition and consequential activation of degradation) as a defect condition and the consequential activation
SF or SD trigger to the control plane (through internal interface of SF or SD trigger to the control plane (through internal interface
with the transport plane). Thus, failure detection (that should with the transport plane). Thus, failure detection (which should
occur at the transport layer closest to the failure) is the only occur at the transport layer closest to the failure) is the only
phase that can not be achieved by the control plane alone. phase that can not be achieved by the control plane alone.
E.Mannie, D.Papadimitriou et al.- Expires October 2005 14
- Phase 2: Failure Localization (and Isolation) - Phase 2: Failure Localization (and Isolation)
Failure localization provides to the deciding entity information Failure localization provides, to the deciding entity, information
about the location (and so the identity) of the transport plane about the location (and thus the identity) of the transport plane
entity that causes the LSP(s)/span(s) failure. The deciding entity entity that causes the LSP(s)/span(s) failure. The deciding entity
can then take accurate decision to achieve finer grained recovery can then make an accurate decision to achieve finer grained recovery
switching action(s). switching action(s).
- Phase 3: Failure Notification - Phase 3: Failure Notification
Failure notification phase is used 1) to inform intermediate nodes Failure notification phase is used 1) to inform intermediate nodes
that LSP(s)/span(s) failure has occurred and has been detected 2) to that LSP(s)/span(s) failure has occurred and has been detected and 2)
inform the recovery deciding entities (which can correspond to any to inform the recovery deciding entities (which can correspond to any
intermediate or end-point of the failed LSP/span) that the intermediate or end-point of the failed LSP/span) that the
corresponding LSP/span is not available. corresponding LSP/span is not available.
- Phase 4: Recovery (Protection or Restoration) - Phase 4: Recovery (Protection or Restoration)
See Section 4.3. See Section 4.3.
- Phase 5: Reversion (Normalization) - Phase 5: Reversion (Normalization)
See Section 4.11. See Section 4.11.
The combination of Failure Detection and Failure Localization and The combination of Failure Detection and Failure Localization and
Notification is referred to as Fault Management. Notification is referred to as Fault Management.
5.1 Entities Involved During Recovery 5.1. Entities Involved During Recovery
The entities involved during the recovery operations can be defined The entities involved during the recovery operations can be defined
as follows; these entities are parts of ingress, egress and as follows; these entities are parts of ingress, egress, and
intermediate nodes as defined previously: intermediate nodes, as defined previously:
A. Detecting Entity (Failure Detection): A. Detecting Entity (Failure Detection):
An entity that detects a failure or group of failures; providing An entity that detects a failure or group of failures; thus providing
thus a non-correlated list of failures. a non-correlated list of failures.
B. Reporting Entity (Failure Correlation and Notification): B. Reporting Entity (Failure Correlation and Notification):
An entity that can make an intelligent decision on fault correlation An entity that can make an intelligent decision on fault correlation
and report the failure to the deciding entity. Fault reporting can and report the failure to the deciding entity. Fault reporting can
be automatically performed by the deciding entity detecting the be automatically performed by the deciding entity detecting the
failure. failure.
C. Deciding Entity (part of the failure recovery decision process): C. Deciding Entity (part of the failure recovery decision process):
An entity that makes the recovery decision or selects the recovery An entity that makes the recovery decision or selects the recovery
resources. This entity communicates the decision to the impacted resources. This entity communicates the decision to the impacted
LSPs/spans with the recovery actions to be performed. LSPs/spans with the recovery actions to be performed.
E.Mannie, D.Papadimitriou et al.- Expires October 2005 15
D. Recovering Entity (part of the failure recovery activation D. Recovering Entity (part of the failure recovery activation
process): process):
An entity that participates in the recovery of the LSPs/spans. An entity that participates in the recovery of the LSPs/spans.
The process of moving failed LSPs from a failed (working) span to a The process of moving failed LSPs from a failed (working) span to a
protection span must be initiated by one of the nodes terminating protection span must be initiated by one of the nodes that terminates
the span, e.g. A or B. The deciding (and recovering) entity is the span, e.g., A or B. The deciding (and recovering) entity is
referred to as the "master" while the other node is called the referred to as the "master", while the other node is called the
"slave" and corresponds to a recovering only entity. "slave" and corresponds to a recovering only entity.
Note: The determination of the master and the slave may be based on Note: The determination of the master and the slave may be based on
configured information or protocol specific requirements. configured information or protocol-specific requirements.
