Internet DRAFT - draft-rhd-mpls-tp-psc-sd
draft-rhd-mpls-tp-psc-sd
MPLS Working Group J. Ryoo
Internet-Draft ETRI
Intended status: Standards Track H. van Helvoort
Expires: March 15, 2014 Huawei Technologies
A. D'Alessandro
Telecom Italia
September 11, 2013
Supporting Signal Degrade in PSC Linear Protection
draft-rhd-mpls-tp-psc-sd-01.txt
Abstract
This document optionally updates [RFC6378], "MPLS Transport Profile
(MPLS-TP) Linear Protection", to support protection against signal
degrade (SD) in an effort to satisfy the ITU-T's protection switching
requirements.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
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-
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 15, 2014.
Copyright Notice
Copyright (c) 2013 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
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
3. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Operation of Protection Switching against Signal Degrade . . 3
5. Updates to the PSC RFC . . . . . . . . . . . . . . . . . . . 4
5.1. Updates to Section 3.1. Local Request Logic . . . . . . . 4
5.2. Updates to Section 3.5. Wait-to-Restore (WTR) Timer . . . 5
5.3. Updates to Section 3.6. PSC Control States . . . . . . . 5
5.4. Updates to Section 4.2.2. PSC Request Field . . . . . . . 5
5.5. Updates to Section 4.2.3. Protection Type (PT) Field . . 6
5.6. Updates to Section 4.2.6. Data Path (Path) Field . . . . 6
5.7. Updates to Section 4.3.2. Priority of Inputs . . . . . . 7
5.8. Updates to Section 4.3.3.1 Normal State . . . . . . . . . 9
5.9. Updates to Section 4.3.3.2 Unavailable State . . . . . . 10
5.10. Updates to Section 4.3.3.3 Protecting Administrative
State . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.11. Updates to Section 4.3.3.4 Protecting Failure State . . . 16
5.12. Updates to Section 4.3.3.5 Wait-to-Restore State . . . . 19
5.13. Updates to Section 4.3.3.6 Do-not-Revert State . . . . . 20
5.14. Updates to Appendix A. PSC State Machine Tables . . . . . 21
6. Security considerations . . . . . . . . . . . . . . . . . . . 25
7. IANA considerations . . . . . . . . . . . . . . . . . . . . . 26
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 26
9.1. Normative References . . . . . . . . . . . . . . . . . . 26
9.2. Informative References . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
1. Introduction
This document optionally updates [RFC6378], "MPLS Transport Profile
(MPLS-TP) Linear Protection", to support protection against signal
degrade in an effort to satisfy the ITU-T's protection switching
requirements shown in the ITU-T's liaison statements [LIAISON1205]
and [LIAISON1234]. In MPLS-TP survivability framework [RFC6372],
fault conditions include both Signal Fail (SF) and Signal Degrade
(SD) that can be used to trigger protection switching.
[RFC6378], which defines the Protection State Coordination (PSC)
protocol, does not specify how the SF and SD are declared and
specifies the protection switching protocol associated with SF only.
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This document is intended to cover the protection switching protocol
associated with SD, and the specifics for the method of identifying
SD is out of the scope of this document similarly to SF for
[RFC6378]. The updates specified in this document do not require any
changes to the protocol's packet format.
2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Acronyms
This draft uses the following acronyms:
FS Forced Switch
LO Lockout of protection
MS Manual Switch
MPLS-TP Transport Profile for MPLS
PSC Protection State Coordination
SD Signal Degrade
SD-P Signal Degrade on the Protection path
SD-W Signal Degrade on the Working path
SF Signal Fail
SF-P Signal Fail on the Protection path
SF-W Signal Fail on the Working path
SFc Clear Signal Fail
4. Operation of Protection Switching against Signal Degrade
In order to maintain the network operation behavior to which
transport network operators have become accustomed, the priorities of
SD-P and SD-W are defined to be equal as in other transport networks,
such as OTN and Ethernet. Once a switch has been completed due to
signal degrade on one path, it will not be overridden by signal
degrade on the other path (first come, first served behavior), to
avoid protection switching that cannot improve signal quality and
flapping.
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When multiple SDs are detected simultaneously, either as local or
remote requests on both working and protection paths, the SD on the
standby path (the path from which the selector does not select the
user data traffic) is considered as having higher priority than the
SD on the active path (the path from which the selector selects the
user data traffic). Therefore, no unnecessary protection switching
is performed and the user data traffic continues to be selected from
the active path.
In the preceding paragraph, "simultaneously" relates to the
occurrence of SD on both the active and standby paths at input to the
PSC Protection State Control Logic at the same time, or as long as a
SD request has not been acknowledged by the remote end in
bidirectional protection switching. In other words, when a local
node that has transmitted a SD message receives a SD message that
indicates a different value of data path (Path) field than the value
of the Path field in the transmitted SD message, both the local and
the remote SD requests are considered to occur simultaneously.
5. Updates to the PSC RFC
This section describes the changes required to support protection
against SD in the PSC protocol defined in [RFC6378]
5.1. Updates to Section 3.1. Local Request Logic
Replace the following two bullet item text:
o Signal Degrade (SD) - if any of the server-layer, control-plane,
or OAM indications signaled a degraded transmission condition on
either the protection path or one of the working paths. The
determination and actions for SD are for further study and may
appear in a separate document. All references to SD input are
placeholders for this extension.
o Clear Signal Fail (SFc) - if all of the server-layer,
controlplane, or OAM indications are no longer indicating a
failure condition on a path that was previously indicating a
failure condition.
