draft-ietf-mpls-tp-aps-updates-04.txt   rfc8234.txt 
MPLS Working Group J. Ryoo Internet Engineering Task Force (IETF) J. Ryoo
Internet-Draft T. Cheung Request for Comments: 8234 T. Cheung
Updates: 7271 (if approved) ETRI Updates: 7271 ETRI
Intended status: Standards Track H. van Helvoort Category: Standards Track H. van Helvoort
Expires: December 5, 2017 Hai Gaoming BV ISSN: 2070-1721 Hai Gaoming BV
I. Busi I. Busi
G. Wen G. Wen
Huawei Technologies Huawei Technologies
June 3, 2017 August 2017
Updates to MPLS Transport Profile (MPLS-TP) Linear Protection in Updates to MPLS Transport Profile (MPLS-TP) Linear Protection in
Automatic Protection Switching (APS) Mode Automatic Protection Switching (APS) Mode
draft-ietf-mpls-tp-aps-updates-04.txt
Abstract Abstract
This document contains updates to MPLS Transport Profile (MPLS-TP) This document contains updates to MPLS Transport Profile (MPLS-TP)
linear protection in Automatic Protection Switching (APS) mode linear protection in Automatic Protection Switching (APS) mode
defined in RFC 7271. The updates provide rules related to the defined in RFC 7271. The updates provide rules related to the
initialization of the Protection State Coordination (PSC) Control initialization of the Protection State Coordination (PSC) Control
Logic, in which the state machine resides, when operating in APS Logic (in which the state machine resides) when operating in APS mode
mode, and clarify some operation related to state transition table and clarify the operation related to state transition table lookup.
lookup.
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
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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 7841.
This Internet-Draft will expire on December 5, 2017. 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/rfc8234.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 3 2. Conventions Used in This Document . . . . . . . . . . . . . . 4
3. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Updates . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Updates . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Initialization Behavior . . . . . . . . . . . . . . . . . 4 4.1. Initialization Behavior . . . . . . . . . . . . . . . . . 5
4.2. State Transition Modification . . . . . . . . . . . . . . 5 4.2. State Transition Modification . . . . . . . . . . . . . . 6
4.3. Operation related to State Transition Table Lookup . . . 6 4.3. Operation Related to State Transition Table Lookup . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 7.1. Normative References . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . 8 7.2. Informative References . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . 8 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction 1. Introduction
MPLS Transport Profile (MPLS-TP) linear protection in Automatic MPLS Transport Profile (MPLS-TP) linear protection in Automatic
Protection Switching (APS) mode is defined in RFC 7271 [RFC7271]. It Protection Switching (APS) mode is defined in RFC 7271 [RFC7271]. It
defines a set of alternate and additional mechanisms to perform some defines a set of alternate and additional mechanisms to perform some
of the functions of linear protection described in RFC 6378 of the functions of linear protection described in RFC 6378
[RFC6378]. The actions performed at initialization of the Protection [RFC6378]. The actions performed at initialization of the Protection
State Coordination (PSC) Control Logic are not described in either State Coordination (PSC) Control Logic are not described in either
[RFC7271] or [RFC6378]. Although it is a common perception that the [RFC7271] or [RFC6378]. Although it is a common perception that the
skipping to change at page 2, line 52 skipping to change at page 3, line 25
specified in any of the documents and various questions have been specified in any of the documents and various questions have been
raised by implementers and in discussions on the MPLS working group raised by implementers and in discussions on the MPLS working group
mailing list concerning the detailed actions that the PSC Control mailing list concerning the detailed actions that the PSC Control
Logic should take. Logic should take.
The state machine described in [RFC7271] operates under the The state machine described in [RFC7271] operates under the
assumption that both end nodes of a linear protection domain start in assumption that both end nodes of a linear protection domain start in
the Normal state. In the case that one node reboots while the other the Normal state. In the case that one node reboots while the other
node is still in operation, various scenarios may arise resulting in node is still in operation, various scenarios may arise resulting in
problematic situations. This document resolves all the problematic problematic situations. This document resolves all the problematic
cases and minimizes traffic disruptions related to initialization cases and minimizes traffic disruptions related to initialization,
including both cold and warm reboots that require re-initialization including both cold and warm reboots that require re-initialization
of the PSC Control Logic. of the PSC Control Logic.