6. Protection Schemes 6. Protection Schemes
This section clarifies the multiple possible protection schemes and This section clarifies the multiple possible protection schemes and
the specific terminology for the protection. the specific terminology for the protection.
6.1 1+1 Protection 6.1. 1+1 Protection
1+1 protection has one working LSP/span, one protection LSP/span and 1+1 protection has one working LSP/span, one protection LSP/span, and
a permanent bridge. At the ingress node, the normal traffic is a permanent bridge. At the ingress node, the normal traffic is
permanently bridged to both the working and protection LSP/span. At permanently bridged to both the working and protection LSP/span. At
the egress node, the normal traffic is selected from the better of the egress node, the normal traffic is selected from the better of
the two LSPs/spans. the two LSPs/spans.
Due to the permanent bridging, the 1+1 protection does not allow an Due to the permanent bridging, the 1+1 protection does not allow an
unprotected extra traffic signal to be provided. unprotected extra traffic signal to be provided.
6.2 1:N (N >= 1) Protection 6.2. 1:N (N >= 1) Protection
1:N protection has N working LSPs/spans carrying normal traffic and 1:N protection has N working LSPs/spans that carry normal traffic and
1 protection LSP/span that may carry extra-traffic. 1 protection LSP/span that may carry extra-traffic.
At the ingress, the normal traffic is either permanently connected At the ingress, the normal traffic is either permanently connected to
to its working LSP/span and may be connected to the protection its working LSP/span and may be connected to the protection LSP/span
LSP/span (case of broadcast bridge), or is connected to either its (case of broadcast bridge), or is connected to either its working
working or the protection LSP/span (case of selector bridge). At the LSP/span or the protection LSP/span (case of selector bridge). At
egress node, the normal traffic is selected from either its working the egress node, the normal traffic is selected from either its
or protection LSP/span. working or protection LSP/span.
Unprotected extra traffic can be transported over the protection Unprotected extra traffic can be transported over the protection
LSP/span whenever the protection LSP/span is not used to carry a LSP/span whenever the protection LSP/span is not used to carry a
normal traffic. normal traffic.
6.3 M:N (M, N > 1, N >= M) Protection 6.3. M:N (M, N > 1, N >= M) Protection
M:N protection has N working LSPs/spans carrying normal traffic and M:N protection has N working LSPs/spans carrying normal traffic and M
M protection LSP/span that may carry extra-traffic. protection LSP/span that may carry extra-traffic.
E.Mannie, D.Papadimitriou et al.- Expires October 2005 16 At the ingress, the normal traffic is either permanently connected to
At the ingress, the normal traffic is either permanently connected its working LSP/span and may be connected to one of the protection
to its working LSP/span and may be connected to one of the LSPs/spans (case of broadcast bridge), or is connected to either its
protection LSPs/spans (case of broadcast bridge), or is connected to working LSP/span or one of the protection LSPs/spans (case of
either its working or one of the protection LSPs/spans (case of
selector bridge). At the egress node, the normal traffic is selected selector bridge). At the egress node, the normal traffic is selected
from either its working or one of the protection LSP/span. from either its working or one of the protection LSP/span.
Unprotected extra traffic can be transported over the M protection Unprotected extra traffic can be transported over the M protection
LSP/span whenever the protection LSPs/spans is not used to carry a LSP/span whenever the protection LSPs/spans is not used to carry a
normal traffic. normal traffic.
6.4 Notes on Protection Schemes 6.4. Notes on Protection Schemes
All protection types are either uni- or bi-directional, obviously, All protection types are either uni- or bi-directional; obviously,
the latter applies only to bi-directional LSP/span and requires the latter applies only to bi-directional LSPs/spans and requires
coordination between the ingress and egress node during protection coordination between the ingress and egress node during protection
switching. switching.
All protection types except 1+1 unidirectional protection switching All protection types except 1+1 unidirectional protection switching
require a communication channel between the ingress and the egress require a communication channel between the ingress and the egress
node. node.
In the GMPLS context, span protection refers to the full or partial In the GMPLS context, span protection refers to the full or partial
span recovery of the LSPs carried over that span (see Section 4.15). span recovery of the LSPs carried over that span (see Section 4.15).
7. Restoration Schemes 7. Restoration Schemes
This section clarifies the multiple possible restoration schemes and This section clarifies the multiple possible restoration schemes and
the specific terminology for the restoration. the specific terminology for the restoration.
