draft-ietf-mpls-tp-psc-itu-04.txt   rfc7271.txt 
MPLS Working Group J. Ryoo, Ed. Internet Engineering Task Force (IETF) J. Ryoo, Ed.
Internet-Draft ETRI Request for Comments: 7271 ETRI
Updates: 6378 (if approved) E. Gray, Ed. Updates: 6378 E. Gray, Ed.
Intended status: Standards Track Ericsson Category: Standards Track Ericsson
Expires: September 29, 2014 H. van Helvoort ISSN: 2070-1721 H. van Helvoort
Huawei Technologies Huawei Technologies
A. D'Alessandro A. D'Alessandro
Telecom Italia Telecom Italia
T. Cheung T. Cheung
ETRI ETRI
E. Osborne E. Osborne
June 2014
March 28, 2014
MPLS Transport Profile (MPLS-TP) Linear Protection to Match the MPLS Transport Profile (MPLS-TP) Linear Protection to Match the
Operational Expectations of SDH, OTN and Ethernet Transport Network Operational Expectations of Synchronous Digital Hierarchy,
Operators Optical Transport Network, and Ethernet Transport Network Operators
draft-ietf-mpls-tp-psc-itu-04.txt
Abstract Abstract
This document describes alternate mechanisms to perform some of the This document describes alternate mechanisms to perform some of the
functions of MPLS Transport Profile (MPLS-TP) linear protection functions of MPLS Transport Profile (MPLS-TP) linear protection
defined in RFC 6378, and also defines additional mechanisms. The defined in RFC 6378, and also defines additional mechanisms. The
purpose of these alternate and additional mechanisms is to provide purpose of these alternate and additional mechanisms is to provide
operator control and experience that more closely models the behavior operator control and experience that more closely models the behavior
of linear protection seen in other transport networks. of linear protection seen in other transport networks.
skipping to change at page 1, line 46 skipping to change at page 2, line 7
This document describes the behavior of the PSC protocol including This document describes the behavior of the PSC protocol including
priority logic and state machine when all the capabilities associated priority logic and state machine when all the capabilities associated
with the APS mode are enabled. with the APS mode are enabled.
This document updates RFC 6378 in that the capability advertisement This document updates RFC 6378 in that the capability advertisement
method defined here is an addition to that document. method defined here is an addition to that document.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on September 29, 2014. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7271.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions Used in This Document . . . . . . . . . . . . . . 5 2. Conventions Used in This Document . . . . . . . . . . . . . . 5
3. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Capability 1: Priority Modification . . . . . . . . . . . . . 6 4. Capability 1: Priority Modification . . . . . . . . . . . . . 6
4.1. Motivation for swapping priorities of FS and SF-P . . . . 6 4.1. Motivation for Swapping Priorities of FS and SF-P . . . . 6
4.2. Motivation for raising the priority of SFc . . . . . . . 7 4.2. Motivation for Raising the Priority of SFc . . . . . . . 7
4.3. Motivation for introducing Freeze command . . . . . . . . 7 4.3. Motivation for Introducing the Freeze Command . . . . . . 7
4.4. Procedures in support of priority modification . . . . . 7 4.4. Procedures in Support of Priority Modification . . . . . 8
5. Capability 2: Non-revertive Behavior Modification . . . . . . 8 5. Capability 2: Non-revertive Behavior Modification . . . . . . 8
6. Capability 3: Support of MS-W Command . . . . . . . . . . . . 8 6. Capability 3: Support of the MS-W Command . . . . . . . . . . 8
6.1. Motivation for adding MS-W . . . . . . . . . . . . . . . 8 6.1. Motivation for adding MS-W . . . . . . . . . . . . . . . 8
6.2. Terminology to support MS-W . . . . . . . . . . . . . . . 9 6.2. Terminology to Support MS-W . . . . . . . . . . . . . . . 9
6.3. Behavior of MS-P and MS-W . . . . . . . . . . . . . . . . 9 6.3. Behavior of MS-P and MS-W . . . . . . . . . . . . . . . . 9
6.4. Equal priority resolution for MS . . . . . . . . . . . . 10 6.4. Equal-Priority Resolution for MS . . . . . . . . . . . . 10
7. Capability 4: Support of Protection against SD . . . . . . . 10 7. Capability 4: Support of Protection against SD . . . . . . . 10
7.1. Motivation for supporting protection against SD . . . . . 10 7.1. Motivation for Supporting Protection against SD . . . . . 10
7.2. Terminology to support SD . . . . . . . . . . . . . . . . 10 7.2. Terminology to Support SD . . . . . . . . . . . . . . . . 10
7.3. Behavior of protection against SD . . . . . . . . . . . . 11 7.3. Behavior of Protection against SD . . . . . . . . . . . . 11
7.4. Equal priority resolution . . . . . . . . . . . . . . . . 12 7.4. Equal-Priority Resolution . . . . . . . . . . . . . . . . 12
8. Capability 5: Support of EXER Command . . . . . . . . . . . . 13 8. Capability 5: Support of EXER Command . . . . . . . . . . . . 13
9. Capabilities and Modes . . . . . . . . . . . . . . . . . . . 14 9. Capabilities and Modes . . . . . . . . . . . . . . . . . . . 14
9.1. Capabilities . . . . . . . . . . . . . . . . . . . . . . 14 9.1. Capabilities . . . . . . . . . . . . . . . . . . . . . . 14
9.1.1. Sending and receiving the Capabilities TLV . . . . . 15 9.1.1. Sending and Receiving the Capabilities TLV . . . . . 15
9.2. Modes . . . . . . . . . . . . . . . . . . . . . . . . . . 16 9.2. Modes . . . . . . . . . . . . . . . . . . . . . . . . . . 16
9.2.1. PSC mode . . . . . . . . . . . . . . . . . . . . . . 16 9.2.1. PSC Mode . . . . . . . . . . . . . . . . . . . . . . 16
9.2.2. APS mode . . . . . . . . . . . . . . . . . . . . . . 16 9.2.2. APS Mode . . . . . . . . . . . . . . . . . . . . . . 16
10. PSC Protocol in APS Mode . . . . . . . . . . . . . . . . . . 16 10. PSC Protocol in APS Mode . . . . . . . . . . . . . . . . . . 17
10.1. Request field in PSC protocol message . . . . . . . . . 16 10.1. Request Field in PSC Protocol Message . . . . . . . . . 17
10.2. Priorities of local inputs and remote requests . . . . . 17 10.2. Priorities of Local Inputs and Remote Requests . . . . . 17
10.2.1. Equal priority requests . . . . . . . . . . . . . . 18 10.2.1. Equal-Priority Requests . . . . . . . . . . . . . . 18
10.3. Acceptance and retention of local inputs . . . . . . . . 19 10.3. Acceptance and Retention of Local Inputs . . . . . . . . 20
11. State Transition Tables in APS Mode . . . . . . . . . . . . . 20 11. State Transition Tables in APS Mode . . . . . . . . . . . . . 20
11.1. State transition by local inputs . . . . . . . . . . . . 22 11.1. State Transition by Local Inputs . . . . . . . . . . . . 23
11.2. State transition by remote messages . . . . . . . . . . 24 11.2. State Transition by Remote Messages . . . . . . . . . . 25
11.3. State transition for 1+1 unidirectional 11.3. State Transition for 1+1 Unidirectional Protection . . . 27
protection . . . . . . . . . . . . . . . . . . . . . . . 26
12. Provisioning Mismatch and Protocol Failure in APS Mode . . . 27 12. Provisioning Mismatch and Protocol Failure in APS Mode . . . 27
13. Security Considerations . . . . . . . . . . . . . . . . . . . 28 13. Security Considerations . . . . . . . . . . . . . . . . . . . 28
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
14.1. MPLS PSC Request Registry . . . . . . . . . . . . . . . 28 14.1. MPLS PSC Request Registry . . . . . . . . . . . . . . . 29
14.2. MPLS PSC TLV Registry . . . . . . . . . . . . . . . . . 28 14.2. MPLS PSC TLV Registry . . . . . . . . . . . . . . . . . 29
14.3. MPLS PSC Capability Flag Registry . . . . . . . . . . . 28 14.3. MPLS PSC Capability Flag Registry . . . . . . . . . . . 29
15. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 29 15. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 30
16. References . . . . . . . . . . . . . . . . . . . . . . . . . 29 16. References . . . . . . . . . . . . . . . . . . . . . . . . . 30
16.1. Normative References . . . . . . . . . . . . . . . . . . 29 16.1. Normative References . . . . . . . . . . . . . . . . . . 30
16.2. Informative References . . . . . . . . . . . . . . . . . 29 16.2. Informative References . . . . . . . . . . . . . . . . . 30
Appendix A. An Example of Out-of-service Scenarios . . . . . . . 30 Appendix A. An Example of an Out-of-Service Scenario . . . . . . 32
Appendix B. An Example of Sequence Diagram Showing Appendix B. An Example of a Sequence Diagram Showing
the Problem with the Priority Level of SFc . . . . . 31 the Problem with the Priority Level of SFc . . . . . 33
Appendix C. Freeze Command . . . . . . . . . . . . . . . . . . . 33 Appendix C. Freeze Command . . . . . . . . . . . . . . . . . . . 34
Appendix D. Operation Examples of the APS Mode . . . . . . . . . 33 Appendix D. Operation Examples of the APS Mode . . . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 37
1. Introduction 1. Introduction
Linear protection mechanisms for the MPLS Transport Profile (MPLS-TP) Linear protection mechanisms for the MPLS Transport Profile (MPLS-TP)
are described in RFC 6378 [RFC6378] to meet the requirements are described in RFC 6378 [RFC6378] to meet the requirements
described in RFC 5654 [RFC5654]. described in RFC 5654 [RFC5654].
This document describes alternate mechanisms to perform some of the This document describes alternate mechanisms to perform some of the
functions of linear protection, and also defines additional functions of linear protection, and also defines additional
mechanisms. The purpose of these alternate and additional mechanisms mechanisms. The purpose of these alternate and additional mechanisms
is to provide operator control and experience that more closely is to provide operator control and experience that more closely
models the behavior of linear protection seen in other transport models the behavior of linear protection seen in other transport
networks, such as Synchronous Digital Hierarchy (SDH), Optical networks, such as Synchronous Digital Hierarchy (SDH), Optical
Transport Network (OTN) and Ethernet transport networks. Linear Transport Network (OTN), and Ethernet transport networks. Linear
protection for SDH, OTN, and Ethernet transport networks are defined protection for SDH, OTN, and Ethernet transport networks is defined
in ITU-T Recommendations G.841 [G841], G.873.1 [G873.1] and G.8031 in ITU-T Recommendations G.841 [G841], G.873.1 [G873.1], and G.8031
[G8031], respectively. [G8031], respectively.
The reader of this document is assumed to be familiar with [RFC6378]. The reader of this document is assumed to be familiar with [RFC6378].
The alternative mechanisms described in this document are for the The alternative mechanisms described in this document are for the
following capabilities: following capabilities:
1. Priority modification, 1. Priority modification,
2. non-revertive behavior modification, 2. non-revertive behavior modification,
and the following capabilities have been added to define additional and the following capabilities have been added to define additional
mechanisms: mechanisms:
3. support of Manual Switch to Working path (MS-W) command, 3. support of the Manual Switch to Working path (MS-W) command,
4. support of protection against Signal Degrade (SD), and 4. support of protection against Signal Degrade (SD), and
5. support of Exercise (EXER) command. 5. support of the Exercise (EXER) command.
The priority modification includes raising the priority of Signal The priority modification includes raising the priority of Signal
Fail on Protection path (SF-P) relative to Forced Switch (FS), and Fail on Protection path (SF-P) relative to Forced Switch (FS), and
raising the priority level of Clear Signal Fail (SFc) above SF-P. raising the priority level of Clear Signal Fail (SFc) above SF-P.
Non-revertive behavior is modified to align with the behavior defined Non-revertive behavior is modified to align with the behavior defined
in RFC 4427 [RFC4427] as well as to follow the behavior of linear in RFC 4427 [RFC4427] as well as to follow the behavior of linear
protection seen in other transport networks. protection seen in other transport networks.
Support of MS-W command to revert traffic to the working path in non- Support of the MS-W command to revert traffic to the working path in
revertive operation is covered in this document. non-revertive operation is covered in this document.
Support of protection switching protocol against SD is covered in Support of the protection-switching protocol against SD is covered in
this document. The specifics for the method of identifying SD is out this document. The specifics for the method of identifying SD are
of the scope for this document and is treated similarly to Signal out of the scope for this document and are treated similarly to
Fail (SF) in [RFC6378]. Signal Fail (SF) in [RFC6378].
Support of EXER command to test if the Protection State Coordination Support of the EXER command to test if the Protection State
(PSC) communication is operating correctly is also covered in this Coordination (PSC) communication is operating correctly is also
document. EXER command tests and validates the linear protection covered in this document. Without actually switching traffic, the
mechanism and PSC protocol including the aliveness of the priority EXER command tests and validates the linear protection mechanism and
logic, the PSC state machine and the PSC message generation and PSC protocol including the aliveness of the priority logic, the PSC
reception, and the integrity of the protection path, without state machine, the PSC message generation and reception, and the
triggering the actual traffic switching. integrity of the protection path.
This document introduces capabilities and modes. A capability is an This document introduces capabilities and modes. A capability is an
individual behavior. The capabilities of a node are advertised using individual behavior. The capabilities of a node are advertised using
the method given in this document. A mode is a particular the method given in this document. A mode is a particular
combination of capabilities. Two modes are defined in this document: combination of capabilities. Two modes are defined in this document:
PSC mode and Automatic Protection Switching (APS) mode. PSC mode and Automatic Protection Switching (APS) mode.