This document contains updates to the MPLS-TP linear protection in This document contains updates to the MPLS-TP linear protection in
APS mode defined in [RFC7271]. The updates provide rules related to APS mode defined in [RFC7271]. The updates provide rules related to
initialization of the PSC Control Logic, in which the state machine initialization of the PSC Control Logic (in which the state machine
resides, when operating in APS mode. The updates also include resides) when operating in APS mode. The updates also include
modifications to the state transition table defined in Section 11.2 modifications to the state transition table defined in Section 11.2
of [RFC7271]. The changes in the state transition table have been of [RFC7271]. The changes in the state transition table have been
examined to make sure that they do not introduce any new problems. examined to make sure that no new problems are introduced.
This document does not introduce backward compatibility issues with This document does not introduce backward compatibility issues with
implementations of [RFC7271]. In case a node implementing this implementations of [RFC7271]. In case a node implementing this
document restarts, the new state changes will not cause problems at document restarts, the new state changes will not cause problems at
the remote node implementing [RFC7271] and the two ends will converge the remote node implementing [RFC7271], and the two ends will
to the same local and remote states. In case a node implementing converge to the same local and remote states. In case a node
[RFC7271] restarts, the two ends behave as today. implementing [RFC7271] restarts, the two ends behave as they do
today.
This document also provides some clarifications on the operation This document also provides some clarifications on the operation
related to state transition table lookup. related to state transition table lookup.
The reader of this document is assumed to be familiar with [RFC7271]. The reader of this document is assumed to be familiar with [RFC7271].
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", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in RFC 2119 [RFC2119]. "OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Acronyms 3. Abbreviations
This document uses the following acronyms:
This document uses the following abbreviations:
APS Automatic Protection Switching APS Automatic Protection Switching
DNR Do-not-Revert DNR Do-not-Revert
E::R Exercise state due to remote EXER message E::R Exercise state due to remote EXER message
EXER Exercise EXER Exercise
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
PF:DW:R Protecting Failure state due to remote SD-W message PF:DW:R Protecting Failure state due to remote SD-W message
PF:W:L Protecting Failure state due to local SF-W PF:W:L Protecting Failure state due to local SF-W
PF:W:R Protecting Failure state due to remote SF-W message PF:W:R Protecting Failure state due to remote SF-W message
PSC Protection State Coordination PSC Protection State Coordination
RR Reverse Request RR Reverse Request
SA:MP:R Switching Administrative state due to remote MS-P message SA:MP:R Switching Administrative state due to remote MS-P 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
SD Signal Degrade SD Signal Degrade
SD-W Signal Degrade on Working path
SF Signal Fail
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
UA:P:L Unavailable state due to local SF-P UA:P:L Unavailable state due to local SF-P
WTR Wait-to-Restore WTR Wait-to-Restore
4. Updates 4. Updates
This section specifies the actions that will be performed at the This section specifies the actions that will be performed at the
initialization of the PSC Control Logic and the modifications of the initialization of the PSC Control Logic and the modifications of the
state transition table defined in Section 11.2 of [RFC7271]. Some state transition table defined in Section 11.2 of [RFC7271]. Some
skipping to change at page 5, line 19 skipping to change at page 5, line 37
* Else (the node being initialized remembers the protection path * Else (the node being initialized remembers the protection path
as the active path), the node starts at the WTR state sending as the active path), the node starts at the WTR state sending
NR(0,1) or at the DNR state sending DNR(0,1) depending on the NR(0,1) or at the DNR state sending DNR(0,1) depending on the
configuration that allows or prevents automatic reversion to configuration that allows or prevents automatic reversion to
the Normal state. the Normal state.
o In case any local SD exists, the local SD MUST be considered as an o In case any local SD exists, the local SD MUST be considered as an
input to the Local Request Logic only after the local node has input to the Local Request Logic only after the local node has
received the first protocol message from the remote node and received the first protocol message from the remote node and
completed the processing (i.e., updated the PSC Control Logic and completed the processing (i.e., updated the PSC Control Logic and
decided which action, if any, to be sent to the PSC Message decided which action, if any, is to be sent to the PSC Message
Generator). Generator).
o If the local node receives an EXER message as the first protocol o If the local node receives an EXER message as the first protocol
message after initialization and the remote EXER becomes the top- message after initialization and the remote EXER becomes the top-
priority global request, the local node MUST set the position of priority global request, the local node MUST set the position of
the bridge and selector according to the Path value in the EXER the bridge and selector according to the Path value in the EXER
message and transit to the E::R state. message and transit to the E::R state.
Remembering the active path in case of no local request minimizes In the case of no local request, remembering the active path
traffic switchovers in cases where the remote node is still in minimizes traffic switchovers when the remote node is still in
operation. This approach does not cause a problem even if the operation. This approach does not cause a problem even if the
remembered active path is no longer valid due to any local input that remembered active path is no longer valid due to any local input that
occurred at the remote node while the initializing node was out of occurred at the remote node while the initializing node was out of
operation. operation.