7.1 Pre-planned LSP Restoration 7.1. Pre-Planned LSP Restoration
Also referred to as pre-planned LSP re-routing. Before failure Also referred to as pre-planned LSP re-routing. Before failure
detection and/or notification, one or more restoration LSPs are detection and/or notification, one or more restoration LSPs are
instantiated between the same ingress-egress node pair than the instantiated between the same ingress-egress node pair as the working
working LSP. Note that the restoration resources must be pre- LSP. Note that the restoration resources must be pre-computed, must
computed, must be signaled and may be selected a priori, but not be signaled, and may be selected a priori, but may not cross-
cross-connected. Thus, the restoration LSP is not able to carry any connected. Thus, the restoration LSP is not able to carry any
extra-traffic. extra-traffic.
The complete establishment of the restoration LSP (i.e. activation) The complete establishment of the restoration LSP (i.e., activation)
occurs only after failure detection and/or notification of the occurs only after failure detection and/or notification of the
working LSP and requires some additional restoration signaling. working LSP and requires some additional restoration signaling.
Therefore, this mechanism protects against working LSP failure(s) Therefore, this mechanism protects against working LSP failure(s) but
but requires activation of the restoration LSP after failure requires activation of the restoration LSP after failure occurrence.
occurrence. After the ingress node has activated the restoration After the ingress node has activated the restoration LSP, the latter
LSP, the latter can carry the normal traffic. can carry the normal traffic.
Note: when each working LSP is recoverable by exactly one
restoration LSP, one refers also to 1:1 (pre-planned) re-routing
without extra-traffic.
E.Mannie, D.Papadimitriou et al.- Expires October 2005 17 Note: when each working LSP is recoverable by exactly one restoration
LSP, one refers also to 1:1 (pre-planned) re-routing without extra-
traffic.
7.1.1 Shared-Mesh Restoration 7.1.1. Shared-Mesh Restoration
"Shared-mesh" restoration is defined as a particular case of pre- "Shared-mesh" restoration is defined as a particular case of pre-
planned LSP re-routing that reduces the restoration resource planned LSP re-routing that reduces the restoration resource
requirements by allowing multiple restoration LSPs (initiated from requirements by allowing multiple restoration LSPs (initiated from
distinct ingress nodes) to share common resources (including links distinct ingress nodes) to share common resources (including links
and nodes.) and nodes.)
7.2 LSP Restoration 7.2. LSP Restoration
Also referred to as LSP re-routing. The ingress node switches the Also referred to as LSP re-routing. The ingress node switches the
normal traffic to an alternate LSP signaled and fully established normal traffic to an alternate LSP that is signaled and fully
(i.e. cross-connected) after failure detection and/or notification. established (i.e., cross-connected) after failure detection and/or
The alternate LSP path may be computed after failure detection notification. The alternate LSP path may be computed after failure
and/or notification. In this case, one also refers to "Full LSP Re- detection and/or notification. In this case, one also refers to
routing." "Full LSP Re-routing."
The alternate LSP is signaled from the ingress node and may reuse The alternate LSP is signaled from the ingress node and may reuse the
intermediate node's resources of the working LSP under failure intermediate node's resources of the working LSP under failure
condition (and may also include additional intermediate nodes.) condition (and may also include additional intermediate nodes.)
7.2.1 Hard LSP Restoration 7.2.1. Hard LSP Restoration
Also referred to as hard LSP re-routing. A re-routing operation Also referred to as hard LSP re-routing. A re-routing operation
where the LSP is released before the full establishment of an where the LSP is released before the full establishment of an
alternate LSP (i.e. break-before-make). alternate LSP (i.e., break-before-make).
7.2.2 Soft LSP Restoration 7.2.2. Soft LSP Restoration
Also referred to as soft LSP re-routing. A re-routing operation Also referred to as soft LSP re-routing. A re-routing operation
where the LSP is released after the full establishment of an where the LSP is released after the full establishment of an
alternate LSP (i.e. make-before-break). alternate LSP (i.e., make-before-break).
8. Security Considerations 8. Security Considerations
Security considerations are detailed in [ANAL] and [FUNCT]. Security considerations are detailed in [RFC4428] and [RFC4426].
9. IANA Considerations
This document defines no new code points and requires no action by
IANA.
10. References
10.1 Normative References
[ANAL] D.Papadimitriou and E.Mannie (Editors), "Analysis of
Generalized Multi-Protocol Label Switching (GMPLS)-
based Recovery Mechanisms (including Protection and
Restoration)", Internet Draft (Work in progress), April
2005.