With:
o Signal Degrade (SD) - if any of the server-layer, control-plane,
or OAM indications signaled a degraded transmission condition on
either the protection path or one of the working paths.
o Clear Signal Fail (SFc) - if all of the server-layer,
controlplane, or OAM indications are no longer indicating a
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failure/degradation condition on a path that was previously
indicating a failure/degradation condition.
5.2. Updates to Section 3.5. Wait-to-Restore (WTR) Timer
Replace the following text in the first paragraph:
The WTR timer is used to delay reversion to Normal state when
recovering from a failure condition on the working path and the
protection domain is configured for revertive behavior.
With:
The WTR timer is used to delay reversion to Normal state when the
protection domain is configured for revertive behavior and
recovering from a failure or a degradation condition on the
working path.
5.3. Updates to Section 3.6. PSC Control States
The second paragraph of Section 4.3.3.2 Unavailable State in
[RFC6378] shows the intention of including the signal degrade on the
protection in the Unavailable state. Even though the protection path
can be partially available under the condition of the signal degrade
on the protection path, this document follows the same state grouping
as [RFC6378] for SD on the protection.
Replace the following bullet item text:
o Unavailable state - The protection path is unavailable -- either
as a result of an operator Lockout command or a failure condition
detected on the protection path.
With:
o Unavailable state - The protection path is unavailable -- either
as a result of an operator Lockout command or a failure/
degradation condition detected on the protection path.
5.4. Updates to Section 4.2.2. PSC Request Field
Replace the following bullet item text:
o (7) Signal Degrade - indicates that the transmitting end point has
identified a degradation of the signal, or integrity of the packet
transmission on either the working or protection path. This
request is presented here only as a placeholder. The specifics
for the method of identifying this degradation is out of scope for
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this document. The details of the actions to be taken for this
situation are left for future specification.
With:
o (7) Signal Degrade - indicates that the transmitting end point has
identified a degradation of the signal, or integrity of the packet
transmission on either the working or protection path. The FPath
field SHALL identify the path that is reporting the degrade
condition (i.e., if protection path, then FPath is set to 0; if
working path, then FPath is set to 1), and the Path field SHALL
indicate where the data traffic is being transported (i.e., if
working path is selected, then Path is set to 0; if protection
path is selected, then Path is set to 1).
5.5. Updates to Section 4.2.3. Protection Type (PT) Field
Add the following text at the end of Section 4.2.3:
If the detection of a SD depends on the presence of user data
packets, such a condition declared on the working path is cleared
following protection switching to the protection path if a
selector bridge is used, possibly resulting in flapping. To avoid
flapping, the selector bridge should duplicate the user data
traffic and feed it to both working and protection paths under SD
condition.
5.6. Updates to Section 4.2.6. Data Path (Path) Field
Replace the following bullet item text:
o 0: indicates that the protection path is not transporting user
data traffic (in 1:n architecture) or transporting redundant user
data traffic (in 1+1 architecture).
With:
o 0: indicates that the protection path is not transporting user
data traffic (in 1:n architecture) or transporting redundant user
data traffic (in 1+1 architecture or under SD condition in 1:n
architecture when the detection of a SD depends on the presence of
user data packets)
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5.7. Updates to Section 4.3.2. Priority of Inputs
Replace the following bullet item text:
o Signal Degrade on working (OAM / control-plane / server
indication)
With:
o Signal Degrade on either working or protection (OAM / control-
plane / server indication)
Replace the following two paragraphs:
As was noted above, the Local Request logic SHALL always select
the local input indicator with the highest priority as the current
local request, i.e., only the highest priority local input will be
used to affect the control logic. All local inputs with lower
priority than this current local request will be ignored.
The remote message from the far-end LER is assigned a priority
just below the similar local input. For example, a remote Forced
Switch would have a priority just below a local Forced Switch but
above a local Signal Fail on protection input. As mentioned in
Section 3.6.1, the state transition is determined by the higher
priority input between the highest priority local input and the
remote message. This also determines the classification of the
state as local or remote. The following subsections detail the
transition based on the current state and the higher priority of
these two inputs.
With:
As was noted above, the Local Request logic SHALL always select
the local input indicator with the highest priority as the current
local request, i.e., only the highest priority local input will be
used to affect the control logic. All local inputs with lower
priority than this current local request will be ignored. For
local inputs with same priority, first-come, first-served rule is
applied. For example, once SD-P (or SD-W) local input is
determined as the highest priority local input, then subsequent
SD-W (or SD-P) local input will not be presented to the PSC
Control logic as the highest local request.
The remote message from the far-end LER is assigned a priority
just below the same local input. For example, a remote Forced
Switch would have a priority just below a local Forced Switch but
above a local Signal Fail on protection input.
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However, if the LER is in a remote state due to a remote message,
a subsequent local input having the same priority but requesting
different action to the control logic, will be considered as
having lower priority than the remote message, and will be
ignored. For example, if the LER is in remote Unavailable state
due to a remote SD-P, then subsequent local SD-W input will be
ignored.
It should be noted that there is a reverse case where one LER
receives a local input and the other LER receives, simultaneously,
a local input with the same priority but requesting different
action. In this case, each of the two LERs receives a subsequent
remote message having the same priority but requesting different
action, while the LER is in a local state due to the local input.
In this case, a priority must be set for the inputs with the same
priority regardless of its origin (local input or remote message).