Other modes may be defined as new combinations of the capabilities Other modes may be defined as new combinations of the capabilities
defined in this document or through the definition of additional defined in this document or through the definition of additional
capabilities. In either case, the specification defining a new mode capabilities. In either case, the specification defining a new mode
will be responsible for documenting the behavior, the priority logic, will be responsible for documenting the behavior, the priority logic,
and the state machine of the PSC protocol when the set of and the state machine of the PSC protocol when the set of
capabilities in the new mode are enabled. capabilities in the new mode is enabled.
This document describes the behavior, the priority logic, and the This document describes the behavior, the priority logic, and the
state machine of the PSC protocol when all the capabilities state machine of the PSC protocol when all the capabilities
associated with the APS mode are enabled. The PSC protocol behavior associated with the APS mode are enabled. The PSC protocol behavior
for the PSC mode is as defined in [RFC6378]. for the PSC mode is as defined in [RFC6378].
This document updates [RFC6378] by adding a capability advertisement This document updates [RFC6378] by adding a capability advertisement
mechanism. It is recommended that existing implementations of the mechanism. It is recommended that existing implementations of the
PSC protocol be updated to support this capability. Backward PSC protocol be updated to support this capability. Backward
compatibility with existing implementations that do not support this compatibility with existing implementations that do not support this
mechanism is described in Section 9.2.1. mechanism is described in Section 9.2.1.
Implementations are expected to be configured to support a specific Implementations are expected to be configured to support a specific
set of capabilities (a mode) and to reject messages that indicate the set of capabilities (a mode) and to reject messages that indicate the
use of a different set of capabilities (a different mode). Thus, the use of a different set of capabilities (a different mode). Thus, the
capabilities advertisement is not a negotiation, but a verification capability advertisement is not a negotiation but a verification that
that peers are using the same mode. peers are using the same mode.
2. Conventions Used in This Document 2. 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 this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
3. Acronyms 3. Acronyms
This document uses the following acronyms: This document uses the following acronyms:
APS Automatic Protection Switching APS Automatic Protection Switching
DNR Do-not-Revert DNR Do-not-Revert
EXER Exercise EXER Exercise
FS Forced Switch FS Forced Switch
LO Lockout of protection LO Lockout of protection
MS Manual Switch MS Manual Switch
MS-P Manual Switch to Protection path MS-P Manual Switch to Protection path
MS-W Manual Switch to Working path MS-W Manual Switch to Working path
skipping to change at page 6, line 21 skipping to change at page 6, line 24
MS Manual Switch MS Manual Switch
MS-P Manual Switch to Protection path MS-P Manual Switch to Protection path
MS-W Manual Switch to Working path MS-W Manual Switch to Working path
MPLS-TP MPLS Transport Profile MPLS-TP MPLS Transport Profile
NR No Request NR No Request
OC Operator Clear OC Operator Clear
OTN Optical Transport Network OTN Optical Transport Network
PSC Protection State Coordination PSC Protection State Coordination
RR Reverse Request RR Reverse Request
SD Signal Degrade SD Signal Degrade
SDH Synchronous Digital Hierarchy
SD-P Signal Degrade on Protection path SD-P Signal Degrade on Protection path
SD-W Signal Degrade on Working path SD-W Signal Degrade on Working path
SDH Synchronous Digital Hierarchy
SF Signal Fail SF Signal Fail
SFc Clear Signal Fail
SFDc Clear Signal Fail or Degrade
SF-P Signal Fail on Protection path SF-P Signal Fail on Protection path
SF-W Signal Fail on Working path SF-W Signal Fail on Working path
SFc Clear Signal Fail
SFDc Clear Signal Fail or Degrade
WTR Wait-to-Restore WTR Wait-to-Restore
4. Capability 1: Priority Modification 4. Capability 1: Priority Modification
[RFC6378] defines the priority of FS to be higher than that of SF-P. [RFC6378] defines the priority of FS to be higher than that of SF-P.
That document also defines the priority of Clear SF (SFc) to be low. That document also defines the priority of Clear SF (SFc) to be low.
This document defines the priority modification capability whereby This document defines the priority modification capability whereby
the relative priorities of FS and SF-P are swapped and the priority the relative priorities of FS and SF-P are swapped, and the priority
of Clear SF (SFc) is raised. In addition, this capability introduces of Clear SF (SFc) is raised. In addition, this capability introduces
the Freeze command as described in Appendix C. The rationale for the Freeze command as described in Appendix C. The rationale for
these changes is detailed in the following sub-sections from both the these changes is detailed in the following subsections from both the
technical and network operational aspects. technical and network operational aspects.
4.1. Motivation for swapping priorities of FS and SF-P 4.1. Motivation for Swapping Priorities of FS and SF-P
Defining the priority of FS higher than that of SF-P can result in a Defining the priority of FS higher than that of SF-P can result in a
situation where the protected traffic is taken out-of-service. When situation where the protected traffic is taken out of service. When
the protection path fails PSC communication may stop as a result. In the protection path fails, PSC communication may stop as a result.
this case, if any input that is supposed to be signaled to the other In this case, if any input that is supposed to be signaled to the
end has a higher priority than SF-P then this can result in other end has a higher priority than SF-P, then this can result in an
unpredictable protection switching state. An example scenario that unpredictable protection-switching state. An example scenario that
may result in an out-of-service situation is presented in Appendix A may result in an out-of-service situation is presented in Appendix A
of this document. of this document.
According to Section 2.4 of [RFC5654] it MUST be possible to operate According to Section 2.4 of [RFC5654], it MUST be possible to operate
an MPLS-TP network without using a control plane. This means that an MPLS-TP network without using a control plane. This means that
the PSC communication channel is very important for the transfer of the PSC communication channel is very important for the transfer of
external switching commands (e.g., FS), and these commands should not external switching commands (e.g., FS), and these commands should not
rely on the presence of a control plane. In consequence, the failure rely on the presence of a control plane. In consequence, the failure
of the PSC communication channel has higher priority than FS. of the PSC communication channel has higher priority than FS.
In other transport networks (such as SDH, OTN, and Ethernet transport In other transport networks (such as SDH, OTN, and Ethernet transport
networks) the priority of SF-P has been higher than that of FS. It networks), the priority of SF-P has been higher than that of FS. It
is therefore important to offer network operators the option of is therefore important to offer network operators the option of
having the same behavior in their MPLS-TP networks so that they can having the same behavior in their MPLS-TP networks so that they can
have the same operational protection switching behavior to which they have the same operational protection-switching behavior to which they
have become accustomed. Typically, FS command is issued before have become accustomed. Typically, an FS command is issued before
network maintenance jobs, (e.g., replacing optical cables or other network maintenance jobs (e.g., replacing optical cables or other
network components). When an operator pulls out a cable on the network components). When an operator pulls out a cable on the
protection path, by mistake, the traffic should continue to be protection path, by mistake, the traffic should continue to be
protected and the operator expects this behavior based on his/her protected, and the operator expects this behavior based on his/her
experience on the traditional transport network operations. experience with traditional transport network operations.
4.2. Motivation for raising the priority of SFc 4.2. Motivation for Raising the Priority of SFc
The priority level of SFc defined in [RFC6378] can cause traffic The priority level of SFc defined in [RFC6378] can cause traffic
disruption when a node that has experienced local signal fails on disruption when a node that has experienced local signal fails on
both the working and the protection paths is recovering from these both the working and the protection paths is recovering from these
failures. failures.
An example of sequence diagram highlighting the problem with the A sequence diagram highlighting the problem with the priority level
priority level of SFc as defined in [RFC6378] is presented in of SFc as defined in [RFC6378] is presented in Appendix B.
Appendix B.
4.3. Motivation for introducing Freeze command 4.3. Motivation for Introducing the Freeze Command
With the priority swapping between FS and SF-P, the traffic is always With the priority swapping between FS and SF-P, the traffic is always
moved back to the working path when SF-P occurs in Protecting moved back to the working path when SF-P occurs in Protecting
Administrative state. In case network operators need an option to Administrative state. In case network operators need an option to
control their networks so that the traffic can remain on the control their networks so that the traffic can remain on the
protection path even when the PSC communication channel is broken, protection path even when the PSC communication channel is broken,
the Freeze command can be used. Freeze is defined to be a "local" the Freeze command can be used. Freeze is defined to be a "local"
command that is not signaled to the remote node. The use of the command that is not signaled to the remote node. The use of the
Freeze command is described in Appendix C. Freeze command is described in Appendix C.
4.4. Procedures in support of priority modification 4.4. Procedures in Support of Priority Modification
When the modified priority order specified in this document is in When the modified priority order specified in this document is in
use, the list of local requests in order of priority SHALL be as use, the list of local requests in order of priority SHALL be as
follows: follows (from highest to lowest):
(from highest to lowest)
o Clear Signal Fail o Clear Signal Fail
o Signal Fail on Protection path o Signal Fail on Protection path
o Forced Switch o Forced Switch
o Signal Fail on Working path o Signal Fail on Working path
This requires modification to the PSC Control Logic (including the This requires modification of the PSC Control Logic (including the
state machine) relative to that described in [RFC6378]. Sections 10 state machine) relative to that described in [RFC6378]. Sections 10
and 11 present the PSC Control Logic when all capabilities of APS and 11 present the PSC Control Logic when all capabilities of APS
mode are enabled. mode are enabled.
5. Capability 2: Non-revertive Behavior Modification 5. Capability 2: Non-revertive Behavior Modification
Non-revertive operation of protection switching is defined in Non-revertive operation of protection switching is defined in
[RFC4427]. In this operation, the traffic does not return to the [RFC4427]. In this operation, the traffic does not return to the
working path when switch-over requests are terminated. working path when switch-over requests are terminated.
skipping to change at page 8, line 38 skipping to change at page 8, line 44
with the behavior in other transport networks and to be consistent with the behavior in other transport networks and to be consistent
with [RFC4427], a node should go into the Do-not-Revert (DNR) state with [RFC4427], a node should go into the Do-not-Revert (DNR) state
not only when a failure condition on the working path is cleared, but not only when a failure condition on the working path is cleared, but
also when an operator command that requested switch-over is cleared. also when an operator command that requested switch-over is cleared.
This requires modification to the PSC Control Logic (including the This requires modification to the PSC Control Logic (including the
state machine) relative to that described in [RFC6378]. Sections 10 state machine) relative to that described in [RFC6378]. Sections 10
and 11 present the PSC Control Logic when all capabilities of APS and 11 present the PSC Control Logic when all capabilities of APS
mode are enabled. mode are enabled.
6. Capability 3: Support of MS-W Command 6. Capability 3: Support of the MS-W Command
6.1. Motivation for adding MS-W 6.1. Motivation for adding MS-W
Changing the non-revertive operation as described in Section 5 Changing the non-revertive operation as described in Section 5
introduces necessity of a new operator command to revert traffic to introduces the necessity of a new operator command to revert traffic
the working path in the DNR state. When the traffic is on the to the working path in the DNR state. When the traffic is on the
protection path in the DNR state, a Manual Switch to Working (MS-W) protection path in the DNR state, a Manual Switch to Working (MS-W)
command is issued to switch the normal traffic back to the working command is issued to switch the normal traffic back to the working
path. According to Section 4.3.3.6 (Do-not-Revert State) in path. According to Section 4.3.3.6 (Do-not-Revert State) in
[RFC6378], "to revert back to the Normal state, the administrator [RFC6378], "To revert back to the Normal state, the administrator
SHALL issue a Lockout of protection (LO) command followed by a Clear SHALL issue a Lockout of protection command followed by a Clear
command." However, using LO command introduces the potential risk of command." However, using the Lockout of protection (LO) command
an unprotected situation while the LO is in effect. introduces the potential risk of an unprotected situation while the
LO is in effect.
Manual Switch-over for recovery LSP/span command is defined in The "Manual switch-over for recovery LSP/span" command is defined in
[RFC4427]. Requirement 83 in [RFC5654] states that the external [RFC4427]. Requirement 83 in [RFC5654] states that the external
commands defined in [RFC4427] MUST be supported. Since there is no commands defined in [RFC4427] MUST be supported. Since there is no
support for this external command in [RFC6378], this functionality support for this external command in [RFC6378], this functionality
should be added to PSC. This support is provided by introducing the should be added to PSC. This support is provided by introducing the
MS-W command. The MS-W command, as described here, corresponds to MS-W command. The MS-W command, as described here, corresponds to
the "Manual Switch-over for recovery LSP/span" command. the "Manual switch-over for recovery LSP/span" command.
6.2. Terminology to support MS-W 6.2. Terminology to Support MS-W
[RFC6378] uses the term "Manual Switch" and its acronym "MS". This [RFC6378] uses the term "Manual Switch" and its acronym "MS". This
document uses the term "Manual Switch to Protection path" and "MS-P" document uses the term "Manual Switch to Protection path" and "MS-P"
to have the same meaning, while avoiding confusion with "Manual to have the same meaning, while avoiding confusion with "Manual
Switch to Working path" and its acronym "MS-W". Switch to Working path" and its acronym "MS-W".
Similarly, we modify the name of "Protecting Administrative" state Similarly, we modify the name of "Protecting Administrative" state
(as defined in [RFC6378]) to be "Switching Administrative" state to (as defined in [RFC6378]) to be "Switching Administrative" state to
include the case where traffic is switched to the working path as a include the case where traffic is switched to the working path as a
result of the external MS-W command. result of the external MS-W command.
skipping to change at page 9, line 40 skipping to change at page 9, line 46
o When two commands are received in succession, the command that is o When two commands are received in succession, the command that is
received after the initial command SHALL be cancelled. received after the initial command SHALL be cancelled.
o If two nodes simultaneously receive commands that indicate o If two nodes simultaneously receive commands that indicate
opposite operations (i.e., one node receives MS-P and the other opposite operations (i.e., one node receives MS-P and the other
node receives MS-W) and transmit the indications to the remote node receives MS-W) and transmit the indications to the remote
node, the MS-W SHALL be considered to have a higher priority, and node, the MS-W SHALL be considered to have a higher priority, and
the MS-P SHALL be cancelled and discarded. the MS-P SHALL be cancelled and discarded.
