--- 1/draft-ietf-ccamp-gmpls-recovery-terminology-02.txt 2006-02-04 22:56:21.000000000 +0100 +++ 2/draft-ietf-ccamp-gmpls-recovery-terminology-03.txt 2006-02-04 22:56:21.000000000 +0100 @@ -1,22 +1,21 @@ CCAMP Working Group CCAMP GMPLS P&R Design Team Internet Draft Category: Standard Track Eric Mannie (Editor) -Expiration Date: November 2003 Dimitri Papadimitriou (Editor) +Expiration Date: June 2004 Dimitri Papadimitriou (Editor) - May 2003 + January 2004 - Recovery (Protection and Restoration) Terminology - for Generalized Multi-Protocol Label Switching (GMPLS) + Recovery (Protection and Restoration) Terminology for GMPLS - draft-ietf-ccamp-gmpls-recovery-terminology-02.txt + draft-ietf-ccamp-gmpls-recovery-terminology-03.txt Status of this Memo This document is an Internet-Draft and is subject to all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. @@ -91,21 +90,21 @@ (GMPLS) based recovery mechanisms (i.e. protection and restoration) that are under consideration by the CCAMP Working Group. The terminology proposed in this document is intended to be independent of the underlying transport technologies and borrows from an ITU-T ongoing effort, the Draft Recommendation [G.808.1] (ex. G.GPS - Generic Protection Switching) and from the G.841 ITU-T Recommendation. The restoration terminology and concepts have been gathered from numerous sources including IETF drafts. -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 2 +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 2 In the context of this document we will use the term "recovery" to denote both protection and restoration. The specific terms "protection" and "restoration" will only be used when differentiation is required. Note that this document focuses on the terminology for the recovery of LSPs controlled by a GMPLS control plane. We focus on end-to-end, segment and span (i.e. link) LSP recovery. Terminology for control plane recovery is not in the scope of this document. @@ -144,21 +143,21 @@ This section defines the following general terms common to both protection and restoration (i.e. recovery). In addition, most of these terms apply to end-to-end, segment and span LSP recovery. Note that span recovery does not protect the nodes at each end of the span, otherwise end-to-end or segment LSP recovery should be used. The terminology and the definitions have been originally taken from G.808.1. However, for generalization, the following language that is -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 3 +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 3 not directly related to recovery has been adapted to GMPLS and the common IETF terminology: An LSP is used as a generic term to designate either an SNC (Sub- Network Connection) or an NC (Network Connection) in ITU-T terminology. The ITU-T uses the term transport entity to designate either a link, an SNC or an NC. The term "Traffic" is used instead of "Traffic Signal". The term protection or restoration "scheme" is used instead of protection or restoration "architecture". @@ -196,23 +195,24 @@ restored. C. Null traffic: Traffic carried over the recovery LSP/span if it is not used to carry normal or extra traffic. Null traffic can be any kind of traffic that conforms to the signal structure of the specific layer, and it is ignored (not selected) at the egress of the recovery LSP/span. +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 4 + 4.3 LSP/Span Protection and Restoration -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 4 The following subtle distinction is generally made between the terms "protection" and "restoration", even though these terms are often used interchangeably [TEWG]. The distinction between protection and restoration is made based on the resource allocation done during the recovery LSP/span establishment. The distinction between different types of restoration is made based on the level of route computation, signaling and resource allocation done during the restoration LSP/span establishment. @@ -245,30 +245,37 @@ establishment of the restoration LSP/span occurs only after a failure of the working LSP/span, and requires some additional signaling. Both protection and restoration require signaling. Signaling to establish the recovery resources and signaling associated with the use of the recovery LSP(s)/span(s) are needed. 