It is worth noting that in some restart scenarios (e.g., cold Note that in some restart scenarios (e.g., cold rebooting), no valid
rebooting) no valid SF/SD indications may be present at the input of SF/SD indications may be present at the input of the Local Request
the Local Request logic. In this case, the PSC Control Logic would Logic. In this case, the PSC Control Logic restarts as if no local
restart as if no local requests are present. If a valid SF/SD requests are present. If a valid SF/SD indication is detected later,
indication is detected later, this would be notified to the PSC the PSC Control Logic is notified and state change is triggered.
Control Logic and trigger state change.
4.2. State Transition Modification 4.2. State Transition Modification
In addition to the initialization behavior described in Section 4.1, In addition to the initialization behavior described in Section 4.1,
four cells of the remote state transition table need to be changed to four cells of the remote state transition table need to be changed to
make two end nodes converge after initialization. State transition make two end nodes converge after initialization. State transition
by remote message defined in Section 11.2 of [RFC7271] is modified as by remote message as defined in Section 11.2 of [RFC7271] is modified
follows (only modified cells are shown): as follows (only modified cells are shown):
| MS-W | MS-P | WTR | EXER | RR | DNR | NR | MS-W | MS-P | WTR | EXER | RR | DNR | NR
--------+---------+---------+-----+------+----+------+---- --------+---------+---------+-----+------+----+------+----
N | | | (13)| | | DNR | N | | | (13)| | | DNR |
PF:W:R | | | | | | DNR | PF:W:R | | | | | | DNR |
PF:DW:R | | | | | | DNR | PF:DW:R | | | | | | DNR |
The changes in two rows of remote protecting failure states lead to The changes in two rows of remote protecting failure states lead to
the replacement of note (10) with DNR, therefore note (10) is no the replacement of note (10) with DNR; therefore, note (10) is no
longer needed. The resultant three rows read: longer needed. The resultant three rows read:
| 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 | (13)| E::R | i | DNR | i N | SA:MW:R | SA:MP:R | (13)| E::R | i | DNR | i
PF:W:R | SA:MW:R | SA:MP:R | (9) | E::R | i | DNR | (11) PF:W:R | SA:MW:R | SA:MP:R | (9) | E::R | i | DNR | (11)
PF:DW:R | SA:MW:R | SA:MP:R | (9) | E::R | i | DNR | (11) PF:DW:R | SA:MW:R | SA:MP:R | (9) | E::R | i | DNR | (11)
In the tables above, the letters 'i' and 'N' stand for "ignore" and In the tables above, the letters 'i' and 'N' stand for "ignore" and
"Normal state", respectively. Other acronyms can be found in "Normal state", respectively. Other abbreviations can be found in
Section 3. Section 3.
4.3. Operation related to State Transition Table Lookup 4.3. Operation Related to State Transition Table Lookup
In addition to the rules related to the state transition table lookup In addition to the rules related to the state transition table lookup
listed in Section 11 of [RFC7271], the following rule is also applied listed in Section 11 of [RFC7271], the following rule is also applied
to the operation related to the state transition table lookup: to the operation related to the state transition table lookup:
o When the local SF-P is cleared and the priorities of the local and o When the local SF-P is cleared and the priorities of the local and
remote requests are re-evaluated, the last received remote message remote requests are re-evaluated, the last received remote message
may not be valid any more due to the previous failure of the may no longer be valid due to the previous failure of the
protection path. Therefore, the last received message MUST be protection path. Therefore, the last received message MUST be
treated as if it were NR and only the local request shall be treated as if it were NR and only the local request shall be
evaluated. evaluated.
The last paragraph in Section 11 of [RFC7271] is modified as follows: The last paragraph in Section 11 of [RFC7271] is modified as follows:
--------- ---------
Old text: Old text:
--------- ---------
In the state transition tables below, the letter 'i' stands for In the state transition tables below, the letter 'i' stands for
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evaluated. evaluated.
The last paragraph in Section 11 of [RFC7271] is modified as follows: The last paragraph in Section 11 of [RFC7271] is modified as follows:
--------- ---------
Old text: Old text:
--------- ---------
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.
--------- ---------
New text: New text:
--------- ---------
In the state transition tables below, the letter 'i' is the In the state transition tables below, the letter 'i' is the
"ignore" flag, and if it is set it means that the top-priority "ignore" flag; if it is set, it means that the top-priority
global request is ignored. global request is ignored.