Two commands, MS-P and MS-W are transmitted using the same Request Two commands, MS-P and MS-W, are transmitted using the same Request
field value, but SHALL indicate in the Fault Path (FPath) value the field value but SHALL indicate in the Fault Path (FPath) value the
path that the traffic is being diverted from. When traffic is path from which the traffic is being diverted. When traffic is
switched to the protection path, the FPath field value SHALL be set switched to the protection path, the FPath field value SHALL be set
to 1, indicating that traffic is being diverted from the working to 1, indicating that traffic is being diverted from the working
path. When traffic is switched to the working path, the FPath field path. When traffic is switched to the working path, the FPath field
value SHALL be set to 0, indicating that traffic is being diverted value SHALL be set to 0, indicating that traffic is being diverted
from the protection path. The Data Path (Path) field SHALL indicate from the protection path. The Data Path (Path) field SHALL indicate
where user data traffic is being transported (i.e., if the working where user data traffic is being transported (i.e., if the working
path is selected, then Path is set to 0; if the protection path is path is selected, then Path is set to 0; if the protection path is
selected, then Path is set to 1). selected, then Path is set to 1).
When an MS command is in effect at a node, any subsequent MS or EXER When an MS command is in effect at a node, any subsequent MS or EXER
command and any other lower priority requests SHALL be ignored. command and any other lower-priority requests SHALL be ignored.
6.4. Equal priority resolution for MS 6.4. Equal-Priority Resolution for MS
[RFC6378] defines only one rule for equal priority condition in [RFC6378] defines only one rule for the equal-priority condition in
Section 4.3.2 as "The remote message from the remote LER is assigned Section 4.3.2 as "The remote message from the far-end LER is assigned
a priority just below the similar local input." In order to support a priority just below the similar local input." In order to support
the manual switch behavior described in Section 6.3, additional rules the Manual Switch behavior described in Section 6.3, additional rules
for equal priority resolution are required. Since the support of for equal-priority resolution are required. Since the support of
protection against signal degrade also requires a similar equal protection against signal degrade also requires a similar equal-
priority resolution, the rules are described in Section 7.4. priority resolution, the rules are described in Section 7.4.
Support of this function requires changes to the PSC Control Logic Support of this function requires changes to the PSC Control Logic
(including the state machine) relative to that shown in [RFC6378]. (including the state machine) relative to that shown in [RFC6378].
Sections 10 and 11 present the PSC Control Logic when all Sections 10 and 11 present the PSC Control Logic when all
capabilities of APS mode are enabled. capabilities of APS mode are enabled.
7. Capability 4: Support of Protection against SD 7. Capability 4: Support of Protection against SD
7.1. Motivation for supporting protection against SD 7.1. Motivation for Supporting Protection against SD
In the MPLS-TP Survivability Framework [RFC6372], both SF and SD In the MPLS-TP Survivability Framework [RFC6372], both SF and SD
fault conditions can be used to trigger protection switching. fault conditions can be used to trigger protection switching.
[RFC6378], which defines the protection switching protocol for MPLS- [RFC6378], which defines the protection-switching protocol for
TP, does not specify how the SF and SD are detected, and specifies MPLS-TP, does not specify how the SF and SD are detected, and
the protection switching protocol associated with SF only. specifies the protection-switching protocol associated with SF only.
The PSC protocol associated with SD is covered in this document, but The PSC protocol associated with SD is covered in this document, but
the specifics for the method of identifying SD is out of scope for the specifics for the method of identifying SD is out of scope for
the protection protocol in the same way that SF detection and MS or the protection protocol in the same way that SF detection and MS or
FS command initiation are out of scope. FS command initiation are out of scope.
7.2. Terminology to support SD 7.2. Terminology to Support SD
In this document the term Clear Signal Fail or Degrade (SFDc) is used In this document, the term Clear Signal Fail or Degrade (SFDc) is
to indicate the clearance of either a degraded condition or a failure used to indicate the clearance of either a degraded condition or a
condition. failure condition.
The second paragraph of Section 4.3.3.2 Unavailable state in The second paragraph of Section 4.3.3.2 (Unavailable State) in
[RFC6378] shows the intention of including Signal Degrade on [RFC6378] shows the intention of including Signal Degrade on
Protection path (SD-P) in the Unavailable state. Even though the Protection path (SD-P) in the Unavailable state. Even though the
protection path can be partially available under the condition of protection path can be partially available under the condition of
SD-P, this document follows the same state grouping as [RFC6378] for SD-P, this document follows the same state grouping as [RFC6378] for
SD-P. SD-P.
The bullet item on the Protecting Failure state in Section 3.6 of The bulleted item on the Protecting Failure state in Section 3.6 of
[RFC6378] includes the degraded condition in the Protecting Failure [RFC6378] includes the degraded condition in the Protecting Failure
state. This document follows the same state grouping as [RFC6378] state. This document follows the same state grouping as [RFC6378]
for Signal Degrade on Working path (SD-W). for Signal Degrade on Working path (SD-W).
7.3. Behavior of protection against SD 7.3. Behavior of Protection against SD
To better align the behavior of MPLS-TP networks with that of other To better align the behavior of MPLS-TP networks with that of other
transport networks (such as SDH, OTN, and Ethernet transport transport networks (such as SDH, OTN, and Ethernet transport
networks) we define the followings: networks), we define the following:
o The priorities of SD-P and SD-W SHALL be equal. o The priorities of SD-P and SD-W SHALL be equal.
o Once a switch has been completed due to SD on one path, it will o Once a switch has been completed due to SD on one path, it will
not be overridden by SD on the other path (first come, first not be overridden by SD on the other path (first come, first
served behavior), to avoid protection switching that cannot served behavior), to avoid protection switching that cannot
improve signal quality. improve signal quality.
The SD message indicates that the transmitting node has identified The SD message indicates that the transmitting node has identified
degradation of the signal or integrity of the packet received on degradation of the signal or integrity of the packet received on
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recovering from the situation, the Wait-to-Restore (WTR) timer SHALL recovering from the situation, the Wait-to-Restore (WTR) timer SHALL
be used if the protected domain is configured for revertive behavior. be used if the protected domain is configured for revertive behavior.
The WTR timer SHALL be started at the node that recovers from a local The WTR timer SHALL be started at the node that recovers from a local
degraded condition on the working path. degraded condition on the working path.
Protection switching against SD is always provided by a selector Protection switching against SD is always provided by a selector
bridge duplicating user data traffic and feeding it to both the bridge duplicating user data traffic and feeding it to both the
working path and the protection path under SD condition. When a working path and the protection path under SD condition. When a
local or remote SD occurs on either the working path or the local or remote SD occurs on either the working path or the
protection path, the node SHALL duplicate user data traffic and SHALL protection path, the node SHALL duplicate user data traffic and SHALL
feed to both the working path and the protection path. The packet feed it to both the working path and the protection path. The packet
duplication SHALL continue as long as any SD condition exists in the duplication SHALL continue as long as any SD condition exists in the
protected domain. When the SD condition is cleared, in revertive protected domain. When the SD condition is cleared, in revertive
operation, the packet duplication SHALL continue in the WTR state and operation, the packet duplication SHALL continue in the WTR state and
SHALL stop when the node leaves the WTR state; while in non-revertive SHALL stop when the node leaves the WTR state; while in non-revertive
operation, the packet duplication SHALL stop immediately. operation, the packet duplication SHALL stop immediately.
The selector bridge with the packet duplication under SD condition, The selector bridge with the packet duplication under SD condition,
which is a non-permanent bridge, is considered to be a 1:1 protection which is a non-permanent bridge, is considered to be a 1:1 protection
architecture. architecture.
Protection switching against SD does not introduce any modification Protection switching against SD does not introduce any modification
to the operation of the selector at the sink node described in to the operation of the selector at the sink node described in
[RFC6378]. The selector chooses either the working or protection [RFC6378]. The selector chooses either the working or protection
path from which to receive the normal traffic in both 1:1 and 1+1 path from which to receive the normal traffic in both 1:1 and 1+1
architectures. The position of the selector, i.e., which path to architectures. The position of the selector, i.e., which path to
receive the traffic, is determined by the PSC protocol in receive the traffic, is determined by the PSC protocol in
bidirectional switching or by the local input in unidirectional bidirectional switching or by the local input in unidirectional
switching. switching.
7.4. Equal priority resolution 7.4. Equal-Priority Resolution
In order to support the MS behavior described in Section 6.3 and the In order to support the MS behavior described in Section 6.3 and the
protection against SD described in Section 7.3, it is necessary to protection against SD described in Section 7.3, it is necessary to
expand rules for treating equal priority inputs. expand rules for treating equal-priority inputs.
For equal priority local inputs, such as MS and SD, apply a simple For equal-priority local inputs, such as MS and SD, apply a simple
first-come, first-served rule. Once a local input is determined as first-come, first-served rule. Once a local input is determined as
the highest priority local input, then a subsequent equal priority the highest priority local input, then a subsequent equal-priority
local input requesting a different action, i.e., the action results local input requesting a different action, i.e., the action results
in the same PSC Request field but different FPath value, will not be in the same PSC Request field but different FPath value, will not be
presented to the PSC Control Logic as the highest local request. presented to the PSC Control Logic as the highest local request.
Furthermore, in the case of MS command, the subsequent local MS Furthermore, in the case of an MS command, the subsequent local MS
command requesting a different action will be cancelled. command requesting a different action will be cancelled.
If a node is in a remote state due to a remote SD (or MS) message, a If a node is in a remote state due to a remote SD (or MS) message, a
subsequent local input having the same priority but requesting a subsequent local input having the same priority but requesting a
different action to the PSC Control Logic, will be considered as different action to the PSC Control Logic will be considered as
having lower priority than the remote message, and will be ignored. having lower priority than the remote message and will be ignored.
For examples, if a node is in remote Switching Administrative state For example, if a node is in remote Switching Administrative state
due to a remote MS-P, then any subsequent local MS-W SHALL be ignored due to a remote MS-P, then any subsequent local MS-W SHALL be ignored
and automatically cancelled. If a node is in remote Unavailable and automatically cancelled. If a node is in remote Unavailable
state due to a remote SD-P, then any subsequent local SD-W input will state due to a remote SD-P, then any subsequent local SD-W input will
be ignored. However, the local SD-W SHALL continue to appear in the be ignored. However, the local SD-W SHALL continue to appear in the
Local Request Logic as long as the SD condition exists, but SHALL NOT Local Request Logic as long as the SD condition exists, but it SHALL
be the top priority global request, which determines the state NOT be the top-priority global request, which determines the state
transition at the PSC Control Logic. transition at the PSC Control Logic.
Cases where two end-points of the protected domain simultaneously Cases where two end-points of the protected domain simultaneously
receive local triggers of the same priority that request different receive local triggers of the same priority that request different
actions (for example, one node receives SD-P and the other receives actions may occur (for example, one node receives SD-P and the other
SD-W) may occur. Subsequently, each node will receive a remote receives SD-W). Subsequently, each node will receive a remote
message with the opposing action indication. To address these cases, message with the opposing action indication. To address these cases,
we define the following priority resolution rules: we define the following priority resolution rules:
o When MS-W and MS-P occur simultaneously at both nodes, MS-W SHALL o When MS-W and MS-P occur simultaneously at both nodes, MS-W SHALL
be considered as having higher priority than MS-P at both nodes. be considered as having higher priority than MS-P at both nodes.
o When SD-W and SD-P occur simultaneously at both nodes, the SD on o When SD-W and SD-P occur simultaneously at both nodes, the SD on
the standby path (the path from which the selector does not select the standby path (the path from which the selector does not select
the user data traffic) is considered as having higher priority the user data traffic) is considered as having higher priority
than the SD on the active path (the path from which the selector than the SD on the active path (the path from which the selector
selects the user data traffic) regardless of its origin (local or selects the user data traffic) regardless of its origin (local or
remote message). Therefore, no unnecessary protection switching remote message). Therefore, no unnecessary protection switching
is performed and the user data traffic continues to be selected is performed, and the user data traffic continues to be selected
from the active path. from the active path.
In the preceding paragraphs, the "simultaneously" refers to the case In the preceding paragraphs, "simultaneously" refers to the case a
a sent SD (or MS) request has not been confirmed by the remote end in sent SD (or MS) request has not been confirmed by the remote end in
bidirectional protection switching. When a local node that has bidirectional protection switching. When a local node that has
transmitted a SD message receives a SD (or MS) message that indicates transmitted an SD message receives an SD (or MS) message that
a different value of Path field from the value of Path field in the indicates a different value of Path field from the value of Path
transmitted SD (or MS) message, both the local and remote SD requests field in the transmitted SD (or MS) message, both the local and
are considered to occur simultaneously. remote SD requests are considered to occur simultaneously.
The addition of support for protection against SD requires The addition of support for protection against SD requires
modification to the PSC Control Logic (including the state machine) modification to the PSC Control Logic (including the state machine)
relative to that described in [RFC6378]. Sections 10 and 11 present relative to that described in [RFC6378]. Sections 10 and 11 present
the PSC Control Logic when all capabilities of APS mode are enabled. the PSC Control Logic when all capabilities of APS mode are enabled.
8. Capability 5: Support of EXER Command 8. Capability 5: Support of EXER Command
The EXER command is used to verify the correct operation of the PSC The EXER command is used to verify the correct operation of the PSC
communication, such as the aliveness of the Local Request Logic, the communication, such as the aliveness of the Local Request Logic, the
skipping to change at page 14, line 6 skipping to change at page 14, line 16
Reverse Request (RR) message with the FPath and Path fields set Reverse Request (RR) message with the FPath and Path fields set
according to the current condition of the node. The RR message SHALL according to the current condition of the node. The RR message SHALL
be generated only in response to a remote EXER message. be generated only in response to a remote EXER message.
