Network Working Group B. Niven-Jenkins, Ed. Internet-Draft BT Intended status: Informational D. Brungard, Ed. Expires:
June 15,July 7, 2009 AT&T M. Betts, Ed. Nortel Networks N. Sprecher Nokia Siemens Networks S. Ueno NTT December 12, 2008January 3, 2009 MPLS-TP Requirements draft-ietf-mpls-tp-requirements-01draft-ietf-mpls-tp-requirements-02 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or sheThis Internet-Draft is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed,submitted to IETF in accordancefull conformance with Section 6the provisions of BCP 78 and BCP 79. 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. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on June 15,July 7, 2009. Copyright Notice Copyright (c) 2009 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. Abstract This document specifies the requirements of an MPLS Transport Profile (MPLS-TP). This document is a product of a joint International Telecommunications Union (ITU)-IETF effort to include an MPLS Transport Profile within the IETF MPLS architecture to support the capabilities and functionalities of a packet transport network as defined by International Telecommunications Union - Telecommunications Standardization Sector (ITU-T). This work is based on two sources of requirements; MPLS architecture as defined by IETF, and packet transport networks as defined by ITU-T. The requirements expressed in this document are for the behavior of the protocol mechanisms and procedures that constitute building blocks out of which the MPLS transport profile is constructed. The requirements are not implementation requirements. Requirements Language 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]. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 56 1.2. Transport network overview . . . . . . . . . . . . . . . . 7 2. MPLS-TP Requirements . . . . . . . . . . . . . . . . . . . . . 8 2.1. General requirements . . . . . . . . . . . . . . . . . . . 89 2.2. Layering requirements . . . . . . . . . . . . . . . . . . 1011 2.3. Data plane requirements . . . . . . . . . . . . . . . . . 11 2.4. Control plane requirements . . . . . . . . . . . . . . . . 12 2.5. Network Management (NM) requirements . . . . . . . . . . . 13 2.6. Operation, Administration and Maintenance (OAM) requirements . . . . . . . . . . . . . . . . . . . . . . . 1314 2.7. Network performance management (PM) requirements . . . . . 1314 2.8. Recovery & Survivability requirements . . . . . . . . . . 1314 2.8.1. Data plane behavior requirements . . . . . . . . . . . 1415 2.8.2. Triggers for protection, restoration, and reversion . 1617 2.8.3. Management plane operation of protection and restoration . . . . . . . . . . . . . . . . . . . . . 1617 2.8.4. Control plane and in-band OAM operation of recovery . 1718 2.8.5. Topology-specific recovery mechanisms . . . . . . . . 1718 2.9. QoS requirements . . . . . . . . . . . . . . . . . . . . . 2122 2.10. Security requirements . . . . . . . . . . . . . . . . . . 22 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 4. Security Considerations . . . . . . . . . . . . . . . . . . . 2223 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 2223 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23 6.1. Normative References . . . . . . . . . . . . . . . . . . . 23 6.2. Informative References . . . . . . . . . . . . . . . . . . 2324 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24 Intellectual Property and Copyright Statements . . . . . . . . . . 2625 1. Introduction For many years, Synchronous Optical Networking (SONET)/Synchronous Digital hierarchy (SDH) has provided carriers with a high benchmark for reliability and operational simplicity. With the accelerating growth of packet-basedand penetration of: o Packet-based services (suchsuch as Ethernet, Voice over IP (VoIP), Layer 2 (L2)/Layer 3 (L3) Virtual Private Networks (VPNs), IP Television (IPTV), Radio Access Network (RAN) backhauling, etc.), carriersetc. o Applications with various bandwidth and QoS requirements. Carriers are in need of capabilities totechnologies capable of efficiently support packet- basedsupporting packet-based services and applications on their transport networks. The need to increase their revenue while remaining competitive forces operators to look for the lowest network Total Cost of Ownership (TCO). Investment in equipment and facilities (Capital Expenditure (CAPEX)) and Operational Expenditure (OPEX) should be minimized. Carriers are considering migrating or evolving to packet transport networks in order to reduce their costs and to improve their ability to support services with guaranteed Service Level Agreements (SLAs). For carriers it is important that migrating from SONET/SDH to packet transport networks should not involve dramatic changes in network operation, should not necessitate extensive retraining, and should not require major changes to existing work practices. The aim is to preserve the look-and-feel to which carriers have become accustomed in deploying their SONET/SDH networks, while providing common, multi- layer operations, resiliency, control and management for packet, circuit and lambda transport networks. Transport carriers require control and deterministic usage of network resources. They need end-to-end control to engineer network paths and to efficiently utilize network resources. They require capabilities to support static (Operational(Operations Support System (OSS) based) or dynamic (control plane) provisioning of deterministic, protected and secured services and their associated resources. Carriers will