If re-evaluation is triggered, it is checked if the ignore flag is If re-evaluation is triggered, the ignore flag is checked. If it
set. If it is, the state machine will transit to the supposed state, is set, the state machine will transit to the supposed state, which
which can be Normal or DNR as indicated in the footnotes to the can be Normal or DNR as indicated in the footnotes to the state
state transition tables. If the ignore flag is not set, the state transition table in Section 11.1 of [RFC7271]. If the ignore flag
machine will transit to the state indicated in the cell of the state is not set, the state machine will transit to the state indicated
transition table. in the cell of the state transition table.
If re-evaluation is not triggered, it is checked if the ignore flag If re-evaluation is not triggered, the ignore flag is checked. If
is set. If it is, the state machine will remain in the current state, it is set, the state machine will remain in the current state, and
and the current PSC message continues to be transmitted. If the the current PSC message continues to be transmitted. If the ignore
ignore flag is not set, the state machine will transit to the state flag is not set, the state machine will transit to the state
indicated in the cell of the state transition table. indicated in the cell of the state transition table.
5. Security Considerations 5. Security Considerations
No specific security issue is raised in addition to those ones No specific security issue is raised in addition to those ones
already documented in [RFC7271]. It may be noted that tightening the already documented in [RFC7271]. Note that tightening the
description of initializing behavior may help to protect networks description of the initializing behavior may help to protect networks
from re-start attacks. from restart attacks.
6. IANA Considerations 6. IANA Considerations
This document makes no request of IANA. This document does not require any IANA actions.
Note to RFC Editor: this section may be removed on publication as an
RFC.
7. Acknowledgements
The authors would like to thank Joaquim Serra for bringing up the
issue related to initialization of the PSC Control Logic at the very
beginning. The authors would also like to thank Adrian Farrel and
Loa Andersson for their valuable comments and suggestions on this
document.
8. References 7. References
8.1. Normative References 7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC7271] Ryoo, J., Ed., Gray, E., Ed., van Helvoort, H., [RFC7271] Ryoo, J., Ed., Gray, E., Ed., van Helvoort, H.,
D'Alessandro, A., Cheung, T., and E. Osborne, "MPLS D'Alessandro, A., Cheung, T., and E. Osborne, "MPLS
Transport Profile (MPLS-TP) Linear Protection to Match the Transport Profile (MPLS-TP) Linear Protection to Match the
Operational Expectations of Synchronous Digital Hierarchy, Operational Expectations of Synchronous Digital Hierarchy,
Optical Transport Network, and Ethernet Transport Network Optical Transport Network, and Ethernet Transport Network
Operators", RFC 7271, DOI 10.17487/RFC7271, June 2014, Operators", RFC 7271, DOI 10.17487/RFC7271, June 2014,
<http://www.rfc-editor.org/info/rfc7271>. <https://www.rfc-editor.org/info/rfc7271>.
8.2. Informative References [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
7.2. Informative References
[RFC6378] Weingarten, Y., Ed., Bryant, S., Osborne, E., Sprecher, [RFC6378] Weingarten, Y., Ed., Bryant, S., Osborne, E., Sprecher,
N., and A. Fulignoli, Ed., "MPLS Transport Profile (MPLS- N., and A. Fulignoli, Ed., "MPLS Transport Profile
TP) Linear Protection", RFC 6378, DOI 10.17487/RFC6378, (MPLS-TP) Linear Protection", RFC 6378,
October 2011, <http://www.rfc-editor.org/info/rfc6378>. DOI 10.17487/RFC6378, October 2011,
<https://www.rfc-editor.org/info/rfc6378>.
Acknowledgements
The authors would like to thank Joaquim Serra for raising the issue
related to initialization of the PSC Control Logic at the very
beginning. The authors would also like to thank Adrian Farrel and
Loa Andersson for their valuable comments and suggestions on this
document.
Authors' Addresses Authors' Addresses
Jeong-dong Ryoo Jeong-dong Ryoo
ETRI ETRI
EMail: ryoo@etri.re.kr Email: ryoo@etri.re.kr
Taesik Cheung Taesik Cheung
ETRI ETRI
EMail: cts@etri.re.kr Email: cts@etri.re.kr
Huub van Helvoort Huub van Helvoort
Hai Gaoming BV Hai Gaoming BV
EMail: huubatwork@gmail.com Email: huubatwork@gmail.com
Italo Busi Italo Busi
Huawei Technologies Huawei Technologies
EMail: Italo.Busi@huawei.com Email: Italo.Busi@huawei.com
Guangjuan Wen Guangjuan Wen
Huawei Technologies Huawei Technologies
EMail: wenguangjuan@huawei.com Email: wenguangjuan@huawei.com
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