For example, one LER receives SD-P as a local input and the other
LER receives SP-W as a local input, simultaneously. In this case,
the SD on the standby path (the path from which the selector does
not select the user data traffic) is considered as having higher
priority than the SD on the active path (the path from which the
selector selects the user data traffic) regardless of its origin
(local or remote message). Therefore, no unnecessary protection
switching is performed and the user data traffic continues to be
selected from the active path. Giving the higher priority to the
SD on the standby path SHALL also be applied to the Local Request
logic when two SDs for different paths happen to be presented to
the Local Request logic exactly at the same time.
In order to resolve the equal priority conditions described above,
following rules are defined:
(a) If two local inputs having same priority but requesting
different action come to the Local Request logic, then the
input coming first SHALL be considered to have a higher
priority than the other coming later (first-come, first-
served).
(b) If the LER receives both a local input and a remote message
with the same priority and requesting the same action, i.e.,
the same PSC Request Field and the same FPath value, then
the local input SHALL be considered to have a higher
priority than the remote message.
(c) If the LER receives both a local input and a remote message
with the same priority but requesting different actions,
i.e., the same PSC Request Field but different FPath value,
then the first-come, first-served rule SHALL be applied. If
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the remote message comes first, then the state SHALL be a
remote state and subsequent local input is ignored.
However, if the local input comes first, the first-come,
first-served rule cannot be applied and must be viewed as
simultaneous condition. This is because the subsequent
remote message will not be an acknowledge of the local input
by the far-end node. In this case, the priority SHALL be
determined by rules for each simultaneous conditions.
(d) If the LER receives both SD-P and SD-W request either as
local input or remote message and the LER is in a local
state, then the SD on the standby path (the path from which
the selector does not select the user data traffic) is
considered as having higher priority than the SD on the
active path (the path from which the selector selects the
user data traffic) regardless of its origin (local or remote
message). This rule of giving the higher priority to the SD
on the standby path SHALL also be applied to the Local
Request logic when two SDs for different paths happen to be
presented to the Local Request logic exactly at the same
time
As mentioned in Section 3.6.1, the state transition is determined
by the higher priority input between the highest priority local
input and the remote message. This also determines the
classification of the state as local or remote. The following
subsections detail the transition based on the current state and
the higher priority of these two inputs.
5.8. Updates to Section 4.3.3.1 Normal State
Add the following bullet item text to the transitions in reaction to
a local input to the LER:
o A local Signal Degrade indication on the protection path (SD-P)
SHALL cause the LER to go into local Unavailable state and begin
transmission of an SD(0,0) message.
o A local Signal Degrade indication on the working path (SD-W) SHALL
cause the LER to go into local Protecting failure state and begin
transmission of an SD(1,1) message.
Add the following bullet item text to the transitions in reaction to
a remote message:
o A remote SD-P message SHALL cause the LER (LER-A) to go into
remote Unavailable state, while continuing to transmit the NR(0,0)
message.
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o A remote SD-W message SHALL cause the LER to go into remote
Protecting failure state, and transmit an NR(0,1) message.
5.9. Updates to Section 4.3.3.2 Unavailable State
The second paragraph of Section 4.3.3.2 Unavailable State in
[RFC6378] shows the intention of including the signal degrade on the
protection in the Unavailable state. This document follows the same
state grouping as [RFC6378] for SD-P, even though the protection path
can be partially available under the condition of the signal degrade
on the protection path.
Replace the following text in the first paragraph of Section 4.3.3.2
Unavailable State for further clarification on SD on the protection
path:
When the protection path is unavailable -- either as a result of a
Lockout operator command, or as a result of a SF detected on the
protection path -- then the protection domain is in the
Unavailable state.
With:
When the protection path is unavailable -- either as a result of a
Lockout operator command, or as a result of a SF/SD detected on
the protection path -- then the protection domain is in the
Unavailable state.
When an LER is in this state due to degradation condition, the
user traffic should be duplicated and fed to both working and
protection paths if the detection of a SD depends on the presence
of user data packets.
Replace the following bullet item text in the transitions in reaction
to a local input:
o A local Forced Switch SHALL be ignored by the PSC Control logic
when in Unavailable state as a result of a (local or remote)
Lockout of protection. If in Unavailable state due to an SF on
protection, then the FS SHALL cause the LER to go into local
Protecting administrative state and begin transmitting an FS(1,1)
message. It should be noted that due to the unavailability of the
protection path (i.e., due to the SF condition) that this FS may
not be received by the far-end until the SF condition is cleared.
With:
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o A local Forced Switch SHALL be ignored by the PSC Control logic
when in Unavailable state as a result of a (local or remote)
Lockout of protection. If in Unavailable state due to an SF/SD on
protection, then the FS SHALL cause the LER to go into local
Protecting administrative state and begin transmitting an FS(1,1)
message. It should be noted that due to the unavailability of the
protection path (i.e., due to the SF condition) that this FS may
not be received by the far-end until the SF condition is cleared.
Replace the following bullet item text in the transitions in reaction
to a local input:
o A local Signal Fail on the protection path input when in local
Unavailable state (by implication, this is due to a local SF on
protection) SHALL cause the LER to remain in local Unavailable
state and transmit an SF(0,0) message.
With:
o A local Signal Fail on the protection path input when in local
Unavailable state SHALL cause the LER to remain in local
Unavailable state and transmit an SF(0,0) message.
Replace the following bullet item text in the transitions in reaction
to a local input:
o A local Signal Fail on the working path input when in remote
Unavailable state SHALL cause the LER to remain in remote
Unavailable state and transmit an SF(1,0) message.