This command is documented in R84 of [RFC5654]. This command is documented in R84 of [RFC5654].
If EXER commands are input at both ends, then a race condition may If EXER commands are input at both ends, then a race condition may
arise. This is resolved as follows: arise. This is resolved as follows:
o If a node has issued EXER and receives EXER before receiving RR, o If a node has issued EXER and receives EXER before receiving RR,
it MUST treat the received EXER as it would an RR, and SHOULD NOT it MUST treat the received EXER as it would an RR, and it SHOULD
respond with RR. NOT respond with RR.
The following PSC Requests are added to the PSC Request field to The following PSC Requests are added to the PSC Request field to
support the Exercise command (see also Section 14.1): support the Exercise command (see also Section 14.1):
(3) Exercise - indicates that the transmitting end point is (3) Exercise - indicates that the transmitting end-point is
exercising the protection channel and mechanism. FPath and Path exercising the protection channel and mechanism. FPath and Path
are set to the same value of the No Request (NR), RR or DNR are set to the same value of the No Request (NR), RR, or DNR
message whose transmission is stopped by EXER. message whose transmission is stopped by EXER.
(2) Reverse Request - indicates that the transmitting end point is (2) Reverse Request - indicates that the transmitting end-point is
responding to an EXER command from the remote node. FPath and responding to an EXER command from the remote node. FPath and
Path are set to the same value of the NR or DNR message whose Path are set to the same value of the NR or DNR message whose
transmission is stopped by RR. transmission is stopped by RR.
The relative priorities of EXER and RR are defined in Section 10.2. The relative priorities of EXER and RR are defined in Section 10.2.
9. Capabilities and Modes 9. Capabilities and Modes
9.1. Capabilities 9.1. Capabilities
skipping to change at page 14, line 43 skipping to change at page 15, line 5
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = Capabilities | Length | | Type = Capabilities | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value = Flags | | Value = Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Format of Capabilities TLV Figure 1: Format of Capabilities TLV
The value of the Type field is TBD pending IANA allocation. The value of the Type field is 1.
The value of the Length field is the length of the Flags field in The value of the Length field is the length of the Flags field in
octets. The length of the Flags field MUST be a multiple of 4 octets octets. The length of the Flags field MUST be a multiple of 4 octets
and MUST be the minimum required to signal all the required and MUST be the minimum required to signal all the required
capabilities. capabilities.
Section 4 to Section 8 discuss five capabilities that are signaled Section 4 to Section 8 discuss five capabilities that are signaled
using the five most significant bits; if a node wishes to signal using the five most significant bits; if a node wishes to signal
these five capabilities, it MUST send a Flags field of 4 octets. A these five capabilities, it MUST send a Flags field of 4 octets. A
node would send a Flags field greater than 4 octets only if it had node would send a Flags field greater than 4 octets only if it had
skipping to change at page 15, line 33 skipping to change at page 15, line 44
0x20000000: support of MS-W command 0x20000000: support of MS-W command
0x10000000: support of protection against SD 0x10000000: support of protection against SD
0x08000000: support of EXER command 0x08000000: support of EXER command
If all the five capabilities should be used, a node SHALL set the If all the five capabilities should be used, a node SHALL set the
Flags field to 0xF8000000. Flags field to 0xF8000000.
9.1.1. Sending and receiving the Capabilities TLV 9.1.1. Sending and Receiving the Capabilities TLV
A node MUST include its Capabilities TLV in every PSC message that it A node MUST include its Capabilities TLV in every PSC message that it
transmits. The transmission and acceptance of the PSC message is transmits. The transmission and acceptance of the PSC message is
described in Section 4.1 of [RFC6378]. described in Section 4.1 of [RFC6378].
When a node receives a Capabilities TLV it MUST compare the Flags When a node receives a Capabilities TLV, it MUST compare the Flags
value to its most recent Flags value transmitted by the node. If the value to its most recent Flags value transmitted by the node. If the
two are equal, the protected domain is said to be running in the mode two are equal, the protected domain is said to be running in the mode
indicated by that set of capabilities (see Section 9.2). If the sent indicated by that set of capabilities (see Section 9.2). If the sent
and received Capabilities TLVs are not equal, this indicates a and received Capabilities TLVs are not equal, this indicates a
capabilities TLV mismatch. When this happens, the node MUST alert Capabilities TLV mismatch. When this happens, the node MUST alert
the operator and MUST NOT perform any protection switching until the the operator and MUST NOT perform any protection switching until the
operator resolves the mismatch between the two end-points. operator resolves the mismatch between the two end-points.
9.2. Modes 9.2. Modes
A mode is a given set of Capabilities. Modes are shorthand; A mode is a given set of Capabilities. Modes are shorthand;
referring to a set of capabilities by their individual values or by referring to a set of capabilities by their individual values or by
the name of their mode does not change the protocol behavior. This the name of their mode does not change the protocol behavior. This
document defines two modes - PSC and APS. Capability TLVs with other document defines two modes -- PSC and APS. Capabilities TLVs with
combinations than the one specified by a mode are not supported in other combinations than the one specified by a mode are not supported
this specification. in this specification.
9.2.1. PSC mode 9.2.1. PSC Mode
PSC mode is defined as the lack of support for any of the additional PSC mode is defined as the lack of support for any of the additional
capabilities defined in this document - that is, a Capabilities set capabilities defined in this document -- that is, a Capabilities set
of 0x0. It is the behavior specified in [RFC6378]. of 0x0. It is the behavior specified in [RFC6378].
There are two ways to declare PSC mode. A node can send no There are two ways to declare PSC mode. A node can send no
Capabilities TLV at all since there are no TLV units defined in Capabilities TLV at all since there are no TLV units defined in
[RFC6378], or it can send a Capabilities TLV with Flags value set to [RFC6378], or it can send a Capabilities TLV with Flags value set to
0x0. In order to allow backward compatibility between two end-points 0x0. In order to allow backward compatibility between two end-points
- one which supports sending the Capabilities TLV, and one which does -- one which supports sending the Capabilities TLV, and one which
not, the node that has the ability to send and process the PSC mode does not, the node that has the ability to send and process the PSC
Capabilities TLV MUST be able to both send the PSC mode Capabilities mode Capabilities TLV MUST be able to both send the PSC mode
TLV and send no Capabilities TLV at all. An implementation MUST be Capabilities TLV and send no Capabilities TLV at all. An
configurable between these two options. implementation MUST be configurable between these two options.
9.2.2. APS mode 9.2.2. APS Mode
APS mode is defined as the use of all the five specific capabilities, APS mode is defined as the use of all the five specific capabilities,
which are described in Section 4 to Section 8 in this document. APS which are described in Sections 4 to 8 in this document. APS mode is
mode is indicated with the Flags value of 0xF8000000. indicated with the Flags value of 0xF8000000.
10. PSC Protocol in APS Mode 10. PSC Protocol in APS Mode
This section and the following section define the behavior of PSC This section and the following section define the behavior of the PSC
protocol when all of the aforementioned capabilities are enabled, protocol when all of the aforementioned capabilities are enabled,
i.e., APS mode. i.e., APS mode.
10.1. Request field in PSC protocol message 10.1. Request Field in PSC Protocol Message
This document defines two new values for the "Request" field in the This document defines two new values for the "Request" field in the
PSC protocol message that is shown in Figure 2 of [RFC6378] as PSC protocol message that is shown in Figure 2 of [RFC6378] as
follows: follows:
(3) Exercise
(2) Reverse Request (2) Reverse Request
(3) Exercise
See also Section 14.1 of this document. See also Section 14.1 of this document.
10.2. Priorities of local inputs and remote requests 10.2. Priorities of Local Inputs and Remote Requests
Based on the description in Sections 3 and 4.3.2 in [RFC6378], the Based on the description in Sections 3 and 4.3.2 in [RFC6378], the
priorities of multiple outstanding local inputs are evaluated in the priorities of multiple outstanding local inputs are evaluated in the
Local Request Logic, where the highest priority local input (highest Local Request Logic, where the highest priority local input (highest
local request) is determined. This highest local request is passed local request) is determined. This highest local request is passed
to the PSC Control Logic, that will determine the higher priority to the PSC Control Logic that will determine the higher-priority
input (top priority global request) between the highest local request input (top-priority global request) between the highest local request
and the last received remote message. When a remote message comes to and the last received remote message. When a remote message comes to
the PSC Control Logic, the top priority global request is determined the PSC Control Logic, the top-priority global request is determined
between this remote message and the highest local request which is between this remote message and the highest local request that is
present. The top priority global request is used to determine the present. The top-priority global request is used to determine the
state transition, which is described in Section 11. In this state transition, which is described in Section 11. In this
document, in order to simplify the description on the PSC Control document, in order to simplify the description on the PSC Control
Logic, we strictly decouple the priority evaluation from the state Logic, we strictly decouple the priority evaluation from the state
transition table lookup. transition table lookup.
The priorities for both local and remote requests are defined as The priorities for both local and remote requests are defined as
follows from highest to lowest: follows from highest to lowest:
o Operator Clear (Local only) o Operator Clear (Local only)
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o WTR Timer Expiry (Local only) o WTR Timer Expiry (Local only)
o WTR (Remote only) o WTR (Remote only)
o Exercise (Local and Remote) o Exercise (Local and Remote)
o Reverse Request (Remote only) o Reverse Request (Remote only)
o Do-Not-Revert (Remote only) o Do-Not-Revert (Remote only)
o No Request (Remote and Local) o No Request (Remote and Local)
Note that the "Local only" requests are not tranmitted to the remote Note that the "Local only" requests are not transmitted to the remote
node. Likewise, the "Remote only" requests do not exist in the Local node. Likewise, the "Remote only" requests do not exist in the Local
Request Logic as local inputs. For example, the priority of WTR only Request Logic as local inputs. For example, the priority of WTR only
applies to the received WTR message, which is generated from the applies to the received WTR message, which is generated from the
remote node. The remote node that is running the WTR timer in the remote node. The remote node that is running the WTR timer in the
WTR state has no local request. WTR state has no local request.
The remote SF and SD on either the working path or the protection The remote SF and SD on either the working path or the protection
path and the remote MS to either the working path or the protection path and the remote MS to either the working path or the protection
path are indicated by the values of the Request and FPath fields in path are indicated by the values of the Request and FPath fields in
the PSC message. the PSC message.
The remote request from the remote node is assigned a priority just The remote request from the remote node is assigned a priority just
below the same local request except NR and equal priority requests, below the same local request except for NR and equal-priority
such as SD and MS. Since a received NR message needs to be used in requests, such as SD and MS. Since a received NR message needs to be
the state transition table lookup when there is no outstanding local used in the state transition table lookup when there is no
request, the remote NR request SHALL have a higher priority than the outstanding local request, the remote NR request SHALL have a higher
local NR. For the equal priority requests, see Section 10.2.1. priority than the local NR. For the equal-priority requests, see
Section 10.2.1.
10.2.1. Equal priority requests 10.2.1. Equal-Priority Requests
As stated in Section 10.2, the remote request from the remote node is As stated in Section 10.2, the remote request from the remote node is
assigned a priority just below the same local request. However, for assigned a priority just below the same local request. However, for
equal priority requests, such as SD and MS, the priority SHALL be equal-priority requests, such as SD and MS, the priority SHALL be
evaluated as described in this section. evaluated as described in this section.
For equal priority local requests, first-come, first-served rule For equal-priority local requests, the first-come, first-served rule
SHALL be applied. Once a local request appears in the Local Request SHALL be applied. Once a local request appears in the Local Request
Logic, a subsequent equal priority local request requesting a Logic, a subsequent equal-priority local request requesting a
different action, i.e., the action results in the same Request value different action, i.e., the action results in the same Request value
but a different FPath value, SHALL be considered to have a lower but a different FPath value, SHALL be considered to have a lower
priority. Furthermore, in the case of MS command, the subsequent priority. Furthermore, in the case of an MS command, the subsequent
local MS command requesting a different action SHALL be rejected and local MS command requesting a different action SHALL be rejected and
cleared. cleared.
When the priority is evaluated in the PSC Control Logic between the When the priority is evaluated in the PSC Control Logic between the
highest local request and a remote request, the following equal highest local request and a remote request, the following equal-
priority resolution rules SHALL be applied: priority resolution rules SHALL be applied:
o If two requests request the same action, i.e., the same Request o If two requests request the same action, i.e., the same Request
and FPath values, then the local request SHALL be considered to and FPath values, then the local request SHALL be considered to
have a higher priority than the remote request. have a higher priority than the remote request.
o When the highest local request comes to the PSC Control Logic, if o When the highest local request comes to the PSC Control Logic, if
the remote request that requests a different action exists, then the remote request that requests a different action exists, then
the highest local request SHALL be ignored and the remote request the highest local request SHALL be ignored and the remote request
SHALL remain to be the top priority global request. In the case SHALL remain to be the top-priority global request. In the case
of MS command, the local MS command requesting a different action of an MS command, the local MS command requesting a different
SHALL be cancelled. action SHALL be cancelled.
o When the remote request comes to the PSC Control Logic, if the o When the remote request comes to the PSC Control Logic, if the
highest local request that requests a different action exists, highest local request that requests a different action exists,
then the top priority global request SHALL be determined by the then the top-priority global request SHALL be determined by the
following rules: following rules:
* For MS requests, the MS-W request SHALL be considered to have a * For MS requests, the MS-W request SHALL be considered to have a
higher priority than the MS-P request. The node that has local higher priority than the MS-P request. The node that has the
MS-W request SHALL maintain the local MS-W request as the top local MS-W request SHALL maintain the local MS-W request as the
priority global request. The other node that has local MS-P top-priority global request. The other node that has the local
request SHALL cancel the MS-P command and SHALL generate MS-P request SHALL cancel the MS-P command and SHALL generate
"Operator Clear" internally as the top priority global request. "Operator Clear" internally as the top-priority global request.
