MPLS Working Group J. Ryoo
Internet-Draft T. Cheung
Updates: 7271 (if approved) ETRI
Intended status: Standards Track H. van Helvoort
Expires: April 19, 2016 Hai Gaoming BV
I. Busi
G. Weng
Huawei Technologies
October 17, 2015
Updates to MPLS Transport Profile (MPLS-TP) Linear Protection in
Automatic Protection Switching (APS) Mode
draft-ryoo-mpls-tp-aps-updates-01.txt
Abstract
This document contains updates to MPLS Transport Profile (MPLS-TP)
linear protection in Automatic Protection Switching (APS) mode
defined in RFC 7271. The updates provide rules related to the
initialization of the Protection State Coordination (PSC) Control
Logic, in which the state machine resides, when operating in APS
mode.
Status of This Memo
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This Internet-Draft will expire on April 19, 2016.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
3. Updates . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Initialization Behavior . . . . . . . . . . . . . . . . . 3
3.2. State Transition Modification . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
6.1. Normative References . . . . . . . . . . . . . . . . . . 5
6.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
MPLS Transport Profile (MPLS-TP) linear protection in Automatic
Protection Switching (APS) mode is defined in RFC 7271 [RFC7271].
The actions being performed at the initialization of the Protection
State Coordination (PSC) Control Logic are not described in either
[RFC7271] or RFC 6378 [RFC6378]. Although it is a common perception
that the state machine starts at the Normal state (but, not
explicitly specified in any of the documents), various questions have
been raised concerning the detailed actions that the PSC Control
Logic should take.
The state machine described in [RFC7271] operates under the
assumption that both end nodes of linear protection domain start in
the Normal state. In the case that one node reboots while the other
node is still in operation, various scenarios may arise resulting in
problematic situations. This document is intended to resolve all the
problematic cases and to minimize traffic disruptions related to
initialization including both cold and warm reboots that require re-
initialization of the PSC Control Logic.
This document contains updates to the MPLS Transport Profile (MPLS-
TP) linear protection in Automatic Protection Switching (APS) mode
defined in [RFC7271]. The updates provide rules related to
initialization of the PSC Control Logic, in which the state machine
resides, when operating in APS mode. The updates also include
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modifications to the state transition table defined in Section 11.2
of [RFC7271]. The changes in the state transition table were
examined to make sure that they do not introduce any new problems.
This document does not introduce backward compatibility issues with
implementations of [RFC7271]. In case a node implementing this
document restarts, the new state changes will not cause problems at
the remote node implementing [RFC7271] and the two ends will converge
to the same local and remote states. In case a node implementing
[RFC7271] restarts, the two ends behave as of today.
The reader of this document is assumed to be familiar with [RFC7271].
This document shares the acronyms defined in Section 3 of [RFC7271].
2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
3. Updates
This document updates [RFC7271] by specifying the actions that will
be performed at the initialization of the PSC Control Logic and
modifies the state transition table defined in Section 11.2 of
[RFC7271].
3.1. Initialization Behavior
When the PSC Control Logic is initialized, the following actions MUST
be performed:
o Stop the WTR timer if it is running.
o Clear any operator command in the Local Request Logic.
o If an SF-W or SF-P exists as the highest local request, transit to
the PF:W:L or UA:P:L state, respectively.
o When the node being initialized has no local request:
* If the node being initialized does not remember the active path
or if the node being initialized remembers the working path as
the active path, send NR(0,0) in Normal state.
* If the node being initialized remembers the protection path as
the active path, send either NR(0,1) in WTR state or DNR(0,1)
in DNR state depending on the configuration.
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o Any local SD MUST be ignored and the detection of a local SD MUST
be (re-)started after the local node completes the initialization
and responds to the first protocol message received from the
remote node.
o When the local node receives an EXER message as the first protocol
message after rebooting and the remote EXER becomes the top-
priority global request, align the position of the bridge and
selector with the Path value in the EXER message and transit to
the E::R state .
Remembering the active path in case of no local request is intended
to minimize traffic switchovers in case that the other node is still
in operation and does not cause any problem even if the remembered
active path is not valid any more due to any local input at the other
node while the initializing node is out of operation.
Note that while the local SD input is being ignored and there exist
no other local requests, the local node restats with no local
request. Since the equal priority resolution stated in Section 7.4
of [RFC7271] does not converge when the active paths that two nodes
remember are different from each other. an SD detection needs to be
(re-)started after both nodes converge to the same view on their
active paths.
It is worth noting that in some restart scenarios (e.g., cold
rebooting), no valid SF/SD indications may be present at the input of
the Local Request logic. In this case, the PSC Control Logic would
restart as if no local requests are present. If a valid SF/SD
indication is detected later on, this would be notified to the PSC
Control Logic and trigger state change.
3.2. State Transition Modification
State transition by remote message defined in Section 11.2 of
[RFC7271] MUST be modified as follows (only modified cells are
shown):
| MS-W | MS-P | WTR | EXER | RR | DNR | NR
--------+---------+---------+-----+------+----+------+----
N | | | (13)| | | DNR |
PF:W:R | | | | | | DNR |
PF:DW:R | | | | | | DNR |
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4. IANA Considerations
This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an
RFC.
5. Security Considerations
No specific security issue is raised in addition to those ones
already documented in [RFC7271]
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC7271] Ryoo, J., Ed., Gray, E., Ed., van Helvoort, H.,
D'Alessandro, A., Cheung, T., and E. Osborne, "MPLS
Transport Profile (MPLS-TP) Linear Protection to Match the
Operational Expectations of Synchronous Digital Hierarchy,
Optical Transport Network, and Ethernet Transport Network
Operators", RFC 7271, DOI 10.17487/RFC7271, June 2014,
<http://www.rfc-editor.org/info/rfc7271>.
6.2. Informative References
[RFC6378] Weingarten, Y., Ed., Bryant, S., Osborne, E., Sprecher,
N., and A. Fulignoli, Ed., "MPLS Transport Profile (MPLS-
TP) Linear Protection", RFC 6378, DOI 10.17487/RFC6378,
October 2011, <http://www.rfc-editor.org/info/rfc6378>.
Authors' Addresses
Jeong-dong Ryoo
ETRI
EMail: ryoo@etri.re.kr
Taesik Cheung
ETRI
EMail: cts@etri.re.kr
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Huub van Helvoort
Hai Gaoming BV
EMail: huubatwork@gmail.com
Italo Busi
Huawei Technologies
EMail: Italo.Busi@huawei.com
Guangjuan Weng
Huawei Technologies
EMail: wenguangjuan@huawei.com
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