still need to cope with legacy networks (which are composed of many layers and technologies), thus the packet transport network should interwork with other packet and transport networks (both horizontally and vertically). Vertical interworking is also known as client/server or network interworking. Horizontal interworking is also known as peer-partition or service interworking. For more details on each type of interworking and some of the issues that may arise (especially with horizontal interworking) see [ITU.Y1401.2008]. MPLS is a maturing packet technology and it is already playing an important role in transport networks and services. However, not all of MPLS's capabilities and mechanisms are needed and/or consistent with transport network operations. There is therefore the need to define an MPLS Transport Profile (MPLS-TP) in order to support the capabilities and functionalities needed for packet transport network services and operations through combining the packet experience of MPLS with the operational experience of SONET/SDH. MPLS-TP will enable the migration of SONET/SDH networks to a packet- based network that will efficiently scale to support packet services in a simple and cost effective way. MPLS-TP needs to combine the necessary existing capabilities of MPLS with additional minimal mechanisms in order that it can be used in a transport role. This document specifies the requirements of an MPLS Transport Profile (MPLS-TP). The requirements are for the the behavior of the protocol mechanisms and procedures that constitute building blocks out of which the MPLS transport profile is constructed. That is, the requirements indicate what features are to be available in the MPLS toolkit for use by MPLS-TP. The requirements in this document do not describe what functions an MPLS-TP implementation supports. The purpose of this document is to identify the toolkit and any new protocol work that is required. This document is a product of a joint ITU-IETF effort to include an MPLS Transport Profile within the IETF MPLS architecture to support the capabilities and functionalities of a packet transport network as defined by ITU-T. This work is based on two sources of requirements, MPLS architecture as defined by IETF and packet transport networks as defined by ITU-T. The requirements of MPLS-TP are provided below. The relevant functions of MPLS are included in MPLS-TP, except where explicitly excluded. Although both static and dynamic configuration of MPLS-TP transport paths (including Operations, Administration and Maintenance (OAM) and protection capabilities) is required by this document, it MUST be possible for operators to be able to completely operate (including OAM and protection capabilities) an MPLS-TP network in the absence of any control plane protocols for dynamic configuration. 1.1. Terminology Domain: A domain represents a collection of entities (for example network elements) that are grouped for a particular purpose, examples of which are administrative and/or managerial responsibilities, trust relationships, addressing schemes, infrastructure capabilities, survivability techniques, distributions of control functionality, etc. Examples of such domains include IGP areas and Autonomous Systems. Layer network: A layer network as defined in G.805 [ITU.G805.2000] provides for the transfer of client information and independent operations (OAM) of the client OAM. For an explanation of how a layer network as described by G.805 relates to the OSI concept of layering see Appendix I of Y.2611 [ITU.Y2611.2006]. Link: A link as defined in G.805 [ITU.G805.2000] is used to describe a fixed relationship between two ports.ports within a layer network. A link is not necessarily a physical link but can also be supported by a transport path in the server layer (e.g. SONET/SDH, OTN or MPLS-TP). Logical Ring: An MPLS-TP logical ring is constructed from a set of LSRs and logical data links (such as MPLS-TP LSP tunnels or MSPL-TP pseudowires) and physical data links that form a ring topology. Path: See Transport path. Physical Ring: An MPLS-TP physical ring is constructed from a set of LSRs and physical data links that form a ring topology. Ring Topology: In an MPLS-TP ring topology each LSR is connected to exactly two other LSRs, each via a single point-to-point bidirectional MPLS-TP capable data link. A ring may also be constructed from only two LSRs where there are also exactly two links. Rings may be connected to other LSRs to form a larger network. Traffic originating or terminating outside the ring may be carried over the ring. Client network nodes (such as CEs) may be connected directly to an LSR in the ring. Section: A section is a MPLS-TP networkserver layer (which may be MPLS-TP or a different technology) which provides for encapsulation and OAM of a MPLS-TP transport path client layer. A section layer may provide for aggregation of multiple MPLS-TP clients. Segment: A segment corresponds tois a single resource or a set of cross-connected resources that constitutes part of a path. A segment may be a single link (hop) within a path, a series of adjacent links (hops) within a path, or the entire end-to-end-path. Service layer: A layer network in which transport paths are used to carry a customer's (individual or bundled) service (may be point-to- point, point-to-multipoint or multipoint-to-multipoint services). Span: A span is synonymous with a link.Tandem Connection: A tandem connection corresponds to a segmentis an arbitrary part of a path. Thistransport path that can be monitored (via OAM) independently from