4.4 Recovery Scope - Recovery can be applied at various levels throughout the network. + Recovery can be applied at various levels throughout the network. An + LSP may be subject to local (span), segment, and/or end-to-end + recovery. + +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 5 Local (span) recovery refers to the recovery of an LSP over a link - between two nodes. Segment recovery refers to the recovery of an LSP - segment (i.e. an SNC in the ITU-T terminology) between two nodes, - i.e. the boundary nodes of the segment. End-to-end recovery refers + between two nodes. -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 5 - to the recovery of an entire LSP from its source to its destination. - An LSP may be subject to local (span), segment, and/or end-to-end - recovery. + End-to-end recovery refers to the recovery of an entire LSP from its + source (ingress node end-point) to its destination (egress node end- + point). + + Segment recovery refers to the recovery over a portion of the + network of a segment LSP (i.e. an SNC in the ITU-T terminology) of + an end-to-end LSP. Such recovery protects against span and/or node + failure over a particular portion of the network traversed by an + end-to-end LSP. 4.5 Recovery Domain A recovery domain is defined as a set of nodes and spans over which one or more recovery schemes are provided. A recovery domain served by one single recovery scheme is referred to as a "single recovery domain", while a recovery domain served by multiple recovery schemes is referred to as a "multi recovery domain". The recovery operation is contained within the recovery domain. A @@ -294,31 +301,30 @@ restoration. B. 0:1 type: unprotected No specific recovery LSP/span protects the working LSP/span. However, the working LSP/span can potentially be restored through any alternate available route/span, with or without any pre-computed restoration route. Note that there are no resources pre-established for this recovery type. +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 6 This type is applicable to LSP/span restoration, but not to LSP/span protection. Span restoration can be for instance achieved by moving all the LSPs transported over of a failed span to a dynamically selected span. C. 1:1 type: dedicated recovery with extra traffic One specific recovery LSP/span protects exactly one specific working LSP/span but the normal traffic is transmitted only over one LSP - -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 6 (working or recovery) at a time. Extra traffic can be transported using the recovery LSP/span resources. This type is applicable to LSP/span protection and LSP restoration, but not to span restoration. D. 1:N (N > 1) type: shared recovery with extra traffic A specific recovery LSP/span is dedicated to the protection of up to N working LSPs/spans. The set of working LSPs/spans is explicitly @@ -347,32 +353,33 @@ A set of M specific recovery LSPs/spans protects a set of up to N specific working LSPs/spans. The two sets are explicitly identified. Extra traffic can be transported over the M recovery LSPs/spans when available. All the LSPs/spans must start and end at the same nodes. Sometimes, the working LSPs/spans are assumed to be resource disjoint in the network so that they do not share any failure probability, but this is not mandatory. Obviously, if several working LSPs/spans in the set of N are concurrently affected by some failure(s), the traffic on only M of these failed LSPs/spans may be + +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 7 recovered. Note that N can be arbitrarily large (i.e. infinite). The choice of N and M is a policy decision. This type is applicable to LSP/span protection and LSP restoration, but not to span restoration. 4.7 Bridge Types A bridge is the function that connects the normal traffic and extra traffic to the working and recovery LSP/span. -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 7 A. Permanent bridge Under a 1+1 type, the bridge connects the normal traffic to both the working and protection LSPs/spans. This type of bridge is not applicable to restoration types. There is of course no extra traffic connected to the recovery LSP/span. B. Broadcast bridge For 1:N and M:N types, the bridge permanently connects the normal @@ -398,33 +405,34 @@ Is a selector that extracts the normal traffic from either the working LSP/span output or the recovery LSP/span output. B. Merging selector For 1:N and M:N protection types, the selector permanently extracts the normal traffic from both the working and recovery LSP/span outputs. This alternative works only in combination with a selector bridge. +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 8 + 4.9 Recovery GMPLS Nodes This section defines the GMPLS nodes involved during recovery. A. Ingress GMPLS node of an end-to-end LSP/segment LSP/span The ingress node of an end-to-end LSP/segment LSP/span is where the normal traffic may be bridged to the recovery end-to-end LSP/segment LSP/span. Also known as source node in the ITU-T terminology. B. Egress GMPLS node of an end-to-end LSP/segment LSP/span -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 8 The egress node of an end-to-end LSP/segment LSP/span is where the normal traffic may be selected from either the working or the recovery end-to-end LSP/segment LSP/span. Also known as sink node in the ITU-T terminology. C. Intermediate GMPLS