* For SD requests, the SD on the standby path (the path from * For SD requests, the SD on the standby path (the path from
which the selector does not select the user data traffic) SHALL which the selector does not select the user data traffic) SHALL
be considered to have a higher priority than the SD on the be considered to have a higher priority than the SD on the
active path (the path from which the selector selects the user active path (the path from which the selector selects the user
data traffic) regardless of its origin (local or remote data traffic) regardless of its origin (local or remote
message). The node that has the SD on the standby path SHALL message). The node that has the SD on the standby path SHALL
maintain the local SD on the standby path request as the top maintain the local SD on the standby path request as the top-
priority global request. The other node that has local SD on priority global request. The other node that has local SD on
the active path SHALL use the remote SD on the standby path as the active path SHALL use the remote SD on the standby path as
the top priority global request to lookup the state transition the top-priority global request to lookup the state transition
table. The differentiation of the active and standby paths is table. The differentiation of the active and standby paths is
based upon which path had been selected for the user data based upon which path had been selected for the user data
traffic "when each node detected its local SD". traffic when each node detected its local SD.
10.3. Acceptance and retention of local inputs 10.3. Acceptance and Retention of Local Inputs
A local input indicating a defect, such as SF-P, SF-W, SD-P and SD-W, A local input indicating a defect, such as SF-P, SF-W, SD-P, and
SHALL be accepted and retained persistently in the Local Request SD-W, SHALL be accepted and retained persistently in the Local
Logic as long as the defect condition exists. If there is any higher Request Logic as long as the defect condition exists. If there is
priority local input than the local defect input, the higher priority any higher-priority local input than the local defect input, the
local input is passed to the PSC Control Logic as the highest local higher-priority local input is passed to the PSC Control Logic as the
request, but the local defect input cannot be removed but remains in highest local request, but the local defect input cannot be removed
the Local Request Logic. When the higher priority local input is but remains in the Local Request Logic. When the higher-priority
cleared, the local defect will become the highest local request if local input is cleared, the local defect will become the highest
the defect condition still exists. local request if the defect condition still exists.
Operator Clear (OC) command, SFDc and WTR Timer Expiry are not The Operator Clear (OC) command, SFDc, and WTR Timer Expiry are not
persistent. Once they appear to the Local Request Logic and complete persistent. Once they appear to the Local Request Logic and complete
all the operations in the protection switching control, they SHALL all the operations in the protection-switching control, they SHALL
disappear. disappear.
LO, FS, MS, and EXER commands SHALL be rejected if there is any The LO, FS, MS, and EXER commands SHALL be rejected if there is any
higher priority local input in the Local Request Logic. If a new higher-priority local input in the Local Request Logic. If a new
higher-priority local request (including an operator command) is higher-priority local request (including an operator command) is
accepted, any previous lower-priority local operator command SHALL be accepted, any previous lower-priority local operator command SHALL be
cancelled. When any higher-priority remote request is received, a cancelled. When any higher-priority remote request is received, a
lower-priority local operator command SHALL be cancelled. The lower-priority local operator command SHALL be cancelled. The
cancelled operator command is cleared. If the operators wish to cancelled operator command is cleared. If the operators wish to
renew the cancelled command then they should reissue the command. renew the cancelled command, then they should reissue the command.
11. State Transition Tables in APS Mode 11. State Transition Tables in APS Mode
When there is a change in the highest local request or in remote PSC When there is a change in the highest local request or in remote PSC
messages, the top priority global request SHALL be evaluated and the messages, the top-priority global request SHALL be evaluated, and the
state transition tables SHALL be looked up in the PSC Control Logic. state transition tables SHALL be looked up in the PSC Control Logic.
The following rules are applied to the operation related to the state The following rules are applied to the operation related to the state
transition table lookup. transition table lookup.
o If the top priority global request, which determines the state o If the top-priority global request, which determines the state
transition, is the highest local request, the local state transition, is the highest local request, the local state
transition table in Section 11.1 SHALL be used to decide the next transition table in Section 11.1 SHALL be used to decide the next
state of the node. Otherwise, the remote state transition table state of the node. Otherwise, the remote state transition table
in Section 11.2 SHALL be used. in Section 11.2 SHALL be used.
o If in remote state, the highest local defect condition (SF-P, o If in remote state, the highest local defect condition (SF-P,
SF-W, SD-P or SD-W) SHALL always be reflected in the Request and SF-W, SD-P, or SD-W) SHALL always be reflected in the Request and
Fpath fields. FPath fields.
o For the node currently in the local state, if the top priority o For the node currently in the local state, if the top-priority
global request is changed to OC or SFDc causing the next state to global request is changed to OC or SFDc, causing the next state to
be Normal, WTR or DNR, then all the local and remote requests be Normal, WTR, or DNR, then all the local and remote requests
SHALL be re-evaluated as if the node is in the state specified in SHALL be re-evaluated as if the node is in the state specified in
the footnotes to the state transition tables, before deciding the the footnotes to the state transition tables, before deciding the
final state. If there are no active requests, the node enters the final state. If there are no active requests, the node enters the
state specified in the footnotes to the state transition tables. state specified in the footnotes to the state transition tables.
This re-evaluation is an internal operation confined within the This re-evaluation is an internal operation confined within the
local node, and the PSC messages are generated according to the local node, and the PSC messages are generated according to the
final state. final state.
o The WTR timer is started only when the node which has recovered o The WTR timer is started only when the node that has recovered
from a local failure or degradation enters the WTR state. A node from a local failure or degradation enters the WTR state. A node
which is entering into the WTR state due to a remote WTR message that is entering into the WTR state due to a remote WTR message
does not start the WTR timer. The WTR timer SHALL be stopped when does not start the WTR timer. The WTR timer SHALL be stopped when
any local or remote request triggers the state change out of the any local or remote request triggers the state change out of the
WTR state. WTR state.
The extended states, as they appear in the table, are as follows: The extended states, as they appear in the table, are as follows:
N Normal state N Normal state
UA:LO:L Unavailable state due to local LO command UA:LO:L Unavailable state due to local LO command
UA:P:L Unavailable state due to local SF-P UA:P:L Unavailable state due to local SF-P
UA:DP:L Unavailable state due to local SD-P UA:DP:L Unavailable state due to local SD-P
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SA:MP:L Switching Administrative state due to local MS-P command SA:MP:L Switching Administrative state due to local MS-P command
SA:F:R Switching Administrative state due to remote FS message SA:F:R Switching Administrative state due to remote FS message
SA:MW:R Switching Administrative state due to remote MS-W message SA:MW:R Switching Administrative state due to remote MS-W message
SA:MP:R Switching Administrative state due to remote MS-P message SA:MP:R Switching Administrative state due to remote MS-P message
WTR Wait-to-Restore state WTR Wait-to-Restore state
DNR Do-not-Revert state DNR Do-not-Revert state
E::L Exercise state due to local EXER command E::L Exercise state due to local EXER command
E::R Exercise state due to remote EXER message E::R Exercise state due to remote EXER message
Each state corresponds to the transmission of a particular set of Each state corresponds to the transmission of a particular set of
Request, FPath and Path fields. The table below lists the message Request, FPath, and Path fields. The table below lists the message
that is generally sent in each particular state. If the message to that is generally sent in each particular state. If the message to
be sent in a particular state deviates from the table below, it is be sent in a particular state deviates from the table below, it is
noted in the footnotes to the state transition tables. noted in the footnotes of the state transition tables.
State Request(FPath,Path) State Request(FPath,Path)
------- ------------------------------------ ------- ------------------------------------
N NR(0,0) N NR(0,0)
UA:LO:L LO(0,0) UA:LO:L LO(0,0)
UA:P:L SF(0,0) UA:P:L SF(0,0)
UA:DP:L SD(0,0) UA:DP:L SD(0,0)
UA:LO:R highest local request(local FPath,0) UA:LO:R highest local request(local FPath,0)
UA:P:R highest local request(local FPath,0) UA:P:R highest local request(local FPath,0)
UA:DP:R highest local request(local FPath,0) UA:DP:R highest local request(local FPath,0)
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WTR WTR(0,1) WTR WTR(0,1)
DNR DNR(0,1) DNR DNR(0,1)
E::L EXER(0,x), where x is the existing Path value E::L EXER(0,x), where x is the existing Path value
when Exercise command is issued. when Exercise command is issued.
E::R RR(0,x), where x is the existing Path value E::R RR(0,x), where x is the existing Path value
when RR message is generated. when RR message is generated.
Some operation examples of APS mode are shown in Appendix D. Some operation examples of APS mode are shown in Appendix D.
In the state transition tables below, the letter 'i' stands for In the state transition tables below, the letter 'i' stands for
"ignore", and is an indication to remain in the current state and "ignore" and is an indication to remain in the current state and
continue transmitting the current PSC message continue transmitting the current PSC message
11.1. State transition by local inputs 11.1. State Transition by Local Inputs
| OC | LO | SFDc | SF-P | FS | SF-W | | OC | LO | SFDc | SF-P | FS | SF-W |
--------+-----+---------+------+--------+--------+--------+ --------+-----+---------+------+--------+--------+--------+
N | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L | N | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
UA:LO:L | (1) | i | i | i | i | i | UA:LO:L | (1) | i | i | i | i | i |
UA:P:L | i | UA:LO:L | (1) | i | i | i | UA:P:L | i | UA:LO:L | (1) | i | i | i |
UA:DP:L | i | UA:LO:L | (1) | UA:P:L | SA:F:L | PF:W:L | UA:DP:L | i | UA:LO:L | (1) | UA:P:L | SA:F:L | PF:W:L |
UA:LO:R | i | UA:LO:L | i | UA:P:L | i | PF:W:L | UA:LO:R | i | UA:LO:L | i | UA:P:L | i | PF:W:L |
UA:P:R | i | UA:LO:L | i | UA:P:L | i | PF:W:L | UA:P:R | i | UA:LO:L | i | UA:P:L | i | PF:W:L |
UA:DP:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L | UA:DP:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
PF:W:L | i | UA:LO:L | (2) | UA:P:L | SA:F:L | i | PF:W:L | i | UA:LO:L | (2) | UA:P:L | SA:F:L | i |
skipping to change at page 23, line 28 skipping to change at page 24, line 5
SA:MW:L | (1) | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L | SA:MW:L | (1) | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
SA:MP:L | (3) | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L | SA:MP:L | (3) | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
SA:F:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L | SA:F:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
SA:MW:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L | SA:MW:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
SA:MP:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L | SA:MP:R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
WTR | (4) | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L | WTR | (4) | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
DNR | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L | DNR | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
E::L | (5) | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L | E::L | (5) | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
E::R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L | E::R | i | UA:LO:L | i | UA:P:L | SA:F:L | PF:W:L |
(Continued)
| SD-P | SD-W | MS-W | MS-P | WTRExp | EXER | SD-P | SD-W | MS-W | MS-P | WTRExp | EXER
--------+---------+---------+---------+---------+--------+------ --------+---------+---------+---------+---------+--------+------
N | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | i | E::L N | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | i | E::L
UA:LO:L | i | i | i | i | i | i UA:LO:L | i | i | i | i | i | i
UA:P:L | i | i | i | i | i | i UA:P:L | i | i | i | i | i | i
UA:DP:L | i | i | i | i | i | i UA:DP:L | i | i | i | i | i | i
UA:LO:R | UA:DP:L | PF:DW:L | i | i | i | i UA:LO:R | UA:DP:L | PF:DW:L | i | i | i | i
UA:P:R | UA:DP:L | PF:DW:L | i | i | i | i UA:P:R | UA:DP:L | PF:DW:L | i | i | i | i
UA:DP:R | UA:DP:L | PF:DW:L | i | i | i | i UA:DP:R | UA:DP:L | PF:DW:L | i | i | i | i
PF:W:L | i | i | i | i | i | i PF:W:L | i | i | i | i | i | i
skipping to change at page 24, line 4 skipping to change at page 24, line 30
SA:F:L | i | i | i | i | i | i SA:F:L | i | i | i | i | i | i
SA:MW:L | UA:DP:L | PF:DW:L | i | i | i | i SA:MW:L | UA:DP:L | PF:DW:L | i | i | i | i
SA:MP:L | UA:DP:L | PF:DW:L | i | i | i | i SA:MP:L | UA:DP:L | PF:DW:L | i | i | i | i
SA:F:R | UA:DP:L | PF:DW:L | i | i | i | i SA:F:R | UA:DP:L | PF:DW:L | i | i | i | i
SA:MW:R | UA:DP:L | PF:DW:L | SA:MW:L | i | i | i SA:MW:R | UA:DP:L | PF:DW:L | SA:MW:L | i | i | i
SA:MP:R | UA:DP:L | PF:DW:L | i | SA:MP:L | i | i SA:MP:R | UA:DP:L | PF:DW:L | i | SA:MP:L | i | i
WTR | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | (6) | i WTR | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | (6) | i
DNR | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | i | E::L DNR | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | i | E::L
E::L | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | i | i E::L | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | i | i
E::R | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | i | E::L E::R | UA:DP:L | PF:DW:L | SA:MW:L | SA:MP:L | i | E::L
NOTES: NOTES:
(1) Re-evaluate to determine final state as if the node is in the (1) Re-evaluate to determine the final state as if the node is in
Normal state. If there are no active requests, the node enters the Normal state. If there are no active requests, the node
the Normal State. enters the Normal State.
(2) In the case that both local input after SFDc and the last (2) In the case that both local input after SFDc and the last
received remote message are no requests, the node enters into received remote message are NR, the node enters into the WTR
the WTR state when the domain is configured for revertive state when the domain is configured for revertive behavior, or
behavior, or the node enters into the DNR state when the domain the node enters into the DNR state when the domain is configured
is configured for non-revertive behavior. In all the other for non-revertive behavior. In all the other cases, where one
cases, where one or more active requests exist, re-evaluate to or more active requests exist, re-evaluate to determine the
determine the final state as if the node is in the Normal state. final state as if the node is in the Normal state.