the end-to-end monitoring (OAM). It may be eithera segment of an LSP (i.e. a sub-path), or oneor more segment(s)any other ordered sequence of contiguous links and/or segments of a PW.transport path. Transport path: A network connection as defined in G.805 [ITU.G805.2000]. A Transport path corresponds to an MPLS-TP LSP or to an MPLS-TP LSP and its associated PW or PWs (Single Segment or Multi-Segment). Transport path layer: A layer network which provides point-to-point or point-to-multipoint transport paths which are used to carry a higher (client) layer network or aggregates of higher (client) layer networks, for example the networktransport service layer. It provides for independent OAM (of the client OAM) in the transport of the clients. Transport service layer: A layer network in which transport paths are used to carry a customer's (individual or bundled) service (may be point-to-point, point-to-multipoint or multipoint-to-multipoint services). Transmission media layer: A layer network which provides sections (two-port point-to-point connections) to carry the aggregate of network transport path or network service layers on various physical media. 1.2. Transport network overview The connection (or transport path) service is the basic service provided by a transport network. The purpose of a transport network is to carry its clients (i.e. the stream of client PDUs or client bits) between endpoints in the network (typically over several intermediate nodes). These endpoints may be service switching points or service terminating points. The connection services offered to customers are aggregated into large transport paths with long-holding times and independent OAM (of the client OAM), which contribute to enabling the efficient and reliable operation of the transport network. These transport paths are modified infrequently. Aggregation and hierarchy are beneficial for achieving scalability and security since: 1. They reduce the number of provisioning and forwarding states in the network core. 2. They reduce load and the cost of implementing service assurance and fault management. 3. Clients are encapsulated and layer associated OAM overhead is added. This allows complete isolation of customer traffic and its management from carrier operations. An important attribute of a transport network is that it is able to function regardless of which clients are using its connection service or over which transmission media it is running. The client, transport network and server layers are from a functional and operations point of view independent layer networks. Another key characteristic of transport networks is the capability to maintain the integrity of the client across the transport network. A transport network must provide the means to commit quality of service objectives to clients. This is achieved by providing a mechanism for client network service demarcation for the network path together with an associated network resiliency mechanism. A transport network must also provide a method of service monitoring in order to verify the delivery of an agreed quality of service. This is enabled by means of carrier-grade OAM tools. Clients are first encapsulated. These encapsulated client signals may then be aggregated into a connection for transport through the network in order to optimize network management. Server layer OAM is used to monitor the transport integrity of the client layer or client aggregate. At any hop, the aggregated signals may be further aggregated in lower layer transport network paths for transport across intermediate shared links. The encapsulated client signals are extracted at the edges of aggregation domains, and are either delivered to the client or forwarded to another domain. In the core of the network, only the server layer aggregated signals are monitored; individual client signals are monitored at the network boundary in the client layer network. Although the connectivity of the client of the transport path layer may be point-to-point, point- to-multipoint or multipoint-to-multipoint, the transport path layer itself only provides point-to-point or point-to-multipoint transport paths which are used to carry the client. Quality-of-service mechanisms are required in the packet transport network to ensure the prioritization of critical services, to guarantee BW and to control jitter and delay. 2. MPLS-TP Requirements 2.1. General requirements 1 The MPLS-TP data plane MUST be a subset of the MPLS data plane as defined by the IETF. When MPLS offers multiple options in this respect, MPLS-TP SHOULD select the minimum sub-set (necessary and sufficient subset) applicable to a transport network application. 2 Any new functionality that is defined to fulfil the requirements for MPLS-TP MUST be agreed within the IETF through the IETF consensus process and MUST re-use (as far as practically possible) existing MPLS standards. 3 Mechanisms and capabilities MUST be able to interoperate, without a gateway function, with existing IETF MPLS [RFC3031] and IETF PWE3 [RFC3985] control and data planes where appropriate. 4 MPLS-TP MUST be a connection-oriented packet switching model with traffic engineering capabilities that allow deterministic control of the use of network resources. 5 MPLS-TP MUST support traffic engineered point to point (P2P) and point to multipoint (P2MP) transport paths. 6 MPLS-TP MUST support the logical separation of the control and management planes from the data plane. 7 MPLS-TP MUST allow the physical separation of the control and management planes from the data plane. 