With:
o A local Signal Fail on the working path input when in local or
remote Unavailable state due to SD-P SHALL cause the LER to go to
local Protecting failure state. If the LER is in remote
Unavailable state due to SF-P or Lockout of protection, the LER
SHALL remain in remote Unavailable state and transmit an SF(1,0)
message.
Add the following bullet item text to the transitions in reaction to
a local input:
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o A local Clear SD of the protection path in local Unavailable state
that is due to an SD on the protection path SHALL cause the LER to
go to Normal state. If the LER is in remote Unavailable state but
has an active local SD condition, then the local Clear SD SHALL
clear the SD local condition and the LER SHALL remain in remote
Unavailable state and begin transmitting NR(0,0) messages. In all
other cases, the local Clear SD SHALL be ignored.
o A local SD-P input when in local Unavailable state (by
implication, this is due to a local SD on protection) SHALL cause
the LER to remain in local Unavailable state and transmit an
SD(0,0) message. When in remote Unavailable state due to LO or
SF-P, the LER SHALL remain in remote unavailable state and begin
transmitting SD(0,0) messages. When in remote Unavailable state
due to SD-P, the LER SHALL enter to local Unavailable state and
begin transmitting SD(0,0) messages.
o A local SD-W input when in remote Unavailable state SHALL cause
the LER to remain in remote Unavailable state and transmit an
SD(1,0) message.
Replace the following bullet item text in the transitions in reaction
to a remote message:
o A remote Lockout of protection message SHALL cause the LER to
remain in Unavailable state (note that if the LER was previously
in local Unavailable state due to a Signal Fail on the protection
path, then it will now be in remote Unavailable state) and
continue transmission of the current message (either NR(0,0) or
LO(0,0) or SF(0,0)).
With:
o A remote Lockout of protection message SHALL cause the LER to
remain in Unavailable state (note that if the LER was previously
in local Unavailable state due to a Signal Fail on the protection
path or a Signal Degrade on the protection path, then it will now
be in remote Unavailable state) and continue transmission of the
current message (either NR(0,0) or LO(0,0) or SF(0,0) or SF(1,0)
or SD(0,0) or SD(1,0)).
Replace the following bullet item text in the transitions in reaction
to a remote message:
o A remote Forced Switch message SHALL be ignored by the PSC Control
logic when in Unavailable state as a result of a (local or remote)
Lockout of protection. If in Unavailable state due to a local or
remote SF on protection, then the FS SHALL cause the LER to go
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into remote Protecting administrative state; if in Unavailable
state due to local SF, begin transmitting an SF(0,1) message.
With:
o A remote Forced Switch message SHALL be ignored by the PSC Control
logic when in Unavailable state as a result of a local Lockout of
protection. If in Unavailable state due to a remote Lockout of
protection, the LER SHALL go to remote Protecting Administrative
state and begin transmitting a message reflecting its local input
with Path=1. If in Unavailable state due to a local or remote
SF-P/SD-P, then the FS SHALL cause the LER to go into remote
Protecting administrative state; if in Unavailable state due to
local SF-P and SD-P, begin transmitting an SF(0,1) and SD(0,1)
message, respectively.
Replace the following bullet item text in the transitions in reaction
to a remote message:
o A remote Signal Fail message that indicates that the failure is on
the protection path SHALL cause the LER to remain in Unavailable
state and continue transmission of the current message (either
NR(0,0) or SF(0,0) or LO(0,0)).
With:
o A remote Signal Fail message that indicates that the failure is on
the protection path SHALL cause the LER to remain in Unavailable
state and continue transmission of the current message (either
NR(0,0) or LO(0,0) or SF(0,0) or SF(1,0) or SD(0,0) or SD(1,0)
Replace the following bullet item text in the transitions in reaction
to a remote message:
o A remote No Request, when the LER is in remote Unavailable state
and there is no active local Signal Fail SHALL cause the LER to go
into Normal state and continue transmission of the current
message. If there is a local Signal Fail on the protection path,
the LER SHALL remain in local Unavailable state and transmit an
SF(0,0) message. If there is a local Signal Fail on the working
path, the LER SHALL go into local Protecting Failure state and
transmit an SF(1,1) message. When in local Unavailable state, the
remote message SHALL be ignored.
With:
o A remote No Request, when the LER is in remote Unavailable state
and there is no active local Signal Fail or Signal Degrade SHALL
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cause the LER to go into Normal state and continue transmission of
the current message. If there is a local Signal Fail on the
protection path, the LER SHALL remain in local Unavailable state
and transmit an SF(0,0) message. If there is a local Signal Fail
on the working path, the LER SHALL go into local Protecting
Failure state and transmit an SF(1,1) message. If there is a
local Signal Degrade on the protection path, the LER SHALL remain
in local Unavailable state and transmit an SD(0,0) message. If
there is a local Signal Degrade on the working path, the LER SHALL
go into local Protecting Failure state and transmit an SD(1,1)
message. When in local Unavailable state, the remote message
SHALL be ignored.
Add the following bullet item text to the transitions in reaction to
a remote message:
o A remote SF-W message SHALL be ignored if the LER is in local
Unavailable state due to LO or SF-P. When in local Unavailable
state due to SD-P, the LER SHALL enter to remote Protecting
Failure state and begin transmitting SD(0,1) messages. If the LER
is in remote Unavailable state, then the SF-W message and the
local input are reevaluated as if the LER is in the Normal state.