(3) Re-evaluate to determine final state as if the node is in the (3) Re-evaluate to determine final state as if the node is in the
Normal state when the domain is configured for revertive Normal state when the domain is configured for revertive
behavior, or as if the node is in the DNR state when the domain behavior, or as if the node is in the DNR state when the domain
is configured for non-revertive behavior. If there are no is configured for non-revertive behavior. If there are no
active requests, the node enters either the Normal state when active requests, the node enters either the Normal state when
the domain is configured for revertive behavior or the DNR state the domain is configured for revertive behavior or the DNR state
when the domain is configured for non-revertive behavior. when the domain is configured for non-revertive behavior.
(4) Remain in the WTR state and send NR(0,1). Stop the WTR timer if (4) Remain in the WTR state and send an NR(0,1) message. Stop the
it is running. In APS mode, OC can cancel the WTR timer and WTR timer if it is running. In APS mode, OC can cancel the WTR
hasten the state transition to the Normal state as in other timer and hasten the state transition to the Normal state as in
transport networks. other transport networks.
(5) If Path value is 0, re-evaluate to determine final state as if (5) If Path value is 0, re-evaluate to determine final state as if
the node is in the Normal state. If Path value is 1, re- the node is in the Normal state. If Path value is 1,
evaluate to determine final state as if the node is in the DNR re-evaluate to determine final state as if the node is in the
state. If there are no active requests, the node enters the DNR state. If there are no active requests, the node enters the
Normal state when Path value is 0, or the DNR state when Path Normal state when Path value is 0, or the DNR state when Path
value is 1. value is 1.
(6) Remain in the WTR state and send NR(0,1). (6) Remain in the WTR state and send an NR(0,1) message.
11.2. State Transition by Remote Messages
11.2. State transition by remote messages
| LO | SF-P | FS | SF-W | SD-P | SD-W | | LO | SF-P | FS | SF-W | SD-P | SD-W |
--------+---------+--------+--------+--------+---------+---------+ --------+---------+--------+--------+--------+---------+---------+
N | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R | N | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
UA:LO:L | i | i | i | i | i | i | UA:LO:L | i | i | i | i | i | i |
UA:P:L | UA:LO:R | i | i | i | i | i | UA:P:L | UA:LO:R | i | i | i | i | i |
UA:DP:L | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | i | (7) | UA:DP:L | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | i | (7) |
UA:LO:R | i | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R | UA:LO:R | i | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
UA:P:R | UA:LO:R | i | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R | UA:P:R | UA:LO:R | i | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
UA:DP:R | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | i | PF:DW:R | UA:DP:R | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | i | PF:DW:R |
PF:W:L | UA:LO:R | UA:P:R | SA:F:R | i | i | i | PF:W:L | UA:LO:R | UA:P:R | SA:F:R | i | i | i |
skipping to change at page 25, line 28 skipping to change at page 26, line 5
SA:MW:L | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R | SA:MW:L | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
SA:MP:L | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R | SA:MP:L | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
SA:F:R | UA:LO:R | UA:P:R | i | PF:W:R | UA:DP:R | PF:DW:R | SA:F:R | UA:LO:R | UA:P:R | i | PF:W:R | UA:DP:R | PF:DW:R |
SA:MW:R | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R | SA:MW:R | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
SA:MP:R | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R | SA:MP:R | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
WTR | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R | WTR | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
DNR | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R | DNR | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
E::L | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R | E::L | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
E::R | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R | E::R | UA:LO:R | UA:P:R | SA:F:R | PF:W:R | UA:DP:R | PF:DW:R |
(Continued)
| MS-W | MS-P | WTR | EXER | RR | DNR | NR | MS-W | MS-P | WTR | EXER | RR | DNR | NR
--------+---------+---------+-----+------+----+------+---- --------+---------+---------+-----+------+----+------+----
N | SA:MW:R | SA:MP:R | i | E::R | i | i | i N | SA:MW:R | SA:MP:R | i | E::R | i | i | i
UA:LO:L | i | i | i | i | i | i | i UA:LO:L | i | i | i | i | i | i | i
UA:P:L | i | i | i | i | i | i | i UA:P:L | i | i | i | i | i | i | i
UA:DP:L | i | i | i | i | i | i | i UA:DP:L | i | i | i | i | i | i | i
UA:LO:R | SA:MW:R | SA:MP:R | i | E::R | i | i | N UA:LO:R | SA:MW:R | SA:MP:R | i | E::R | i | i | N
UA:P:R | SA:MW:R | SA:MP:R | i | E::R | i | i | N UA:P:R | SA:MW:R | SA:MP:R | i | E::R | i | i | N
UA:DP:R | SA:MW:R | SA:MP:R | i | E::R | i | i | N UA:DP:R | SA:MW:R | SA:MP:R | i | E::R | i | i | N
PF:W:L | i | i | i | i | i | i | i PF:W:L | i | i | i | i | i | i | i
skipping to change at page 26, line 4 skipping to change at page 26, line 30
SA:F:L | i | i | i | i | i | i | i SA:F:L | i | i | i | i | i | i | i
SA:MW:L | i | i | i | i | i | i | i SA:MW:L | i | i | i | i | i | i | i
SA:MP:L | i | i | i | i | i | i | i SA:MP:L | i | i | i | i | i | i | i
SA:F:R | SA:MW:R | SA:MP:R | i | E::R | i | DNR | N SA:F:R | SA:MW:R | SA:MP:R | i | E::R | i | DNR | N
SA:MW:R | i | SA:MP:R | i | E::R | i | i | N SA:MW:R | i | SA:MP:R | i | E::R | i | i | N
SA:MP:R | SA:MW:R | i | i | E::R | i | DNR | N SA:MP:R | SA:MW:R | i | i | E::R | i | DNR | N
WTR | SA:MW:R | SA:MP:R | i | i | i | i | (12) WTR | SA:MW:R | SA:MP:R | i | i | i | i | (12)
DNR | SA:MW:R | SA:MP:R | (13)| E::R | i | i | i DNR | SA:MW:R | SA:MP:R | (13)| E::R | i | i | i
E::L | SA:MW:R | SA:MP:R | i | i | i | i | i E::L | SA:MW:R | SA:MP:R | i | i | i | i | i
E::R | SA:MW:R | SA:MP:R | i | i | i | DNR | N E::R | SA:MW:R | SA:MP:R | i | i | i | DNR | N
NOTES: NOTES:
(7) If the received SD-W message has Path=0, ignore the message. If (7) If the received SD-W message has Path=0, ignore the message. If
the received SD-W message has Path=1, go to the PF:DW:R state the received SD-W message has Path=1, go to the PF:DW:R state
and transmit SD(0,1) and transmit an SD(0,1) message.
(8) If the received SD-P message has Path=1, ignore the message. If (8) If the received SD-P message has Path=1, ignore the message. If
the received SD-P message has Path=0, go to the UA:DP:R state the received SD-P message has Path=0, go to the UA:DP:R state
and transmit SD(1,0). and transmit an SD(1,0) message.
(9) Transition to the WTR state and continue to send the current (9) Transition to the WTR state and continue to send the current
message. message.
(10) Transition to the DNR state and continue to send the current (10) Transition to the DNR state and continue to send the current
message. message.
(11) If the received NR message has Path=1, transition to the WTR (11) If the received NR message has Path=1, transition to the WTR
state if domain configured for revertive behavior, else state if the domain is configured for revertive behavior, else
transition to the DNR state. If the received NR message has transition to the DNR state. If the received NR message has
Path=0, transition to the Normal state. Path=0, transition to the Normal state.
(12) If the receiving node's WTR timer is running, maintain current (12) If the receiving node's WTR timer is running, maintain the
state and message. If the WTR timer is not running, transition current state and message. If the WTR timer is not running,
to the Normal state. transition to the Normal state.
(13) Transit to the WTR state and send NR(0,1) message. The WTR (13) Transit to the WTR state and send an NR(0,1) message. The WTR
timer is not initiated. timer is not initiated.
11.3. State transition for 1+1 unidirectional protection 11.3. State Transition for 1+1 Unidirectional Protection
The state transition tables given in Sections 11.1 and 11.2 are for The state transition tables given in Sections 11.1 and 11.2 are for
bidirectional protection switching, where remote PSC protocol bidirectional protection switching, where remote PSC protocol
messages are used to determine the protection switching actions. 1+1 messages are used to determine the protection-switching actions. 1+1
unidirectional protection switching does not require the remote unidirectional protection switching does not require the remote
information in PSC protocol message and acts upon local inputs only. information in the PSC protocol message and acts upon local inputs
The state transition by local inputs in Section 11.1 SHALL be reused only. The state transition by local inputs in Section 11.1 SHALL be
for 1+1 unidirectional protection under the following conditions: reused for 1+1 unidirectional protection under the following
conditions:
o The value of Request field in the received remote message is o The value of Request field in the received remote message is
ignored and always assumed to be no request. ignored and always assumed to be no request.
o Replace footnote (4) with "Stop the WTR timer and transit to the o Replace footnote (4) with "Stop the WTR timer and transit to the
Normal state." Normal state."
o Replace footnote (6) with "Transit to the Normal state." o Replace footnote (6) with "Transit to the Normal state."
o Exercise command is not relevant. o Exercise command is not relevant.
skipping to change at page 27, line 17 skipping to change at page 27, line 45
The remote PSC message that is received from the remote node is The remote PSC message that is received from the remote node is
subject to the detection of provisioning mismatch and protocol subject to the detection of provisioning mismatch and protocol
failure conditions. In APS mode, provisioning mismatches are handled failure conditions. In APS mode, provisioning mismatches are handled
as follows: as follows:
o If the PSC message is received from the working path due to o If the PSC message is received from the working path due to
working/protection path configuration mismatch, the node MUST working/protection path configuration mismatch, the node MUST
alert the operator and MUST NOT perform any protection switching alert the operator and MUST NOT perform any protection switching
until the operator resolves this path configuration mismatch. until the operator resolves this path configuration mismatch.
o In the case that the mismatch happens in two-bit "Protection Type o In the case that the mismatch happens in the two-bit "Protection
(PT)" field, which indicates permanent/selector bridge type and Type (PT)" field, which indicates permanent/selector bridge type
uni/bidirectional switching type, and uni/bidirectional switching type:
* If the value of the PT field of one side is 2 (i.e., selector * If the value of the PT field of one side is 2 (i.e., selector
bridge) and the value of PT field of the other side is 1 or 3 bridge) and that of the other side is 1 or 3 (i.e., permanent
(i.e., permanent bridge), then this event MUST be notified to bridge), then this event MUST be notified to the operator and
the operator and each node MUST NOT perform any protection each node MUST NOT perform any protection switching until the
switching until the operator resolves this bridge type operator resolves this bridge type mismatch.
mismatch.
* If the bridge type matches but the switching type mismatches, * If the bridge type matches but the switching type mismatches,
i.e., one side has PT=1 (unidirectional switching) while the i.e., one side has PT=1 (unidirectional switching) while the
other side has PT=2 or 3 (bidirectional switching), then the other side has PT=2 or 3 (bidirectional switching), then the
node provisioned for bidirectional switching SHOULD fall back node provisioned for bidirectional switching SHOULD fall back
to unidirectional switching to allow interworking. The node to unidirectional switching to allow interworking. The node
SHOULD notify the operator of this event. SHOULD notify the operator of this event.
o If the "Revertive (R)" bit mismatches, two sides will interwork o If the "Revertive (R)" bit mismatches, two sides will interwork
and traffic is protected according to the state transition and traffic is protected according to the state transition
definition given in Section 11. The node SHOULD notify the definition given in Section 11. The node SHOULD notify the
operator of this event. operator of this event.
o If the Capabilities TLV mismatches, the node MUST alert the o If the Capabilities TLV mismatches, the node MUST alert the
operator and MUST NOT perform any protection switching until the operator and MUST NOT perform any protection switching until the
operator resolves the mismatch in the Capabilities TLV. operator resolves the mismatch in the Capabilities TLV.
The followings are the protocol failure situations and the actions to The following are the protocol failure situations and the actions to
be taken: be taken:
o No match in sent "Data Path (Path)" and received "Data Path o No match in sent "Data Path (Path)" and received "Data Path
(Path)" for more than 50 ms: The node MAY continue to perform (Path)" for more than 50 ms: The node MAY continue to perform
protection switching and SHOULD notify the operator of this event. protection switching and SHOULD notify the operator of this event.
o No PSC message is received on the protection path during at least o No PSC message is received on the protection path during at least
3.5 times the long PSC message interval, (e.g. at least 17.5 3.5 times the long PSC message interval (e.g., at least 17.5
seconds with a default message interval of 5 seconds) and there is seconds with a default message interval of 5 seconds), and there
no defect on the protection path: The node MUST alert the operator is no defect on the protection path: The node MUST alert the
and MUST NOT perform any protection switching until the operator operator and MUST NOT perform any protection switching until the
resolves this defect. operator resolves this defect.
13. Security Considerations 13. Security Considerations
This document introduces no new security risks. [RFC6378] points out This document introduces no new security risks. [RFC6378] points out
that MPLS relies on assumptions about traffic injection difficulty that MPLS relies on assumptions about the difficulty of traffic
and assumes that the control plane does not have end-to-end security. injection and assumes that the control plane does not have end-to-end
[RFC5920] describes MPLS security issues and generic methods for security. [RFC5920] describes MPLS security issues and generic
securing traffic privacy and integrity. MPLS use should conform such methods for securing traffic privacy and integrity. MPLS use should
advice. conform to such advice.
14. IANA Considerations 14. IANA Considerations
14.1. MPLS PSC Request Registry 14.1. MPLS PSC Request Registry
In the "Generic Associated Channel (G-ACh) Parameters" registry, IANA In the "Generic Associated Channel (G-ACh) Parameters" registry, IANA
maintains the "MPLS PSC Request Registry". maintains the "MPLS PSC Request Registry".