8 MPLS-TP MUST support static provisioning of transport paths via a Network Management System (NMS) or Operational Support Syste (OSS),an OSS, i.e. via the management plane. 9 Mechanisms in an MPLS-TP network that satisfy functional requirements that are common to general transport networks (i.e., independent of technology) SHOULD be manageable in a way that is coherent with the way the equivalent mechanisms are managed in other transport networks. 10 Static provisioning MUST NOT depend on the presence of any element of a control plane. 11 MPLS-TP MUST support the capability for network operation (including OAM)OAM and recovery) via the management plane (without the use of any control plane protocols). 12 A solution MUST be provided to support dynamic provisioning of MPLS-TP transport paths via a control plane. 13 The MPLS-TP data plane MUST be capable of forwarding data and taken recovery actions independently of the control or management plane used to operate the MPLS-TP layer network. That is, the MPLS-TP data plane MUST continue to operate normally if the management plane or control plane that configured the transport paths fails. 14 MPLS-TP SHOULD support mechanisms to avoid or minimize traffic impact (e.g. packet delay, reordering and loss) during network reconfiguration. 15 MPLS-TP MUST support transport paths through multiple homogeneous domains. 1516 MPLS-TP MUST NOT dictate the deployment of any particular network topology either physical or logical, however: A. It MUST be possible to deploy MPLS-TP in rings. B. It MUST be possible to deploy MPLS-TP in arbitrarily interconnected rings with one or two points of interconnection. C. MPLS-TP MUST support rings of at least 16 nodes in order to support the upgrade of existing TDM rings to MPLS-TP. MPLS-TP SHOULD support rings with more than 16 nodes. D. It MUST be possible to construct rings from equipment supplied by different vendors and to interconnect rings made wholly from equipment from different vendors. [Editor's note: This requirement comes from work provided by ITU-T Q9/15. Unless someone can provide a reason why this would not be the case we should remove this requirement. It is equivalent to saying that all correct implementations of MPLS-TP MUST interwork.] 1617 MPLS-TP MUST be able to scale gracefully with growing and increasingly complex network topologies as well as with increasing bandwidth demands, number of customers, and number of services. 1718 MPLS-TP SHOULD support mechanisms to safeguard against the provisioning of transport paths which contain forwarding loops. 2.2. Layering requirements 1819 An MPLS-TP network MUST be able to support one or more client network layers, and MUST be able to use one or more server network layers. 1920 A solution MUST be provided to support the transport of MPLS-TP and nontransport paths over MPLS-TP (MPLS-TP as a client of MPLS-TP) 21 A generic and extensible solution MUST be provided to support the transport of any client layer networksnetwork (e.g. Ethernet, ATM, FR, etc.) over an MPLS-TP layer network. 2022 A solution MUST be provided to support the transport of anMPLS-TP layer networktransport paths over MPLS-TP and non MPLS-TPany server layer networksnetwork (such as Ethernet, SONET/SDH, OTN, etc.) 21etc.). 23 In an environment where an MPLS-TP layer network is supporting a client network, and the MPLS-TP layer network is supported by a server layer network then operation of the MPLS-TP layer network MUST be possible without any dependencies on the server or client network. 2224 It MUST be possible to operate the layers of a multi-layer network that includes an MPLS-TP layer autonomously. The above are not only technology requirements, but also operational. Different administrative groups may be responsible for the same layer network or different layer networks. 2325 It MUST be possible to hide MPLS-TP layer network addressing and other information (e.g. topology) from client layers. 2.3. Data plane requirements 2426 The identification of each transport path within its aggregate MUST be supported. 2527 A label in a particular sectionlink MUST uniquely identify the transport path. 26path within that link. 28 A transport path's source MUST be identifiable at its destination. 27destination within its layer network. 29 MPLS-TP MUST support MPLS labels that are assigned by the downstream (with respect to data flow) node per [RFC3031] and [RFC3473] and MAY support context-specific MPLS labels as defined in [RFC5331]. 2830 It MUST be possible to operate and configure the MPLS-TP data (transport) plane without any IP forwarding capability in the MPLS-TP data plane. 2931 MPLS-TP MUST support both unidirectional and bidirectional point- to-point transport paths. 3032 An MPLS-TP network MUST require the forward and backward directions of a bidirectional transport path to follow the same path at each layer. 3133 The intermediate nodes at each layer MUST be aware about the pairing relationship of the forward and the backward directions belonging to the same bi-directional transport path. 3234 MPLS-TP MAY support transport paths with asymmetric bandwidth requirements, i.e. the amount of reserved bandwidth differs between the forward and backward directions. 3335 MPLS-TP MUST support unidirectional point-to-multipoint transport paths. 3436 MPLS-TP MUST be ableextensible in order to accommodate new types of client networks and services. 35 MPLS-TP SHOULD support mechanisms to minimize traffic impact during network reconfiguration. 