In the case that the LER is in remote Unavailable state due to
remote SD-P, the reevaluation will cause the LER to enter remote
Protecting Failure state and continue to send the current messages
with Path=1.
o A remote MS message SHALL be ignored if the LER is in local
Unavailable state. If the LER is in remote Unavailable state,
then the MS message and the local input are reevaluated as if the
LER is in the Normal state.
o A remote SD-P message shall be ignored if the LER is in local
Unavailable state. If the LER is in remote Unavailable state due
to LO or SF-P, then the SD-P message and the local input are
reevaluated as if the LER is in the Normal state. If the LER is
in remote Unavailable state due to SD-P, then the remote SD-P
message will be ignored
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o A remote SD-W message shall be reevaluated with the local input as
if the LER is in the Normal state, A remote SD-W message shall be
ignored if the LER is in local Unavailable state due to LO or
SF-P. When in local Unavailable state due to SD-P, the LER shall
examine the Path value in the remote SD-W message. If the Path
value of the received SD-W message is the same as the Path value
that the LER indicates in its current outgoing PSC message, then
the LER shall ignore the SD-W message. Otherwise, as the local
SD-P and the remote SD-W are considered to occur simultaneously,
perform the followings:
* If the working path was the active path at the time when local
SD-P was selected as the highest local request, the LER remains
in the local Unavailabe state and continue transmission of the
current message.
* If the working path was the standby path at the time when local
SD-P was selected as the highest local request, the LER enters
into the remote Protection Failure state and begin transmitting
SD(0,1) messages.
5.10. Updates to Section 4.3.3.3 Protecting Administrative State
Add the following bullet item text to the transitions in reaction to
a local input:
o A local SD-P SHALL cause the LER to go to local Unavailabe state
and begin transmitting an SD(0,0) message, if the current state is
due to a (local or remote) MS command. If the LER is in remote
Protecting administrative state due to a remote Forced Switch
command, then this local indication SHALL cause the LER to remain
in remote Protecting administrative state and transmit an SD(0,1)
message. If the LER is in local Protecting administrative state
due to a local FS command, then this indication SHALL be ignored
(i.e., the indication should have been blocked by the Local
Request logic).
o A local SD-W SHALL cause the LER to go to local Unavailabe state
and begin transmitting an SD(1,1) message, it the current state is
due to a (local or remote) MS command. If the LER is in remote
Protecting administrative state due to a remote Forced Switch
command, then this local indication SHALL cause the LER to remain
in remote Protecting administrative state and transmit an SD(1,1)
message. If the LER is in local Protecting administrative state
due to a local FS command, then this indication SHALL be ignored
(i.e., the indication should have been blocked by the Local
Request logic).
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Add the following bullet item text to the transitions in reaction to
a remote message:
o A remote SD-P SHALL cause the LER to go into remote Unavailable
state and begin transmitting an NR(0,0) message, if the Protecting
administrative state is due to a (local or remote) MS command. It
should be noted that this automatically cancels the current MS
command and data traffic is reverted to the working path. If the
LER is in remote Protecting administrative state due to a remote
FS command, then the SD-P message and the local input are
reevaluated as if the LER is in the Normal state. If the LER is
in local Protecting administrative state due to a local FS
command, then this indication SHALL be ignored (i.e., the
indication should have been blocked by the Local Request logic).
o A remote SD-W message SHALL cause the LER to go into remote
Unavailable state and begin transmitting an NR(0,1) message, if
the Protecting administrative state is due to a (local or remote)
MS command. If the LER is in remote Protecting administrative
state due to a remote FS command, then the SD-W message and the
local input are reevaluated as if the LER is in the Normal state.
If the LER is in local Protecting administrative state due to a
local FS command, then this indication SHALL be ignored
5.11. Updates to Section 4.3.3.4 Protecting Failure State
The bullet item of "Protecting failure state" in Section 3.6. PSC
Control States in [RFC6378] includes the degrade condition in
Protection failure state. This document follows the same state
grouping as [RFC6378] for SD on the working path.
Replace the following text in the first paragraph of Section 4.3.3.4
Protecting Failure State for further clarification on the SD on the
working path:
When the protection mechanism has been triggered and the
protection domain has performed a protection switch, the domain is
in the Protecting failure state. In this state, the normal data
traffic SHALL be transported on the protection path. When an LER
is in this state, it implies that there either was a local SF
condition or it received a remote SF PSC message. The SF
condition or message indicated that the failure is on the working
path.
This state may be overridden by the Unavailable state triggers,
i.e., Lockout of protection or SF on the protection path, or by
issuing an FS operator command. This state will be cleared when
the SF condition is cleared. In order to prevent flapping due to
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an intermittent fault, the LER SHOULD employ a Wait-to-Restore
timer to delay return to Normal state until the network has
stabilized (see Section 3.5).
With:
When the protection mechanism has been triggered and the
protection domain has performed a protection switch, the domain is
in the Protecting failure state. In this state, the normal data
traffic SHALL be transported on the protection path. When an LER
is in this state, it implies that there either was a local SF/SD
condition or it received a remote SF/SD PSC message. The SF/SD
condition or message indicated that the failure/degradation is on
the working path.
This state may be overridden by the Unavailable state triggers,
i.e., Lockout of protection or SF on the protection path, or by
issuing an FS operator command. This state will be cleared when
the SF/SD condition is cleared. In order to prevent flapping due
to an intermittent fault, the LER SHOULD employ a Wait-to-Restore
timer to delay return to Normal state until the network has
stabilized (see Section 3.5).
When an LER is in this state due to degradation condition, the
user traffic should be duplicated and fed to both working and
protection paths if the detection of a SD depends on the presence
of user data packets.