IANA is requested to assign two new code points from this registry. IANA has assigned the following two new code points from this
The values shall be allocated as follows: registry.
Value Description Reference Value Description Reference
----- --------------------- --------------- ----- --------------------- ---------------
2 Reverse Request (this document) 2 Reverse Request (this document)
3 Exercise (this document) 3 Exercise (this document)
14.2. MPLS PSC TLV Registry 14.2. MPLS PSC TLV Registry
In the "Generic Associated Channel (G-ACh) Parameters" registry, IANA In the "Generic Associated Channel (G-ACh) Parameters" registry, IANA
maintains the "MPLS PSC TLV Registry". maintains the "MPLS PSC TLV Registry".
This document defines a new value for the Capabilities TLV type in This document defines the following new value for the Capabilities
the "MPLS PSC TLV Registry". TLV type in the "MPLS PSC TLV Registry".
Value Description Reference Value Description Reference
------ --------------------- --------------- ------ --------------------- ---------------
TBD Capabilities (this document) 1 Capabilities (this document)
14.3. MPLS PSC Capability Flag Registry 14.3. MPLS PSC Capability Flag Registry
IANA is requested to create and maintain a new registry within the IANA has created and now maintains a new registry within the "Generic
"Generic Associated Channel (G-ACh) Parameters" registry called "MPLS Associated Channel (G-ACh) Parameters" registry called "MPLS PSC
PSC Capability Flag Registry". All flags within this registry SHALL Capability Flag Registry". All flags within this registry SHALL be
be allocated according to the "Standards Action" procedures as allocated according to the "Standards Action" procedures as specified
specified in RFC 5226 [RFC5226]. in RFC 5226 [RFC5226].
The length of the flags MUST be a multiple of 4 octets. This The length of each flag MUST be a multiple of 4 octets. This
document defines 4 octet flags. Flags greater than 4 octets SHALL be document defines 4-octet flags. Flags greater than 4 octets SHALL be
used only if more than 32 Capabilities need to be defined. Flags used only if more than 32 Capabilities need to be defined. The flags
defined in this document are: defined in this document are:
Bit Hex Value Capability Reference Bit Hex Value Capability Reference
---- ---------- ----------------------------------- --------------- ---- ---------- ----------------------------------- ---------------
0 0x80000000 priority modification (this document) 0 0x80000000 priority modification (this document)
1 0x40000000 non-revertive behavior modification (this document) 1 0x40000000 non-revertive behavior modification (this document)
2 0x20000000 support of MS-W command (this document) 2 0x20000000 support of MS-W command (this document)
3 0x10000000 support of protection against SD (this document) 3 0x10000000 support of protection against SD (this document)
4 0x08000000 support of EXER command (this document) 4 0x08000000 support of EXER command (this document)
5-31 Unassigned (this document) 5-31 Unassigned (this document)
15. Acknowledgements 15. Acknowledgements
The authors would like to thank Yaacov Weingarten, Yuji Tochio, The authors would like to thank Yaacov Weingarten, Yuji Tochio,
Malcolm Betts, Ross Callon, Qin Wu and Xian Zhang for their valuable Malcolm Betts, Ross Callon, Qin Wu, and Xian Zhang for their valuable
comments and suggestions on this document. comments and suggestions on this document.
We would also like to acknowledge explicit text provided by Loa We would also like to acknowledge explicit text provided by Loa
Andersson and Adrian Farrel. Andersson and Adrian Farrel.
16. References 16. References
16.1. Normative References 16.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
skipping to change at page 29, line 49 skipping to change at page 30, line 35
[RFC5654] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., [RFC5654] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N.,
and S. Ueno, "Requirements of an MPLS Transport Profile", and S. Ueno, "Requirements of an MPLS Transport Profile",
RFC 5654, September 2009. RFC 5654, September 2009.
[RFC6378] Weingarten, Y., Bryant, S., Osborne, E., Sprecher, N., and [RFC6378] Weingarten, Y., Bryant, S., Osborne, E., Sprecher, N., and
A. Fulignoli, "MPLS Transport Profile (MPLS-TP) Linear A. Fulignoli, "MPLS Transport Profile (MPLS-TP) Linear
Protection", RFC 6378, October 2011. Protection", RFC 6378, October 2011.
16.2. Informative References 16.2. Informative References
[RFC4427] Mannie, E. and D. Papadimitriou, "Recovery (Protection and [G8031] International Telecommunication Union, "Ethernet Linear
Restoration) Terminology for Generalized Multi-Protocol Protection Switching", ITU-T Recommendation G.8031/Y.1342,
Label Switching (GMPLS)", RFC 4427, March 2006. June 2011.
[RFC5920] Fang, L., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.
[RFC6372] Sprecher, N. and A. Farrel, "MPLS Transport Profile (MPLS-
TP) Survivability Framework", RFC 6372, September 2011.
[G841] International Telecommunications Union, "Types and [G841] International Telecommunication Union, "Types and
characteristics of SDH network protection architectures", characteristics of SDH network protection architectures",
ITU-T Recommendation G.841, October 1998. ITU-T Recommendation G.841, October 1998.
[G873.1] International Telecommunications Union, "Optical Transport [G873.1] International Telecommunication Union, "Optical Transport
Network (OTN): Linear protection", ITU-T Recommendation Network (OTN): Linear protection", ITU-T Recommendation
G.873.1, July 2011. G.873.1, July 2011.
[G8031] International Telecommunications Union, "Ethernet Linear [RFC4427] Mannie, E. and D. Papadimitriou, "Recovery (Protection and
Protection Switching", ITU-T Recommendation G.8031/Y.1342, Restoration) Terminology for Generalized Multi-Protocol
June 2011. Label Switching (GMPLS)", RFC 4427, March 2006.
Appendix A. An Example of Out-of-service Scenarios [RFC5920] Fang, L., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.
[RFC6372] Sprecher, N. and A. Farrel, "MPLS Transport Profile
(MPLS-TP) Survivability Framework", RFC 6372, September
2011.
Appendix A. An Example of an Out-of-Service Scenario
The sequence diagram shown is an example of the out-of-service The sequence diagram shown is an example of the out-of-service
scenarios based on the priority level defined in [RFC6378]. The scenarios based on the priority level defined in [RFC6378]. The
first PSC message which differs from the previous PSC message is first PSC message that differs from the previous PSC message is
shown. shown.
A Z A Z
| | | |
(1) |-- NR(0,0) ------>| (1) (1) |-- NR(0,0) ------>| (1)
|<----- NR(0,0) ---| |<----- NR(0,0) ---|
| | | |
| | | |
| (FS issued at Z) | (2) | (FS issued at Z) | (2)
(3) |<------ FS(1,1) --| (3) |<------ FS(1,1) --|
skipping to change at page 30, line 49 skipping to change at page 32, line 31
| | | |
| | | |
(4) | (SF on P(A<-Z)) | (4) | (SF on P(A<-Z)) |
| | | |
| | | |
| (Clear FS at Z) | (5) | (Clear FS at Z) | (5)
(6) | X <- NR(0,0) --| (6) | X <- NR(0,0) --|
| | | |
| | | |
(1) Each end is in the Normal state, and transmits NR(0,0) messages. (1) Each end is in the Normal state and transmits NR(0,0) messages.
(2) When a FS command is issued at node Z, node Z goes into local (2) When a FS command is issued at node Z, node Z goes into local
Protecting Administrative state (PA:F:L) and begins transmission of Protecting Administrative state (PA:F:L) and begins transmission
an FS(1,1) messages. of an FS(1,1) message.
(3) A remote FS message causes node A to go into remote Protecting (3) A remote FS message causes node A to go into remote Protecting
Administrative state (PA:F:R), and node A begins transmitting NR(0,1) Administrative state (PA:F:R), and node A begins transmitting
messages. NR(0,1) messages.
(4) When node A detects a unidirectional SF-P, node A keeps sending (4) When node A detects a unidirectional SF-P, node A keeps sending
NR(0,1) message because SF-P is ignored under the PA:F:R state. an NR(0,1) message because SF-P is ignored under the PA:F:R
state.
(5) When a Clear command is issued at node Z, node Z goes into the (5) When a Clear command is issued at node Z, node Z goes into the
Normal state and begins transmission of NR(0,0) messages. Normal state and begins transmission of NR(0,0) messages.
(6) But, node A cannot receive PSC message because of local (6) But, node A cannot receive PSC message because of local
unidirectional SF-P. Because no valid PSC message is received, over unidirectional SF-P. Because no valid PSC message is received
a period of several successive message intervals, the last valid over a period of several successive message intervals, the last
received message remains applicable and the node A continue to valid received message remains applicable, and the node A
transmit an NR(0,1) message in the PA:F:R state. continue to transmit an NR(0,1) message in the PA:F:R state.
Now, there exists a mismatch between the bridge/selector positions of Now, there exists a mismatch between the selector and bridge
node A (transmitting an NR(0,1)) and node Z (transmitting an positions of node A (transmitting an NR(0,1) message) and node Z
NR(0,0)). It results in out-of-service even when there is neither (transmitting an NR(0,0) message). It results in an out-of-service
SF-W nor FS. situation even when there is neither SF-W nor FS.
Appendix B. An Example of Sequence Diagram Showing the Problem with the Appendix B. An Example of a Sequence Diagram Showing the Problem with
Priority Level of SFc the Priority Level of SFc
An example of sequence diagram showing the problem with the priority An example of a sequence diagram showing the problem with the
level of SFc defined in [RFC6378] is given below. The following priority level of SFc defined in [RFC6378] is given below. The
sequence diagram is depicted for the case of bidirectional signal following sequence diagram depicts the case when the bidirectional
fails. However, other cases with unidirectional signal fails can signal fails. However, other cases with unidirectional signal fails
result in the same problem. The first PSC message which differs from can result in the same problem. The first PSC message that differs
the previous PSC message is shown. from the previous PSC message is shown.
A Z A Z
| | | |
(1) |-- NR(0,0) ------>| (1) (1) |-- NR(0,0) ------>| (1)
|<----- NR(0,0) ---| |<----- NR(0,0) ---|
| | | |
| | | |
(2) | (SF on P(A<->Z)) | (2) (2) | (SF on P(A<->Z)) | (2)
|-- SF(0,0) ------>| |-- SF(0,0) ------>|
|<------ SF(0,0) --| |<------ SF(0,0) --|
skipping to change at page 32, line 26 skipping to change at page 33, line 41
(3) | (SF on W(A<->Z)) | (3) (3) | (SF on W(A<->Z)) | (3)
| | | |
| | | |
(4) | (Clear SF-P) | (4) (4) | (Clear SF-P) | (4)
| | | |
| | | |
(5) | (Clear SF-W) | (5) (5) | (Clear SF-W) | (5)
| | | |
| | | |
(1) Each end is in the Normal state, and transmits NR(0,0) messages. (1) Each end is in the Normal state and transmits NR(0,0) messages.
(2) When SF-P occurs, each node enters into the UA:P:L state and (2) When SF-P occurs, each node enters into the UA:P:L state and
transmits SF(0,0) messages. Traffic remains on the working path. transmits SF(0,0) messages. Traffic remains on the working
path.
(3) When SF-W occurs, each node remains in the UA:P:L state as SF-W (3) When SF-W occurs, each node remains in the UA:P:L state as SF-W
has a lower priority than SF-P. Traffic is still on the working has a lower priority than SF-P. Traffic is still on the working
path. Traffic cannot be delivered as both the working path and the path. Traffic cannot be delivered, as both the working path and
protection path are experiencing signal fails. the protection path are experiencing signal fails.
(4) When SF-P is cleared, local "Clear SF-P" request cannot be (4) When SF-P is cleared, the local "Clear SF-P" request cannot be
presented to the PSC Control Logic, which takes the highest local presented to the PSC Control Logic, which takes the highest
request and runs PSC state machine, since the priority of "Clear local request and runs the PSC state machine, since the priority
SF-P" is lower than that of SF-W. Consequently, there is no change of "Clear SF-P" is lower than that of SF-W. Consequently, there
in state, and the selector and/or bridge keep pointing at the working is no change in state, and the selector and/or bridge keep
path, which has signal fail condition. pointing at the working path, which has SF condition.
Now, traffic cannot be delivered while the protection path is Now, traffic cannot be delivered while the protection path is
recovered and available. It should be noted that the same problem recovered and available. It should be noted that the same problem
will occur in the case that the sequence of SF-P and SF-W events is will occur in the case that the sequence of SF-P and SF-W events is
changed. changed.
If we further continue with this sequence to see what will happen If we further continue with this sequence to see what will happen
after SF-W is cleared, after SF-W is cleared:
(5) When SF-W is cleared, local "Clear SF-W" request can be passed to (5) When SF-W is cleared, the local "Clear SF-W" request can be
the PSC Control Logic as there is no higher priority local input, but passed to the PSC Control Logic, as there is no higher-priority
this will be ignored in the PSC Control Logic according to the state local input, but it will be ignored in the PSC Control Logic
transition definition in [RFC6378]. There will be no change in state according to the state transition definition in [RFC6378].
or protocol message transmitted. There will be no change in state or protocol message
transmitted.
As SF-W is now cleared and the selector and/or bridge are still As SF-W is now cleared and the selector and/or bridge are still
pointing at the working path, traffic delivery is resumed. However, pointing at the working path, traffic delivery is resumed. However,
each node is in the UA:P:L state and transmitting SF(0,0) message, each node is in the UA:P:L state and transmitting SF(0,0) messages,
while there exists no outstanding request for protection switching. while there exists no outstanding request for protection switching.
Moreover, any future legitimate protection switching requests, such Moreover, any future legitimate protection-switching requests, such
as SF-W, will be rejected as each node thinks the protection path is as SF-W, will be rejected as each node thinks the protection path is
unavailable. unavailable.