node of an end-to-end LSP/segment LSP A node along either the working or recovery end-to-end LSP/segment LSP route between the corresponding ingress and egress nodes. Also known as intermediate node in the ITU-T terminology. @@ -451,33 +459,34 @@ A revertive recovery operation refers to a recovery switching operation, where the traffic returns to (or remains on) the working LSP/span if the switch requests are terminated; i.e. when the working LSP/span has recovered from the failure. Therefore a non-revertive recovery switching operation is when the traffic does not return to the working LSP/span if the switch requests are terminated. +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 9 + 4.12 Failure Reporting This section gives (for information) several signal types commonly used in transport planes to report a failure condition. Note that fault reporting may require additional signaling mechanisms. A. Signal Degrade (SD): a signal indicating that the associated data has degraded. B. Signal Fail (SF): a signal indicating that the associated data has failed. -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 9 C. Signal Degrade Group (SDG): a signal indicating that the associated group data has degraded. D. Signal Fail Group (SFG): a signal indicating that the associated group has failed. Note: SDG and SFG definitions are under discussion at the ITU-T. 4.13 External commands @@ -503,34 +512,33 @@ action to be taken, and as such freezes the current state. D. Forced switch for normal traffic: A switch action initiated externally that switches normal traffic to the recovery LSP/span, unless an equal or higher priority switch command is in effect. E. Manual switch for normal traffic: +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 10 A switch action initiated externally that switches normal traffic to the recovery LSP/span, unless a fault condition exists on other LSPs/spans (including the recovery LSP/span) or an equal or higher priority switch command is in effect. F. Manual switch for recovery LSP/span: A switch action initiated externally that switches normal traffic to the working LSP/span, unless a fault condition exists on the working LSP/span or an equal or higher priority switch command is in effect. G. Clear: - -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 10 An action initiated externally that clears the active external command. 4.14 Unidirectional versus Bi-Directional Recovery Switching A. Unidirectional recovery switching: A recovery switching mode in which, for a unidirectional fault (i.e. a fault affecting only one direction of transmission), only the normal traffic transported in the affected direction (of the LSP or @@ -557,31 +565,32 @@ A. Full Span Recovery All the S LSP carried over a given span are recovered under span failure condition. Full span recovery is also referred to as "bulk recovery". B. Partial Span Recovery Only a subset s of the S LSP carried over a given span are recovered under span failure condition. Both selection criteria of the + +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 11 entities belonging to this subset and the decision concerning the recovery of the remaining (S - s) LSP are based on local policy. 4.16 Recovery Schemes Related Time and Durations This section gives several typical timing definitions that are of importance for recovery schemes. A. Detection time: -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 11 The time between the occurrence of the fault or degradation and its detection. Note that this is a rather theoretical time since in practice this is difficult to measure. B. Correlation time: The time between detection of the fault or degradation and the reporting of the signal fail or degrade. This time is typically used in correlating related failures or degradations. @@ -611,31 +620,31 @@ 4.17 Impairment A defect or performance degradation, which may lead to SF or SD trigger. 4.18 Recovery Ratio The quotient of the actually recovery bandwidth divided by the traffic bandwidth which is intended to be protected. +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 12 + 4.19 Hitless Protection Switch Protection switch, which does not cause data loss, data duplication, data disorder, or bit errors upon recovery switching action. 4.20 Network Survivability The set of capabilities that allow a network to restore affected traffic in the event of a failure. The degree of survivability is - -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 12 determined by the networkÆs capability to survive single and multiple failures. 4.21 Survivable Network A network that is capable of restoring traffic in the event of a failure. 