Replace the following bullet item text in the transitions in reaction
to a local input:
o A local Clear SF SHALL be ignored if in remote Protecting failure
state. If in local Protecting failure state and the LER is
configured for revertive behavior, then this input SHALL cause the
LER to go into Wait-to-Restore state, start the WTR timer, and
begin transmitting a WTR(0,1) message. If in local Protecting
failure state and the LER is configured for non-revertive
behavior, then this input SHALL cause the LER to go into Do-not-
Revert state and begin transmitting a DNR(0,1) message.
With:
o A local Clear SF for clearing local SF-W SHALL be ignored if in
remote Protecting failure state due to remote SF-W. In local
Protecting failure state due to local SF-W, clearing local SF-W
SHALL cause the LER to go into WTR state, start the WTR timer, and
begin transmitting a WTR(0,1) message, if the LER is configured
for revertive behavior. Clear local SF-W in local Protecting
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failure state due to local SF-W SHALL cause the LER to go into Do-
not- Revert state and begin transmitting a DNR(0,1) message for
non-revertive configuration. In local Protecting Failure state
due to local SD-W, if the SF/SD being cleared is SD-W and there is
no local SD-P, then go to WTR or DNR state depending on the
configuration for revertive behavior. If there is local SD-P when
local SD-W is cleared in local Protecting Failure state due to
SD-W, go to local Unavailable state and begin transmitting SD(0.0)
message. If the SF/SD being cleared is SD-P in local Protecting
Failure due to SD-W, then ignore. In remote Protection Failure
state due to remote SD-W, if the SF/SD being cleared is SD-P, then
remain in current state and begin transmitting NR(0,1), otherwise,
ignore.
Add the following bullet item text to the transitions in reaction to
a local input:
o A local SD-P SHALL be ignored if the LER is in local Protecting
Failure state. If in remote Protecting Failure state,the LER
SHALL remain in the current state and begin transmission of an
SD(0,1) message.
o A local SD-W SHALL be ignored if the LER is in local Protecting
Failure state. If in remote Protecting Failure state, the LER
SHALL remain in the current state and begin transmission of an
SD(1,1) message.
Add the following SD related sentences to the end of each bullet item
text for describing the reaction to remote PSC messages:
remote Lockout of protection: If the LER is in local Protecting
Failure state due to local SD-W, then go to remote Unavailable
state and begin sending SD(1,0) If in remote Protecting Failure
state due to remote SD-W, then go to remote Unavailable state and
continue to send the current message with Path=0.
remote Forced Switch: If the LER is in the Protecting Failure state
due to local or remote SD-W, go to remote Protecting
Administrative state and continue to send the current message.
remote Signal Fail on the protection path: If the LER is in the
Protecting Failure state due to local or remote SD-W, go to remote
Unavailable state and continue to send the current message with
Path=0.
Add the following bullet item text to the transitions in reaction to
a remote message:
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o A remote SF-W message received in Protecting Failure state due to
local or remote SD-W SHALL cause the LER to remain in Protecting
Failure state and continue to send the current message.
o A remote SD-P message can cause the LER to react differently
depending on the cause and locality of current state as follows:
* In Protecting Failure state due to remote SF-W, if there is no
local request, transition to remote Unavailable state and send
NR(0,0). If there is local SD-W input, then transition to
remote Unavailable state and send SD(1,0) message. If the
local input is SD-P, then transition to local Unavailable state
and send SD(0,0) message.
* In Protecting Failure state due to remote SD-W, if the local
input is SD-P, then transition to local Unavailable state.
Else, transition to N state.
* In Protecting Failure state due to local SD-W, if the received
SD-P message has Path=1, ignore the message. If the received
SD-P message has Path=0 and the active path just before the
SD-W is selected as the highest local input was the working
path, then go to remote Unavailable state and transmit SD(1,0).
If the received SD-P message has Path=0 and the active path
just before the SD-W is selected as the highest local input was
the protection path, then ignore the received SD-P message.
o A remote Manual Switch message received in Protecting Failure due
to remote SD-W SHALL cause the LER to reevaluate the MS message
and local input as if the LER is in the Normal state.
5.12. Updates to Section 4.3.3.5 Wait-to-Restore State
Replace the following paragraph in Section 4.3.3.5 Wait-to-Restore
State:
o When recovering from a failure condition on the working path, the
Wait-to-Restore state is used by the PSC protocol to delay
reverting to the Normal state, for the period of the WTR timer to
allow the recovering failure to stabilize. While in the Wait-to-
Restore state, the data traffic SHALL continue to be transported
on the protection path. The natural transition from the Wait-to-
Restore state to Normal state will occur when the WTR timer
expires.
With:
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o When recovering from a failure or degradation condition on the
working path, the Wait-to-Restore state is used by the PSC
protocol to delay reverting to the Normal state, for the period of
the WTR timer to allow the recovering failure/degradation to
stabilize. While in the Wait-to-Restore state, the data traffic
SHALL continue to be transported on the protection path. The
natural transition from the Wait-to-Restore state to Normal state
will occur when the WTR timer expires.
o When an LER is in this state following the recovery of degradation
condition, the user traffic will continue to be duplicated and fed
to both working and protection paths if the detection of a SD
depends on the presence of user data packets.
Add the following bullet item text to the transitions in reaction to
a local input:
o A local SD-P SHALL send the Stop command to the WTR timer, go into
local Unavailable state, and begin transmission of an SD(0,0)
message.
o A local SD-W SHALL send the Stop command to the WTR timer, go into
local Protecting failure state, and begin transmission of an
SD(1,1) message.
