MPLS Working Group J. Ryoo Internet-Draft ETRI Intended status: Standards Track H. van Helvoort Expires: September 13, 2013 Huawei Technologies A. D'Alessandro Telecom Italia March 12, 2013 Supporting the Signal Degrade in the PSC Linear Protection draft-rhd-mpls-tp-psc-sd-00.txt Abstract This document contains the updates to [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- Drafts is at http://datatracker.ietf.org/drafts/current/. 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 September 13, 2013. 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 Ryoo, et al. Expires September 13, 2013 [Page 1] Internet-Draft SD in PSC Linear Protection March 2013 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 . . . 4 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 . . . . . . 6 5.8. Updates to Section 4.3.3.1 Normal State . . . . . . . . . 9 5.9. Updates to Section 4.3.3.2 Unavailable State . . . . . . 9 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 . . . . . . . . . . . . . . . . . . . . . 25 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 9.1. Normative References . . . . . . . . . . . . . . . . . . 26 9.2. Informative References . . . . . . . . . . . . . . . . . 26 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 1. Introduction This document contains the updates to [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], a fault condition includes both Signal Fail (SF) and Signal Degrade (SD) that can be used to trigger protection switching. The PSC document [RFC6378] does not specify how the SF and SD are declared but specifies the protection switching protocol associated with SF only. Ryoo, et al. Expires September 13, 2013 [Page 2] Internet-Draft SD in PSC Linear Protection March 2013 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 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 behaviour 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 behaviour), to avoid protection switching that cannot improve signal quality and flapping. 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. Ryoo, et al. Expires September 13, 2013 [Page 3] Internet-Draft SD in PSC Linear Protection March 2013 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 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: Ryoo, et al. Expires September 13, 2013 [Page 4] Internet-Draft SD in PSC Linear Protection March 2013 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 recovering from a failure or a degradation condition on the working path and the protection domain is configured for revertive behavior. 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 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 Ryoo, et al. Expires September 13, 2013 [Page 5] Internet-Draft SD in PSC Linear Protection March 2013 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) 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) Ryoo, et al. Expires September 13, 2013 [Page 6] Internet-Draft SD in PSC Linear Protection March 2013 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. 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 Ryoo, et al. Expires September 13, 2013 [Page 7] Internet-Draft SD in PSC Linear Protection March 2013 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 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 Ryoo, et al. Expires September 13, 2013 [Page 8] Internet-Draft SD in PSC Linear Protection March 2013 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. 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 Ryoo, et al. Expires September 13, 2013 [Page 9] Internet-Draft SD in PSC Linear Protection March 2013 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: 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 Ryoo, et al. Expires September 13, 2013 [Page 10] Internet-Draft SD in PSC Linear Protection March 2013 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: 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 Ryoo, et al. Expires September 13, 2013 [Page 11] Internet-Draft SD in PSC Linear Protection March 2013 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 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 Ryoo, et al. Expires September 13, 2013 [Page 12] Internet-Draft SD in PSC Linear Protection March 2013 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 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. Ryoo, et al. Expires September 13, 2013 [Page 13] Internet-Draft SD in PSC Linear Protection March 2013 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 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. Ryoo, et al. Expires September 13, 2013 [Page 14] Internet-Draft SD in PSC Linear Protection March 2013 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, 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(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). 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. Ryoo, et al. Expires September 13, 2013 [Page 15] Internet-Draft SD in PSC Linear Protection March 2013 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 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. Ryoo, et al. Expires September 13, 2013 [Page 16] Internet-Draft SD in PSC Linear Protection March 2013 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 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 behaviour. 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. Ryoo, et al. Expires September 13, 2013 [Page 17] Internet-Draft SD in PSC Linear Protection March 2013 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: 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. Ryoo, et al. Expires September 13, 2013 [Page 18] Internet-Draft SD in PSC Linear Protection March 2013 * 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: 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. Ryoo, et al. Expires September 13, 2013 [Page 19] Internet-Draft SD in PSC Linear Protection March 2013 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. 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. Ryoo, et al. Expires September 13, 2013 [Page 20] Internet-Draft SD in PSC Linear Protection March 2013 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 | | | | | | | 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 | | | | | | Ryoo, et al. Expires September 13, 2013 [Page 21] Internet-Draft SD in PSC Linear Protection March 2013 | 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 | | 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 | Ryoo, et al. Expires September 13, 2013 [Page 22] Internet-Draft SD in PSC Linear Protection March 2013 | 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: 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). Ryoo, et al. Expires September 13, 2013 [Page 23] Internet-Draft SD in PSC Linear Protection March 2013 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 behaviour. 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. 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). Ryoo, et al. Expires September 13, 2013 [Page 24] Internet-Draft SD in PSC Linear Protection March 2013 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] 7. IANA considerations This document makes no request of IANA. Note to RFC Editor: this section may be removed on publication as an RFC. Ryoo, et al. Expires September 13, 2013 [Page 25] Internet-Draft SD in PSC Linear Protection March 2013 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 Ryoo, et al. Expires September 13, 2013 [Page 26] Internet-Draft SD in PSC Linear Protection March 2013 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 Ryoo, et al. Expires September 13, 2013 [Page 27]