4.22 Escalation @@ -663,32 +672,33 @@ about the location (and so the identity) of the transport plane entity that causes the LSP(s)/span(s) failure. The deciding entity can then take accurate decision to achieve finer grained recovery switching action(s). - Phase 3: Failure Notification Failure notification phase is used 1) to inform intermediate nodes that LSP(s)/span(s) failure has occurred and has been detected 2) to inform the recovery deciding entities (which can correspond to any + +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 13 intermediate or end-point of the failed LSP/span) that the corresponding LSP/span is not available. - Phase 4: Recovery (Protection or Restoration) See above. - Phase 5: Reversion (Normalization) See above. -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 13 The combination of Failure Detection and Failure Localization and Notification is referred to as Fault Management. 5.1 Entities Involved During Recovery The entities involved during the recovery operations can be defined as follows; these entities are parts of ingress, egress and intermediate nodes as defined previously: A. Detecting Entity (Failure Detection): @@ -716,32 +726,32 @@ The process of moving failed LSPs from a failed (working) span to a protection span must be initiated by one of the nodes terminating the span, e.g. A or B. The deciding (and recovering) entity is referred to as the "master" while the other node is called the "slave" and corresponds to a recovering only entity. Note: The determination of the master and the slave may be based on configured information or protocol specific requirements. +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 14 + 6. Protection Schemes This section clarifies the multiple possible protection schemes and the specific terminology for the protection. 6.1 1+1 protection 1+1 protection has one working LSP/span, one protection LSP/span and a permanent bridge. At the ingress node, the normal traffic is permanently bridged to both the working and protection LSP/span. At - -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 14 the egress node, the normal traffic is selected from the better of the two LSPs/spans. Due to the permanent bridging, the 1+1 protection does not allow an unprotected extra traffic signal to be provided. 6.2 1:N (N >= 1) Protection 1:N protection has N working LSPs/spans carrying normal traffic and 1 protecting LSP/span that may carry extra-traffic. @@ -750,105 +760,105 @@ its working LSP/span and may be connected to the protection LSP/span (case of broadcast bridge), or is connected to either its working or the protection LSP/span (case of selector bridge). At the egress node, the normal traffic is selected from either its working or protection LSP/span. Unprotected extra traffic can be transported over the protection LSP/span whenever the protection LSP/span is not used to carry a normal traffic. -6.3 M:N (N >= M) Protection +6.3 M:N (M, N > 1, M =< N) Protection M:N protection has N working LSPs/spans carrying normal traffic and M protecting LSP/span that may carry extra-traffic. At the ingress, a normal traffic is either permanently connected to its working LSP/span and may be connected to one of the protection LSPs/spans (case of broadcast bridge), or is connected to either its working or one of the protection LSPs/spans (case of selector bridge). At the egress node, the normal traffic is selected from either its working or one of the protection LSP/span. Unprotected extra traffic can be transported over the M protection LSP/span whenever the protection LSPs/spans is not used to carry a normal traffic. Note1: all protection types are either uni- or bi-directional, obviously, the latter applies only to bi-directional LSP/span and requires coordination between the ingress and egress node during protection switching. +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 15 Note2: all protection types except 1+1 unidirectional protection switching require a communication channel between the ingress and the egress node. Note3: in the GMPLS context, span protection refers to the full or partial span recovery of the LSPs carried over that span (see Section 4.15). 7. Restoration Schemes -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 15 This section clarifies the multiple possible restoration schemes and the specific terminology for the restoration. 7.1 Pre-planned LSP Restoration Also referred to as pre-planned LSP re-routing. Before failure detection and/or notification, one or more restoration LSPs are instantiated between the same ingress-egress node pair than the working LSP. Note that the restoration resources must be pre- computed, must be signaled and may be selected a priori, but not - cross-connected and thus are able to carry extra-traffic. + cross-connected. Thus, the restoration LSP is not able to carry any + extra-traffic. The complete establishment of the restoration LSP (i.e. activation) occurs only after failure detection and/or notification of the working LSP and requires some additional restoration signaling. Therefore, this mechanism protects against working LSP failure(s) but requires activation of the restoration LSP after failure occurrence. After the ingress node has activated the restoration LSP, the latter can carry the normal traffic. Note: when each working LSP is recoverable by exactly one - restoration LSP, one refers also to 1:1 re-routing without extra- - traffic. + restoration LSP, one refers also to 1:1 (pre-planned) re-routing + without extra-traffic. 