3637 MPLS-TP SHOULD support mechanisms to enable the reserved bandwidth associated with a transport path to be increased without impacting the > existing traffic on that transport path 3738 MPLS-TP SHOULD support mechanisms to enable the reserved bandwidth of a transport path to be decreased without impacting the existing traffic on that transport path, provided that the level of existing traffic is smaller than the reserved bandwidth following the decrease. 3839 MPLS-TP SHOULDMUST support mechanisms which ensure the integrity of the transported customer's service traffic. 3940 MPLS-TP MUST support an unambiguous and reliable means of distinguishing users' (client) packets from MPLS-TP control packets (e.g. control plane, management plane, OAM and protection switching packets). 2.4. Control plane requirements This section defines the requirements that apply to MPLS-TP when a control plane is deployed. The requirements for ASON signalling and routing and the requirements for multi-region and multi-layer networks as specified in [RFC4139], [RFC4258] and [RFC5212] respectively apply to MPLS-TP. [ITU-T Comment: the MPLS-TP control plane should meet the requirements for ASON architecture (G.8080, ...) unless explicitly excluded as well as the additional MPLS-TP specific requirements explicitly added.] [Editors' Note: Following other comments on above references, need to produce consolidated text that references correct documents & requirements.] Additionally: 4041 The MPLS-TP control pane SHOULD support control plane topologies that are independent of thetopology and data plane topology. 41topology independence. 42 The MPLS-TP control plane MUST be able to be operated independent of any particular client or server layer control plane. 4243 The MPLS-TP control plane MUST support establishing all the connectivity patterns defined for the MPLS-TP data plane (e.g., unidirectional and bidirectional P2P, unidirectional P2MP, etc.) including configuration of protection functions and any associated maintenance functions. 4344 The MPLS-TP control pane MUST support the configuration and modification of OAM maintenance points as well as the activation/ deactivation of OAM when the transport path is established or modified. 4445 An MPLS-TP control plane MUST support operation of the recovery functions described in Section 2.8. 4546 An MPLS-TP control plane MUST scale gracefully to support a large number of transport paths. 46paths, nodes and links. 47 An MPLS-TP control plane SHOULD provide a common control mechanism for architecturally similar operations. 2.5. Network Management (NM) requirements For requirements related to NM functionality (Management Plane in ITU-T terminology) for MPLS-TP, see the MPLS-TP NM requirements document [I-D.gray-mpls-tp-nm-req]. 2.6. Operation, Administration and Maintenance (OAM) requirements For requirements related to OAM functionality for MPLS-TP, see the MPLS-TP OAM requirements document [I-D.vigoureux-mpls-tp-oam-requirements]. 2.7. Network performance management (PM) requirements For requirements related to PM functionality for MPLS-TP, see the MPLS-TP OAM requirements document [I-D.vigoureux-mpls-tp-oam-requirements]. 2.8. Recovery & Survivability requirements Network survivability plays a critical role in the delivery of reliable services. Network availability is a significant contributor to revenue and profit. Service guarantees in the form of SLAs require a resilient network that rapidly detects facility or node failures and restores network operation in accordance with the terms of the SLA. The requirements in this section use the recovery terminology defined in RFC 4427 [RFC4427]. 4748 MPLS-TP MUST provide protection and restoration mechanisms. A. Recovery techniques used for P2P and P2MP SHOULD be identical to simplify implementation and operation. However, this MUST NOT override any other requirement. 4849 MPLS-TP recovery mechanisms MUST be applicable at various levels throughout the network including support for span,link, path segment and end-to-end path, and pseudowire segment, and end-to-end pseudowire recovery. 4950 MPLS-TP recovery paths MUST meet the SLA protection objectives of the service. A. MPLS-TP MUST provide mechanisms to guarantee 50ms recovery times from the moment of fault detection in networks with spans less than 1200 km. B. For protection it MUST be possible to require protection of 100% of the traffic on the protected path. C. Recovery objectives SHOULD be configurable per transport path, and SHOULD include bandwidth and QoS. 5051 The recovery mechanisms MUST all be applicable to any topology. 5152 The recovery mechanisms MUST operate in synergy with (including coordination of timing) the recovery mechanisms present in any underlying server transport network (for example, Ethernet, SDH, OTN, WDM) to avoid race conditions between the layers. 5253 MPLS-TP protection mechanisms MUST support priority logic to negotiate and accommodate coexisting requests (i.e., multiple requests) for protection switching (e.g., administrative requests and requests due to link/node failures). 5354 MPLS-TP recovery and reversion mechanisms MUST prevent frequent operation of recovery in the event of an intermittent defect. [Editors' Note: ITU-T Q9/15 and Q12/15 will provide by <TBD> a requirement for protection switching time in case of linear protection (e.g. within 50 ms) together with a reference network.] 2.8.1. Data plane behavior requirements General protection and survivability requirements are expressed in terms of the behavior in the data plane. 