Add the following bullet item text to the transitions in reaction to
a remote PSC message:
o A remote SD-P message SHALL send the Stop command to the WTR
timer, go into remote Unavailable state, and begin transmission of
an NR(0,0) message.
o A remote SD-W message SHALL send the Stop command to the WTR
timer, go into remote Protecting failure state, and begin
transmission of an NR(0,1) message.
5.13. Updates to Section 4.3.3.6 Do-not-Revert State
Add the following bullet item text to the transitions in reaction to
a local input:
o A local SD-P SHALL cause the LER to go into local Unavailable
state, and begin transmission of an SD(0,0) message.
o A local SD-W SHALL cause the LER go into local Protecting failure
state, and begin transmission of an SD(1,1) message.
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Add the following bullet item text to the transitions in reaction to
a remote PSC message:
o A remote SD-P message SHALL cause the LER to go into remote
Unavailable state, and begin transmission of an NR(0,0) message.
o A remote SD-W message SHALL cause the LER to go into remote
Protecting failure state, and begin transmission of an NR(0,1)
message.
5.14. Updates to Appendix A. PSC State Machine Tables
Add the following extended states:
UA:DP:L Unavailable state due to local SD on protection path
UA:DP:R Unavailable state due to remote SD-P message
PF:DW:L Protecting failure state due to local SD on working path
PF:DW:R Protecting failure state due to remote SD-W message
Add the following default messages:
State REQ(FP, P)
------- ----------
UA:DP:L SD(0,0)
UA:DP:R NR(0,0)
PF:DW:L SD(1,1)
PF:DW:R NR(0,1)
Add the following text before the state machine table:
The letter 'r' in the table below stands for reevaluation, and is
an indication to reevaluate all inputs (both the local input and
the remote message) as if the LER is in the Normal state. See
4.3.3.
Modify the state machine as follows (only modified cells are shown):
Part 1: Local input state machine
+---------+----+---------+--------+--------+--------+
| | OC | LO | SF-P | FS | SF-W |
+---------+----+---------+--------+--------+--------+
| N | | | | | |
| UA:LO:L | | | | | |
| UA:P:L | | | | | |
| UA:DP:L | i | UA:LO:L | UA:P:L | PA:F:L | PA:W:L |
| UA:LO:R | | | | | |
| UA:P:R | | | | | |
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| UA:DP:R | i | UA:LO:L | UA:P:L | PA:F:L | PF:W:L |
| PF:W:L | | | | | |
| PF:DW:L | i | UA:LO:L | UA:P:L | PA:F:L | PF:W:L |
| PF:W:R | | | | | |
| PF:DW:R | i | UA:LO:L | UA:P:L | PA:F:L | PF:W:L |
| PA:F:L | | | | | |
| PA:M:L | | | | | |
| PA:F:R | | | | | |
| PA:M:R | | | | | |
| WTR | | | | | |
| DNR | | | | | |
+---------+----+---------+--------+--------+--------+
+---------+---------+---------+------+----+--------+
| | SD-P | SD-W | SFc | MS | WTRExp |
+---------+---------+---------+------+----+--------+
| N | UA:DP:L | PF:DW:L | | | |
| UA:LO:L | i | i | | | |
| UA:P:L | i | i | [5] | | |
| UA:DP:L | i | i | [20] | i | i |
| UA:LO:R | [21] | [22] | | | |
| UA:P:R | [21] | [22] | | | |
| UA:DP:R | UA:DP:L | [22] | [23] | i | i |
| PF:W:L | i | i | | | |
| PF:DW:L | i | i | [24] | i | i |
| PF:W:R | [25] | [26] | | | |
| PF:DW:R | [25] | PF:DW:L | [27] | i | i |
| PA:F:L | i | i | | | |
| PA:M:L | UA:DP:L | PF:DW:L | | | |
| PA:F:R | [25] | [26] | | | |
| PA:M:R | UA:DP:L | PF:DW:L | | | |
| WTR | UA:DP:L | PF:DW:L | | | |
| DNR | UA:DP:L | PF:DW:L | | | |
+---------+---------+---------+------+----+--------+
Part 2: Remote messages state machine
+---------+------+------+------+------+---------+---------+
| | LO | SF-P | FS | SF-W | SD-P | SD-W |
+---------+------+------+------+------+---------+---------+
| N | | | | | UA:DP:R | PF:DW:R |
| UA:LO:L | | | | | i | i |
| UA:P:L | | | | | i | i |
| UA:DP:L | [28] | [29] | [30] | [31] | i | [32] |
| UA:LO:R | | | | | r | r |
| UA:P:R | | | | | r | r |
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| UA:DP:R | [33] | [34] | [35] | [36] | i | r |
| PF:W:L | | | | | i | i |
| PF:DW:L | [37] | [38] | [39] | [40] | [41] | i |
| PF:W:R | | | | | [42] | i |
| PF:DW:R | [43] | [44] | [45] | [46] | [47] | i |
| PA:F:L | | | | | i | i |
| PA:M:L | | | | | UA:DP:R | PF:DW:R |
| PA:F:R | | | | | r | r |
| PA:M:R | | | | | UA:DP:R | PF:DW:R |
| WTR | | | | | UA:DP:R | PF:DW:R |
| DNR | | | | | UA:DP:R | PF:DW:R |
+---------+------+------+------+------+---------+---------+
+---------+----+------+------+----+
| | MS | WTR | DNR | NR |
+---------+----+------+------+----+
| N | | | | |
| UA:LO:L | | | | |
| UA:P:L | | | | |
| UA:DP:L | i | i | i | i |
| UA:LO:R | | | | |
| UA:P:R | | | | |
| UA:DP:R | r | i | i | r |
| PF:W:L | | | | |
| PF:DW:L | i | i | i | i |
| PF:W:R | | | | |
| PF:DW:R | r | [14] | [15] | N |
| PA:F:L | | | | |
| PA:M:L | | | | |
| PA:F:R | | | | |
| PA:M:R | | | | |
| WTR | | | | |
| DNR | | | | |
+---------+----+------+------+----+
Replace the following footnote:
5 If the SF being cleared is SF-P, transition to N. If it's SF-W,
ignore the clear.