Appendix C. Freeze Command Appendix C. Freeze Command
The "Freeze" command applies only to the local node of the protection The "Freeze" command applies only to the local node of the protection
group and is not signaled to the remote node. This command freezes group and is not signaled to the remote node. This command freezes
the state of the protection group. Until the Freeze is cleared, the state of the protection group. Until the Freeze is cleared,
additional local commands are rejected and condition changes and additional local commands are rejected, and condition changes and
received PSC information are ignored. received PSC information are ignored.
"Clear Freeze" command clears the local freeze. When the Freeze The "Clear Freeze" command clears the local freeze. When the Freeze
command is cleared, the state of the protection group is recomputed command is cleared, the state of the protection group is recomputed
based on the persistent condition of the local triggers. based on the persistent condition of the local triggers.
Because the freeze is local, if the freeze is issued at one end only, Because the freeze is local, if the freeze is issued at one end only,
a failure of protocol can occur as the other end is open to accept a failure of protocol can occur as the other end is open to accept
any operator command or a fault condition. any operator command or a fault condition.
Appendix D. Operation Examples of the APS Mode Appendix D. Operation Examples of the APS Mode
The sequence diagrams shown in this section are only a few examples The sequence diagrams shown in this section are only a few examples
of the APS mode operations. The first PSC protocol message which of the APS mode operations. The first PSC protocol message that
differs from the previous message is shown. The operation of hold- differs from the previous message is shown. The operation of the
off timer is omitted. The Request, FPath and Path fields, whose hold-off timer is omitted. The Request, FPath, and Path fields whose
values are changed during PSC message exchange are shown. For an values are changed during PSC message exchange are shown. For an
example, SF(1,0) represents an PSC message with the following field example, SF(1,0) represents a PSC message with the following field
values: Request=SF, FPath=1 and Path=1. The values of the other values: Request=SF, FPath=1, and Path=0. The values of the other
fields remain unchanged from the initial configuration. W(A->Z) and fields remain unchanged from the initial configuration. W(A->Z) and
P(A->Z) indicate the working path and the protection path in the P(A->Z) indicate the working path and the protection path in the
direction of A to Z, respectively. direction of A to Z, respectively.
Example 1. 1:1 bidirectional protection switching (revertive Example 1. 1:1 bidirectional protection switching (revertive
operation) - Unidirectional SF case operation) - Unidirectional SF case
A Z A Z
| | | |
(1) |<---- NR(0,0)---->| (1) (1) |<---- NR(0,0)---->| (1)
| | | |
| | | |
(2) | (SF on W(Z->A)) | (2) | (SF on W(Z->A)) |
|---- SF(1,1)----->| (3) |---- SF(1,1)----->| (3)
(4) |<----- NR(0,1)----| (4) |<----- NR(0,1)----|
| | | |
| | | |
skipping to change at page 34, line 26 skipping to change at page 35, line 43
/| | /| |
| | | | | |
WTR timer | | WTR timer | |
| | | | | |
\| | \| |
(6) |---- NR(0,1)----->| (7) (6) |---- NR(0,1)----->| (7)
(8) |<----- NR(0,0)----| (8) |<----- NR(0,0)----|
|---- NR(0,0)----->| (9) |---- NR(0,0)----->| (9)
| | | |
(1) The protected domain is operating without any defect, and the (1) The protected domain is operating without any defect, and the
working path is used for delivering the traffic in the Normal state. working path is used for delivering the traffic in the Normal
state.
(2) SF-W occurs in the Z to A direction. Node A enters into the (2) SF-W occurs in the Z to A direction. Node A enters into the
PF:W:L state and generates SF(1,1) message. Selector and bridge of PF:W:L state and generates an SF(1,1) message. Both the
node A are pointing at the protection path. selector and bridge of node A are pointing at the protection
path.
(3) Upon receiving SF(1,1), node Z sets selector and bridge to the (3) Upon receiving an SF(1,1) message, node Z sets both the selector
protection path. As there is no local request in node Z, node Z and bridge to the protection path. As there is no local request
generates NR(0,1) message in the PF:W:R state. in node Z, node Z generates an NR(0,1) message in the PF:W:R
state.
(4) Node A confirms that the remote node is also selecting the (4) Node A confirms that the remote node is also selecting the
protection path. protection path.
(5) Node A detects clearing of SF condition, starts the WTR timer, (5) Node A detects clearing of SF condition, starts the WTR timer,
and sends WTR(0,1) message in the WTR state. and sends a WTR(0,1) message in the WTR state.
(6) At expiration of the WTR timer, node A sets selector and bridge (6) Upon expiration of the WTR timer, node A sets both the selector
to the working path and sends NR(0,1) message. and bridge to the working path and sends an NR(0,1) message.
(7) Node Z is notified that the remote request has been cleared. (7) Node Z is notified that the remote request has been cleared.
Node Z transits to the Normal state and sends NR(0,0) message. Node Z transits to the Normal state and sends an NR(0,0)
message.
(8) Upon receiving NR(0,0) message, node A transits to the Normal (8) Upon receiving an NR(0,0) message, node A transits to the Normal
state and sends NR(0,0) message. state and sends an NR(0,0) message.
(9) It is confirmed that the remote node is also selecting the (9) It is confirmed that the remote node is also selecting the
working path. working path.
Example 2. 1:1 bidirectional protection switching (revertive Example 2. 1:1 bidirectional protection switching (revertive
operation) - Bidirectional SF case - Inconsistent WTR timers operation) - Bidirectional SF case - Inconsistent WTR timers
A Z A Z
| | | |
(1) |<---- NR(0,0)---->| (1) (1) |<---- NR(0,0)---->| (1)
| | | |
| | | |
(2) | (SF on W(A<->Z)) | (2) (2) | (SF on W(A<->Z)) | (2)
|<---- SF(1,1)---->| |<---- SF(1,1)---->|
| | | |
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| | | | | | | |
| | |/ | | |/
| |<------ NR(0,1)---| (5) | |<------ NR(0,1)---| (5)
| | | | | |
\| | \| |
(6) |--- NR(0,1)------>| (6) |--- NR(0,1)------>|
|<------ NR(0,0)---| (7) |<------ NR(0,0)---| (7)
(8) |--- NR(0,0)------>| (8) |--- NR(0,0)------>|
| | | |
(1) Each end is in the Normal state, and transmits NR(0,0) messages. (1) Each end is in the Normal state and transmits NR(0,0) messages.
(2) When SF-W occurs, each node enters into the PF:W:L state and (2) When SF-W occurs, each node enters into the PF:W:L state and
transmits SF(1,1) messages. Traffic is switched to the protection transmits SF(1,1) messages. Traffic is switched to the
path. Upon receiving SF(1,1), each node confirms that the remote protection path. Upon receiving an SF(1,1) message, each node
node is also sending and receiving the traffic from the protection confirms that the remote node is also sending and receiving the
path. traffic from the protection path.
(3) When SF-W is cleared, each node transits to the PF:W:R state and (3) When SF-W is cleared, each node transits to the PF:W:R state and
transmits NR(0,1) messages as the last received message is SF-W. transmits NR(0,1) messages as the last received message is SF-W.
(4) Upon receiving NR(0,1) messages, each node goes into the WTR (4) Upon receiving NR(0,1) messages, each node goes into the WTR
state, starts the WTR timer, and sends the WTR(0,1) messages. state, starts the WTR timer, and sends the WTR(0,1) messages.
(5) At expiration of the WTR timer in node Z, node Z sends NR(0,1) as (5) Upon expiration of the WTR timer in node Z, node Z sends an
the last received APS message was WTR. When NR(0,1) arrives at node NR(0,1) message as the last received APS message was WTR. When
A, node A maintains the WTR state and keeps sending current WTR the NR(0,1) message arrives at node A, node A maintains the WTR
messages as described in the state transition table. state and keeps sending current WTR messages as described in the
state transition table.
(6) At expiration of the WTR timer in node A, node A sends NR(0,1). (6) Upon expiration of the WTR timer in node A, node A sends an
NR(0,1) message.
(7) When the NR(0,1) message arrives at node Z, node Z moves to the (7) When the NR(0,1) message arrives at node Z, node Z moves to the
Normal state, sets selector and bridge to the working path, and sends Normal state, sets both the selector and bridge to the working
NR(0,0) message. path, and sends an NR(0,0) message.
(8) The received NR(0,0) message causes node A to go to the Normal (8) The received NR(0,0) message causes node A to go to the Normal
state. Now, the traffic is switched back to the working path. state. Now, the traffic is switched back to the working path.
Example 3. 1:1 bidirectional protection switching - R bit mismatch Example 3. 1:1 bidirectional protection switching - R bit mismatch
This example shows that both sides will interwork and the traffic is This example shows that both sides will interwork and the traffic is
protected when one side (node A) is configured as revertive operation protected when one side (node A) is configured as revertive operation
and the other (node Z) is configured as non-revertive operation. The and the other (node Z) is configured as non-revertive operation. The
interworking is covered in the state transition tables. interworking is covered in the state transition tables.
(revertive) A Z (non-revertive) (revertive) A Z (non-revertive)
| | | |
(1) |<---- NR(0,0)---->| (1) (1) |<---- NR(0,0)---->| (1)
| | | |
skipping to change at page 36, line 47 skipping to change at page 38, line 46
| | | | | |
WTR timer | | WTR timer | |
| | | | | |
| | | | | |
\| | \| |
(6) |--- NR(0,1)------>| (6) |--- NR(0,1)------>|
|<------ NR(0,0)---| (7) |<------ NR(0,0)---| (7)
(8) |--- NR(0,0)------>| (8) |--- NR(0,0)------>|
| | | |
(1) Each end is in the Normal state, and transmits NR(0,0) messages. (1) Each end is in the Normal state and transmits NR(0,0) messages.
(2) When SF-W occurs, each node enters into the PF:W:L state and (2) When SF-W occurs, each node enters into the PF:W:L state and
transmits SF(l,l) messages. Traffic is switched to the protection transmits SF(l,l) messages. Traffic is switched to the
path. Upon receiving SF(1,1), each node confirms that the remote protection path. Upon receiving an SF(1,1) message, each node
node is also sending and receiving the traffic on the protection confirms that the remote node is also sending and receiving the
path. traffic on the protection path.
(3) When SF-W is cleared, each node transits to the PF:W:R state and (3) When SF-W is cleared, each node transits to the PF:W:R state and
transmits NR(0,1) messages as the last received message is SF-W. transmits NR(0,1) messages as the last received message is SF-W.
(4) Upon receiving NR(0,1) messages, node A goes into the WTR state, (4) Upon receiving NR(0,1) messages, node A goes into the WTR state,
starts the WTR timer, and sends WTR(0,1) messages. At the same time, starts the WTR timer, and sends WTR(0,1) messages. At the same
node Z transits to the DNR state and sends DNR(0,1) message. time, node Z transits to the DNR state and sends a DNR(0,1)
message.
(5) When the WTR message arrives at node Z, node Z transits to the (5) When the WTR message arrives at node Z, node Z transits to the
WTR state and send NR(0,1) message according to the state transition WTR state and sends an NR(0,1) message according to the state
table. At the same time, the DNR message arrived at node Z is transition table. At the same time, the DNR message arrived at
ignored according to the state transition table. Therefore, node Z, node Z is ignored according to the state transition table.
which is configured as non-revertive operation, is operating as if in Therefore, node Z, which is configured as non-revertive
revertive operation. operation, is operating as if in revertive operation.
(6) At expiration of the WTR timer in node A, node A sends NR(0,1). (6) Upon expiration of the WTR timer in node A, node A sends an
NR(0,1) message.
(7) When the NR(0,1) message arrives at node Z, node Z moves to the (7) When the NR(0,1) message arrives at node Z, node Z moves to the
Normal state, sets selector and bridge to the working path, and sends Normal state, sets both the selector and bridge to the working
NR(0,0) message. path, and sends an NR(0,0) message.
(8) The received NR(0,0) message causes node A to transits to the (8) The received NR(0,0) message causes node A to transit to the
Normal state. Now, the traffic is switched back to the working path. Normal state. Now, the traffic is switched back to the working
path.
Authors' Addresses Authors' Addresses
Jeong-dong Ryoo (editor) Jeong-dong Ryoo (editor)
ETRI ETRI
218 Gajeongno 218 Gajeongno
Yuseong-gu, Daejeon 305-700 Yuseong-gu, Daejeon 305-700
South Korea South Korea
Phone: +82-42-860-5384 Phone: +82-42-860-5384
Email: ryoo@etri.re.kr EMail: ryoo@etri.re.kr
Eric Gray (editor) Eric Gray (editor)
Ericsson Ericsson
EMail: eric.gray@ericsson.com
Email: eric.gray@ericsson.com
Huub van Helvoort Huub van Helvoort
Huawei Technologies Huawei Technologies
Karspeldreef 4, Karspeldreef 4,
Amsterdam 1101 CJ Amsterdam 1101 CJ
the Netherlands The Netherlands
Phone: +31 20 4300936 Phone: +31 20 4300936
Email: huub.van.helvoort@huawei.com EMail: huub.van.helvoort@huawei.com
Alessandro D'Alessandro Alessandro D'Alessandro
Telecom Italia Telecom Italia
via Reiss Romoli, 274 via Reiss Romoli, 274
Torino 10148 Torino 10148
Italy Italy
Phone: +39 011 2285887 Phone: +39 011 2285887
Email: alessandro.dalessandro@telecomitalia.it EMail: alessandro.dalessandro@telecomitalia.it
Taesik Cheung Taesik Cheung
ETRI ETRI
218 Gajeongno 218 Gajeongno
Yuseong-gu, Daejeon 305-700 Yuseong-gu, Daejeon 305-700
South Korea South Korea
Phone: +82-42-860-5646 Phone: +82-42-860-5646
Email: cts@etri.re.kr EMail: cts@etri.re.kr
Eric Osborne Eric Osborne
EMail: eric.osborne@notcom.com
Email: eric.osborne@notcom.com
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