220.127.116.11. Protection 5455 MPLS-TP MUST support 1+1 Protection. A. MPLS-TP 1+1 support MUST include bidirectional protection switching for P2P connectivity, and this SHOULD be the default behavior. B. Unidirectional 1+1 protection for P2MP connectivity MUST be supported. C. Unidirectional 1+1 protection for P2P connectivity is NOT REQUIRED. 5556 MPLS-TP MUST support 1:n Protection (including 1:1 protection). A. MPLS-TP 1:n support MUST include bidirectional protection switching for P2P connectivity, and this SHOULD be the default behavior. B. Unidirectional 1:n protection for P2MP connectivity MUST be supported. C. Unidirectional 1:n protection for P2P connectivity is NOT REQUIRED. D. The action of protection switching MUST NOT cause user data to loop. Backtracking is allowed. 5657 MPLS-TP SHOULD support extra traffic carried on 1:n protection resources when protection is not in use. 18.104.22.168. Restoration 5758 The restoration LSP MUST be able to share resources with the LSP being replaced (sometimes known as soft rerouting). 5859 Restoration priority MUST be supported so that an implementation can determine the order in which transport paths should be restored (to minimize service restoration time as well as to gain access to available spare capacity on the best paths). 5960 Preemption priority MUST be supported to allow restoration to displace other transport paths in the event of resource constraint. 6061 Recovery mechanisms MUST be bidirectional. 22.214.171.124. Sharing of protection resources 6162 MPLS-TP SHOULD support 1:n (including 1:1) shared mesh restoration. 6263 MPLS-TP MUST support the sharing of protection bandwidth by allowing best effort traffic. 6364 MPLS-TP MUST support the definition of shared protection groups to allow the coordination of protection actions resulting from triggers caused by events at different locations in the network. 6465 MPLS-TP MUST support sharing of protection resources such that protection paths that are known not to be required concurrently can share the same resources. 126.96.36.199. Reversion 6566 MPLS-TP protection mechanisms MUST support revertive and non- revertive behavior. Reversion MUST be the default behavior. 6667 MPLS-TP restoration mechanisms MAY support revertive and non- revertive behavior. 2.8.2. Triggers for protection, restoration, and reversion Recovery actions may be triggered from different places as follows: 6768 MPLS-TP MUST support physical layer fault indication triggers. 6869 MPLS-TP MUST support OAM-based triggers. 6970 MPLS-TP MUST support management plane triggers (e.g., forced switch, etc.). 7071 There MUST be a mechanism to allow administrative recovery actions to be distinguished from recovery actions initiated by other triggers. 7172 Where a control plane is present, MPLS-TP SHOULD support control plane triggers. 2.8.3. Management plane operation of protection and restoration All functions described here are for control by the operator. 7273 It MUST be possible to configure of protection paths and protection-to-working path relationships (sometimes known as protection groups). 7374 There MUST be support for pre-calculation of recovery paths. 7475 There MUST be support for pre-provisioning of recovery paths. 7576 The following administrative control MUST be supported: A. lockout B. forced switchover C. manual switchover D. simulated fault 7677 There MUST be support for the configuration of timers used for recovery operation. 7778 Restoration resources MAY be pre-planned and selected a priori, or computed after failure occurrence. 7879 When preemption is supported for recovery purposes, it MUST be possible for the operator to configure it. 7980 The management plane MUST provide indications of protection events and triggers. 8081 The management plane MUST allow the current protection status of all transport paths to be determined. 2.8.4. Control plane and in-band OAM operation of recovery 8182 The MPLS-TP control plane (which is not mandatory in an MPLS-TP implementation) MUST support: A. establishment and maintenance of all recovery entities and functions B. signaling of administrative control C. protection state coordination (PSC) 8283 In-band OAM MAY be used for: A. signaling of administrative control B. protection state coordination 2.8.5. Topology-specific recovery mechanisms 8384 MPLS-TP MAY support recovery mechanisms that are optimized for specific network topologies. These mechanisms MUST be interoperable with the mechanisms defined for arbitrary topology (mesh) networks to enable protection of end-to-end transport paths. Note that topology-specific recovery mechanisms are subject to the development of requirements using the normal IETF process. 188.8.131.52. Ring protection Several service providers have expressed a high level of interest in operating MPLS-TP in ring topologies and require a high level of survivability function in these topologies. The requirements listed below have been collected from these service providers and from the ITU-T. The main objective in considering a specific topology (such as a ring) is to determine whether it is possible to optimize any mechanisms such that the performance of those mechanisms within the topology is significantly better than the performance of the generic mechanisms in the same topology. The benefits of such optimizations are traded against the costs of developing, implementing, deploying, and operating the additional optimized mechanisms noting that the generic mechanisms MUST continue to be supported. Within the context of recovery in MPLS-TP networks, the optimization criteria considered in ring topologies are as follows: a. Minimize the number of OAM MEs that are