7.1.1 Shared-Mesh Restoration "Shared-mesh" restoration is defined as a particular case of pre- planned LSP re-routing that reduces the restoration resource requirements by allowing multiple restoration LSPs (initiated from distinct ingress nodes) to share common resources (including links and nodes.) 7.2 LSP Restoration Also referred to as LSP re-routing. The ingress node switches the normal traffic to an alternate LSP signaled and fully established (i.e. cross-connected) after failure detection and/or notification. - The alternate LSP path may be pre-computed after failure detection - and/or notification. In this case, one refers to "Full LSP Re- + The alternate LSP path may be computed after failure detection + and/or notification. In this case, one also refers to "Full LSP Re- routing." +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 16 The alternate LSP is signaled from the ingress node and may reuse intermediate node's resources of the working LSP under failure condition (and may also include additional intermediate nodes.) 7.2.1 Hard LSP Restoration Also referred to as hard LSP re-routing. A re-routing operation where the LSP is released before the full establishment of an alternate LSP (i.e. break-before-make). -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 16 - 7.2.2 Soft LSP Restoration Also referred to as soft LSP re-routing. A re-routing operation where the LSP is released after the full establishment of an alternate LSP (i.e. make-before-break). 8. Security Considerations This document does not introduce or imply any specific security consideration. @@ -874,36 +884,32 @@ The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights, which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. 10. References 10.1 Normative References +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 17 [G.707] ITU-T, "Network Node Interface for the Synchronous Digital Hierarchy (SDH)," Recommendation G.707, October 2000. [G.841] ITU-T, "Types and Characteristics of SDH Network Protection Architectures," Recommendation G.841, October 1998. [G.842] ITU-T, "Interworking of SDH network protection architectures," Recommendation G.842, October 1998. -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 17 - [GMPLS-ARCH] E.Mannie (Editor), "Generalized MPLS Architecture," - Internet Draft, Work in progress, draft-ietf-ccamp- - gmpls-architecture-06.txt, April 2003. - [RFC-2026] S.Bradner, "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996. [RFC-2119] S.Bradner, "Key words for use in RFCs to Indicate Requirement Levels," BCP 14, RFC 2119, March 1997. [T1.105] ANSI, "Synchronous Optical Network (SONET): Basic Description Including Multiplex Structure, Rates, and Formats," ANSI T1.105, January 2001. @@ -919,45 +925,49 @@ Recommendation G.783, October 2000. [G.806] ITU-T, "Characteristics of Transport Equipment û Description Methodology and Generic Functionality," Recommendation G.806, October 2000. [G.808.1] ITU-T, "Generic Protection Switching û Linear trail and subnetwork protection," Draft Recommendation (work in progress), Version 0.5, January 2003. + [GMPLS-ARCH] E.Mannie (Editor), "Generalized MPLS Architecture," + Internet Draft, Work in progress, draft-ietf-ccamp- + gmpls-architecture-06.txt, April 2003. + [SUDHEER] S.Dharanikota et al., "NNI Protection and restoration requirements," OIF Contribution 507, 2001. [TEWG] W.S.Lai, et al., "Network Hierarchy and Multilayer Survivability," Internet Draft, Work in progress, draft-ietf-tewg-restore-hierarchy-01.txt, June 2002. +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 18 + 11. Acknowledgments Valuable comments and input were received from many people. 12. Author's Addresses Eric Mannie (Consult) Email: eric_mannie@hotmail.com Dimitri Papadimitriou (Alcatel) Francis Wellesplein, 1 B-2018 Antwerpen, Belgium - -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 18 Phone: +32 3 240-8491 Email: dimitri.papadimitriou@alcatel.be -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 19 +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 19 Full Copyright Statement "Copyright (C) The Internet Society (date). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this @@ -972,11 +982,11 @@ The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE." -E.Mannie, D.Papadimitriou et al.- Internet Draft - November 2003 20 +E.Mannie, D.Papadimitriou et al.- Internet Draft - June 2004 20