E.Mannie, D.Papadimitriou et al.- Expires October 2005 18
[FUNCT] J.P.Lang, B.Rajagopalan and D.Papadimitriou (Editors),
"Generalized MPLS Recovery Functional Specification,"
Internet Draft (Work in progress), April 2005.
[RFC2026] S.Bradner, "The Internet Standards Process -- Revision 9. References
3", BCP 9, RFC 2026, October 1996.
[RFC2119] S.Bradner, "Key words for use in RFCs to Indicate 9.1. Normative References
Requirement Levels," BCP 14, RFC 2119, March 1997.
[RFC3667] S.Bradner, "IETF Rights in Contributions", BCP 78, [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
RFC 3667, February 2004. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3668] S.Bradner, Ed., "Intellectual Property Rights in IETF 9.2. Informative References
Technology", BCP 79, RFC 3668, February 2004.
10.2 Informative References [RFC3386] Lai, W. and D. McDysan, "Network Hierarchy and
Multilayer Survivability", RFC 3386, November 2002.
[RFC3386] W.S.Lai, et al., "Network Hierarchy and Multilayer [RFC3945] Mannie, E., "Generalized Multi-Protocol Label Switching
Survivability," RFC 3386, November 2002. (GMPLS) Architecture", RFC 3945, October 2004.
[RFC3945] E.Mannie (Editor), "Generalized Multi-Protocol Label [RFC4426] Lang, J., Rajagopalan B., and D.Papadimitriou, Editors,
Switching (GMPLS) Architecture," RFC 3945, October "Generalized Multiprotocol Label Switching (GMPLS)
2004. Recovery Functional Specification", RFC 4426, March
2006.
[T1.105] ANSI, "Synchronous Optical Network (SONET): Basic [RFC4428] Papadimitriou D. and E.Mannie, Editors, "Analysis of
Description Including Multiplex Structure, Rates, and Generalized Multi-Protocol Label Switching (GMPLS)-based
Formats," ANSI T1.105, January 2001. Recovery Mechanisms (including Protection and
Restoration)", RFC 4428, March 2006.
For information on the availability of the following documents, For information on the availability of the following documents,
please see http://www.itu.int please see http://www.itu.int
[G.707] ITU-T, "Network Node Interface for the Synchronous
Digital Hierarchy (SDH)," Recommendation G.707, October
2000.
[G.783] ITU-T, "Characteristics of Synchronous Digital
Hierarchy (SDH) Equipment Functional Blocks,"
Recommendation G.783, October 2000.
[G.806] ITU-T, "Characteristics of Transport Equipment -
Description Methodology and Generic Functionality,"
Recommendation G.806, October 2000.
[G.808.1] ITU-T, "Generic Protection Switching - Linear trail and [G.808.1] ITU-T, "Generic Protection Switching - Linear trail and
subnetwork protection," Recommendation G.808.1, subnetwork protection," Recommendation G.808.1, December
December 2003. 2003.
[G.841] ITU-T, "Types and Characteristics of SDH Network [G.841] ITU-T, "Types and Characteristics of SDH Network
Protection Architectures," Recommendation G.841, Protection Architectures," Recommendation G.841, October
October 1998. 1998.
E.Mannie, D.Papadimitriou et al.- Expires October 2005 19
[G.842] ITU-T, "Interworking of SDH network protection
architectures," Recommendation G.842, October 1998.
11. Acknowledgments 10. Acknowledgements
Many thanks to Adrian Farrel for having thoroughly review this Many thanks to Adrian Farrel for having thoroughly review this
document. document.
12. Editor's Addresses Editors' Addresses
Eric Mannie Eric Mannie
EMail: eric_mannie@hotmail.com Perceval
Rue Tenbosch, 9
1000 Brussels
Belgium
Phone: +32-2-6409194
EMail: eric.mannie@perceval.net
Dimitri Papadimitriou Dimitri Papadimitriou
Alcatel Alcatel
Francis Wellesplein, 1 Francis Wellesplein, 1
B-2018 Antwerpen, Belgium B-2018 Antwerpen, Belgium
Phone: +32 3 240-8491 Phone: +32 3 240-8491
EMail: dimitri.papadimitriou@alcatel.be EMail: dimitri.papadimitriou@alcatel.be
E.Mannie, D.Papadimitriou et al.- Expires October 2005 20 Full Copyright Statement
Intellectual Property Statement Copyright (C) The Internet Society (2006).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
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This document and the information contained herein are provided on
an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE
INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2005). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
E.Mannie, D.Papadimitriou et al.- Expires October 2005 21 Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
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