needed to trigger the recovery operation - less than are required by other recovery mechanisms. b. Minimize the number of elements of recovery in the ring - less than are required by other recovery mechanisms. c. Minimize the number of labels required for the protection paths across the ring - less than are required by other recovery mechanisms. d. Minimize the amount of management plane transactions during a maintenance operation (e.g., ring upgrade) - less than are required by other recovery mechanisms. It may be observed that this list is fully compatible with the generic requirements expressed above, and that no requirements that are specific to ring topologies have been identified. [Editors' Note: This statement is to be confirmed at the end of the work and may be removed if it does not hold.] In the list of requirements below, those requirements that are generic are marked "[G]"; those that are Ring-specific are marked "[R]". [Editors' Note: Still need to mark up the requirements below as [R] and [G].] 8485 MPLS-TP MUST include recovery mechanisms that operate in any single ring supported in MPLS-TP, and continue to operate within the single rings even when the rings are interconnected. 8586 When a network is constructed from interconnected rings, MPLS-TP MUST support recovery mechanisms that protect user data that traverses more than one ring. This includes the possibility of failure of the ring-interconnect nodes and links. 8687 MPLS-TP recovery in a ring MUST protect unidirectional and bidirectional P2P transport paths. 8788 MPLS-TP recovery in a ring MUST protect unidirectional P2MP transport paths. 8889 MPLS-TP 1+1 and 1:1 protection in a ring MUST support switching time within 50 ms from the moment of fault detection in a network with a 16 nodes ring with less than 1200 km of fiber. This is NOT REQUIRED when extra traffic is present. [Editor note: the opinion of some people in the T103 room in Geneva is that support for extra traffic is NOT REQUIRED in ring topologies. It may be further NOT REQUIRED in any topology. This is for further discussion especially with respect to G.8131.] 8990 The protection switching time in a ring MUST be independent of the number of LSPs crossing the ring. 9091 Recovery actions in a ring MUST be data plane functions triggered by different elements of control. The triggers are configured by management or control planes and are subject to configurable policy. 9192 The configuration and operation of recovery mechanisms in a ring MUST scale well with: A. the number of transport paths (must be better than linear scaling) B. the number of nodes on the ring (must be at least as good as linear scaling) C. the number of ring interconnects (must be at least as good as linear scaling) 9293 MPLS-TP recovery in ring topologies MAY support multiple failures without reconfiguring the protection actions. 9394 Recovery techniques used in a ring MUST NOT prevent the ring from being connected to a general MPLS-TP network in any arbitrary way, and MUST NOT prevent the operation of recovery techniques in the rest of the network. 9495 MPLS-TP Recovery mechanisms applicable to a ring MUST be equally applicable in physical and logical rings. 9596 Recovery techniques in a ring SHOULD be identical to those in general networks to simplify implementation. However, this MUST NOT override any other requirement. 9697 Recovery techniques in logical and physical rings SHOULD be identical to simplify implementation and operation. However, this MUST NOT override any other requirement. 9798 The default recovery scheme in a ring MUST be bidirectional recovery in order to simplify the recovery operation. 9899 The recovery mechanism in a ring MUST support revertive switching, which MUST be the default behaviour. This allows optimization of the use of the ring resources, and restores the preferred quality conditions for normal traffic (e.g., delay) when the recovery mechanism is no longer needed. 99100 The recovery mechanisms in a ring MUST support ways to allow administrative protection switching, to be distinguished from protection switching initiated by other triggers. 100101 It MUST be possible to disable protection mechanisms on selected links in a ring (depending on operator's need). [Editor note: This requirement was originated from ITU-T Q9/15 and needs further clarification. If it means that a lockout is required for use on specific spans, then this is already covered by a general requirement, and this requirement could be deleted or rewritten for clarity. On the other hand, there may be another meaning in which case the requirement needs to be rewritten.] 101102 MPLS-TP recovery mechanisms in a ring MUST include a mechanism to allow an implementation to handle coexisting requests (i.e., multiple requests - not necessarily arriving simultaneously) for protection switching based on priority. 102103 MPLS-TP recovery and reversion mechanisms in a ring MUST offer a way to prevent frequent operation of recovery in the event of an intermittent defect. 103104 MPLS-TP MUST support the sharing of protection bandwidth in a ring by allowing best effort traffic. 104105 MPLS-TP MUST support sharing of ring protection resources such that protection paths that are known not to be required concurrently can share the same resources. 105106 MUST support the coordination of triggers caused by events at different locations in a ring. Note that this is the ring equivalent of the definition of shared protection groups. 