With:
5 If the SF being cleared is SF-P, transition to N. Otherwise,
ignore the clear.
Add the following footnotes for the table:
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20 If the SF/SD being cleared is SD-P, transition to N. Otherwise,
ignore the clear.
21 Remain in the current state and transmit SD(0,0).
22 Remain in the current state and transmit SD(1,0).
23 If the SF/SD being cleared is SD-W, then remain in current state
(UA:DP:R) and begin transmitting NR(0,0). Otherwise, ignore the
SFc.
24 If the SF/SD being cleared is SD-W and there is no local SD-P,
then go to WTR or DNR depending on the configuration for
revertive behavior. If there is local SD-P when local SD-W is
cleared, go to UA:DP:L state. If the SF/SD being cleared is
SD-P then ignore.
25 Remain in the current state and transmit SD(0,1).
26 Remain in the current state and transmit SD(1,1).
27 If the SF/SD being cleared is SD-P, then remain in current state
(PF:DW:R) and begin transmitting NR(0,1). Otherwise, ignore.
28 Transition to (UA:LO:R) and continue sending SD(0,0)
29 Transition to (UA:P:R) and continue sending SD(0,0)
30 Transition to (PA:F:R) and send SD(0,1).
31 Transition to (PF:W:R) and send SD(0,1)
32 If the active path just before the SD is selected as the highest
local input was the working path, then ignore. Otherwise, go to
PF:DW:R and transmit SD(0,1)
33 Transition to (UA:LO:R) state and continue to send the current
message.
34 Transition to (UA:P:R) state and continue to send the current
message.
35 Transition to (PA:F:R) state and continue to send the current
message with Path=1.
36 Transition to (PF:W:R) state and continue to send the current
message with Path=1.
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37 Transition to (UA:LO:R) and send SD(1,0)
38 Transition to (UA:P:R) and send SD(1,0)
39 Transition to (PA:F:R) and continue to send the current message,
SD(1,1).
40 Transition to (PF:W:R) and continue to send the current message,
SD(1,1).
41 If the received SD-P message has Path=1, ignore the message. If
the received SD-P message has Path=0 and the active path just
before the SD is selected as the highest local input was the
working path, then go to UA:DP:R and transmit SD(1,0). If the
received SD-P message has Path=0 and the active path just before
the SD is selected as the highest local input was the protection
path, then ignore the received SD-P message.
42 If there is no local request, transition to UA:DP:R and send
NR(0,0). If the local input is SD-W, then transition to UA:DP:R
and send SD(1,0) message. If the local input is SD-P, then
transition to UA:DP:L and send SD(0,0) message.
43 Transition to (UA:LO:R) state and continue to send the current
message with Path=0.
44 Transition to (UA:P:R) state and continue to send the current
Message with Path=0.
45 Transition to (PA:F:R) state and continue to send the current
message.
46 Transition to (PF:W:R) state and continue to send the current
message.
47 If the local input is SD-P, then transition to UA:DP:L. Else,
transition to N state.
6. Security considerations
No specific security issue is raised in addition to those ones
already documented in [RFC6378]
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7. IANA considerations
This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an
RFC.
8. Acknowledgements
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6372] Sprecher, N. and A. Farrel, "MPLS Transport Profile (MPLS-
TP) Survivability Framework", RFC 6372, September 2011.
[RFC6378] Weingarten, Y., Bryant, S., Osborne, E., Sprecher, N., and
A. Fulignoli, "MPLS Transport Profile (MPLS-TP) Linear
Protection", RFC 6378, October 2011.
9.2. Informative References
[LIAISON1205]
ITU-T SG15, ., "Liaison Statement: Recommendation ITU-T
G.8131/Y.1382 revision - Linear protection switching for
MPLS-TP networks ", https://datatracker.ietf.org/liaison/
1205/ , October 2012.
[LIAISON1234]
ITU-T SG15, ., "Liaison Statement: Recommendation ITU-T
G.8131 revision - Linear protection switching for MPLS-TP
networks ", https://datatracker.ietf.org/liaison/1234/ ,
February 2013.
Authors' Addresses
Jeong-dong Ryoo
ETRI
218 Gajeongno
Yuseong-gu, Daejeon 305-700
South Korea
Phone: +82-42-860-5384
Email: ryoo@etri.re.kr
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Huub van Helvoort
Huawei Technologies
Karspeldreef 4,
Amsterdam 1101 CJ
the Netherlands
Phone: +31 20 4300832
Email: huub.van.helvoort@huawei.com
Alessandro D'Alessandro
Telecom Italia
via Reiss Romoli, 274
Torino 10141
Italy
Phone: +39 011 2285887
Email: alessandro.dalessandro@telecomitalia.it
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