2.9. QoS requirements Carriers require advanced traffic management capabilities to enforce and guarantee the QoS parameters of customers' SLAs. Quality of service mechanisms are REQUIRED in an MPLS-TP network to ensure: 106107 Support for differentiated services and different traffic types with traffic class separation associated with different traffic. 107108 Prioritization of critical services. 108109 Enabling the provisioning and the guarantee of Service Level Specifications (SLS), with support for hard and relative end-to- end bandwidth guaranteed. 109 Controlled110 Support of services, which are sensitive to jitter and delay. 110111 Guarantee of fair accessaccess, within a particular class, to shared resources. 111 Resources112 Guaranteed resources for in-band control and management plane packets so that data plane traffic,traffic regardless of the amount, will not cause control and management functions to become inoperative. 112amount of data plane traffic. 113 Carriers are provided with the capability to efficiently support service demands over the MPLS-TP network. This MUST include support for a flexible bandwidth allocation scheme. [Editors' Note: Should we refer here to the requirements specified in RFC 2702?] 2.10. Security requirements For a description of the security threats relevant in the context of MPLS and GMPLS and the defensive techniques to combat those threats see the Security Framework for MPLS & GMPLS Networks [I-D.draft-ietf-mpls-mpls-and-gmpls-security-framework]. 3. IANA Considerations This document makes no request of IANA. Note to RFC Editor: this section may be removed on publication as an RFC. 4. Security Considerations For a description of the security threats relevant in the context of MPLS and GMPLS and the defensive techniques to combat those threats see the Security Framework for MPLS & GMPLS Networks [I-D.draft-ietf-mpls-mpls-and-gmpls-security-framework]. 5. Acknowledgements The authors would like to thank all members of the teams (the Joint Working Team, the MPLS Interoperability Design Team in the IETF, and the T-MPLS Ad Hoc Group in the ITU-T) involved in the definition and specification of MPLS Transport Profile. The authors would also like to thank Loa Andersson, Lou Berger, Italo Busi, John Drake, Adrian Farrel, Neil Harrison, Wataru Imajuku, Julien Meuric, Tom Nadeau, Hiroshi Ohta and Tomonori Takeda for their comments and enhancements to the text. An ad hoc discussion group consisting of Stewart Bryant, Italo Busi, Andrea Digiglio, Li Fang, Adrian Farrel, Jia He, Huub van Helvoort, Feng Huang, Harald Kullman, Han Li, Hao Long and Nurit Sprecher provided valuable input to the requirements for deployment and survivability in ring topologies. 6. References 6.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [I-D.gray-mpls-tp-nm-req] Lam, H., Mansfield, S., and E. Gray, "MPLS TP Network Management Requirements", draft-gray-mpls-tp-nm-req-01 (work in progress), July 2008. [I-D.vigoureux-mpls-tp-oam-requirements] Vigoureux, M., Ward, D., and M. Betts, "Requirements for OAM in MPLS Transport Networks", draft-vigoureux-mpls-tp-oam-requirements-00 (work in progress), July 2008. 6.2. Informative References [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, January 2001. [RFC3473] Berger, L., "Multiprotocol Label Switching Architecture", RFC 3473, January 2003. [RFC3985] Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to- Edge (PWE3) Architecture", RFC 3985, March 2005. [RFC4139] Papadimitriou, D., Drake, J., Ash, J., Farrel, A., and L. Ong, "Requirements for Generalized MPLS (GMPLS) Signaling Usage and Extensions for Automatically Switched Optical Network (ASON)", RFC 4139, July 2005. [RFC4258] Brungard, D., "Requirements for Generalized Multi-Protocol Label Switching (GMPLS) Routing for the Automatically Switched Optical Network (ASON)", RFC 4258, November 2005. [RFC4427] Mannie, E. and D. Papadimitriou, "Recovery (Protection and Restoration) Terminology for Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4427, March 2006. [RFC5212] Shiomoto, K., Papadimitriou, D., Le Roux, JL., Vigoureux, M., and D. Brungard, "Requirements for GMPLS-Based Multi- Region and Multi-Layer Networks (MRN/MLN)", RFC 5212, July 2008. [RFC5331] Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream Label Assignment and Context-Specific Label Space", RFC 5331, August 2008. [I-D.draft-ietf-mpls-mpls-and-gmpls-security-framework] Fang, L. and M. Behringer, "Security Framework for MPLS and GMPLS Networks", draft-ietf-mpls-mpls-and-gmpls-security-framework-03 (work in progress), July 2008. [ITU.Y2611.2006] International Telecommunications Union, "High-level architecture of future packet-based networks", ITU- T Recommendation Y.2611, December 2006. [ITU.Y1401.2008] International Telecommunications Union, "Principles of interworking", ITU-T Recommendation Y.1401, February 2008. [ITU.G805.2000] International Telecommunications Union, "Generic functional architecture of transport networks", ITU- T Recommendation G.805, March 2000. Authors' Addresses Ben Niven-Jenkins (editor) BT 208 Callisto House, Adastral Park Ipswich, Suffolk IP5 3RE UK Email: email@example.com Deborah Brungard (editor) AT&T Rm. D1-3C22 - 200 S. Laurel Ave. Middletown, NJ 07748 USA Email: firstname.lastname@example.org Malcolm Betts (editor) Nortel Networks 3500 Carling Avenue Ottawa, Ontario K2H 8E9 Canada Email: email@example.com Nurit Sprecher Nokia Siemens Networks 3 Hanagar St. Neve Ne'eman B Hod Hasharon, 45241 Israel Email: firstname.lastname@example.org Satoshi Ueno NTT Email: email@example.com Full Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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